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6d0111f6c7
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
Chris Lattner 6d0111f6c7 populate instcombine's initial worklist more carefully, causing 
it to visit instructions from the start of the function to the
end of the function in the first path.  This greatly speeds up
some pathological cases (e.g. PR5150). 



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83814 91177308-0d34-0410-b5e6-96231b3b80d8
2009-10-11 23:17:43 +00:00

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//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
// instructions. This pass does not modify the CFG. This pass is where
// algebraic simplification happens.
//
// This pass combines things like:
// %Y = add i32 %X, 1
// %Z = add i32 %Y, 1
// into:
// %Z = add i32 %X, 2
//
// This is a simple worklist driven algorithm.
//
// This pass guarantees that the following canonicalizations are performed on
// the program:
// 1. If a binary operator has a constant operand, it is moved to the RHS
// 2. Bitwise operators with constant operands are always grouped so that
// shifts are performed first, then or's, then and's, then xor's.
// 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible
// 4. All cmp instructions on boolean values are replaced with logical ops
// 5. add X, X is represented as (X*2) => (X << 1)
// 6. Multiplies with a power-of-two constant argument are transformed into
// shifts.
// ... etc.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "instcombine"
#include "llvm/Transforms/Scalar.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Pass.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Operator.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/MallocHelper.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/PatternMatch.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
#include <climits>
using namespace llvm;
using namespace llvm::PatternMatch;
STATISTIC(NumCombined , "Number of insts combined");
STATISTIC(NumConstProp, "Number of constant folds");
STATISTIC(NumDeadInst , "Number of dead inst eliminated");
STATISTIC(NumDeadStore, "Number of dead stores eliminated");
STATISTIC(NumSunkInst , "Number of instructions sunk");
namespace {
/// InstCombineWorklist - This is the worklist management logic for
/// InstCombine.
class InstCombineWorklist {
SmallVector<Instruction*, 256> Worklist;
DenseMap<Instruction*, unsigned> WorklistMap;
void operator=(const InstCombineWorklist&RHS); // DO NOT IMPLEMENT
InstCombineWorklist(const InstCombineWorklist&); // DO NOT IMPLEMENT
public:
InstCombineWorklist() {}
bool isEmpty() const { return Worklist.empty(); }
/// Add - Add the specified instruction to the worklist if it isn't already
/// in it.
void Add(Instruction *I) {
if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
DEBUG(errs() << "IC: ADD: " << *I << '\n');
Worklist.push_back(I);
}
}
void AddValue(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
Add(I);
}
/// AddInitialGroup - Add the specified batch of stuff in reverse order.
/// which should only be done when the worklist is empty and when the group
/// has no duplicates.
void AddInitialGroup(Instruction *const *List, unsigned NumEntries) {
assert(Worklist.empty() && "Worklist must be empty to add initial group");
Worklist.reserve(NumEntries+16);
DEBUG(errs() << "IC: ADDING: " << NumEntries << " instrs to worklist\n");
for (; NumEntries; --NumEntries) {
Instruction *I = List[NumEntries-1];
WorklistMap.insert(std::make_pair(I, Worklist.size()));
Worklist.push_back(I);
}
}
// Remove - remove I from the worklist if it exists.
void Remove(Instruction *I) {
DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
if (It == WorklistMap.end()) return; // Not in worklist.
// Don't bother moving everything down, just null out the slot.
Worklist[It->second] = 0;
WorklistMap.erase(It);
}
Instruction *RemoveOne() {
Instruction *I = Worklist.back();
Worklist.pop_back();
WorklistMap.erase(I);
return I;
}
/// AddUsersToWorkList - When an instruction is simplified, add all users of
/// the instruction to the work lists because they might get more simplified
/// now.
///
void AddUsersToWorkList(Instruction &I) {
for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
UI != UE; ++UI)
Add(cast<Instruction>(*UI));
}
/// Zap - check that the worklist is empty and nuke the backing store for
/// the map if it is large.
void Zap() {
assert(WorklistMap.empty() && "Worklist empty, but map not?");
// Do an explicit clear, this shrinks the map if needed.
WorklistMap.clear();
}
};
} // end anonymous namespace.
namespace {
/// InstCombineIRInserter - This is an IRBuilder insertion helper that works
/// just like the normal insertion helper, but also adds any new instructions
/// to the instcombine worklist.
class InstCombineIRInserter : public IRBuilderDefaultInserter<true> {
InstCombineWorklist &Worklist;
public:
InstCombineIRInserter(InstCombineWorklist &WL) : Worklist(WL) {}
void InsertHelper(Instruction *I, const Twine &Name,
BasicBlock *BB, BasicBlock::iterator InsertPt) const {
IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
Worklist.Add(I);
}
};
} // end anonymous namespace
namespace {
class InstCombiner : public FunctionPass,
public InstVisitor<InstCombiner, Instruction*> {
TargetData *TD;
bool MustPreserveLCSSA;
bool MadeIRChange;
public:
/// Worklist - All of the instructions that need to be simplified.
InstCombineWorklist Worklist;
/// Builder - This is an IRBuilder that automatically inserts new
/// instructions into the worklist when they are created.
typedef IRBuilder<true, ConstantFolder, InstCombineIRInserter> BuilderTy;
BuilderTy *Builder;
static char ID; // Pass identification, replacement for typeid
InstCombiner() : FunctionPass(&ID), TD(0), Builder(0) {}
LLVMContext *Context;
LLVMContext *getContext() const { return Context; }
public:
virtual bool runOnFunction(Function &F);
bool DoOneIteration(Function &F, unsigned ItNum);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreservedID(LCSSAID);
AU.setPreservesCFG();
}
TargetData *getTargetData() const { return TD; }
// Visitation implementation - Implement instruction combining for different
// instruction types. The semantics are as follows:
// Return Value:
// null - No change was made
// I - Change was made, I is still valid, I may be dead though
// otherwise - Change was made, replace I with returned instruction
//
Instruction *visitAdd(BinaryOperator &I);
Instruction *visitFAdd(BinaryOperator &I);
Instruction *visitSub(BinaryOperator &I);
Instruction *visitFSub(BinaryOperator &I);
Instruction *visitMul(BinaryOperator &I);
Instruction *visitFMul(BinaryOperator &I);
Instruction *visitURem(BinaryOperator &I);
Instruction *visitSRem(BinaryOperator &I);
Instruction *visitFRem(BinaryOperator &I);
bool SimplifyDivRemOfSelect(BinaryOperator &I);
Instruction *commonRemTransforms(BinaryOperator &I);
Instruction *commonIRemTransforms(BinaryOperator &I);
Instruction *commonDivTransforms(BinaryOperator &I);
Instruction *commonIDivTransforms(BinaryOperator &I);
Instruction *visitUDiv(BinaryOperator &I);
Instruction *visitSDiv(BinaryOperator &I);
Instruction *visitFDiv(BinaryOperator &I);
Instruction *FoldAndOfICmps(Instruction &I, ICmpInst *LHS, ICmpInst *RHS);
Instruction *FoldAndOfFCmps(Instruction &I, FCmpInst *LHS, FCmpInst *RHS);
Instruction *visitAnd(BinaryOperator &I);
Instruction *FoldOrOfICmps(Instruction &I, ICmpInst *LHS, ICmpInst *RHS);
Instruction *FoldOrOfFCmps(Instruction &I, FCmpInst *LHS, FCmpInst *RHS);
Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op,
Value *A, Value *B, Value *C);
Instruction *visitOr (BinaryOperator &I);
Instruction *visitXor(BinaryOperator &I);
Instruction *visitShl(BinaryOperator &I);
Instruction *visitAShr(BinaryOperator &I);
Instruction *visitLShr(BinaryOperator &I);
Instruction *commonShiftTransforms(BinaryOperator &I);
Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
Constant *RHSC);
Instruction *visitFCmpInst(FCmpInst &I);
Instruction *visitICmpInst(ICmpInst &I);
Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
Instruction *LHS,
ConstantInt *RHS);
Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
ICmpInst::Predicate Cond, Instruction &I);
Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
BinaryOperator &I);
Instruction *commonCastTransforms(CastInst &CI);
Instruction *commonIntCastTransforms(CastInst &CI);
Instruction *commonPointerCastTransforms(CastInst &CI);
Instruction *visitTrunc(TruncInst &CI);
Instruction *visitZExt(ZExtInst &CI);
Instruction *visitSExt(SExtInst &CI);
Instruction *visitFPTrunc(FPTruncInst &CI);
Instruction *visitFPExt(CastInst &CI);
Instruction *visitFPToUI(FPToUIInst &FI);
Instruction *visitFPToSI(FPToSIInst &FI);
Instruction *visitUIToFP(CastInst &CI);
Instruction *visitSIToFP(CastInst &CI);
Instruction *visitPtrToInt(PtrToIntInst &CI);
Instruction *visitIntToPtr(IntToPtrInst &CI);
Instruction *visitBitCast(BitCastInst &CI);
Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI);
Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
Instruction *visitSelectInst(SelectInst &SI);
Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
Instruction *visitCallInst(CallInst &CI);
Instruction *visitInvokeInst(InvokeInst &II);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocationInst(AllocationInst &AI);
Instruction *visitFreeInst(FreeInst &FI);
Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitStoreInst(StoreInst &SI);
Instruction *visitBranchInst(BranchInst &BI);
Instruction *visitSwitchInst(SwitchInst &SI);
Instruction *visitInsertElementInst(InsertElementInst &IE);
Instruction *visitExtractElementInst(ExtractElementInst &EI);
Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
Instruction *visitExtractValueInst(ExtractValueInst &EV);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return 0; }
private:
Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);
Instruction *transformCallThroughTrampoline(CallSite CS);
Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform = true);
bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
DbgDeclareInst *hasOneUsePlusDeclare(Value *V);
public:
// InsertNewInstBefore - insert an instruction New before instruction Old
// in the program. Add the new instruction to the worklist.
//
Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
assert(New && New->getParent() == 0 &&
"New instruction already inserted into a basic block!");
BasicBlock *BB = Old.getParent();
BB->getInstList().insert(&Old, New); // Insert inst
Worklist.Add(New);
return New;
}
// ReplaceInstUsesWith - This method is to be used when an instruction is
// found to be dead, replacable with another preexisting expression. Here
// we add all uses of I to the worklist, replace all uses of I with the new
// value, then return I, so that the inst combiner will know that I was
// modified.
//
Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.
// If we are replacing the instruction with itself, this must be in a
// segment of unreachable code, so just clobber the instruction.
if (&I == V)
V = UndefValue::get(I.getType());
I.replaceAllUsesWith(V);
return &I;
}
// EraseInstFromFunction - When dealing with an instruction that has side
// effects or produces a void value, we can't rely on DCE to delete the
// instruction. Instead, visit methods should return the value returned by
// this function.
Instruction *EraseInstFromFunction(Instruction &I) {
DEBUG(errs() << "IC: ERASE " << I << '\n');
assert(I.use_empty() && "Cannot erase instruction that is used!");
// Make sure that we reprocess all operands now that we reduced their
// use counts.
if (I.getNumOperands() < 8) {
for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(*i))
Worklist.Add(Op);
}
Worklist.Remove(&I);
I.eraseFromParent();
MadeIRChange = true;
return 0; // Don't do anything with FI
}
void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
APInt &KnownOne, unsigned Depth = 0) const {
return llvm::ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth);
}
bool MaskedValueIsZero(Value *V, const APInt &Mask,
unsigned Depth = 0) const {
return llvm::MaskedValueIsZero(V, Mask, TD, Depth);
}
unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0) const {
return llvm::ComputeNumSignBits(Op, TD, Depth);
}
private:
/// SimplifyCommutative - This performs a few simplifications for
/// commutative operators.
bool SimplifyCommutative(BinaryOperator &I);
/// SimplifyCompare - This reorders the operands of a CmpInst to get them in
/// most-complex to least-complex order.
bool SimplifyCompare(CmpInst &I);
/// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
/// based on the demanded bits.
Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
APInt& KnownZero, APInt& KnownOne,
unsigned Depth);
bool SimplifyDemandedBits(Use &U, APInt DemandedMask,
APInt& KnownZero, APInt& KnownOne,
unsigned Depth=0);
/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
/// SimplifyDemandedBits knows about. See if the instruction has any
/// properties that allow us to simplify its operands.
bool SimplifyDemandedInstructionBits(Instruction &Inst);
Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
APInt& UndefElts, unsigned Depth = 0);
// FoldOpIntoPhi - Given a binary operator, cast instruction, or select
// which has a PHI node as operand #0, see if we can fold the instruction
// into the PHI (which is only possible if all operands to the PHI are
// constants).
//
// If AllowAggressive is true, FoldOpIntoPhi will allow certain transforms
// that would normally be unprofitable because they strongly encourage jump
// threading.
Instruction *FoldOpIntoPhi(Instruction &I, bool AllowAggressive = false);
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
// inputs, and do the operation once, to the result of the PHI.
Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
ConstantInt *AndRHS, BinaryOperator &TheAnd);
Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
bool isSub, Instruction &I);
Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
bool isSigned, bool Inside, Instruction &IB);
Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocationInst &AI);
Instruction *MatchBSwap(BinaryOperator &I);
bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
Instruction *SimplifyMemSet(MemSetInst *MI);
Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
bool CanEvaluateInDifferentType(Value *V, const Type *Ty,
unsigned CastOpc, int &NumCastsRemoved);
unsigned GetOrEnforceKnownAlignment(Value *V,
unsigned PrefAlign = 0);
};
} // end anonymous namespace
char InstCombiner::ID = 0;
static RegisterPass<InstCombiner>
X("instcombine", "Combine redundant instructions");
// getComplexity: Assign a complexity or rank value to LLVM Values...
// 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
static unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) ||
BinaryOperator::isFNeg(V) ||
BinaryOperator::isNot(V))
return 3;
return 4;
}
if (isa<Argument>(V)) return 3;
return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}
// isOnlyUse - Return true if this instruction will be deleted if we stop using
// it.
static bool isOnlyUse(Value *V) {
return V->hasOneUse() || isa<Constant>(V);
}
// getPromotedType - Return the specified type promoted as it would be to pass
// though a va_arg area...
static const Type *getPromotedType(const Type *Ty) {
if (const IntegerType* ITy = dyn_cast<IntegerType>(Ty)) {
if (ITy->getBitWidth() < 32)
return Type::getInt32Ty(Ty->getContext());
}
return Ty;
}
/// getBitCastOperand - If the specified operand is a CastInst, a constant
/// expression bitcast, or a GetElementPtrInst with all zero indices, return the
/// operand value, otherwise return null.
static Value *getBitCastOperand(Value *V) {
if (Operator *O = dyn_cast<Operator>(V)) {
if (O->getOpcode() == Instruction::BitCast)
return O->getOperand(0);
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
if (GEP->hasAllZeroIndices())
return GEP->getPointerOperand();
}
return 0;
}
/// This function is a wrapper around CastInst::isEliminableCastPair. It
/// simply extracts arguments and returns what that function returns.
static Instruction::CastOps
isEliminableCastPair(
const CastInst *CI, ///< The first cast instruction
unsigned opcode, ///< The opcode of the second cast instruction
const Type *DstTy, ///< The target type for the second cast instruction
TargetData *TD ///< The target data for pointer size
) {
const Type *SrcTy = CI->getOperand(0)->getType(); // A from above
const Type *MidTy = CI->getType(); // B from above
// Get the opcodes of the two Cast instructions
Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode());
Instruction::CastOps secondOp = Instruction::CastOps(opcode);
unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
DstTy,
TD ? TD->getIntPtrType(CI->getContext()) : 0);
// We don't want to form an inttoptr or ptrtoint that converts to an integer
// type that differs from the pointer size.
if ((Res == Instruction::IntToPtr &&
(!TD || SrcTy != TD->getIntPtrType(CI->getContext()))) ||
(Res == Instruction::PtrToInt &&
(!TD || DstTy != TD->getIntPtrType(CI->getContext()))))
Res = 0;
return Instruction::CastOps(Res);
}
/// ValueRequiresCast - Return true if the cast from "V to Ty" actually results
/// in any code being generated. It does not require codegen if V is simple
/// enough or if the cast can be folded into other casts.
static bool ValueRequiresCast(Instruction::CastOps opcode, const Value *V,
const Type *Ty, TargetData *TD) {
if (V->getType() == Ty || isa<Constant>(V)) return false;
// If this is another cast that can be eliminated, it isn't codegen either.
if (const CastInst *CI = dyn_cast<CastInst>(V))
if (isEliminableCastPair(CI, opcode, Ty, TD))
return false;
return true;
}
// SimplifyCommutative - This performs a few simplifications for commutative
// operators:
//
// 1. Order operands such that they are listed from right (least complex) to
// left (most complex). This puts constants before unary operators before
// binary operators.
//
// 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
// 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
//
bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
bool Changed = false;
if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
Changed = !I.swapOperands();
if (!I.isAssociative()) return Changed;
Instruction::BinaryOps Opcode = I.getOpcode();
if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
if (isa<Constant>(I.getOperand(1))) {
Constant *Folded = ConstantExpr::get(I.getOpcode(),
cast<Constant>(I.getOperand(1)),
cast<Constant>(Op->getOperand(1)));
I.setOperand(0, Op->getOperand(0));
I.setOperand(1, Folded);
return true;
} else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
isOnlyUse(Op) && isOnlyUse(Op1)) {
Constant *C1 = cast<Constant>(Op->getOperand(1));
Constant *C2 = cast<Constant>(Op1->getOperand(1));
// Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
Instruction *New = BinaryOperator::Create(Opcode, Op->getOperand(0),
Op1->getOperand(0),
Op1->getName(), &I);
Worklist.Add(New);
I.setOperand(0, New);
I.setOperand(1, Folded);
return true;
}
}
return Changed;
}
/// SimplifyCompare - For a CmpInst this function just orders the operands
/// so that theyare listed from right (least complex) to left (most complex).
/// This puts constants before unary operators before binary operators.
bool InstCombiner::SimplifyCompare(CmpInst &I) {
if (getComplexity(I.getOperand(0)) >= getComplexity(I.getOperand(1)))
return false;
I.swapOperands();
// Compare instructions are not associative so there's nothing else we can do.
return true;
}
// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
// if the LHS is a constant zero (which is the 'negate' form).
//
static inline Value *dyn_castNegVal(Value *V) {
if (BinaryOperator::isNeg(V))
return BinaryOperator::getNegArgument(V);
// Constants can be considered to be negated values if they can be folded.
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantExpr::getNeg(C);
if (ConstantVector *C = dyn_cast<ConstantVector>(V))
if (C->getType()->getElementType()->isInteger())
return ConstantExpr::getNeg(C);
return 0;
}
// dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the
// instruction if the LHS is a constant negative zero (which is the 'negate'
// form).
//
static inline Value *dyn_castFNegVal(Value *V) {
if (BinaryOperator::isFNeg(V))
return BinaryOperator::getFNegArgument(V);
// Constants can be considered to be negated values if they can be folded.
if (ConstantFP *C = dyn_cast<ConstantFP>(V))
return ConstantExpr::getFNeg(C);
if (ConstantVector *C = dyn_cast<ConstantVector>(V))
if (C->getType()->getElementType()->isFloatingPoint())
return ConstantExpr::getFNeg(C);
return 0;
}
static inline Value *dyn_castNotVal(Value *V) {
if (BinaryOperator::isNot(V))
return BinaryOperator::getNotArgument(V);
// Constants can be considered to be not'ed values...
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantInt::get(C->getType(), ~C->getValue());
return 0;
}
// dyn_castFoldableMul - If this value is a multiply that can be folded into
// other computations (because it has a constant operand), return the
// non-constant operand of the multiply, and set CST to point to the multiplier.
// Otherwise, return null.
//
static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
if (V->hasOneUse() && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V)) {
if (I->getOpcode() == Instruction::Mul)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
return I->getOperand(0);
if (I->getOpcode() == Instruction::Shl)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
// The multiplier is really 1 << CST.
uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
uint32_t CSTVal = CST->getLimitedValue(BitWidth);
CST = ConstantInt::get(V->getType()->getContext(),
APInt(BitWidth, 1).shl(CSTVal));
return I->getOperand(0);
}
}
return 0;
}
/// AddOne - Add one to a ConstantInt
static Constant *AddOne(Constant *C) {
return ConstantExpr::getAdd(C,
ConstantInt::get(C->getType(), 1));
}
/// SubOne - Subtract one from a ConstantInt
static Constant *SubOne(ConstantInt *C) {
return ConstantExpr::getSub(C,
ConstantInt::get(C->getType(), 1));
}
/// MultiplyOverflows - True if the multiply can not be expressed in an int
/// this size.
static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
uint32_t W = C1->getBitWidth();
APInt LHSExt = C1->getValue(), RHSExt = C2->getValue();
if (sign) {
LHSExt.sext(W * 2);
RHSExt.sext(W * 2);
} else {
LHSExt.zext(W * 2);
RHSExt.zext(W * 2);
}
APInt MulExt = LHSExt * RHSExt;
if (sign) {
APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
return MulExt.slt(Min) || MulExt.sgt(Max);
} else
return MulExt.ugt(APInt::getLowBitsSet(W * 2, W));
}
/// ShrinkDemandedConstant - Check to see if the specified operand of the
/// specified instruction is a constant integer. If so, check to see if there
/// are any bits set in the constant that are not demanded. If so, shrink the
/// constant and return true.
static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
APInt Demanded) {
assert(I && "No instruction?");
assert(OpNo < I->getNumOperands() && "Operand index too large");
// If the operand is not a constant integer, nothing to do.
ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
if (!OpC) return false;
// If there are no bits set that aren't demanded, nothing to do.
Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
if ((~Demanded & OpC->getValue()) == 0)
return false;
// This instruction is producing bits that are not demanded. Shrink the RHS.
Demanded &= OpC->getValue();
I->setOperand(OpNo, ConstantInt::get(OpC->getType(), Demanded));
return true;
}
// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
// set of known zero and one bits, compute the maximum and minimum values that
// could have the specified known zero and known one bits, returning them in
// min/max.
static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero,
const APInt& KnownOne,
APInt& Min, APInt& Max) {
assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
KnownZero.getBitWidth() == Min.getBitWidth() &&
KnownZero.getBitWidth() == Max.getBitWidth() &&
"KnownZero, KnownOne and Min, Max must have equal bitwidth.");
APInt UnknownBits = ~(KnownZero|KnownOne);
// The minimum value is when all unknown bits are zeros, EXCEPT for the sign
// bit if it is unknown.
Min = KnownOne;
Max = KnownOne|UnknownBits;
if (UnknownBits.isNegative()) { // Sign bit is unknown
Min.set(Min.getBitWidth()-1);
Max.clear(Max.getBitWidth()-1);
}
}
// ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and
// a set of known zero and one bits, compute the maximum and minimum values that
// could have the specified known zero and known one bits, returning them in
// min/max.
static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero,
const APInt &KnownOne,
APInt &Min, APInt &Max) {
assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
KnownZero.getBitWidth() == Min.getBitWidth() &&
KnownZero.getBitWidth() == Max.getBitWidth() &&
"Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
APInt UnknownBits = ~(KnownZero|KnownOne);
// The minimum value is when the unknown bits are all zeros.
Min = KnownOne;
// The maximum value is when the unknown bits are all ones.
Max = KnownOne|UnknownBits;
}
/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
/// SimplifyDemandedBits knows about. See if the instruction has any
/// properties that allow us to simplify its operands.
bool InstCombiner::SimplifyDemandedInstructionBits(Instruction &Inst) {
unsigned BitWidth = Inst.getType()->getScalarSizeInBits();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
APInt DemandedMask(APInt::getAllOnesValue(BitWidth));
Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask,
KnownZero, KnownOne, 0);
if (V == 0) return false;
if (V == &Inst) return true;
ReplaceInstUsesWith(Inst, V);
return true;
}
/// SimplifyDemandedBits - This form of SimplifyDemandedBits simplifies the
/// specified instruction operand if possible, updating it in place. It returns
/// true if it made any change and false otherwise.
bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask,
APInt &KnownZero, APInt &KnownOne,
unsigned Depth) {
Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask,
KnownZero, KnownOne, Depth);
if (NewVal == 0) return false;
U = NewVal;
return true;
}
/// SimplifyDemandedUseBits - This function attempts to replace V with a simpler
/// value based on the demanded bits. When this function is called, it is known
/// that only the bits set in DemandedMask of the result of V are ever used
/// downstream. Consequently, depending on the mask and V, it may be possible
/// to replace V with a constant or one of its operands. In such cases, this
/// function does the replacement and returns true. In all other cases, it
/// returns false after analyzing the expression and setting KnownOne and known
/// to be one in the expression. KnownZero contains all the bits that are known
/// to be zero in the expression. These are provided to potentially allow the
/// caller (which might recursively be SimplifyDemandedBits itself) to simplify
/// the expression. KnownOne and KnownZero always follow the invariant that
/// KnownOne & KnownZero == 0. That is, a bit can't be both 1 and 0. Note that
/// the bits in KnownOne and KnownZero may only be accurate for those bits set
/// in DemandedMask. Note also that the bitwidth of V, DemandedMask, KnownZero
/// and KnownOne must all be the same.
///
/// This returns null if it did not change anything and it permits no
/// simplification. This returns V itself if it did some simplification of V's
/// operands based on the information about what bits are demanded. This returns
/// some other non-null value if it found out that V is equal to another value
/// in the context where the specified bits are demanded, but not for all users.
Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
APInt &KnownZero, APInt &KnownOne,
unsigned Depth) {
assert(V != 0 && "Null pointer of Value???");
assert(Depth <= 6 && "Limit Search Depth");
uint32_t BitWidth = DemandedMask.getBitWidth();
const Type *VTy = V->getType();
assert((TD || !isa<PointerType>(VTy)) &&
"SimplifyDemandedBits needs to know bit widths!");
assert((!TD || TD->getTypeSizeInBits(VTy->getScalarType()) == BitWidth) &&
(!VTy->isIntOrIntVector() ||
VTy->getScalarSizeInBits() == BitWidth) &&
KnownZero.getBitWidth() == BitWidth &&
KnownOne.getBitWidth() == BitWidth &&
"Value *V, DemandedMask, KnownZero and KnownOne "
"must have same BitWidth");
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
// We know all of the bits for a constant!
KnownOne = CI->getValue() & DemandedMask;
KnownZero = ~KnownOne & DemandedMask;
return 0;
}
if (isa<ConstantPointerNull>(V)) {
// We know all of the bits for a constant!
KnownOne.clear();
KnownZero = DemandedMask;
return 0;
}
KnownZero.clear();
KnownOne.clear();
if (DemandedMask == 0) { // Not demanding any bits from V.
if (isa<UndefValue>(V))
return 0;
return UndefValue::get(VTy);
}
if (Depth == 6) // Limit search depth.
return 0;
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
APInt &RHSKnownZero = KnownZero, &RHSKnownOne = KnownOne;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) {
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
return 0; // Only analyze instructions.
}
// If there are multiple uses of this value and we aren't at the root, then
// we can't do any simplifications of the operands, because DemandedMask
// only reflects the bits demanded by *one* of the users.
if (Depth != 0 && !I->hasOneUse()) {
// Despite the fact that we can't simplify this instruction in all User's
// context, we can at least compute the knownzero/knownone bits, and we can
// do simplifications that apply to *just* the one user if we know that
// this instruction has a simpler value in that context.
if (I->getOpcode() == Instruction::And) {
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(I->getOperand(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(0), DemandedMask & ~RHSKnownZero,
LHSKnownZero, LHSKnownOne, Depth+1);
// If all of the demanded bits are known 1 on one side, return the other.
// These bits cannot contribute to the result of the 'and' in this
// context.
if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
(DemandedMask & ~LHSKnownZero))
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
(DemandedMask & ~RHSKnownZero))
return I->getOperand(1);
// If all of the demanded bits in the inputs are known zeros, return zero.
if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
return Constant::getNullValue(VTy);
} else if (I->getOpcode() == Instruction::Or) {
// We can simplify (X|Y) -> X or Y in the user's context if we know that
// only bits from X or Y are demanded.
// If either the LHS or the RHS are One, the result is One.
ComputeMaskedBits(I->getOperand(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(0), DemandedMask & ~RHSKnownOne,
LHSKnownZero, LHSKnownOne, Depth+1);
// If all of the demanded bits are known zero on one side, return the
// other. These bits cannot contribute to the result of the 'or' in this
// context.
if ((DemandedMask & ~LHSKnownOne & RHSKnownZero) ==
(DemandedMask & ~LHSKnownOne))
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
(DemandedMask & ~RHSKnownOne))
return I->getOperand(1);
// If all of the potentially set bits on one side are known to be set on
// the other side, just use the 'other' side.
if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) ==
(DemandedMask & (~RHSKnownZero)))
return I->getOperand(0);
if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
(DemandedMask & (~LHSKnownZero)))
return I->getOperand(1);
}
// Compute the KnownZero/KnownOne bits to simplify things downstream.
ComputeMaskedBits(I, DemandedMask, KnownZero, KnownOne, Depth);
return 0;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the DemandedMask to all bits so that we can try to simplify the
// operands. This allows visitTruncInst (for example) to simplify the
// operand of a trunc without duplicating all the logic below.
if (Depth == 0 && !V->hasOneUse())
DemandedMask = APInt::getAllOnesValue(BitWidth);
switch (I->getOpcode()) {
default:
ComputeMaskedBits(I, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
break;
case Instruction::And:
// If either the LHS or the RHS are Zero, the result is zero.
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownZero,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
// If all of the demanded bits are known 1 on one side, return the other.
// These bits cannot contribute to the result of the 'and'.
if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
(DemandedMask & ~LHSKnownZero))
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
(DemandedMask & ~RHSKnownZero))
return I->getOperand(1);
// If all of the demanded bits in the inputs are known zeros, return zero.
if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
return Constant::getNullValue(VTy);
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnownZero))
return I;
// Output known-1 bits are only known if set in both the LHS & RHS.
RHSKnownOne &= LHSKnownOne;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
RHSKnownZero |= LHSKnownZero;
break;
case Instruction::Or:
// If either the LHS or the RHS are One, the result is One.
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownOne,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'or'.
if ((DemandedMask & ~LHSKnownOne & RHSKnownZero) ==
(DemandedMask & ~LHSKnownOne))
return I->getOperand(0);
if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
(DemandedMask & ~RHSKnownOne))
return I->getOperand(1);
// If all of the potentially set bits on one side are known to be set on
// the other side, just use the 'other' side.
if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) ==
(DemandedMask & (~RHSKnownZero)))
return I->getOperand(0);
if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
(DemandedMask & (~LHSKnownZero)))
return I->getOperand(1);
// If the RHS is a constant, see if we can simplify it.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return I;
// Output known-0 bits are only known if clear in both the LHS & RHS.
RHSKnownZero &= LHSKnownZero;
// Output known-1 are known to be set if set in either the LHS | RHS.
RHSKnownOne |= LHSKnownOne;
break;
case Instruction::Xor: {
if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
// If all of the demanded bits are known zero on one side, return the other.
// These bits cannot contribute to the result of the 'xor'.
if ((DemandedMask & RHSKnownZero) == DemandedMask)
return I->getOperand(0);
if ((DemandedMask & LHSKnownZero) == DemandedMask)
return I->getOperand(1);
// Output known-0 bits are known if clear or set in both the LHS & RHS.
APInt KnownZeroOut = (RHSKnownZero & LHSKnownZero) |
(RHSKnownOne & LHSKnownOne);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
APInt KnownOneOut = (RHSKnownZero & LHSKnownOne) |
(RHSKnownOne & LHSKnownZero);
// If all of the demanded bits are known to be zero on one side or the
// other, turn this into an *inclusive* or.
// e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
if ((DemandedMask & ~RHSKnownZero & ~LHSKnownZero) == 0) {
Instruction *Or =
BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
I->getName());
return InsertNewInstBefore(Or, *I);
}
// If all of the demanded bits on one side are known, and all of the set
// bits on that side are also known to be set on the other side, turn this
// into an AND, as we know the bits will be cleared.
// e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask) {
// all known
if ((RHSKnownOne & LHSKnownOne) == RHSKnownOne) {
Constant *AndC = Constant::getIntegerValue(VTy,
~RHSKnownOne & DemandedMask);
Instruction *And =
BinaryOperator::CreateAnd(I->getOperand(0), AndC, "tmp");
return InsertNewInstBefore(And, *I);
}
}
// If the RHS is a constant, see if we can simplify it.
// FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
if (ShrinkDemandedConstant(I, 1, DemandedMask))
return I;
// If our LHS is an 'and' and if it has one use, and if any of the bits we
// are flipping are known to be set, then the xor is just resetting those
// bits to zero. We can just knock out bits from the 'and' and the 'xor',
// simplifying both of them.
if (Instruction *LHSInst = dyn_cast<Instruction>(I->getOperand(0)))
if (LHSInst->getOpcode() == Instruction::And && LHSInst->hasOneUse() &&
isa<ConstantInt>(I->getOperand(1)) &&
isa<ConstantInt>(LHSInst->getOperand(1)) &&
(LHSKnownOne & RHSKnownOne & DemandedMask) != 0) {
ConstantInt *AndRHS = cast<ConstantInt>(LHSInst->getOperand(1));
ConstantInt *XorRHS = cast<ConstantInt>(I->getOperand(1));
APInt NewMask = ~(LHSKnownOne & RHSKnownOne & DemandedMask);
Constant *AndC =
ConstantInt::get(I->getType(), NewMask & AndRHS->getValue());
Instruction *NewAnd =
BinaryOperator::CreateAnd(I->getOperand(0), AndC, "tmp");
InsertNewInstBefore(NewAnd, *I);
Constant *XorC =
ConstantInt::get(I->getType(), NewMask & XorRHS->getValue());
Instruction *NewXor =
BinaryOperator::CreateXor(NewAnd, XorC, "tmp");
return InsertNewInstBefore(NewXor, *I);
}
RHSKnownZero = KnownZeroOut;
RHSKnownOne = KnownOneOut;
break;
}
case Instruction::Select:
if (SimplifyDemandedBits(I->getOperandUse(2), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
// If the operands are constants, see if we can simplify them.
if (ShrinkDemandedConstant(I, 1, DemandedMask) ||
ShrinkDemandedConstant(I, 2, DemandedMask))
return I;
// Only known if known in both the LHS and RHS.
RHSKnownOne &= LHSKnownOne;
RHSKnownZero &= LHSKnownZero;
break;
case Instruction::Trunc: {
unsigned truncBf = I->getOperand(0)->getType()->getScalarSizeInBits();
DemandedMask.zext(truncBf);
RHSKnownZero.zext(truncBf);
RHSKnownOne.zext(truncBf);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
DemandedMask.trunc(BitWidth);
RHSKnownZero.trunc(BitWidth);
RHSKnownOne.trunc(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
break;
}
case Instruction::BitCast:
if (!I->getOperand(0)->getType()->isIntOrIntVector())
return false; // vector->int or fp->int?
if (const VectorType *DstVTy = dyn_cast<VectorType>(I->getType())) {
if (const VectorType *SrcVTy =
dyn_cast<VectorType>(I->getOperand(0)->getType())) {
if (DstVTy->getNumElements() != SrcVTy->getNumElements())
// Don't touch a bitcast between vectors of different element counts.
return false;
} else
// Don't touch a scalar-to-vector bitcast.
return false;
} else if (isa<VectorType>(I->getOperand(0)->getType()))
// Don't touch a vector-to-scalar bitcast.
return false;
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
break;
case Instruction::ZExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits();
DemandedMask.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
DemandedMask.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
// The top bits are known to be zero.
RHSKnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
break;
}
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits();
APInt InputDemandedBits = DemandedMask &
APInt::getLowBitsSet(BitWidth, SrcBitWidth);
APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
// If any of the sign extended bits are demanded, we know that the sign
// bit is demanded.
if ((NewBits & DemandedMask) != 0)
InputDemandedBits.set(SrcBitWidth-1);
InputDemandedBits.trunc(SrcBitWidth);
RHSKnownZero.trunc(SrcBitWidth);
RHSKnownOne.trunc(SrcBitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), InputDemandedBits,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
InputDemandedBits.zext(BitWidth);
RHSKnownZero.zext(BitWidth);
RHSKnownOne.zext(BitWidth);
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
// If the input sign bit is known zero, or if the NewBits are not demanded
// convert this into a zero extension.
if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) {
// Convert to ZExt cast
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName());
return InsertNewInstBefore(NewCast, *I);
} else if (RHSKnownOne[SrcBitWidth-1]) { // Input sign bit known set
RHSKnownOne |= NewBits;
}
break;
}
case Instruction::Add: {
// Figure out what the input bits are. If the top bits of the and result
// are not demanded, then the add doesn't demand them from its input
// either.
unsigned NLZ = DemandedMask.countLeadingZeros();
// If there is a constant on the RHS, there are a variety of xformations
// we can do.
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
// If null, this should be simplified elsewhere. Some of the xforms here
// won't work if the RHS is zero.
if (RHS->isZero())
break;
// If the top bit of the output is demanded, demand everything from the
// input. Otherwise, we demand all the input bits except NLZ top bits.
APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ));
// Find information about known zero/one bits in the input.
if (SimplifyDemandedBits(I->getOperandUse(0), InDemandedBits,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
// If the RHS of the add has bits set that can't affect the input, reduce
// the constant.
if (ShrinkDemandedConstant(I, 1, InDemandedBits))
return I;
// Avoid excess work.
if (LHSKnownZero == 0 && LHSKnownOne == 0)
break;
// Turn it into OR if input bits are zero.
if ((LHSKnownZero & RHS->getValue()) == RHS->getValue()) {
Instruction *Or =
BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
I->getName());
return InsertNewInstBefore(Or, *I);
}
// We can say something about the output known-zero and known-one bits,
// depending on potential carries from the input constant and the
// unknowns. For example if the LHS is known to have at most the 0x0F0F0
// bits set and the RHS constant is 0x01001, then we know we have a known
// one mask of 0x00001 and a known zero mask of 0xE0F0E.
// To compute this, we first compute the potential carry bits. These are
// the bits which may be modified. I'm not aware of a better way to do
// this scan.
const APInt &RHSVal = RHS->getValue();
APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal));
// Now that we know which bits have carries, compute the known-1/0 sets.
// Bits are known one if they are known zero in one operand and one in the
// other, and there is no input carry.
RHSKnownOne = ((LHSKnownZero & RHSVal) |
(LHSKnownOne & ~RHSVal)) & ~CarryBits;
// Bits are known zero if they are known zero in both operands and there
// is no input carry.
RHSKnownZero = LHSKnownZero & ~RHSVal & ~CarryBits;
} else {
// If the high-bits of this ADD are not demanded, then it does not demand
// the high bits of its LHS or RHS.
if (DemandedMask[BitWidth-1] == 0) {
// Right fill the mask of bits for this ADD to demand the most
// significant bit and all those below it.
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
}
}
break;
}
case Instruction::Sub:
// If the high-bits of this SUB are not demanded, then it does not demand
// the high bits of its LHS or RHS.
if (DemandedMask[BitWidth-1] == 0) {
// Right fill the mask of bits for this SUB to demand the most
// significant bit and all those below it.
uint32_t NLZ = DemandedMask.countLeadingZeros();
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
}
// Otherwise just hand the sub off to ComputeMaskedBits to fill in
// the known zeros and ones.
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
break;
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero <<= ShiftAmt;
RHSKnownOne <<= ShiftAmt;
// low bits known zero.
if (ShiftAmt)
RHSKnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
}
break;
case Instruction::LShr:
// For a logical shift right
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
// Unsigned shift right.
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
if (ShiftAmt) {
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero |= HighBits; // high bits known zero.
}
}
break;
case Instruction::AShr:
// If this is an arithmetic shift right and only the low-bit is set, we can
// always convert this into a logical shr, even if the shift amount is
// variable. The low bit of the shift cannot be an input sign bit unless
// the shift amount is >= the size of the datatype, which is undefined.
if (DemandedMask == 1) {
// Perform the logical shift right.
Instruction *NewVal = BinaryOperator::CreateLShr(
I->getOperand(0), I->getOperand(1), I->getName());
return InsertNewInstBefore(NewVal, *I);
}
// If the sign bit is the only bit demanded by this ashr, then there is no
// need to do it, the shift doesn't change the high bit.
if (DemandedMask.isSignBit())
return I->getOperand(0);
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t ShiftAmt = SA->getLimitedValue(BitWidth);
// Signed shift right.
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
// If any of the "high bits" are demanded, we should set the sign bit as
// demanded.
if (DemandedMask.countLeadingZeros() <= ShiftAmt)
DemandedMaskIn.set(BitWidth-1);
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
RHSKnownZero, RHSKnownOne, Depth+1))
return I;
assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
// Compute the new bits that are at the top now.
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
// Handle the sign bits.
APInt SignBit(APInt::getSignBit(BitWidth));
// Adjust to where it is now in the mask.
SignBit = APIntOps::lshr(SignBit, ShiftAmt);
// If the input sign bit is known to be zero, or if none of the top bits
// are demanded, turn this into an unsigned shift right.
if (BitWidth <= ShiftAmt || RHSKnownZero[BitWidth-ShiftAmt-1] ||
(HighBits & ~DemandedMask) == HighBits) {
// Perform the logical shift right.
Instruction *NewVal = BinaryOperator::CreateLShr(
I->getOperand(0), SA, I->getName());
return InsertNewInstBefore(NewVal, *I);
} else if ((RHSKnownOne & SignBit) != 0) { // New bits are known one.
RHSKnownOne |= HighBits;
}
}
break;
case Instruction::SRem:
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
APInt RA = Rem->getValue().abs();
if (RA.isPowerOf2()) {
if (DemandedMask.ult(RA)) // srem won't affect demanded bits
return I->getOperand(0);
APInt LowBits = RA - 1;
APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), Mask2,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits))
LHSKnownZero |= ~LowBits;
KnownZero |= LHSKnownZero & DemandedMask;
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
}
}
break;
case Instruction::URem: {
APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
APInt AllOnes = APInt::getAllOnesValue(BitWidth);
if (SimplifyDemandedBits(I->getOperandUse(0), AllOnes,
KnownZero2, KnownOne2, Depth+1) ||
SimplifyDemandedBits(I->getOperandUse(1), AllOnes,
KnownZero2, KnownOne2, Depth+1))
return I;
unsigned Leaders = KnownZero2.countLeadingOnes();
Leaders = std::max(Leaders,
KnownZero2.countLeadingOnes());
KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask;
break;
}
case Instruction::Call:
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::bswap: {
// If the only bits demanded come from one byte of the bswap result,
// just shift the input byte into position to eliminate the bswap.
unsigned NLZ = DemandedMask.countLeadingZeros();
unsigned NTZ = DemandedMask.countTrailingZeros();
// Round NTZ down to the next byte. If we have 11 trailing zeros, then
// we need all the bits down to bit 8. Likewise, round NLZ. If we
// have 14 leading zeros, round to 8.
NLZ &= ~7;
NTZ &= ~7;
// If we need exactly one byte, we can do this transformation.
if (BitWidth-NLZ-NTZ == 8) {
unsigned ResultBit = NTZ;
unsigned InputBit = BitWidth-NTZ-8;
// Replace this with either a left or right shift to get the byte into
// the right place.
Instruction *NewVal;
if (InputBit > ResultBit)
NewVal = BinaryOperator::CreateLShr(I->getOperand(1),
ConstantInt::get(I->getType(), InputBit-ResultBit));
else
NewVal = BinaryOperator::CreateShl(I->getOperand(1),
ConstantInt::get(I->getType(), ResultBit-InputBit));
NewVal->takeName(I);
return InsertNewInstBefore(NewVal, *I);
}
// TODO: Could compute known zero/one bits based on the input.
break;
}
}
}
ComputeMaskedBits(V, DemandedMask, RHSKnownZero, RHSKnownOne, Depth);
break;
}
// If the client is only demanding bits that we know, return the known
// constant.
if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask)
return Constant::getIntegerValue(VTy, RHSKnownOne);
return false;
}
/// SimplifyDemandedVectorElts - The specified value produces a vector with
/// any number of elements. DemandedElts contains the set of elements that are
/// actually used by the caller. This method analyzes which elements of the
/// operand are undef and returns that information in UndefElts.
///
/// If the information about demanded elements can be used to simplify the
/// operation, the operation is simplified, then the resultant value is
/// returned. This returns null if no change was made.
Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
APInt& UndefElts,
unsigned Depth) {
unsigned VWidth = cast<VectorType>(V->getType())->getNumElements();
APInt EltMask(APInt::getAllOnesValue(VWidth));
assert((DemandedElts & ~EltMask) == 0 && "Invalid DemandedElts!");
if (isa<UndefValue>(V)) {
// If the entire vector is undefined, just return this info.
UndefElts = EltMask;
return 0;
} else if (DemandedElts == 0) { // If nothing is demanded, provide undef.
UndefElts = EltMask;
return UndefValue::get(V->getType());
}
UndefElts = 0;
if (ConstantVector *CP = dyn_cast<ConstantVector>(V)) {
const Type *EltTy = cast<VectorType>(V->getType())->getElementType();
Constant *Undef = UndefValue::get(EltTy);
std::vector<Constant*> Elts;
for (unsigned i = 0; i != VWidth; ++i)
if (!DemandedElts[i]) { // If not demanded, set to undef.
Elts.push_back(Undef);
UndefElts.set(i);
} else if (isa<UndefValue>(CP->getOperand(i))) { // Already undef.
Elts.push_back(Undef);
UndefElts.set(i);
} else { // Otherwise, defined.
Elts.push_back(CP->getOperand(i));
}
// If we changed the constant, return it.
Constant *NewCP = ConstantVector::get(Elts);
return NewCP != CP ? NewCP : 0;
} else if (isa<ConstantAggregateZero>(V)) {
// Simplify the CAZ to a ConstantVector where the non-demanded elements are
// set to undef.
// Check if this is identity. If so, return 0 since we are not simplifying
// anything.
if (DemandedElts == ((1ULL << VWidth) -1))
return 0;
const Type *EltTy = cast<VectorType>(V->getType())->getElementType();
Constant *Zero = Constant::getNullValue(EltTy);
Constant *Undef = UndefValue::get(EltTy);
std::vector<Constant*> Elts;
for (unsigned i = 0; i != VWidth; ++i) {
Constant *Elt = DemandedElts[i] ? Zero : Undef;
Elts.push_back(Elt);
}
UndefElts = DemandedElts ^ EltMask;
return ConstantVector::get(Elts);
}
// Limit search depth.
if (Depth == 10)
return 0;
// If multiple users are using the root value, procede with
// simplification conservatively assuming that all elements
// are needed.
if (!V->hasOneUse()) {
// Quit if we find multiple users of a non-root value though.
// They'll be handled when it's their turn to be visited by
// the main instcombine process.
if (Depth != 0)
// TODO: Just compute the UndefElts information recursively.
return 0;
// Conservatively assume that all elements are needed.
DemandedElts = EltMask;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return 0; // Only analyze instructions.
bool MadeChange = false;
APInt UndefElts2(VWidth, 0);
Value *TmpV;
switch (I->getOpcode()) {
default: break;
case Instruction::InsertElement: {
// If this is a variable index, we don't know which element it overwrites.
// demand exactly the same input as we produce.
ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
if (Idx == 0) {
// Note that we can't propagate undef elt info, because we don't know
// which elt is getting updated.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
break;
}
// If this is inserting an element that isn't demanded, remove this
// insertelement.
unsigned IdxNo = Idx->getZExtValue();
if (IdxNo >= VWidth || !DemandedElts[IdxNo]) {
Worklist.Add(I);
return I->getOperand(0);
}
// Otherwise, the element inserted overwrites whatever was there, so the
// input demanded set is simpler than the output set.
APInt DemandedElts2 = DemandedElts;
DemandedElts2.clear(IdxNo);
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts2,
UndefElts, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
// The inserted element is defined.
UndefElts.clear(IdxNo);
break;
}
case Instruction::ShuffleVector: {
ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I);
uint64_t LHSVWidth =
cast<VectorType>(Shuffle->getOperand(0)->getType())->getNumElements();
APInt LeftDemanded(LHSVWidth, 0), RightDemanded(LHSVWidth, 0);
for (unsigned i = 0; i < VWidth; i++) {
if (DemandedElts[i]) {
unsigned MaskVal = Shuffle->getMaskValue(i);
if (MaskVal != -1u) {
assert(MaskVal < LHSVWidth * 2 &&
"shufflevector mask index out of range!");
if (MaskVal < LHSVWidth)
LeftDemanded.set(MaskVal);
else
RightDemanded.set(MaskVal - LHSVWidth);
}
}
}
APInt UndefElts4(LHSVWidth, 0);
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), LeftDemanded,
UndefElts4, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
APInt UndefElts3(LHSVWidth, 0);
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), RightDemanded,
UndefElts3, Depth+1);
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
bool NewUndefElts = false;
for (unsigned i = 0; i < VWidth; i++) {
unsigned MaskVal = Shuffle->getMaskValue(i);
if (MaskVal == -1u) {
UndefElts.set(i);
} else if (MaskVal < LHSVWidth) {
if (UndefElts4[MaskVal]) {
NewUndefElts = true;
UndefElts.set(i);
}
} else {
if (UndefElts3[MaskVal - LHSVWidth]) {
NewUndefElts = true;
UndefElts.set(i);
}
}
}
if (NewUndefElts) {
// Add additional discovered undefs.
std::vector<Constant*> Elts;
for (unsigned i = 0; i < VWidth; ++i) {
if (UndefElts[i])
Elts.push_back(UndefValue::get(Type::getInt32Ty(*Context)));
else
Elts.push_back(ConstantInt::get(Type::getInt32Ty(*Context),
Shuffle->getMaskValue(i)));
}
I->setOperand(2, ConstantVector::get(Elts));
MadeChange = true;
}
break;
}
case Instruction::BitCast: {
// Vector->vector casts only.
const VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());
if (!VTy) break;
unsigned InVWidth = VTy->getNumElements();
APInt InputDemandedElts(InVWidth, 0);
unsigned Ratio;
if (VWidth == InVWidth) {
// If we are converting from <4 x i32> -> <4 x f32>, we demand the same
// elements as are demanded of us.
Ratio = 1;
InputDemandedElts = DemandedElts;
} else if (VWidth > InVWidth) {
// Untested so far.
break;
// If there are more elements in the result than there are in the source,
// then an input element is live if any of the corresponding output
// elements are live.
Ratio = VWidth/InVWidth;
for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) {
if (DemandedElts[OutIdx])
InputDemandedElts.set(OutIdx/Ratio);
}
} else {
// Untested so far.
break;
// If there are more elements in the source than there are in the result,
// then an input element is live if the corresponding output element is
// live.
Ratio = InVWidth/VWidth;
for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
if (DemandedElts[InIdx/Ratio])
InputDemandedElts.set(InIdx);
}
// div/rem demand all inputs, because they don't want divide by zero.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), InputDemandedElts,
UndefElts2, Depth+1);
if (TmpV) {
I->setOperand(0, TmpV);
MadeChange = true;
}
UndefElts = UndefElts2;
if (VWidth > InVWidth) {
llvm_unreachable("Unimp");
// If there are more elements in the result than there are in the source,
// then an output element is undef if the corresponding input element is
// undef.
for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
if (UndefElts2[OutIdx/Ratio])
UndefElts.set(OutIdx);
} else if (VWidth < InVWidth) {
llvm_unreachable("Unimp");
// If there are more elements in the source than there are in the result,
// then a result element is undef if all of the corresponding input
// elements are undef.
UndefElts = ~0ULL >> (64-VWidth); // Start out all undef.
for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
if (!UndefElts2[InIdx]) // Not undef?
UndefElts.clear(InIdx/Ratio); // Clear undef bit.
}
break;
}
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
// div/rem demand all inputs, because they don't want divide by zero.
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
UndefElts, Depth+1);
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
// Output elements are undefined if both are undefined. Consider things
// like undef&0. The result is known zero, not undef.
UndefElts &= UndefElts2;
break;
case Instruction::Call: {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
if (!II) break;
switch (II->getIntrinsicID()) {
default: break;
// Binary vector operations that work column-wise. A dest element is a
// function of the corresponding input elements from the two inputs.
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse_min_ss:
case Intrinsic::x86_sse_max_ss:
case Intrinsic::x86_sse2_sub_sd:
case Intrinsic::x86_sse2_mul_sd:
case Intrinsic::x86_sse2_min_sd:
case Intrinsic::x86_sse2_max_sd:
TmpV = SimplifyDemandedVectorElts(II->getOperand(1), DemandedElts,
UndefElts, Depth+1);
if (TmpV) { II->setOperand(1, TmpV); MadeChange = true; }
TmpV = SimplifyDemandedVectorElts(II->getOperand(2), DemandedElts,
UndefElts2, Depth+1);
if (TmpV) { II->setOperand(2, TmpV); MadeChange = true; }
// If only the low elt is demanded and this is a scalarizable intrinsic,
// scalarize it now.
if (DemandedElts == 1) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse2_sub_sd:
case Intrinsic::x86_sse2_mul_sd:
// TODO: Lower MIN/MAX/ABS/etc
Value *LHS = II->getOperand(1);
Value *RHS = II->getOperand(2);
// Extract the element as scalars.
LHS = InsertNewInstBefore(ExtractElementInst::Create(LHS,
ConstantInt::get(Type::getInt32Ty(*Context), 0U, false), "tmp"), *II);
RHS = InsertNewInstBefore(ExtractElementInst::Create(RHS,
ConstantInt::get(Type::getInt32Ty(*Context), 0U, false), "tmp"), *II);
switch (II->getIntrinsicID()) {
default: llvm_unreachable("Case stmts out of sync!");
case Intrinsic::x86_sse_sub_ss:
case Intrinsic::x86_sse2_sub_sd:
TmpV = InsertNewInstBefore(BinaryOperator::CreateFSub(LHS, RHS,
II->getName()), *II);
break;
case Intrinsic::x86_sse_mul_ss:
case Intrinsic::x86_sse2_mul_sd:
TmpV = InsertNewInstBefore(BinaryOperator::CreateFMul(LHS, RHS,
II->getName()), *II);
break;
}
Instruction *New =
InsertElementInst::Create(
UndefValue::get(II->getType()), TmpV,
ConstantInt::get(Type::getInt32Ty(*Context), 0U, false), II->getName());
InsertNewInstBefore(New, *II);
return New;
}
}
// Output elements are undefined if both are undefined. Consider things
// like undef&0. The result is known zero, not undef.
UndefElts &= UndefElts2;
break;
}
break;
}
}
return MadeChange ? I : 0;
}
/// AssociativeOpt - Perform an optimization on an associative operator. This
/// function is designed to check a chain of associative operators for a
/// potential to apply a certain optimization. Since the optimization may be
/// applicable if the expression was reassociated, this checks the chain, then
/// reassociates the expression as necessary to expose the optimization
/// opportunity. This makes use of a special Functor, which must define
/// 'shouldApply' and 'apply' methods.
///
template<typename Functor>
static Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
unsigned Opcode = Root.getOpcode();
Value *LHS = Root.getOperand(0);
// Quick check, see if the immediate LHS matches...
if (F.shouldApply(LHS))
return F.apply(Root);
// Otherwise, if the LHS is not of the same opcode as the root, return.
Instruction *LHSI = dyn_cast<Instruction>(LHS);
while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
// Should we apply this transform to the RHS?
bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
// If not to the RHS, check to see if we should apply to the LHS...
if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
ShouldApply = true;
}
// If the functor wants to apply the optimization to the RHS of LHSI,
// reassociate the expression from ((? op A) op B) to (? op (A op B))
if (ShouldApply) {
// Now all of the instructions are in the current basic block, go ahead
// and perform the reassociation.
Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
// First move the selected RHS to the LHS of the root...
Root.setOperand(0, LHSI->getOperand(1));
// Make what used to be the LHS of the root be the user of the root...
Value *ExtraOperand = TmpLHSI->getOperand(1);
if (&Root == TmpLHSI) {
Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
return 0;
}
Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
BasicBlock::iterator ARI = &Root; ++ARI;
TmpLHSI->moveBefore(ARI); // Move TmpLHSI to after Root
ARI = Root;
// Now propagate the ExtraOperand down the chain of instructions until we
// get to LHSI.
while (TmpLHSI != LHSI) {
Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
// Move the instruction to immediately before the chain we are
// constructing to avoid breaking dominance properties.
NextLHSI->moveBefore(ARI);
ARI = NextLHSI;
Value *NextOp = NextLHSI->getOperand(1);
NextLHSI->setOperand(1, ExtraOperand);
TmpLHSI = NextLHSI;
ExtraOperand = NextOp;
}
// Now that the instructions are reassociated, have the functor perform
// the transformation...
return F.apply(Root);
}
LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
}
return 0;
}
namespace {
// AddRHS - Implements: X + X --> X << 1
struct AddRHS {
Value *RHS;
explicit AddRHS(Value *rhs) : RHS(rhs) {}
bool shouldApply(Value *LHS) const { return LHS == RHS; }
Instruction *apply(BinaryOperator &Add) const {
return BinaryOperator::CreateShl(Add.getOperand(0),
ConstantInt::get(Add.getType(), 1));
}
};
// AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
// iff C1&C2 == 0
struct AddMaskingAnd {
Constant *C2;
explicit AddMaskingAnd(Constant *c) : C2(c) {}
bool shouldApply(Value *LHS) const {
ConstantInt *C1;
return match(LHS, m_And(m_Value(), m_ConstantInt(C1))) &&
ConstantExpr::getAnd(C1, C2)->isNullValue();
}
Instruction *apply(BinaryOperator &Add) const {
return BinaryOperator::CreateOr(Add.getOperand(0), Add.getOperand(1));
}
};
}
static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
InstCombiner *IC) {
if (CastInst *CI = dyn_cast<CastInst>(&I))
return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType());
// Figure out if the constant is the left or the right argument.
bool ConstIsRHS = isa<Constant>(I.getOperand(1));
Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
if (Constant *SOC = dyn_cast<Constant>(SO)) {
if (ConstIsRHS)
return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
}
Value *Op0 = SO, *Op1 = ConstOperand;
if (!ConstIsRHS)
std::swap(Op0, Op1);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1,
SO->getName()+".op");
if (ICmpInst *CI = dyn_cast<ICmpInst>(&I))
return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
SO->getName()+".cmp");
if (FCmpInst *CI = dyn_cast<FCmpInst>(&I))
return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
SO->getName()+".cmp");
llvm_unreachable("Unknown binary instruction type!");
}
// FoldOpIntoSelect - Given an instruction with a select as one operand and a
// constant as the other operand, try to fold the binary operator into the
// select arguments. This also works for Cast instructions, which obviously do
// not have a second operand.
static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
InstCombiner *IC) {
// Don't modify shared select instructions
if (!SI->hasOneUse()) return 0;
Value *TV = SI->getOperand(1);
Value *FV = SI->getOperand(2);
if (isa<Constant>(TV) || isa<Constant>(FV)) {
// Bool selects with constant operands can be folded to logical ops.
if (SI->getType() == Type::getInt1Ty(*IC->getContext())) return 0;
Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, IC);
Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, IC);
return SelectInst::Create(SI->getCondition(), SelectTrueVal,
SelectFalseVal);
}
return 0;
}
/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
/// has a PHI node as operand #0, see if we can fold the instruction into the
/// PHI (which is only possible if all operands to the PHI are constants).
///
/// If AllowAggressive is true, FoldOpIntoPhi will allow certain transforms
/// that would normally be unprofitable because they strongly encourage jump
/// threading.
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
bool AllowAggressive) {
AllowAggressive = false;
PHINode *PN = cast<PHINode>(I.getOperand(0));
unsigned NumPHIValues = PN->getNumIncomingValues();
if (NumPHIValues == 0 ||
// We normally only transform phis with a single use, unless we're trying
// hard to make jump threading happen.
(!PN->hasOneUse() && !AllowAggressive))
return 0;
// Check to see if all of the operands of the PHI are simple constants
// (constantint/constantfp/undef). If there is one non-constant value,
// remember the BB it is in. If there is more than one or if *it* is a PHI,
// bail out. We don't do arbitrary constant expressions here because moving
// their computation can be expensive without a cost model.
BasicBlock *NonConstBB = 0;
for (unsigned i = 0; i != NumPHIValues; ++i)
if (!isa<Constant>(PN->getIncomingValue(i)) ||
isa<ConstantExpr>(PN->getIncomingValue(i))) {
if (NonConstBB) return 0; // More than one non-const value.
if (isa<PHINode>(PN->getIncomingValue(i))) return 0; // Itself a phi.
NonConstBB = PN->getIncomingBlock(i);
// If the incoming non-constant value is in I's block, we have an infinite
// loop.
if (NonConstBB == I.getParent())
return 0;
}
// If there is exactly one non-constant value, we can insert a copy of the
// operation in that block. However, if this is a critical edge, we would be
// inserting the computation one some other paths (e.g. inside a loop). Only
// do this if the pred block is unconditionally branching into the phi block.
if (NonConstBB != 0 && !AllowAggressive) {
BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
if (!BI || !BI->isUnconditional()) return 0;
}
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = PHINode::Create(I.getType(), "");
NewPN->reserveOperandSpace(PN->getNumOperands()/2);
InsertNewInstBefore(NewPN, *PN);
NewPN->takeName(PN);
// Next, add all of the operands to the PHI.
if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
// We only currently try to fold the condition of a select when it is a phi,
// not the true/false values.
Value *TrueV = SI->getTrueValue();
Value *FalseV = SI->getFalseValue();
BasicBlock *PhiTransBB = PN->getParent();
for (unsigned i = 0; i != NumPHIValues; ++i) {
BasicBlock *ThisBB = PN->getIncomingBlock(i);
Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB);
Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB);
Value *InV = 0;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
InV = SelectInst::Create(PN->getIncomingValue(i), TrueVInPred,
FalseVInPred,
"phitmp", NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, ThisBB);
}
} else if (I.getNumOperands() == 2) {
Constant *C = cast<Constant>(I.getOperand(1));
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV = 0;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
if (CmpInst *CI = dyn_cast<CmpInst>(&I))
InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C);
else
InV = ConstantExpr::get(I.getOpcode(), InC, C);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
InV = BinaryOperator::Create(BO->getOpcode(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else if (CmpInst *CI = dyn_cast<CmpInst>(&I))
InV = CmpInst::Create(CI->getOpcode(),
CI->getPredicate(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else
llvm_unreachable("Unknown binop!");
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
} else {
CastInst *CI = cast<CastInst>(&I);
const Type *RetTy = CI->getType();
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
InV = CastInst::Create(CI->getOpcode(), PN->getIncomingValue(i),
I.getType(), "phitmp",
NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
}
return ReplaceInstUsesWith(I, NewPN);
}
/// WillNotOverflowSignedAdd - Return true if we can prove that:
/// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS))
/// This basically requires proving that the add in the original type would not
/// overflow to change the sign bit or have a carry out.
bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) {
// There are different heuristics we can use for this. Here are some simple
// ones.
// Add has the property that adding any two 2's complement numbers can only
// have one carry bit which can change a sign. As such, if LHS and RHS each
// have at least two sign bits, we know that the addition of the two values will
// sign extend fine.
if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1)
return true;
// If one of the operands only has one non-zero bit, and if the other operand
// has a known-zero bit in a more significant place than it (not including the
// sign bit) the ripple may go up to and fill the zero, but won't change the
// sign. For example, (X & ~4) + 1.
// TODO: Implement.
return false;
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
// X + undef -> undef
if (isa<UndefValue>(RHS))
return ReplaceInstUsesWith(I, RHS);
// X + 0 --> X
if (RHSC->isNullValue())
return ReplaceInstUsesWith(I, LHS);
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
// X + (signbit) --> X ^ signbit
const APInt& Val = CI->getValue();
uint32_t BitWidth = Val.getBitWidth();
if (Val == APInt::getSignBit(BitWidth))
return BinaryOperator::CreateXor(LHS, RHS);
// See if SimplifyDemandedBits can simplify this. This handles stuff like
// (X & 254)+1 -> (X&254)|1
if (SimplifyDemandedInstructionBits(I))
return &I;
// zext(bool) + C -> bool ? C + 1 : C
if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
if (ZI->getSrcTy() == Type::getInt1Ty(*Context))
return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
}
if (isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
ConstantInt *XorRHS = 0;
Value *XorLHS = 0;
if (isa<ConstantInt>(RHSC) &&
match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
const APInt& RHSVal = cast<ConstantInt>(RHSC)->getValue();
uint32_t Size = TySizeBits / 2;
APInt C0080Val(APInt(TySizeBits, 1ULL).shl(Size - 1));
APInt CFF80Val(-C0080Val);
do {
if (TySizeBits > Size) {
// If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
// If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
if ((RHSVal == CFF80Val && XorRHS->getValue() == C0080Val) ||
(RHSVal == C0080Val && XorRHS->getValue() == CFF80Val)) {
// This is a sign extend if the top bits are known zero.
if (!MaskedValueIsZero(XorLHS,
APInt::getHighBitsSet(TySizeBits, TySizeBits - Size)))
Size = 0; // Not a sign ext, but can't be any others either.
break;
}
}
Size >>= 1;
C0080Val = APIntOps::lshr(C0080Val, Size);
CFF80Val = APIntOps::ashr(CFF80Val, Size);
} while (Size >= 1);
// FIXME: This shouldn't be necessary. When the backends can handle types
// with funny bit widths then this switch statement should be removed. It
// is just here to get the size of the "middle" type back up to something
// that the back ends can handle.
const Type *MiddleType = 0;
switch (Size) {
default: break;
case 32: MiddleType = Type::getInt32Ty(*Context); break;
case 16: MiddleType = Type::getInt16Ty(*Context); break;
case 8: MiddleType = Type::getInt8Ty(*Context); break;
}
if (MiddleType) {
Value *NewTrunc = Builder->CreateTrunc(XorLHS, MiddleType, "sext");
return new SExtInst(NewTrunc, I.getType(), I.getName());
}
}
}
if (I.getType() == Type::getInt1Ty(*Context))
return BinaryOperator::CreateXor(LHS, RHS);
// X + X --> X << 1
if (I.getType()->isInteger()) {
if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS)))
return Result;
if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
if (RHSI->getOpcode() == Instruction::Sub)
if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
return ReplaceInstUsesWith(I, RHSI->getOperand(0));
}
if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if (LHSI->getOpcode() == Instruction::Sub)
if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
return ReplaceInstUsesWith(I, LHSI->getOperand(0));
}
}
// -A + B --> B - A
// -A + -B --> -(A + B)
if (Value *LHSV = dyn_castNegVal(LHS)) {
if (LHS->getType()->isIntOrIntVector()) {
if (Value *RHSV = dyn_castNegVal(RHS)) {
Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
return BinaryOperator::CreateNeg(NewAdd);
}
}
return BinaryOperator::CreateSub(RHS, LHSV);
}
// A + -B --> A - B
if (!isa<Constant>(RHS))
if (Value *V = dyn_castNegVal(RHS))
return BinaryOperator::CreateSub(LHS, V);
ConstantInt *C2;
if (Value *X = dyn_castFoldableMul(LHS, C2)) {
if (X == RHS) // X*C + X --> X * (C+1)
return BinaryOperator::CreateMul(RHS, AddOne(C2));
// X*C1 + X*C2 --> X * (C1+C2)
ConstantInt *C1;
if (X == dyn_castFoldableMul(RHS, C1))
return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
}
// X + X*C --> X * (C+1)
if (dyn_castFoldableMul(RHS, C2) == LHS)
return BinaryOperator::CreateMul(LHS, AddOne(C2));
// X + ~X --> -1 since ~X = -X-1
if (dyn_castNotVal(LHS) == RHS ||
dyn_castNotVal(RHS) == LHS)
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
// (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2)))
return R;
// A+B --> A|B iff A and B have no bits set in common.
if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
APInt LHSKnownOne(IT->getBitWidth(), 0);
APInt LHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
if (LHSKnownZero != 0) {
APInt RHSKnownOne(IT->getBitWidth(), 0);
APInt RHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
// No bits in common -> bitwise or.
if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
return BinaryOperator::CreateOr(LHS, RHS);
}
}
// W*X + Y*Z --> W * (X+Z) iff W == Y
if (I.getType()->isIntOrIntVector()) {
Value *W, *X, *Y, *Z;
if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
if (W != Y) {
if (W == Z) {
std::swap(Y, Z);
} else if (Y == X) {
std::swap(W, X);
} else if (X == Z) {
std::swap(Y, Z);
std::swap(W, X);
}
}
if (W == Y) {
Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
return BinaryOperator::CreateMul(W, NewAdd);
}
}
}
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
Value *X = 0;
if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
return BinaryOperator::CreateSub(SubOne(CRHS), X);
// (X & FF00) + xx00 -> (X+xx00) & FF00
if (LHS->hasOneUse() &&
match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
if (Anded == CRHS) {
// See if all bits from the first bit set in the Add RHS up are included
// in the mask. First, get the rightmost bit.
const APInt& AddRHSV = CRHS->getValue();
// Form a mask of all bits from the lowest bit added through the top.
APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
// See if the and mask includes all of these bits.
APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
if (AddRHSHighBits == AddRHSHighBitsAnd) {
// Okay, the xform is safe. Insert the new add pronto.
Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
return BinaryOperator::CreateAnd(NewAdd, C2);
}
}
}
// Try to fold constant add into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
}
// add (select X 0 (sub n A)) A --> select X A n
{
SelectInst *SI = dyn_cast<SelectInst>(LHS);
Value *A = RHS;
if (!SI) {
SI = dyn_cast<SelectInst>(RHS);
A = LHS;
}
if (SI && SI->hasOneUse()) {
Value *TV = SI->getTrueValue();
Value *FV = SI->getFalseValue();
Value *N;
// Can we fold the add into the argument of the select?
// We check both true and false select arguments for a matching subtract.
if (match(FV, m_Zero()) &&
match(TV, m_Sub(m_Value(N), m_Specific(A))))
// Fold the add into the true select value.
return SelectInst::Create(SI->getCondition(), N, A);
if (match(TV, m_Zero()) &&
match(FV, m_Sub(m_Value(N), m_Specific(A))))
// Fold the add into the false select value.
return SelectInst::Create(SI->getCondition(), A, N);
}
}
// Check for (add (sext x), y), see if we can merge this into an
// integer add followed by a sext.
if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
// (add (sext x), cst) --> (sext (add x, cst'))
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
Constant *CI =
ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
if (LHSConv->hasOneUse() &&
ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
// Insert the new, smaller add.
Value *NewAdd = Builder->CreateAdd(LHSConv->getOperand(0),
CI, "addconv");
return new SExtInst(NewAdd, I.getType());
}
}
// (add (sext x), (sext y)) --> (sext (add int x, y))
if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
// Only do this if x/y have the same type, if at last one of them has a
// single use (so we don't increase the number of sexts), and if the
// integer add will not overflow.
if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
(LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
WillNotOverflowSignedAdd(LHSConv->getOperand(0),
RHSConv->getOperand(0))) {
// Insert the new integer add.
Value *NewAdd = Builder->CreateAdd(LHSConv->getOperand(0),
RHSConv->getOperand(0), "addconv");
return new SExtInst(NewAdd, I.getType());
}
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
// X + 0 --> X
if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
if (CFP->isExactlyValue(ConstantFP::getNegativeZero
(I.getType())->getValueAPF()))
return ReplaceInstUsesWith(I, LHS);
}
if (isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// -A + B --> B - A
// -A + -B --> -(A + B)
if (Value *LHSV = dyn_castFNegVal(LHS))
return BinaryOperator::CreateFSub(RHS, LHSV);
// A + -B --> A - B
if (!isa<Constant>(RHS))
if (Value *V = dyn_castFNegVal(RHS))
return BinaryOperator::CreateFSub(LHS, V);
// Check for X+0.0. Simplify it to X if we know X is not -0.0.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS))
return ReplaceInstUsesWith(I, LHS);
// Check for (add double (sitofp x), y), see if we can merge this into an
// integer add followed by a promotion.
if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
// (add double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
// ... if the constant fits in the integer value. This is useful for things
// like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
// requires a constant pool load, and generally allows the add to be better
// instcombined.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
Constant *CI =
ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
if (LHSConv->hasOneUse() &&
ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
// Insert the new integer add.
Value *NewAdd = Builder->CreateAdd(LHSConv->getOperand(0),
CI, "addconv");
return new SIToFPInst(NewAdd, I.getType());
}
}
// (add double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
// Only do this if x/y have the same type, if at last one of them has a
// single use (so we don't increase the number of int->fp conversions),
// and if the integer add will not overflow.
if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
(LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
WillNotOverflowSignedAdd(LHSConv->getOperand(0),
RHSConv->getOperand(0))) {
// Insert the new integer add.
Value *NewAdd = Builder->CreateAdd(LHSConv->getOperand(0),
RHSConv->getOperand(0), "addconv");
return new SIToFPInst(NewAdd, I.getType());
}
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Op0 == Op1) // sub X, X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// If this is a 'B = x-(-A)', change to B = x+A...
if (Value *V = dyn_castNegVal(Op1))
return BinaryOperator::CreateAdd(Op0, V);
if (isa<UndefValue>(Op0))
return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
// Replace (-1 - A) with (~A)...
if (C->isAllOnesValue())
return BinaryOperator::CreateNot(Op1);
// C - ~X == X + (1+C)
Value *X = 0;
if (match(Op1, m_Not(m_Value(X))))
return BinaryOperator::CreateAdd(X, AddOne(C));
// -(X >>u 31) -> (X >>s 31)
// -(X >>s 31) -> (X >>u 31)
if (C->isZero()) {
if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op1)) {
if (SI->getOpcode() == Instruction::LShr) {
if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
// Check to see if we are shifting out everything but the sign bit.
if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
SI->getType()->getPrimitiveSizeInBits()-1) {
// Ok, the transformation is safe. Insert AShr.
return BinaryOperator::Create(Instruction::AShr,
SI->getOperand(0), CU, SI->getName());
}
}
}
else if (SI->getOpcode() == Instruction::AShr) {
if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
// Check to see if we are shifting out everything but the sign bit.
if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
SI->getType()->getPrimitiveSizeInBits()-1) {
// Ok, the transformation is safe. Insert LShr.
return BinaryOperator::CreateLShr(
SI->getOperand(0), CU, SI->getName());
}
}
}
}
}
// Try to fold constant sub into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
// C - zext(bool) -> bool ? C - 1 : C
if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
if (ZI->getSrcTy() == Type::getInt1Ty(*Context))
return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
}
if (I.getType() == Type::getInt1Ty(*Context))
return BinaryOperator::CreateXor(Op0, Op1);
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
if (Op1I->getOpcode() == Instruction::Add) {
if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
return BinaryOperator::CreateNeg(Op1I->getOperand(1),
I.getName());
else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
return BinaryOperator::CreateNeg(Op1I->getOperand(0),
I.getName());
else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
// C1-(X+C2) --> (C1-C2)-X
return BinaryOperator::CreateSub(
ConstantExpr::getSub(CI1, CI2), Op1I->getOperand(0));
}
}
if (Op1I->hasOneUse()) {
// Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
// is not used by anyone else...
//
if (Op1I->getOpcode() == Instruction::Sub) {
// Swap the two operands of the subexpr...
Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
Op1I->setOperand(0, IIOp1);
Op1I->setOperand(1, IIOp0);
// Create the new top level add instruction...
return BinaryOperator::CreateAdd(Op0, Op1);
}
// Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
//
if (Op1I->getOpcode() == Instruction::And &&
(Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
Value *NewNot = Builder->CreateNot(OtherOp, "B.not");
return BinaryOperator::CreateAnd(Op0, NewNot);
}
// 0 - (X sdiv C) -> (X sdiv -C)
if (Op1I->getOpcode() == Instruction::SDiv)
if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
if (CSI->isZero())
if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
return BinaryOperator::CreateSDiv(Op1I->getOperand(0),
ConstantExpr::getNeg(DivRHS));
// X - X*C --> X * (1-C)
ConstantInt *C2 = 0;
if (dyn_castFoldableMul(Op1I, C2) == Op0) {
Constant *CP1 =
ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
C2);
return BinaryOperator::CreateMul(Op0, CP1);
}
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
if (Op0I->getOpcode() == Instruction::Add) {
if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(1));
else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(0));
} else if (Op0I->getOpcode() == Instruction::Sub) {
if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
return BinaryOperator::CreateNeg(Op0I->getOperand(1),
I.getName());
}
}
ConstantInt *C1;
if (Value *X = dyn_castFoldableMul(Op0, C1)) {
if (X == Op1) // X*C - X --> X * (C-1)
return BinaryOperator::CreateMul(Op1, SubOne(C1));
ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
if (X == dyn_castFoldableMul(Op1, C2))
return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
}
return 0;
}
Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// If this is a 'B = x-(-A)', change to B = x+A...
if (Value *V = dyn_castFNegVal(Op1))
return BinaryOperator::CreateFAdd(Op0, V);
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
if (Op1I->getOpcode() == Instruction::FAdd) {
if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
return BinaryOperator::CreateFNeg(Op1I->getOperand(1),
I.getName());
else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
return BinaryOperator::CreateFNeg(Op1I->getOperand(0),
I.getName());
}
}
return 0;
}
/// isSignBitCheck - Given an exploded icmp instruction, return true if the
/// comparison only checks the sign bit. If it only checks the sign bit, set
/// TrueIfSigned if the result of the comparison is true when the input value is
/// signed.
static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS,
bool &TrueIfSigned) {
switch (pred) {
case ICmpInst::ICMP_SLT: // True if LHS s< 0
TrueIfSigned = true;
return RHS->isZero();
case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
TrueIfSigned = true;
return RHS->isAllOnesValue();
case ICmpInst::ICMP_SGT: // True if LHS s> -1
TrueIfSigned = false;
return RHS->isAllOnesValue();
case ICmpInst::ICMP_UGT:
// True if LHS u> RHS and RHS == high-bit-mask - 1
TrueIfSigned = true;
return RHS->getValue() ==
APInt::getSignedMaxValue(RHS->getType()->getPrimitiveSizeInBits());
case ICmpInst::ICMP_UGE:
// True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
TrueIfSigned = true;
return RHS->getValue().isSignBit();
default:
return false;
}
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1)) // undef * X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// Simplify mul instructions with a constant RHS.
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1C)) {
// ((X << C1)*C2) == (X * (C2 << C1))
if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0))
if (SI->getOpcode() == Instruction::Shl)
if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
return BinaryOperator::CreateMul(SI->getOperand(0),
ConstantExpr::getShl(CI, ShOp));
if (CI->isZero())
return ReplaceInstUsesWith(I, Op1C); // X * 0 == 0
if (CI->equalsInt(1)) // X * 1 == X
return ReplaceInstUsesWith(I, Op0);
if (CI->isAllOnesValue()) // X * -1 == 0 - X
return BinaryOperator::CreateNeg(Op0, I.getName());
const APInt& Val = cast<ConstantInt>(CI)->getValue();
if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C
return BinaryOperator::CreateShl(Op0,
ConstantInt::get(Op0->getType(), Val.logBase2()));
}
} else if (isa<VectorType>(Op1C->getType())) {
if (Op1C->isNullValue())
return ReplaceInstUsesWith(I, Op1C);
if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1C)) {
if (Op1V->isAllOnesValue()) // X * -1 == 0 - X
return BinaryOperator::CreateNeg(Op0, I.getName());
// As above, vector X*splat(1.0) -> X in all defined cases.
if (Constant *Splat = Op1V->getSplatValue()) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Splat))
if (CI->equalsInt(1))
return ReplaceInstUsesWith(I, Op0);
}
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
if (Op0I->getOpcode() == Instruction::Add && Op0I->hasOneUse() &&
isa<ConstantInt>(Op0I->getOperand(1)) && isa<ConstantInt>(Op1C)) {
// Canonicalize (X+C1)*C2 -> X*C2+C1*C2.
Value *Add = Builder->CreateMul(Op0I->getOperand(0), Op1C, "tmp");
Value *C1C2 = Builder->CreateMul(Op1C, Op0I->getOperand(1));
return BinaryOperator::CreateAdd(Add, C1C2);
}
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(Op1))
return BinaryOperator::CreateMul(Op0v, Op1v);
// (X / Y) * Y = X - (X % Y)
// (X / Y) * -Y = (X % Y) - X
{
Value *Op1C = Op1;
BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
if (!BO ||
(BO->getOpcode() != Instruction::UDiv &&
BO->getOpcode() != Instruction::SDiv)) {
Op1C = Op0;
BO = dyn_cast<BinaryOperator>(Op1);
}
Value *Neg = dyn_castNegVal(Op1C);
if (BO && BO->hasOneUse() &&
(BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
(BO->getOpcode() == Instruction::UDiv ||
BO->getOpcode() == Instruction::SDiv)) {
Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
// If the division is exact, X % Y is zero.
if (SDivOperator *SDiv = dyn_cast<SDivOperator>(BO))
if (SDiv->isExact()) {
if (Op1BO == Op1C)
return ReplaceInstUsesWith(I, Op0BO);
return BinaryOperator::CreateNeg(Op0BO);
}
Value *Rem;
if (BO->getOpcode() == Instruction::UDiv)
Rem = Builder->CreateURem(Op0BO, Op1BO);
else
Rem = Builder->CreateSRem(Op0BO, Op1BO);
Rem->takeName(BO);
if (Op1BO == Op1C)
return BinaryOperator::CreateSub(Op0BO, Rem);
return BinaryOperator::CreateSub(Rem, Op0BO);
}
}
/// i1 mul -> i1 and.
if (I.getType() == Type::getInt1Ty(*Context))
return BinaryOperator::CreateAnd(Op0, Op1);
// X*(1 << Y) --> X << Y
// (1 << Y)*X --> X << Y
{
Value *Y;
if (match(Op0, m_Shl(m_One(), m_Value(Y))))
return BinaryOperator::CreateShl(Op1, Y);
if (match(Op1, m_Shl(m_One(), m_Value(Y))))
return BinaryOperator::CreateShl(Op0, Y);
}
// If one of the operands of the multiply is a cast from a boolean value, then
// we know the bool is either zero or one, so this is a 'masking' multiply.
// X * Y (where Y is 0 or 1) -> X & (0-Y)
if (!isa<VectorType>(I.getType())) {
// -2 is "-1 << 1" so it is all bits set except the low one.
APInt Negative2(I.getType()->getPrimitiveSizeInBits(), -2, true);
Value *BoolCast = 0, *OtherOp = 0;
if (MaskedValueIsZero(Op0, Negative2))
BoolCast = Op0, OtherOp = Op1;
else if (MaskedValueIsZero(Op1, Negative2))
BoolCast = Op1, OtherOp = Op0;
if (BoolCast) {
Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
BoolCast, "tmp");
return BinaryOperator::CreateAnd(V, OtherOp);
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Simplify mul instructions with a constant RHS...
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1C)) {
// "In IEEE floating point, x*1 is not equivalent to x for nans. However,
// ANSI says we can drop signals, so we can do this anyway." (from GCC)
if (Op1F->isExactlyValue(1.0))
return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
} else if (isa<VectorType>(Op1C->getType())) {
if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1C)) {
// As above, vector X*splat(1.0) -> X in all defined cases.
if (Constant *Splat = Op1V->getSplatValue()) {
if (ConstantFP *F = dyn_cast<ConstantFP>(Splat))
if (F->isExactlyValue(1.0))
return ReplaceInstUsesWith(I, Op0);
}
}
}
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *Op0v = dyn_castFNegVal(Op0)) // -X * -Y = X*Y
if (Value *Op1v = dyn_castFNegVal(Op1))
return BinaryOperator::CreateFMul(Op0v, Op1v);
return Changed ? &I : 0;
}
/// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
/// instruction.
bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
SelectInst *SI = cast<SelectInst>(I.getOperand(1));
// div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
int NonNullOperand = -1;
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
if (ST->isNullValue())
NonNullOperand = 2;
// div/rem X, (Cond ? Y : 0) -> div/rem X, Y
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
if (ST->isNullValue())
NonNullOperand = 1;
if (NonNullOperand == -1)
return false;
Value *SelectCond = SI->getOperand(0);
// Change the div/rem to use 'Y' instead of the select.
I.setOperand(1, SI->getOperand(NonNullOperand));
// Okay, we know we replace the operand of the div/rem with 'Y' with no
// problem. However, the select, or the condition of the select may have
// multiple uses. Based on our knowledge that the operand must be non-zero,
// propagate the known value for the select into other uses of it, and
// propagate a known value of the condition into its other users.
// If the select and condition only have a single use, don't bother with this,
// early exit.
if (SI->use_empty() && SelectCond->hasOneUse())
return true;
// Scan the current block backward, looking for other uses of SI.
BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
while (BBI != BBFront) {
--BBI;
// If we found a call to a function, we can't assume it will return, so
// information from below it cannot be propagated above it.
if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
break;
// Replace uses of the select or its condition with the known values.
for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
I != E; ++I) {
if (*I == SI) {
*I = SI->getOperand(NonNullOperand);
Worklist.Add(BBI);
} else if (*I == SelectCond) {
*I = NonNullOperand == 1 ? ConstantInt::getTrue(*Context) :
ConstantInt::getFalse(*Context);
Worklist.Add(BBI);
}
}
// If we past the instruction, quit looking for it.
if (&*BBI == SI)
SI = 0;
if (&*BBI == SelectCond)
SelectCond = 0;
// If we ran out of things to eliminate, break out of the loop.
if (SelectCond == 0 && SI == 0)
break;
}
return true;
}
/// This function implements the transforms on div instructions that work
/// regardless of the kind of div instruction it is (udiv, sdiv, or fdiv). It is
/// used by the visitors to those instructions.
/// @brief Transforms common to all three div instructions
Instruction *InstCombiner::commonDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// undef / X -> 0 for integer.
// undef / X -> undef for FP (the undef could be a snan).
if (isa<UndefValue>(Op0)) {
if (Op0->getType()->isFPOrFPVector())
return ReplaceInstUsesWith(I, Op0);
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
// X / undef -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1);
return 0;
}
/// This function implements the transforms common to both integer division
/// instructions (udiv and sdiv). It is called by the visitors to those integer
/// division instructions.
/// @brief Common integer divide transforms
Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// (sdiv X, X) --> 1 (udiv X, X) --> 1
if (Op0 == Op1) {
if (const VectorType *Ty = dyn_cast<VectorType>(I.getType())) {
Constant *CI = ConstantInt::get(Ty->getElementType(), 1);
std::vector<Constant*> Elts(Ty->getNumElements(), CI);
return ReplaceInstUsesWith(I, ConstantVector::get(Elts));
}
Constant *CI = ConstantInt::get(I.getType(), 1);
return ReplaceInstUsesWith(I, CI);
}
if (Instruction *Common = commonDivTransforms(I))
return Common;
// Handle cases involving: [su]div X, (select Cond, Y, Z)
// This does not apply for fdiv.
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
return &I;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// div X, 1 == X
if (RHS->equalsInt(1))
return ReplaceInstUsesWith(I, Op0);
// (X / C1) / C2 -> X / (C1*C2)
if (Instruction *LHS = dyn_cast<Instruction>(Op0))
if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
if (MultiplyOverflows(RHS, LHSRHS,
I.getOpcode()==Instruction::SDiv))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
else
return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
ConstantExpr::getMul(RHS, LHSRHS));
}
if (!RHS->isZero()) { // avoid X udiv 0
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
}
// 0 / X == 0, we don't need to preserve faults!
if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// It can't be division by zero, hence it must be division by one.
if (I.getType() == Type::getInt1Ty(*Context))
return ReplaceInstUsesWith(I, Op0);
if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1)) {
if (ConstantInt *X = cast_or_null<ConstantInt>(Op1V->getSplatValue()))
// div X, 1 == X
if (X->isOne())
return ReplaceInstUsesWith(I, Op0);
}
return 0;
}
Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
// X udiv C^2 -> X >> C
// Check to see if this is an unsigned division with an exact power of 2,
// if so, convert to a right shift.
if (C->getValue().isPowerOf2()) // 0 not included in isPowerOf2
return BinaryOperator::CreateLShr(Op0,
ConstantInt::get(Op0->getType(), C->getValue().logBase2()));
// X udiv C, where C >= signbit
if (C->getValue().isNegative()) {
Value *IC = Builder->CreateICmpULT( Op0, C);
return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
ConstantInt::get(I.getType(), 1));
}
}
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
if (BinaryOperator *RHSI = dyn_cast<BinaryOperator>(I.getOperand(1))) {
if (RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(RHSI->getOperand(0))) {
const APInt& C1 = cast<ConstantInt>(RHSI->getOperand(0))->getValue();
if (C1.isPowerOf2()) {
Value *N = RHSI->getOperand(1);
const Type *NTy = N->getType();
if (uint32_t C2 = C1.logBase2())
N = Builder->CreateAdd(N, ConstantInt::get(NTy, C2), "tmp");
return BinaryOperator::CreateLShr(Op0, N);
}
}
}
// udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
// where C1&C2 are powers of two.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
const APInt &TVA = STO->getValue(), &FVA = SFO->getValue();
if (TVA.isPowerOf2() && FVA.isPowerOf2()) {
// Compute the shift amounts
uint32_t TSA = TVA.logBase2(), FSA = FVA.logBase2();
// Construct the "on true" case of the select
Constant *TC = ConstantInt::get(Op0->getType(), TSA);
Value *TSI = Builder->CreateLShr(Op0, TC, SI->getName()+".t");
// Construct the "on false" case of the select
Constant *FC = ConstantInt::get(Op0->getType(), FSA);
Value *FSI = Builder->CreateLShr(Op0, FC, SI->getName()+".f");
// construct the select instruction and return it.
return SelectInst::Create(SI->getOperand(0), TSI, FSI, SI->getName());
}
}
return 0;
}
Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// sdiv X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::CreateNeg(Op0);
// sdiv X, C --> ashr X, log2(C)
if (cast<SDivOperator>(&I)->isExact() &&
RHS->getValue().isNonNegative() &&
RHS->getValue().isPowerOf2()) {
Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
RHS->getValue().exactLogBase2());
return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName());
}
// -X/C --> X/-C provided the negation doesn't overflow.
if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
if (isa<Constant>(Sub->getOperand(0)) &&
cast<Constant>(Sub->getOperand(0))->isNullValue() &&
Sub->hasNoSignedWrap())
return BinaryOperator::CreateSDiv(Sub->getOperand(1),
ConstantExpr::getNeg(RHS));
}
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a udiv.
if (I.getType()->isInteger()) {
APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
if (MaskedValueIsZero(Op0, Mask)) {
if (MaskedValueIsZero(Op1, Mask)) {
// X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
}
ConstantInt *ShiftedInt;
if (match(Op1, m_Shl(m_ConstantInt(ShiftedInt), m_Value())) &&
ShiftedInt->getValue().isPowerOf2()) {
// X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
// Safe because the only negative value (1 << Y) can take on is
// INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
// the sign bit set.
return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
}
}
}
return 0;
}
Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
return commonDivTransforms(I);
}
/// This function implements the transforms on rem instructions that work
/// regardless of the kind of rem instruction it is (urem, srem, or frem). It
/// is used by the visitors to those instructions.
/// @brief Transforms common to all three rem instructions
Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op0)) { // undef % X -> 0
if (I.getType()->isFPOrFPVector())
return ReplaceInstUsesWith(I, Op0); // X % undef -> undef (could be SNaN)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
// Handle cases involving: rem X, (select Cond, Y, Z)
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
return &I;
return 0;
}
/// This function implements the transforms common to both integer remainder
/// instructions (urem and srem). It is called by the visitors to those integer
/// remainder instructions.
/// @brief Common integer remainder transforms
Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *common = commonRemTransforms(I))
return common;
// 0 % X == 0 for integer, we don't need to preserve faults!
if (Constant *LHS = dyn_cast<Constant>(Op0))
if (LHS->isNullValue())
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// X % 0 == undef, we don't need to preserve faults!
if (RHS->equalsInt(0))
return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
if (RHS->equalsInt(1)) // X % 1 == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
} else if (isa<PHINode>(Op0I)) {
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// See if we can fold away this rem instruction.
if (SimplifyDemandedInstructionBits(I))
return &I;
}
}
return 0;
}
Instruction *InstCombiner::visitURem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Instruction *common = commonIRemTransforms(I))
return common;
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// X urem C^2 -> X and C
// Check to see if this is an unsigned remainder with an exact power of 2,
// if so, convert to a bitwise and.
if (ConstantInt *C = dyn_cast<ConstantInt>(RHS))
if (C->getValue().isPowerOf2())
return BinaryOperator::CreateAnd(Op0, SubOne(C));
}
if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
// Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
if (RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(RHSI->getOperand(0))) {
if (cast<ConstantInt>(RHSI->getOperand(0))->getValue().isPowerOf2()) {
Constant *N1 = Constant::getAllOnesValue(I.getType());
Value *Add = Builder->CreateAdd(RHSI, N1, "tmp");
return BinaryOperator::CreateAnd(Op0, Add);
}
}
}
// urem X, (select Cond, 2^C1, 2^C2) --> select Cond, (and X, C1), (and X, C2)
// where C1&C2 are powers of two.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
// STO == 0 and SFO == 0 handled above.
if ((STO->getValue().isPowerOf2()) &&
(SFO->getValue().isPowerOf2())) {
Value *TrueAnd = Builder->CreateAnd(Op0, SubOne(STO),
SI->getName()+".t");
Value *FalseAnd = Builder->CreateAnd(Op0, SubOne(SFO),
SI->getName()+".f");
return SelectInst::Create(SI->getOperand(0), TrueAnd, FalseAnd);
}
}
}
return 0;
}
Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Handle the integer rem common cases
if (Instruction *Common = commonIRemTransforms(I))
return Common;
if (Value *RHSNeg = dyn_castNegVal(Op1))
if (!isa<Constant>(RHSNeg) ||
(isa<ConstantInt>(RHSNeg) &&
cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
// X % -Y -> X % Y
Worklist.AddValue(I.getOperand(1));
I.setOperand(1, RHSNeg);
return &I;
}
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a urem.
if (I.getType()->isInteger()) {
APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
// X srem Y -> X urem Y, iff X and Y don't have sign bit set
return BinaryOperator::CreateURem(Op0, Op1, I.getName());
}
}
// If it's a constant vector, flip any negative values positive.
if (ConstantVector *RHSV = dyn_cast<ConstantVector>(Op1)) {
unsigned VWidth = RHSV->getNumOperands();
bool hasNegative = false;
for (unsigned i = 0; !hasNegative && i != VWidth; ++i)
if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i)))
if (RHS->getValue().isNegative())
hasNegative = true;
if (hasNegative) {
std::vector<Constant *> Elts(VWidth);
for (unsigned i = 0; i != VWidth; ++i) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i))) {
if (RHS->getValue().isNegative())
Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
else
Elts[i] = RHS;
}
}
Constant *NewRHSV = ConstantVector::get(Elts);
if (NewRHSV != RHSV) {
Worklist.AddValue(I.getOperand(1));
I.setOperand(1, NewRHSV);
return &I;
}
}
}
return 0;
}
Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
return commonRemTransforms(I);
}
// isOneBitSet - Return true if there is exactly one bit set in the specified
// constant.
static bool isOneBitSet(const ConstantInt *CI) {
return CI->getValue().isPowerOf2();
}
// isHighOnes - Return true if the constant is of the form 1+0+.
// This is the same as lowones(~X).
static bool isHighOnes(const ConstantInt *CI) {
return (~CI->getValue() + 1).isPowerOf2();
}
/// getICmpCode - Encode a icmp predicate into a three bit mask. These bits
/// are carefully arranged to allow folding of expressions such as:
///
/// (A < B) | (A > B) --> (A != B)
///
/// Note that this is only valid if the first and second predicates have the
/// same sign. Is illegal to do: (A u< B) | (A s> B)
///
/// Three bits are used to represent the condition, as follows:
/// 0 A > B
/// 1 A == B
/// 2 A < B
///
/// <=> Value Definition
/// 000 0 Always false
/// 001 1 A > B
/// 010 2 A == B
/// 011 3 A >= B
/// 100 4 A < B
/// 101 5 A != B
/// 110 6 A <= B
/// 111 7 Always true
///
static unsigned getICmpCode(const ICmpInst *ICI) {
switch (ICI->getPredicate()) {
// False -> 0
case ICmpInst::ICMP_UGT: return 1; // 001
case ICmpInst::ICMP_SGT: return 1; // 001
case ICmpInst::ICMP_EQ: return 2; // 010
case ICmpInst::ICMP_UGE: return 3; // 011
case ICmpInst::ICMP_SGE: return 3; // 011
case ICmpInst::ICMP_ULT: return 4; // 100
case ICmpInst::ICMP_SLT: return 4; // 100
case ICmpInst::ICMP_NE: return 5; // 101
case ICmpInst::ICMP_ULE: return 6; // 110
case ICmpInst::ICMP_SLE: return 6; // 110
// True -> 7
default:
llvm_unreachable("Invalid ICmp predicate!");
return 0;
}
}
/// getFCmpCode - Similar to getICmpCode but for FCmpInst. This encodes a fcmp
/// predicate into a three bit mask. It also returns whether it is an ordered
/// predicate by reference.
static unsigned getFCmpCode(FCmpInst::Predicate CC, bool &isOrdered) {
isOrdered = false;
switch (CC) {
case FCmpInst::FCMP_ORD: isOrdered = true; return 0; // 000
case FCmpInst::FCMP_UNO: return 0; // 000
case FCmpInst::FCMP_OGT: isOrdered = true; return 1; // 001
case FCmpInst::FCMP_UGT: return 1; // 001
case FCmpInst::FCMP_OEQ: isOrdered = true; return 2; // 010
case FCmpInst::FCMP_UEQ: return 2; // 010
case FCmpInst::FCMP_OGE: isOrdered = true; return 3; // 011
case FCmpInst::FCMP_UGE: return 3; // 011
case FCmpInst::FCMP_OLT: isOrdered = true; return 4; // 100
case FCmpInst::FCMP_ULT: return 4; // 100
case FCmpInst::FCMP_ONE: isOrdered = true; return 5; // 101
case FCmpInst::FCMP_UNE: return 5; // 101
case FCmpInst::FCMP_OLE: isOrdered = true; return 6; // 110
case FCmpInst::FCMP_ULE: return 6; // 110
// True -> 7
default:
// Not expecting FCMP_FALSE and FCMP_TRUE;
llvm_unreachable("Unexpected FCmp predicate!");
return 0;
}
}
/// getICmpValue - This is the complement of getICmpCode, which turns an
/// opcode and two operands into either a constant true or false, or a brand
/// new ICmp instruction. The sign is passed in to determine which kind
/// of predicate to use in the new icmp instruction.
static Value *getICmpValue(bool sign, unsigned code, Value *LHS, Value *RHS,
LLVMContext *Context) {
switch (code) {
default: llvm_unreachable("Illegal ICmp code!");
case 0: return ConstantInt::getFalse(*Context);
case 1:
if (sign)
return new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS);
else
return new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS);
case 2: return new ICmpInst(ICmpInst::ICMP_EQ, LHS, RHS);
case 3:
if (sign)
return new ICmpInst(ICmpInst::ICMP_SGE, LHS, RHS);
else
return new ICmpInst(ICmpInst::ICMP_UGE, LHS, RHS);
case 4:
if (sign)
return new ICmpInst(ICmpInst::ICMP_SLT, LHS, RHS);
else
return new ICmpInst(ICmpInst::ICMP_ULT, LHS, RHS);
case 5: return new ICmpInst(ICmpInst::ICMP_NE, LHS, RHS);
case 6:
if (sign)
return new ICmpInst(ICmpInst::ICMP_SLE, LHS, RHS);
else
return new ICmpInst(ICmpInst::ICMP_ULE, LHS, RHS);
case 7: return ConstantInt::getTrue(*Context);
}
}
/// getFCmpValue - This is the complement of getFCmpCode, which turns an
/// opcode and two operands into either a FCmp instruction. isordered is passed
/// in to determine which kind of predicate to use in the new fcmp instruction.
static Value *getFCmpValue(bool isordered, unsigned code,
Value *LHS, Value *RHS, LLVMContext *Context) {
switch (code) {
default: llvm_unreachable("Illegal FCmp code!");
case 0:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_ORD, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_UNO, LHS, RHS);
case 1:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_OGT, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_UGT, LHS, RHS);
case 2:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_OEQ, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_UEQ, LHS, RHS);
case 3:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_OGE, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_UGE, LHS, RHS);
case 4:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_OLT, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_ULT, LHS, RHS);
case 5:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_ONE, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_UNE, LHS, RHS);
case 6:
if (isordered)
return new FCmpInst(FCmpInst::FCMP_OLE, LHS, RHS);
else
return new FCmpInst(FCmpInst::FCMP_ULE, LHS, RHS);
case 7: return ConstantInt::getTrue(*Context);
}
}
/// PredicatesFoldable - Return true if both predicates match sign or if at
/// least one of them is an equality comparison (which is signless).
static bool PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
return (ICmpInst::isSignedPredicate(p1) == ICmpInst::isSignedPredicate(p2)) ||
(ICmpInst::isSignedPredicate(p1) && ICmpInst::isEquality(p2)) ||
(ICmpInst::isSignedPredicate(p2) && ICmpInst::isEquality(p1));
}
namespace {
// FoldICmpLogical - Implements (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
struct FoldICmpLogical {
InstCombiner &IC;
Value *LHS, *RHS;
ICmpInst::Predicate pred;
FoldICmpLogical(InstCombiner &ic, ICmpInst *ICI)
: IC(ic), LHS(ICI->getOperand(0)), RHS(ICI->getOperand(1)),
pred(ICI->getPredicate()) {}
bool shouldApply(Value *V) const {
if (ICmpInst *ICI = dyn_cast<ICmpInst>(V))
if (PredicatesFoldable(pred, ICI->getPredicate()))
return ((ICI->getOperand(0) == LHS && ICI->getOperand(1) == RHS) ||
(ICI->getOperand(0) == RHS && ICI->getOperand(1) == LHS));
return false;
}
Instruction *apply(Instruction &Log) const {
ICmpInst *ICI = cast<ICmpInst>(Log.getOperand(0));
if (ICI->getOperand(0) != LHS) {
assert(ICI->getOperand(1) == LHS);
ICI->swapOperands(); // Swap the LHS and RHS of the ICmp
}
ICmpInst *RHSICI = cast<ICmpInst>(Log.getOperand(1));
unsigned LHSCode = getICmpCode(ICI);
unsigned RHSCode = getICmpCode(RHSICI);
unsigned Code;
switch (Log.getOpcode()) {
case Instruction::And: Code = LHSCode & RHSCode; break;
case Instruction::Or: Code = LHSCode | RHSCode; break;
case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
default: llvm_unreachable("Illegal logical opcode!"); return 0;
}
bool isSigned = ICmpInst::isSignedPredicate(RHSICI->getPredicate()) ||
ICmpInst::isSignedPredicate(ICI->getPredicate());
Value *RV = getICmpValue(isSigned, Code, LHS, RHS, IC.getContext());
if (Instruction *I = dyn_cast<Instruction>(RV))
return I;
// Otherwise, it's a constant boolean value...
return IC.ReplaceInstUsesWith(Log, RV);
}
};
} // end anonymous namespace
// OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
// the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
// guaranteed to be a binary operator.
Instruction *InstCombiner::OptAndOp(Instruction *Op,
ConstantInt *OpRHS,
ConstantInt *AndRHS,
BinaryOperator &TheAnd) {
Value *X = Op->getOperand(0);
Constant *Together = 0;
if (!Op->isShift())
Together = ConstantExpr::getAnd(AndRHS, OpRHS);
switch (Op->getOpcode()) {
case Instruction::Xor:
if (Op->hasOneUse()) {
// (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
Value *And = Builder->CreateAnd(X, AndRHS);
And->takeName(Op);
return BinaryOperator::CreateXor(And, Together);
}
break;
case Instruction::Or:
if (Together == AndRHS) // (X | C) & C --> C
return ReplaceInstUsesWith(TheAnd, AndRHS);
if (Op->hasOneUse() && Together != OpRHS) {
// (X | C1) & C2 --> (X | (C1&C2)) & C2
Value *Or = Builder->CreateOr(X, Together);
Or->takeName(Op);
return BinaryOperator::CreateAnd(Or, AndRHS);
}
break;
case Instruction::Add:
if (Op->hasOneUse()) {
// Adding a one to a single bit bit-field should be turned into an XOR
// of the bit. First thing to check is to see if this AND is with a
// single bit constant.
const APInt& AndRHSV = cast<ConstantInt>(AndRHS)->getValue();
// If there is only one bit set...
if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
// Ok, at this point, we know that we are masking the result of the
// ADD down to exactly one bit. If the constant we are adding has
// no bits set below this bit, then we can eliminate the ADD.
const APInt& AddRHS = cast<ConstantInt>(OpRHS)->getValue();
// Check to see if any bits below the one bit set in AndRHSV are set.
if ((AddRHS & (AndRHSV-1)) == 0) {
// If not, the only thing that can effect the output of the AND is
// the bit specified by AndRHSV. If that bit is set, the effect of
// the XOR is to toggle the bit. If it is clear, then the ADD has
// no effect.
if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
TheAnd.setOperand(0, X);
return &TheAnd;
} else {
// Pull the XOR out of the AND.
Value *NewAnd = Builder->CreateAnd(X, AndRHS);
NewAnd->takeName(Op);
return BinaryOperator::CreateXor(NewAnd, AndRHS);
}
}
}
}
break;
case Instruction::Shl: {
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now!
//
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShlMask(APInt::getHighBitsSet(BitWidth, BitWidth-OpRHSVal));
ConstantInt *CI = ConstantInt::get(*Context, AndRHS->getValue() & ShlMask);
if (CI->getValue() == ShlMask) {
// Masking out bits that the shift already masks
return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
} else if (CI != AndRHS) { // Reducing bits set in and.
TheAnd.setOperand(1, CI);
return &TheAnd;
}
break;
}
case Instruction::LShr:
{
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now! This only applies to
// unsigned shifts, because a signed shr may bring in set bits!
//
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
ConstantInt *CI = ConstantInt::get(*Context, AndRHS->getValue() & ShrMask);
if (CI->getValue() == ShrMask) {
// Masking out bits that the shift already masks.
return ReplaceInstUsesWith(TheAnd, Op);
} else if (CI != AndRHS) {
TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
return &TheAnd;
}
break;
}
case Instruction::AShr:
// Signed shr.
// See if this is shifting in some sign extension, then masking it out
// with an and.
if (Op->hasOneUse()) {
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
Constant *C = ConstantInt::get(*Context, AndRHS->getValue() & ShrMask);
if (C == AndRHS) { // Masking out bits shifted in.
// (Val ashr C1) & C2 -> (Val lshr C1) & C2
// Make the argument unsigned.
Value *ShVal = Op->getOperand(0);
ShVal = Builder->CreateLShr(ShVal, OpRHS, Op->getName());
return BinaryOperator::CreateAnd(ShVal, AndRHS, TheAnd.getName());
}
}
break;
}
return 0;
}
/// InsertRangeTest - Emit a computation of: (V >= Lo && V < Hi) if Inside is
/// true, otherwise (V < Lo || V >= Hi). In pratice, we emit the more efficient
/// (V-Lo) <u Hi-Lo. This method expects that Lo <= Hi. isSigned indicates
/// whether to treat the V, Lo and HI as signed or not. IB is the location to
/// insert new instructions.
Instruction *InstCombiner::InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
bool isSigned, bool Inside,
Instruction &IB) {
assert(cast<ConstantInt>(ConstantExpr::getICmp((isSigned ?
ICmpInst::ICMP_SLE:ICmpInst::ICMP_ULE), Lo, Hi))->getZExtValue() &&
"Lo is not <= Hi in range emission code!");
if (Inside) {
if (Lo == Hi) // Trivially false.
return new ICmpInst(ICmpInst::ICMP_NE, V, V);
// V >= Min && V < Hi --> V < Hi
if (cast<ConstantInt>(Lo)->isMinValue(isSigned)) {
ICmpInst::Predicate pred = (isSigned ?
ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT);
return new ICmpInst(pred, V, Hi);
}
// Emit V-Lo <u Hi-Lo
Constant *NegLo = ConstantExpr::getNeg(Lo);
Value *Add = Builder->CreateAdd(V, NegLo, V->getName()+".off");
Constant *UpperBound = ConstantExpr::getAdd(NegLo, Hi);
return new ICmpInst(ICmpInst::ICMP_ULT, Add, UpperBound);
}
if (Lo == Hi) // Trivially true.
return new ICmpInst(ICmpInst::ICMP_EQ, V, V);
// V < Min || V >= Hi -> V > Hi-1
Hi = SubOne(cast<ConstantInt>(Hi));
if (cast<ConstantInt>(Lo)->isMinValue(isSigned)) {
ICmpInst::Predicate pred = (isSigned ?
ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT);
return new ICmpInst(pred, V, Hi);
}
// Emit V-Lo >u Hi-1-Lo
// Note that Hi has already had one subtracted from it, above.
ConstantInt *NegLo = cast<ConstantInt>(ConstantExpr::getNeg(Lo));
Value *Add = Builder->CreateAdd(V, NegLo, V->getName()+".off");
Constant *LowerBound = ConstantExpr::getAdd(NegLo, Hi);
return new ICmpInst(ICmpInst::ICMP_UGT, Add, LowerBound);
}
// isRunOfOnes - Returns true iff Val consists of one contiguous run of 1s with
// any number of 0s on either side. The 1s are allowed to wrap from LSB to
// MSB, so 0x000FFF0, 0x0000FFFF, and 0xFF0000FF are all runs. 0x0F0F0000 is
// not, since all 1s are not contiguous.
static bool isRunOfOnes(ConstantInt *Val, uint32_t &MB, uint32_t &ME) {
const APInt& V = Val->getValue();
uint32_t BitWidth = Val->getType()->getBitWidth();
if (!APIntOps::isShiftedMask(BitWidth, V)) return false;
// look for the first zero bit after the run of ones
MB = BitWidth - ((V - 1) ^ V).countLeadingZeros();
// look for the first non-zero bit
ME = V.getActiveBits();
return true;
}
/// FoldLogicalPlusAnd - This is part of an expression (LHS +/- RHS) & Mask,
/// where isSub determines whether the operator is a sub. If we can fold one of
/// the following xforms:
///
/// ((A & N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == Mask
/// ((A | N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
/// ((A ^ N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
///
/// return (A +/- B).
///
Value *InstCombiner::FoldLogicalPlusAnd(Value *LHS, Value *RHS,
ConstantInt *Mask, bool isSub,
Instruction &I) {
Instruction *LHSI = dyn_cast<Instruction>(LHS);
if (!LHSI || LHSI->getNumOperands() != 2 ||
!isa<ConstantInt>(LHSI->getOperand(1))) return 0;
ConstantInt *N = cast<ConstantInt>(LHSI->getOperand(1));
switch (LHSI->getOpcode()) {
default: return 0;
case Instruction::And:
if (ConstantExpr::getAnd(N, Mask) == Mask) {
// If the AndRHS is a power of two minus one (0+1+), this is simple.
if ((Mask->getValue().countLeadingZeros() +
Mask->getValue().countPopulation()) ==
Mask->getValue().getBitWidth())
break;
// Otherwise, if Mask is 0+1+0+, and if B is known to have the low 0+
// part, we don't need any explicit masks to take them out of A. If that
// is all N is, ignore it.
uint32_t MB = 0, ME = 0;
if (isRunOfOnes(Mask, MB, ME)) { // begin/end bit of run, inclusive
uint32_t BitWidth = cast<IntegerType>(RHS->getType())->getBitWidth();
APInt Mask(APInt::getLowBitsSet(BitWidth, MB-1));
if (MaskedValueIsZero(RHS, Mask))
break;
}
}
return 0;
case Instruction::Or:
case Instruction::Xor:
// If the AndRHS is a power of two minus one (0+1+), and N&Mask == 0
if ((Mask->getValue().countLeadingZeros() +
Mask->getValue().countPopulation()) == Mask->getValue().getBitWidth()
&& ConstantExpr::getAnd(N, Mask)->isNullValue())
break;
return 0;
}
if (isSub)
return Builder->CreateSub(LHSI->getOperand(0), RHS, "fold");
return Builder->CreateAdd(LHSI->getOperand(0), RHS, "fold");
}
/// FoldAndOfICmps - Fold (icmp)&(icmp) if possible.
Instruction *InstCombiner::FoldAndOfICmps(Instruction &I,
ICmpInst *LHS, ICmpInst *RHS) {
Value *Val, *Val2;
ConstantInt *LHSCst, *RHSCst;
ICmpInst::Predicate LHSCC, RHSCC;
// This only handles icmp of constants: (icmp1 A, C1) & (icmp2 B, C2).
if (!match(LHS, m_ICmp(LHSCC, m_Value(Val),
m_ConstantInt(LHSCst))) ||
!match(RHS, m_ICmp(RHSCC, m_Value(Val2),
m_ConstantInt(RHSCst))))
return 0;
// (icmp ult A, C) & (icmp ult B, C) --> (icmp ult (A|B), C)
// where C is a power of 2
if (LHSCst == RHSCst && LHSCC == RHSCC && LHSCC == ICmpInst::ICMP_ULT &&
LHSCst->getValue().isPowerOf2()) {
Value *NewOr = Builder->CreateOr(Val, Val2);
return new ICmpInst(LHSCC, NewOr, LHSCst);
}
// From here on, we only handle:
// (icmp1 A, C1) & (icmp2 A, C2) --> something simpler.
if (Val != Val2) return 0;
// ICMP_[US][GL]E X, CST is folded to ICMP_[US][GL]T elsewhere.
if (LHSCC == ICmpInst::ICMP_UGE || LHSCC == ICmpInst::ICMP_ULE ||
RHSCC == ICmpInst::ICMP_UGE || RHSCC == ICmpInst::ICMP_ULE ||
LHSCC == ICmpInst::ICMP_SGE || LHSCC == ICmpInst::ICMP_SLE ||
RHSCC == ICmpInst::ICMP_SGE || RHSCC == ICmpInst::ICMP_SLE)
return 0;
// We can't fold (ugt x, C) & (sgt x, C2).
if (!PredicatesFoldable(LHSCC, RHSCC))
return 0;
// Ensure that the larger constant is on the RHS.
bool ShouldSwap;
if (ICmpInst::isSignedPredicate(LHSCC) ||
(ICmpInst::isEquality(LHSCC) &&
ICmpInst::isSignedPredicate(RHSCC)))
ShouldSwap = LHSCst->getValue().sgt(RHSCst->getValue());
else
ShouldSwap = LHSCst->getValue().ugt(RHSCst->getValue());
if (ShouldSwap) {
std::swap(LHS, RHS);
std::swap(LHSCst, RHSCst);
std::swap(LHSCC, RHSCC);
}
// At this point, we know we have have two icmp instructions
// comparing a value against two constants and and'ing the result
// together. Because of the above check, we know that we only have
// icmp eq, icmp ne, icmp [su]lt, and icmp [SU]gt here. We also know
// (from the FoldICmpLogical check above), that the two constants
// are not equal and that the larger constant is on the RHS
assert(LHSCst != RHSCst && "Compares not folded above?");
switch (LHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X == 13 & X == 15) -> false
case ICmpInst::ICMP_UGT: // (X == 13 & X > 15) -> false
case ICmpInst::ICMP_SGT: // (X == 13 & X > 15) -> false
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
case ICmpInst::ICMP_NE: // (X == 13 & X != 15) -> X == 13
case ICmpInst::ICMP_ULT: // (X == 13 & X < 15) -> X == 13
case ICmpInst::ICMP_SLT: // (X == 13 & X < 15) -> X == 13
return ReplaceInstUsesWith(I, LHS);
}
case ICmpInst::ICMP_NE:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_ULT:
if (LHSCst == SubOne(RHSCst)) // (X != 13 & X u< 14) -> X < 13
return new ICmpInst(ICmpInst::ICMP_ULT, Val, LHSCst);
break; // (X != 13 & X u< 15) -> no change
case ICmpInst::ICMP_SLT:
if (LHSCst == SubOne(RHSCst)) // (X != 13 & X s< 14) -> X < 13
return new ICmpInst(ICmpInst::ICMP_SLT, Val, LHSCst);
break; // (X != 13 & X s< 15) -> no change
case ICmpInst::ICMP_EQ: // (X != 13 & X == 15) -> X == 15
case ICmpInst::ICMP_UGT: // (X != 13 & X u> 15) -> X u> 15
case ICmpInst::ICMP_SGT: // (X != 13 & X s> 15) -> X s> 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_NE:
if (LHSCst == SubOne(RHSCst)){// (X != 13 & X != 14) -> X-13 >u 1
Constant *AddCST = ConstantExpr::getNeg(LHSCst);
Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
return new ICmpInst(ICmpInst::ICMP_UGT, Add,
ConstantInt::get(Add->getType(), 1));
}
break; // (X != 13 & X != 15) -> no change
}
break;
case ICmpInst::ICMP_ULT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X u< 13 & X == 15) -> false
case ICmpInst::ICMP_UGT: // (X u< 13 & X u> 15) -> false
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
case ICmpInst::ICMP_SGT: // (X u< 13 & X s> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X u< 13 & X != 15) -> X u< 13
case ICmpInst::ICMP_ULT: // (X u< 13 & X u< 15) -> X u< 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_SLT: // (X u< 13 & X s< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_SLT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X s< 13 & X == 15) -> false
case ICmpInst::ICMP_SGT: // (X s< 13 & X s> 15) -> false
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
case ICmpInst::ICMP_UGT: // (X s< 13 & X u> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X s< 13 & X != 15) -> X < 13
case ICmpInst::ICMP_SLT: // (X s< 13 & X s< 15) -> X < 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_ULT: // (X s< 13 & X u< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_UGT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X u> 13 & X == 15) -> X == 15
case ICmpInst::ICMP_UGT: // (X u> 13 & X u> 15) -> X u> 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_SGT: // (X u> 13 & X s> 15) -> no change
break;
case ICmpInst::ICMP_NE:
if (RHSCst == AddOne(LHSCst)) // (X u> 13 & X != 14) -> X u> 14
return new ICmpInst(LHSCC, Val, RHSCst);
break; // (X u> 13 & X != 15) -> no change
case ICmpInst::ICMP_ULT: // (X u> 13 & X u< 15) -> (X-14) <u 1
return InsertRangeTest(Val, AddOne(LHSCst),
RHSCst, false, true, I);
case ICmpInst::ICMP_SLT: // (X u> 13 & X s< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_SGT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X s> 13 & X == 15) -> X == 15
case ICmpInst::ICMP_SGT: // (X s> 13 & X s> 15) -> X s> 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_UGT: // (X s> 13 & X u> 15) -> no change
break;
case ICmpInst::ICMP_NE:
if (RHSCst == AddOne(LHSCst)) // (X s> 13 & X != 14) -> X s> 14
return new ICmpInst(LHSCC, Val, RHSCst);
break; // (X s> 13 & X != 15) -> no change
case ICmpInst::ICMP_SLT: // (X s> 13 & X s< 15) -> (X-14) s< 1
return InsertRangeTest(Val, AddOne(LHSCst),
RHSCst, true, true, I);
case ICmpInst::ICMP_ULT: // (X s> 13 & X u< 15) -> no change
break;
}
break;
}
return 0;
}
Instruction *InstCombiner::FoldAndOfFCmps(Instruction &I, FCmpInst *LHS,
FCmpInst *RHS) {
if (LHS->getPredicate() == FCmpInst::FCMP_ORD &&
RHS->getPredicate() == FCmpInst::FCMP_ORD) {
// (fcmp ord x, c) & (fcmp ord y, c) -> (fcmp ord x, y)
if (ConstantFP *LHSC = dyn_cast<ConstantFP>(LHS->getOperand(1)))
if (ConstantFP *RHSC = dyn_cast<ConstantFP>(RHS->getOperand(1))) {
// If either of the constants are nans, then the whole thing returns
// false.
if (LHSC->getValueAPF().isNaN() || RHSC->getValueAPF().isNaN())
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
return new FCmpInst(FCmpInst::FCMP_ORD,
LHS->getOperand(0), RHS->getOperand(0));
}
// Handle vector zeros. This occurs because the canonical form of
// "fcmp ord x,x" is "fcmp ord x, 0".
if (isa<ConstantAggregateZero>(LHS->getOperand(1)) &&
isa<ConstantAggregateZero>(RHS->getOperand(1)))
return new FCmpInst(FCmpInst::FCMP_ORD,
LHS->getOperand(0), RHS->getOperand(0));
return 0;
}
Value *Op0LHS = LHS->getOperand(0), *Op0RHS = LHS->getOperand(1);
Value *Op1LHS = RHS->getOperand(0), *Op1RHS = RHS->getOperand(1);
FCmpInst::Predicate Op0CC = LHS->getPredicate(), Op1CC = RHS->getPredicate();
if (Op0LHS == Op1RHS && Op0RHS == Op1LHS) {
// Swap RHS operands to match LHS.
Op1CC = FCmpInst::getSwappedPredicate(Op1CC);
std::swap(Op1LHS, Op1RHS);
}
if (Op0LHS == Op1LHS && Op0RHS == Op1RHS) {
// Simplify (fcmp cc0 x, y) & (fcmp cc1 x, y).
if (Op0CC == Op1CC)
return new FCmpInst((FCmpInst::Predicate)Op0CC, Op0LHS, Op0RHS);
if (Op0CC == FCmpInst::FCMP_FALSE || Op1CC == FCmpInst::FCMP_FALSE)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
if (Op0CC == FCmpInst::FCMP_TRUE)
return ReplaceInstUsesWith(I, RHS);
if (Op1CC == FCmpInst::FCMP_TRUE)
return ReplaceInstUsesWith(I, LHS);
bool Op0Ordered;
bool Op1Ordered;
unsigned Op0Pred = getFCmpCode(Op0CC, Op0Ordered);
unsigned Op1Pred = getFCmpCode(Op1CC, Op1Ordered);
if (Op1Pred == 0) {
std::swap(LHS, RHS);
std::swap(Op0Pred, Op1Pred);
std::swap(Op0Ordered, Op1Ordered);
}
if (Op0Pred == 0) {
// uno && ueq -> uno && (uno || eq) -> ueq
// ord && olt -> ord && (ord && lt) -> olt
if (Op0Ordered == Op1Ordered)
return ReplaceInstUsesWith(I, RHS);
// uno && oeq -> uno && (ord && eq) -> false
// uno && ord -> false
if (!Op0Ordered)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
// ord && ueq -> ord && (uno || eq) -> oeq
return cast<Instruction>(getFCmpValue(true, Op1Pred,
Op0LHS, Op0RHS, Context));
}
}
return 0;
}
Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1)) // X & undef -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// and X, X = X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Op1);
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(I))
return &I;
if (isa<VectorType>(I.getType())) {
if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) {
if (CP->isAllOnesValue()) // X & <-1,-1> -> X
return ReplaceInstUsesWith(I, I.getOperand(0));
} else if (isa<ConstantAggregateZero>(Op1)) {
return ReplaceInstUsesWith(I, Op1); // X & <0,0> -> <0,0>
}
}
if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(Op1)) {
const APInt &AndRHSMask = AndRHS->getValue();
APInt NotAndRHS(~AndRHSMask);
// Optimize a variety of ((val OP C1) & C2) combinations...
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
Value *Op0LHS = Op0I->getOperand(0);
Value *Op0RHS = Op0I->getOperand(1);
switch (Op0I->getOpcode()) {
default: break;
case Instruction::Xor:
case Instruction::Or:
// If the mask is only needed on one incoming arm, push it up.
if (!Op0I->hasOneUse()) break;
if (MaskedValueIsZero(Op0LHS, NotAndRHS)) {
// Not masking anything out for the LHS, move to RHS.
Value *NewRHS = Builder->CreateAnd(Op0RHS, AndRHS,
Op0RHS->getName()+".masked");
return BinaryOperator::Create(Op0I->getOpcode(), Op0LHS, NewRHS);
}
if (!isa<Constant>(Op0RHS) &&
MaskedValueIsZero(Op0RHS, NotAndRHS)) {
// Not masking anything out for the RHS, move to LHS.
Value *NewLHS = Builder->CreateAnd(Op0LHS, AndRHS,
Op0LHS->getName()+".masked");
return BinaryOperator::Create(Op0I->getOpcode(), NewLHS, Op0RHS);
}
break;
case Instruction::Add:
// ((A & N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == AndRHS.
// ((A | N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
// ((A ^ N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
return BinaryOperator::CreateAnd(V, AndRHS);
if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
return BinaryOperator::CreateAnd(V, AndRHS); // Add commutes
break;
case Instruction::Sub:
// ((A & N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == AndRHS.
// ((A | N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
// ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
return BinaryOperator::CreateAnd(V, AndRHS);
// (A - N) & AndRHS -> -N & AndRHS iff A&AndRHS==0 and AndRHS
// has 1's for all bits that the subtraction with A might affect.
if (Op0I->hasOneUse()) {
uint32_t BitWidth = AndRHSMask.getBitWidth();
uint32_t Zeros = AndRHSMask.countLeadingZeros();
APInt Mask = APInt::getLowBitsSet(BitWidth, BitWidth - Zeros);
ConstantInt *A = dyn_cast<ConstantInt>(Op0LHS);
if (!(A && A->isZero()) && // avoid infinite recursion.
MaskedValueIsZero(Op0LHS, Mask)) {
Value *NewNeg = Builder->CreateNeg(Op0RHS);
return BinaryOperator::CreateAnd(NewNeg, AndRHS);
}
}
break;
case Instruction::Shl:
case Instruction::LShr:
// (1 << x) & 1 --> zext(x == 0)
// (1 >> x) & 1 --> zext(x == 0)
if (AndRHSMask == 1 && Op0LHS == AndRHS) {
Value *NewICmp =
Builder->CreateICmpEQ(Op0RHS, Constant::getNullValue(I.getType()));
return new ZExtInst(NewICmp, I.getType());
}
break;
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
return Res;
} else if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
// If this is an integer truncation or change from signed-to-unsigned, and
// if the source is an and/or with immediate, transform it. This
// frequently occurs for bitfield accesses.
if (Instruction *CastOp = dyn_cast<Instruction>(CI->getOperand(0))) {
if ((isa<TruncInst>(CI) || isa<BitCastInst>(CI)) &&
CastOp->getNumOperands() == 2)
if (ConstantInt *AndCI = dyn_cast<ConstantInt>(CastOp->getOperand(1))) {
if (CastOp->getOpcode() == Instruction::And) {
// Change: and (cast (and X, C1) to T), C2
// into : and (cast X to T), trunc_or_bitcast(C1)&C2
// This will fold the two constants together, which may allow
// other simplifications.
Value *NewCast = Builder->CreateTruncOrBitCast(
CastOp->getOperand(0), I.getType(),
CastOp->getName()+".shrunk");
// trunc_or_bitcast(C1)&C2
Constant *C3 = ConstantExpr::getTruncOrBitCast(AndCI,I.getType());
C3 = ConstantExpr::getAnd(C3, AndRHS);
return BinaryOperator::CreateAnd(NewCast, C3);
} else if (CastOp->getOpcode() == Instruction::Or) {
// Change: and (cast (or X, C1) to T), C2
// into : trunc(C1)&C2 iff trunc(C1)&C2 == C2
Constant *C3 = ConstantExpr::getTruncOrBitCast(AndCI,I.getType());
if (ConstantExpr::getAnd(C3, AndRHS) == AndRHS)
// trunc(C1)&C2
return ReplaceInstUsesWith(I, AndRHS);
}
}
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// (~A & ~B) == (~(A | B)) - De Morgan's Law
if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Value *Or = Builder->CreateOr(Op0NotVal, Op1NotVal,
I.getName()+".demorgan");
return BinaryOperator::CreateNot(Or);
}
{
Value *A = 0, *B = 0, *C = 0, *D = 0;
if (match(Op0, m_Or(m_Value(A), m_Value(B)))) {
if (A == Op1 || B == Op1) // (A | ?) & A --> A
return ReplaceInstUsesWith(I, Op1);
// (A|B) & ~(A&B) -> A^B
if (match(Op1, m_Not(m_And(m_Value(C), m_Value(D))))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::CreateXor(A, B);
}
}
if (match(Op1, m_Or(m_Value(A), m_Value(B)))) {
if (A == Op0 || B == Op0) // A & (A | ?) --> A
return ReplaceInstUsesWith(I, Op0);
// ~(A&B) & (A|B) -> A^B
if (match(Op0, m_Not(m_And(m_Value(C), m_Value(D))))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::CreateXor(A, B);
}
}
if (Op0->hasOneUse() &&
match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
if (A == Op1) { // (A^B)&A -> A&(A^B)
I.swapOperands(); // Simplify below
std::swap(Op0, Op1);
} else if (B == Op1) { // (A^B)&B -> B&(B^A)
cast<BinaryOperator>(Op0)->swapOperands();
I.swapOperands(); // Simplify below
std::swap(Op0, Op1);
}
}
if (Op1->hasOneUse() &&
match(Op1, m_Xor(m_Value(A), m_Value(B)))) {
if (B == Op0) { // B&(A^B) -> B&(B^A)
cast<BinaryOperator>(Op1)->swapOperands();
std::swap(A, B);
}
if (A == Op0) // A&(A^B) -> A & ~B
return BinaryOperator::CreateAnd(A, Builder->CreateNot(B, "tmp"));
}
// (A&((~A)|B)) -> A&B
if (match(Op0, m_Or(m_Not(m_Specific(Op1)), m_Value(A))) ||
match(Op0, m_Or(m_Value(A), m_Not(m_Specific(Op1)))))
return BinaryOperator::CreateAnd(A, Op1);
if (match(Op1, m_Or(m_Not(m_Specific(Op0)), m_Value(A))) ||
match(Op1, m_Or(m_Value(A), m_Not(m_Specific(Op0)))))
return BinaryOperator::CreateAnd(A, Op0);
}
if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1)) {
// (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
return R;
if (ICmpInst *LHS = dyn_cast<ICmpInst>(Op0))
if (Instruction *Res = FoldAndOfICmps(I, LHS, RHS))
return Res;
}
// fold (and (cast A), (cast B)) -> (cast (and A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0))
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (Op0C->getOpcode() == Op1C->getOpcode()) { // same cast kind ?
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (SrcTy == Op1C->getOperand(0)->getType() &&
SrcTy->isIntOrIntVector() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
I.getType(), TD) &&
ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
I.getType(), TD)) {
Value *NewOp = Builder->CreateAnd(Op0C->getOperand(0),
Op1C->getOperand(0), I.getName());
return CastInst::Create(Op0C->getOpcode(), NewOp, I.getType());
}
}
// (X >> Z) & (Y >> Z) -> (X&Y) >> Z for all shifts.
if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
SI0->getOperand(1) == SI1->getOperand(1) &&
(SI0->hasOneUse() || SI1->hasOneUse())) {
Value *NewOp =
Builder->CreateAnd(SI0->getOperand(0), SI1->getOperand(0),
SI0->getName());
return BinaryOperator::Create(SI1->getOpcode(), NewOp,
SI1->getOperand(1));
}
}
// If and'ing two fcmp, try combine them into one.
if (FCmpInst *LHS = dyn_cast<FCmpInst>(I.getOperand(0))) {
if (FCmpInst *RHS = dyn_cast<FCmpInst>(I.getOperand(1)))
if (Instruction *Res = FoldAndOfFCmps(I, LHS, RHS))
return Res;
}
return Changed ? &I : 0;
}
/// CollectBSwapParts - Analyze the specified subexpression and see if it is
/// capable of providing pieces of a bswap. The subexpression provides pieces
/// of a bswap if it is proven that each of the non-zero bytes in the output of
/// the expression came from the corresponding "byte swapped" byte in some other
/// value. For example, if the current subexpression is "(shl i32 %X, 24)" then
/// we know that the expression deposits the low byte of %X into the high byte
/// of the bswap result and that all other bytes are zero. This expression is
/// accepted, the high byte of ByteValues is set to X to indicate a correct
/// match.
///
/// This function returns true if the match was unsuccessful and false if so.
/// On entry to the function the "OverallLeftShift" is a signed integer value
/// indicating the number of bytes that the subexpression is later shifted. For
/// example, if the expression is later right shifted by 16 bits, the
/// OverallLeftShift value would be -2 on entry. This is used to specify which
/// byte of ByteValues is actually being set.
///
/// Similarly, ByteMask is a bitmask where a bit is clear if its corresponding
/// byte is masked to zero by a user. For example, in (X & 255), X will be
/// processed with a bytemask of 1. Because bytemask is 32-bits, this limits
/// this function to working on up to 32-byte (256 bit) values. ByteMask is
/// always in the local (OverallLeftShift) coordinate space.
///
static bool CollectBSwapParts(Value *V, int OverallLeftShift, uint32_t ByteMask,
SmallVector<Value*, 8> &ByteValues) {
if (Instruction *I = dyn_cast<Instruction>(V)) {
// If this is an or instruction, it may be an inner node of the bswap.
if (I->getOpcode() == Instruction::Or) {
return CollectBSwapParts(I->getOperand(0), OverallLeftShift, ByteMask,
ByteValues) ||
CollectBSwapParts(I->getOperand(1), OverallLeftShift, ByteMask,
ByteValues);
}
// If this is a logical shift by a constant multiple of 8, recurse with
// OverallLeftShift and ByteMask adjusted.
if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) {
unsigned ShAmt =
cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U);
// Ensure the shift amount is defined and of a byte value.
if ((ShAmt & 7) || (ShAmt > 8*ByteValues.size()))
return true;
unsigned ByteShift = ShAmt >> 3;
if (I->getOpcode() == Instruction::Shl) {
// X << 2 -> collect(X, +2)
OverallLeftShift += ByteShift;
ByteMask >>= ByteShift;
} else {
// X >>u 2 -> collect(X, -2)
OverallLeftShift -= ByteShift;
ByteMask <<= ByteShift;
ByteMask &= (~0U >> (32-ByteValues.size()));
}
if (OverallLeftShift >= (int)ByteValues.size()) return true;
if (OverallLeftShift <= -(int)ByteValues.size()) return true;
return CollectBSwapParts(I->getOperand(0), OverallLeftShift, ByteMask,
ByteValues);
}
// If this is a logical 'and' with a mask that clears bytes, clear the
// corresponding bytes in ByteMask.
if (I->getOpcode() == Instruction::And &&
isa<ConstantInt>(I->getOperand(1))) {
// Scan every byte of the and mask, seeing if the byte is either 0 or 255.
unsigned NumBytes = ByteValues.size();
APInt Byte(I->getType()->getPrimitiveSizeInBits(), 255);
const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue();
for (unsigned i = 0; i != NumBytes; ++i, Byte <<= 8) {
// If this byte is masked out by a later operation, we don't care what
// the and mask is.
if ((ByteMask & (1 << i)) == 0)
continue;
// If the AndMask is all zeros for this byte, clear the bit.
APInt MaskB = AndMask & Byte;
if (MaskB == 0) {
ByteMask &= ~(1U << i);
continue;
}
// If the AndMask is not all ones for this byte, it's not a bytezap.
if (MaskB != Byte)
return true;
// Otherwise, this byte is kept.
}
return CollectBSwapParts(I->getOperand(0), OverallLeftShift, ByteMask,
ByteValues);
}
}
// Okay, we got to something that isn't a shift, 'or' or 'and'. This must be
// the input value to the bswap. Some observations: 1) if more than one byte
// is demanded from this input, then it could not be successfully assembled
// into a byteswap. At least one of the two bytes would not be aligned with
// their ultimate destination.
if (!isPowerOf2_32(ByteMask)) return true;
unsigned InputByteNo = CountTrailingZeros_32(ByteMask);
// 2) The input and ultimate destinations must line up: if byte 3 of an i32
// is demanded, it needs to go into byte 0 of the result. This means that the
// byte needs to be shifted until it lands in the right byte bucket. The
// shift amount depends on the position: if the byte is coming from the high
// part of the value (e.g. byte 3) then it must be shifted right. If from the
// low part, it must be shifted left.
unsigned DestByteNo = InputByteNo + OverallLeftShift;
if (InputByteNo < ByteValues.size()/2) {
if (ByteValues.size()-1-DestByteNo != InputByteNo)
return true;
} else {
if (ByteValues.size()-1-DestByteNo != InputByteNo)
return true;
}
// If the destination byte value is already defined, the values are or'd
// together, which isn't a bswap (unless it's an or of the same bits).
if (ByteValues[DestByteNo] && ByteValues[DestByteNo] != V)
return true;
ByteValues[DestByteNo] = V;
return false;
}
/// MatchBSwap - Given an OR instruction, check to see if this is a bswap idiom.
/// If so, insert the new bswap intrinsic and return it.
Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
const IntegerType *ITy = dyn_cast<IntegerType>(I.getType());
if (!ITy || ITy->getBitWidth() % 16 ||
// ByteMask only allows up to 32-byte values.
ITy->getBitWidth() > 32*8)
return 0; // Can only bswap pairs of bytes. Can't do vectors.
/// ByteValues - For each byte of the result, we keep track of which value
/// defines each byte.
SmallVector<Value*, 8> ByteValues;
ByteValues.resize(ITy->getBitWidth()/8);
// Try to find all the pieces corresponding to the bswap.
uint32_t ByteMask = ~0U >> (32-ByteValues.size());
if (CollectBSwapParts(&I, 0, ByteMask, ByteValues))
return 0;
// Check to see if all of the bytes come from the same value.
Value *V = ByteValues[0];
if (V == 0) return 0; // Didn't find a byte? Must be zero.
// Check to make sure that all of the bytes come from the same value.
for (unsigned i = 1, e = ByteValues.size(); i != e; ++i)
if (ByteValues[i] != V)
return 0;
const Type *Tys[] = { ITy };
Module *M = I.getParent()->getParent()->getParent();
Function *F = Intrinsic::getDeclaration(M, Intrinsic::bswap, Tys, 1);
return CallInst::Create(F, V);
}
/// MatchSelectFromAndOr - We have an expression of the form (A&C)|(B&D). Check
/// If A is (cond?-1:0) and either B or D is ~(cond?-1,0) or (cond?0,-1), then
/// we can simplify this expression to "cond ? C : D or B".
static Instruction *MatchSelectFromAndOr(Value *A, Value *B,
Value *C, Value *D,
LLVMContext *Context) {
// If A is not a select of -1/0, this cannot match.
Value *Cond = 0;
if (!match(A, m_SelectCst<-1, 0>(m_Value(Cond))))
return 0;
// ((cond?-1:0)&C) | (B&(cond?0:-1)) -> cond ? C : B.
if (match(D, m_SelectCst<0, -1>(m_Specific(Cond))))
return SelectInst::Create(Cond, C, B);
if (match(D, m_Not(m_SelectCst<-1, 0>(m_Specific(Cond)))))
return SelectInst::Create(Cond, C, B);
// ((cond?-1:0)&C) | ((cond?0:-1)&D) -> cond ? C : D.
if (match(B, m_SelectCst<0, -1>(m_Specific(Cond))))
return SelectInst::Create(Cond, C, D);
if (match(B, m_Not(m_SelectCst<-1, 0>(m_Specific(Cond)))))
return SelectInst::Create(Cond, C, D);
return 0;
}
/// FoldOrOfICmps - Fold (icmp)|(icmp) if possible.
Instruction *InstCombiner::FoldOrOfICmps(Instruction &I,
ICmpInst *LHS, ICmpInst *RHS) {
Value *Val, *Val2;
ConstantInt *LHSCst, *RHSCst;
ICmpInst::Predicate LHSCC, RHSCC;
// This only handles icmp of constants: (icmp1 A, C1) | (icmp2 B, C2).
if (!match(LHS, m_ICmp(LHSCC, m_Value(Val),
m_ConstantInt(LHSCst))) ||
!match(RHS, m_ICmp(RHSCC, m_Value(Val2),
m_ConstantInt(RHSCst))))
return 0;
// From here on, we only handle:
// (icmp1 A, C1) | (icmp2 A, C2) --> something simpler.
if (Val != Val2) return 0;
// ICMP_[US][GL]E X, CST is folded to ICMP_[US][GL]T elsewhere.
if (LHSCC == ICmpInst::ICMP_UGE || LHSCC == ICmpInst::ICMP_ULE ||
RHSCC == ICmpInst::ICMP_UGE || RHSCC == ICmpInst::ICMP_ULE ||
LHSCC == ICmpInst::ICMP_SGE || LHSCC == ICmpInst::ICMP_SLE ||
RHSCC == ICmpInst::ICMP_SGE || RHSCC == ICmpInst::ICMP_SLE)
return 0;
// We can't fold (ugt x, C) | (sgt x, C2).
if (!PredicatesFoldable(LHSCC, RHSCC))
return 0;
// Ensure that the larger constant is on the RHS.
bool ShouldSwap;
if (ICmpInst::isSignedPredicate(LHSCC) ||
(ICmpInst::isEquality(LHSCC) &&
ICmpInst::isSignedPredicate(RHSCC)))
ShouldSwap = LHSCst->getValue().sgt(RHSCst->getValue());
else
ShouldSwap = LHSCst->getValue().ugt(RHSCst->getValue());
if (ShouldSwap) {
std::swap(LHS, RHS);
std::swap(LHSCst, RHSCst);
std::swap(LHSCC, RHSCC);
}
// At this point, we know we have have two icmp instructions
// comparing a value against two constants and or'ing the result
// together. Because of the above check, we know that we only have
// ICMP_EQ, ICMP_NE, ICMP_LT, and ICMP_GT here. We also know (from the
// FoldICmpLogical check above), that the two constants are not
// equal.
assert(LHSCst != RHSCst && "Compares not folded above?");
switch (LHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ:
if (LHSCst == SubOne(RHSCst)) {
// (X == 13 | X == 14) -> X-13 <u 2
Constant *AddCST = ConstantExpr::getNeg(LHSCst);
Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
return new ICmpInst(ICmpInst::ICMP_ULT, Add, AddCST);
}
break; // (X == 13 | X == 15) -> no change
case ICmpInst::ICMP_UGT: // (X == 13 | X u> 14) -> no change
case ICmpInst::ICMP_SGT: // (X == 13 | X s> 14) -> no change
break;
case ICmpInst::ICMP_NE: // (X == 13 | X != 15) -> X != 15
case ICmpInst::ICMP_ULT: // (X == 13 | X u< 15) -> X u< 15
case ICmpInst::ICMP_SLT: // (X == 13 | X s< 15) -> X s< 15
return ReplaceInstUsesWith(I, RHS);
}
break;
case ICmpInst::ICMP_NE:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X != 13 | X == 15) -> X != 13
case ICmpInst::ICMP_UGT: // (X != 13 | X u> 15) -> X != 13
case ICmpInst::ICMP_SGT: // (X != 13 | X s> 15) -> X != 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_NE: // (X != 13 | X != 15) -> true
case ICmpInst::ICMP_ULT: // (X != 13 | X u< 15) -> true
case ICmpInst::ICMP_SLT: // (X != 13 | X s< 15) -> true
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
}
break;
case ICmpInst::ICMP_ULT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X u< 13 | X == 14) -> no change
break;
case ICmpInst::ICMP_UGT: // (X u< 13 | X u> 15) -> (X-13) u> 2
// If RHSCst is [us]MAXINT, it is always false. Not handling
// this can cause overflow.
if (RHSCst->isMaxValue(false))
return ReplaceInstUsesWith(I, LHS);
return InsertRangeTest(Val, LHSCst, AddOne(RHSCst),
false, false, I);
case ICmpInst::ICMP_SGT: // (X u< 13 | X s> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X u< 13 | X != 15) -> X != 15
case ICmpInst::ICMP_ULT: // (X u< 13 | X u< 15) -> X u< 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_SLT: // (X u< 13 | X s< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_SLT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X s< 13 | X == 14) -> no change
break;
case ICmpInst::ICMP_SGT: // (X s< 13 | X s> 15) -> (X-13) s> 2
// If RHSCst is [us]MAXINT, it is always false. Not handling
// this can cause overflow.
if (RHSCst->isMaxValue(true))
return ReplaceInstUsesWith(I, LHS);
return InsertRangeTest(Val, LHSCst, AddOne(RHSCst),
true, false, I);
case ICmpInst::ICMP_UGT: // (X s< 13 | X u> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X s< 13 | X != 15) -> X != 15
case ICmpInst::ICMP_SLT: // (X s< 13 | X s< 15) -> X s< 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_ULT: // (X s< 13 | X u< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_UGT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X u> 13 | X == 15) -> X u> 13
case ICmpInst::ICMP_UGT: // (X u> 13 | X u> 15) -> X u> 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_SGT: // (X u> 13 | X s> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X u> 13 | X != 15) -> true
case ICmpInst::ICMP_ULT: // (X u> 13 | X u< 15) -> true
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
case ICmpInst::ICMP_SLT: // (X u> 13 | X s< 15) -> no change
break;
}
break;
case ICmpInst::ICMP_SGT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X s> 13 | X == 15) -> X > 13
case ICmpInst::ICMP_SGT: // (X s> 13 | X s> 15) -> X > 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_UGT: // (X s> 13 | X u> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X s> 13 | X != 15) -> true
case ICmpInst::ICMP_SLT: // (X s> 13 | X s< 15) -> true
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
case ICmpInst::ICMP_ULT: // (X s> 13 | X u< 15) -> no change
break;
}
break;
}
return 0;
}
Instruction *InstCombiner::FoldOrOfFCmps(Instruction &I, FCmpInst *LHS,
FCmpInst *RHS) {
if (LHS->getPredicate() == FCmpInst::FCMP_UNO &&
RHS->getPredicate() == FCmpInst::FCMP_UNO &&
LHS->getOperand(0)->getType() == RHS->getOperand(0)->getType()) {
if (ConstantFP *LHSC = dyn_cast<ConstantFP>(LHS->getOperand(1)))
if (ConstantFP *RHSC = dyn_cast<ConstantFP>(RHS->getOperand(1))) {
// If either of the constants are nans, then the whole thing returns
// true.
if (LHSC->getValueAPF().isNaN() || RHSC->getValueAPF().isNaN())
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
// Otherwise, no need to compare the two constants, compare the
// rest.
return new FCmpInst(FCmpInst::FCMP_UNO,
LHS->getOperand(0), RHS->getOperand(0));
}
// Handle vector zeros. This occurs because the canonical form of
// "fcmp uno x,x" is "fcmp uno x, 0".
if (isa<ConstantAggregateZero>(LHS->getOperand(1)) &&
isa<ConstantAggregateZero>(RHS->getOperand(1)))
return new FCmpInst(FCmpInst::FCMP_UNO,
LHS->getOperand(0), RHS->getOperand(0));
return 0;
}
Value *Op0LHS = LHS->getOperand(0), *Op0RHS = LHS->getOperand(1);
Value *Op1LHS = RHS->getOperand(0), *Op1RHS = RHS->getOperand(1);
FCmpInst::Predicate Op0CC = LHS->getPredicate(), Op1CC = RHS->getPredicate();
if (Op0LHS == Op1RHS && Op0RHS == Op1LHS) {
// Swap RHS operands to match LHS.
Op1CC = FCmpInst::getSwappedPredicate(Op1CC);
std::swap(Op1LHS, Op1RHS);
}
if (Op0LHS == Op1LHS && Op0RHS == Op1RHS) {
// Simplify (fcmp cc0 x, y) | (fcmp cc1 x, y).
if (Op0CC == Op1CC)
return new FCmpInst((FCmpInst::Predicate)Op0CC,
Op0LHS, Op0RHS);
if (Op0CC == FCmpInst::FCMP_TRUE || Op1CC == FCmpInst::FCMP_TRUE)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0CC == FCmpInst::FCMP_FALSE)
return ReplaceInstUsesWith(I, RHS);
if (Op1CC == FCmpInst::FCMP_FALSE)
return ReplaceInstUsesWith(I, LHS);
bool Op0Ordered;
bool Op1Ordered;
unsigned Op0Pred = getFCmpCode(Op0CC, Op0Ordered);
unsigned Op1Pred = getFCmpCode(Op1CC, Op1Ordered);
if (Op0Ordered == Op1Ordered) {
// If both are ordered or unordered, return a new fcmp with
// or'ed predicates.
Value *RV = getFCmpValue(Op0Ordered, Op0Pred|Op1Pred,
Op0LHS, Op0RHS, Context);
if (Instruction *I = dyn_cast<Instruction>(RV))
return I;
// Otherwise, it's a constant boolean value...
return ReplaceInstUsesWith(I, RV);
}
}
return 0;
}
/// FoldOrWithConstants - This helper function folds:
///
/// ((A | B) & C1) | (B & C2)
///
/// into:
///
/// (A & C1) | B
///
/// when the XOR of the two constants is "all ones" (-1).
Instruction *InstCombiner::FoldOrWithConstants(BinaryOperator &I, Value *Op,
Value *A, Value *B, Value *C) {
ConstantInt *CI1 = dyn_cast<ConstantInt>(C);
if (!CI1) return 0;
Value *V1 = 0;
ConstantInt *CI2 = 0;
if (!match(Op, m_And(m_Value(V1), m_ConstantInt(CI2)))) return 0;
APInt Xor = CI1->getValue() ^ CI2->getValue();
if (!Xor.isAllOnesValue()) return 0;
if (V1 == A || V1 == B) {
Value *NewOp = Builder->CreateAnd((V1 == A) ? B : A, CI1);
return BinaryOperator::CreateOr(NewOp, V1);
}
return 0;
}
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1)) // X | undef -> -1
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
// or X, X = X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Op0);
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(I))
return &I;
if (isa<VectorType>(I.getType())) {
if (isa<ConstantAggregateZero>(Op1)) {
return ReplaceInstUsesWith(I, Op0); // X | <0,0> -> X
} else if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) {
if (CP->isAllOnesValue()) // X | <-1,-1> -> <-1,-1>
return ReplaceInstUsesWith(I, I.getOperand(1));
}
}
// or X, -1 == -1
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
ConstantInt *C1 = 0; Value *X = 0;
// (X & C1) | C2 --> (X | C2) & (C1|C2)
if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) &&
isOnlyUse(Op0)) {
Value *Or = Builder->CreateOr(X, RHS);
Or->takeName(Op0);
return BinaryOperator::CreateAnd(Or,
ConstantInt::get(*Context, RHS->getValue() | C1->getValue()));
}
// (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
if (match(Op0, m_Xor(m_Value(X), m_ConstantInt(C1))) &&
isOnlyUse(Op0)) {
Value *Or = Builder->CreateOr(X, RHS);
Or->takeName(Op0);
return BinaryOperator::CreateXor(Or,
ConstantInt::get(*Context, C1->getValue() & ~RHS->getValue()));
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
Value *A = 0, *B = 0;
ConstantInt *C1 = 0, *C2 = 0;
if (match(Op0, m_And(m_Value(A), m_Value(B))))
if (A == Op1 || B == Op1) // (A & ?) | A --> A
return ReplaceInstUsesWith(I, Op1);
if (match(Op1, m_And(m_Value(A), m_Value(B))))
if (A == Op0 || B == Op0) // A | (A & ?) --> A
return ReplaceInstUsesWith(I, Op0);
// (A | B) | C and A | (B | C) -> bswap if possible.
// (A >> B) | (C << D) and (A << B) | (B >> C) -> bswap if possible.
if (match(Op0, m_Or(m_Value(), m_Value())) ||
match(Op1, m_Or(m_Value(), m_Value())) ||
(match(Op0, m_Shift(m_Value(), m_Value())) &&
match(Op1, m_Shift(m_Value(), m_Value())))) {
if (Instruction *BSwap = MatchBSwap(I))
return BSwap;
}
// (X^C)|Y -> (X|Y)^C iff Y&C == 0
if (Op0->hasOneUse() &&
match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op1, C1->getValue())) {
Value *NOr = Builder->CreateOr(A, Op1);
NOr->takeName(Op0);
return BinaryOperator::CreateXor(NOr, C1);
}
// Y|(X^C) -> (X|Y)^C iff Y&C == 0
if (Op1->hasOneUse() &&
match(Op1, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op0, C1->getValue())) {
Value *NOr = Builder->CreateOr(A, Op0);
NOr->takeName(Op0);
return BinaryOperator::CreateXor(NOr, C1);
}
// (A & C)|(B & D)
Value *C = 0, *D = 0;
if (match(Op0, m_And(m_Value(A), m_Value(C))) &&
match(Op1, m_And(m_Value(B), m_Value(D)))) {
Value *V1 = 0, *V2 = 0, *V3 = 0;
C1 = dyn_cast<ConstantInt>(C);
C2 = dyn_cast<ConstantInt>(D);
if (C1 && C2) { // (A & C1)|(B & C2)
// If we have: ((V + N) & C1) | (V & C2)
// .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0
// replace with V+N.
if (C1->getValue() == ~C2->getValue()) {
if ((C2->getValue() & (C2->getValue()+1)) == 0 && // C2 == 0+1+
match(A, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == B && MaskedValueIsZero(V2, C2->getValue()))
return ReplaceInstUsesWith(I, A);
if (V2 == B && MaskedValueIsZero(V1, C2->getValue()))
return ReplaceInstUsesWith(I, A);
}
// Or commutes, try both ways.
if ((C1->getValue() & (C1->getValue()+1)) == 0 &&
match(B, m_Add(m_Value(V1), m_Value(V2)))) {
// Add commutes, try both ways.
if (V1 == A && MaskedValueIsZero(V2, C1->getValue()))
return ReplaceInstUsesWith(I, B);
if (V2 == A && MaskedValueIsZero(V1, C1->getValue()))
return ReplaceInstUsesWith(I, B);
}
}
V1 = 0; V2 = 0; V3 = 0;
}
// Check to see if we have any common things being and'ed. If so, find the
// terms for V1 & (V2|V3).
if (isOnlyUse(Op0) || isOnlyUse(Op1)) {
if (A == B) // (A & C)|(A & D) == A & (C|D)
V1 = A, V2 = C, V3 = D;
else if (A == D) // (A & C)|(B & A) == A & (B|C)
V1 = A, V2 = B, V3 = C;
else if (C == B) // (A & C)|(C & D) == C & (A|D)
V1 = C, V2 = A, V3 = D;
else if (C == D) // (A & C)|(B & C) == C & (A|B)
V1 = C, V2 = A, V3 = B;
if (V1) {
Value *Or = Builder->CreateOr(V2, V3, "tmp");
return BinaryOperator::CreateAnd(V1, Or);
}
}
// (A & (C0?-1:0)) | (B & ~(C0?-1:0)) -> C0 ? A : B, and commuted variants
if (Instruction *Match = MatchSelectFromAndOr(A, B, C, D, Context))
return Match;
if (Instruction *Match = MatchSelectFromAndOr(B, A, D, C, Context))
return Match;
if (Instruction *Match = MatchSelectFromAndOr(C, B, A, D, Context))
return Match;
if (Instruction *Match = MatchSelectFromAndOr(D, A, B, C, Context))
return Match;
// ((A&~B)|(~A&B)) -> A^B
if ((match(C, m_Not(m_Specific(D))) &&
match(B, m_Not(m_Specific(A)))))
return BinaryOperator::CreateXor(A, D);
// ((~B&A)|(~A&B)) -> A^B
if ((match(A, m_Not(m_Specific(D))) &&
match(B, m_Not(m_Specific(C)))))
return BinaryOperator::CreateXor(C, D);
// ((A&~B)|(B&~A)) -> A^B
if ((match(C, m_Not(m_Specific(B))) &&
match(D, m_Not(m_Specific(A)))))
return BinaryOperator::CreateXor(A, B);
// ((~B&A)|(B&~A)) -> A^B
if ((match(A, m_Not(m_Specific(B))) &&
match(D, m_Not(m_Specific(C)))))
return BinaryOperator::CreateXor(C, B);
}
// (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts.
if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
SI0->getOperand(1) == SI1->getOperand(1) &&
(SI0->hasOneUse() || SI1->hasOneUse())) {
Value *NewOp = Builder->CreateOr(SI0->getOperand(0), SI1->getOperand(0),
SI0->getName());
return BinaryOperator::Create(SI1->getOpcode(), NewOp,
SI1->getOperand(1));
}
}
// ((A|B)&1)|(B&-2) -> (A&1) | B
if (match(Op0, m_And(m_Or(m_Value(A), m_Value(B)), m_Value(C))) ||
match(Op0, m_And(m_Value(C), m_Or(m_Value(A), m_Value(B))))) {
Instruction *Ret = FoldOrWithConstants(I, Op1, A, B, C);
if (Ret) return Ret;
}
// (B&-2)|((A|B)&1) -> (A&1) | B
if (match(Op1, m_And(m_Or(m_Value(A), m_Value(B)), m_Value(C))) ||
match(Op1, m_And(m_Value(C), m_Or(m_Value(A), m_Value(B))))) {
Instruction *Ret = FoldOrWithConstants(I, Op0, A, B, C);
if (Ret) return Ret;
}
if (match(Op0, m_Not(m_Value(A)))) { // ~A | Op1
if (A == Op1) // ~A | A == -1
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
} else {
A = 0;
}
// Note, A is still live here!
if (match(Op1, m_Not(m_Value(B)))) { // Op0 | ~B
if (Op0 == B)
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
// (~A | ~B) == (~(A & B)) - De Morgan's Law
if (A && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Value *And = Builder->CreateAnd(A, B, I.getName()+".demorgan");
return BinaryOperator::CreateNot(And);
}
}
// (icmp1 A, B) | (icmp2 A, B) --> (icmp3 A, B)
if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1))) {
if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
return R;
if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
if (Instruction *Res = FoldOrOfICmps(I, LHS, RHS))
return Res;
}
// fold (or (cast A), (cast B)) -> (cast (or A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (Op0C->getOpcode() == Op1C->getOpcode()) {// same cast kind ?
if (!isa<ICmpInst>(Op0C->getOperand(0)) ||
!isa<ICmpInst>(Op1C->getOperand(0))) {
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (SrcTy == Op1C->getOperand(0)->getType() &&
SrcTy->isIntOrIntVector() &&
// Only do this if the casts both really cause code to be
// generated.
ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
I.getType(), TD) &&
ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
I.getType(), TD)) {
Value *NewOp = Builder->CreateOr(Op0C->getOperand(0),
Op1C->getOperand(0), I.getName());
return CastInst::Create(Op0C->getOpcode(), NewOp, I.getType());
}
}
}
}
// (fcmp uno x, c) | (fcmp uno y, c) -> (fcmp uno x, y)
if (FCmpInst *LHS = dyn_cast<FCmpInst>(I.getOperand(0))) {
if (FCmpInst *RHS = dyn_cast<FCmpInst>(I.getOperand(1)))
if (Instruction *Res = FoldOrOfFCmps(I, LHS, RHS))
return Res;
}
return Changed ? &I : 0;
}
namespace {
// XorSelf - Implements: X ^ X --> 0
struct XorSelf {
Value *RHS;
XorSelf(Value *rhs) : RHS(rhs) {}
bool shouldApply(Value *LHS) const { return LHS == RHS; }
Instruction *apply(BinaryOperator &Xor) const {
return &Xor;
}
};
}
Instruction *InstCombiner::visitXor(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<UndefValue>(Op1)) {
if (isa<UndefValue>(Op0))
// Handle undef ^ undef -> 0 special case. This is a common
// idiom (misuse).
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
return ReplaceInstUsesWith(I, Op1); // X ^ undef -> undef
}
// xor X, X = 0, even if X is nested in a sequence of Xor's.
if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
assert(Result == &I && "AssociativeOpt didn't work?"); Result=Result;
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(I))
return &I;
if (isa<VectorType>(I.getType()))
if (isa<ConstantAggregateZero>(Op1))
return ReplaceInstUsesWith(I, Op0); // X ^ <0,0> -> X
// Is this a ~ operation?
if (Value *NotOp = dyn_castNotVal(&I)) {
// ~(~X & Y) --> (X | ~Y) - De Morgan's Law
// ~(~X | Y) === (X & ~Y) - De Morgan's Law
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(NotOp)) {
if (Op0I->getOpcode() == Instruction::And ||
Op0I->getOpcode() == Instruction::Or) {
if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
Value *NotY =
Builder->CreateNot(Op0I->getOperand(1),
Op0I->getOperand(1)->getName()+".not");
if (Op0I->getOpcode() == Instruction::And)
return BinaryOperator::CreateOr(Op0NotVal, NotY);
return BinaryOperator::CreateAnd(Op0NotVal, NotY);
}
}
}
}
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
if (RHS->isOne() && Op0->hasOneUse()) {
// xor (cmp A, B), true = not (cmp A, B) = !cmp A, B
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Op0))
return new ICmpInst(ICI->getInversePredicate(),
ICI->getOperand(0), ICI->getOperand(1));
if (FCmpInst *FCI = dyn_cast<FCmpInst>(Op0))
return new FCmpInst(FCI->getInversePredicate(),
FCI->getOperand(0), FCI->getOperand(1));
}
// fold (xor(zext(cmp)), 1) and (xor(sext(cmp)), -1) to ext(!cmp).
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
if (CmpInst *CI = dyn_cast<CmpInst>(Op0C->getOperand(0))) {
if (CI->hasOneUse() && Op0C->hasOneUse()) {
Instruction::CastOps Opcode = Op0C->getOpcode();
if ((Opcode == Instruction::ZExt || Opcode == Instruction::SExt) &&
(RHS == ConstantExpr::getCast(Opcode,
ConstantInt::getTrue(*Context),
Op0C->getDestTy()))) {
CI->setPredicate(CI->getInversePredicate());
return CastInst::Create(Opcode, CI, Op0C->getType());
}
}
}
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
// ~(c-X) == X-c-1 == X+(-c-1)
if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
ConstantInt::get(I.getType(), 1));
return BinaryOperator::CreateAdd(Op0I->getOperand(1), ConstantRHS);
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
if (Op0I->getOpcode() == Instruction::Add) {
// ~(X-c) --> (-c-1)-X
if (RHS->isAllOnesValue()) {
Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
return BinaryOperator::CreateSub(
ConstantExpr::getSub(NegOp0CI,
ConstantInt::get(I.getType(), 1)),
Op0I->getOperand(0));
} else if (RHS->getValue().isSignBit()) {
// (X + C) ^ signbit -> (X + C + signbit)
Constant *C = ConstantInt::get(*Context,
RHS->getValue() + Op0CI->getValue());
return BinaryOperator::CreateAdd(Op0I->getOperand(0), C);
}
} else if (Op0I->getOpcode() == Instruction::Or) {
// (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
if (MaskedValueIsZero(Op0I->getOperand(0), Op0CI->getValue())) {
Constant *NewRHS = ConstantExpr::getOr(Op0CI, RHS);
// Anything in both C1 and C2 is known to be zero, remove it from
// NewRHS.
Constant *CommonBits = ConstantExpr::getAnd(Op0CI, RHS);
NewRHS = ConstantExpr::getAnd(NewRHS,
ConstantExpr::getNot(CommonBits));
Worklist.Add(Op0I);
I.setOperand(0, Op0I->getOperand(0));
I.setOperand(1, NewRHS);
return &I;
}
}
}
}
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
if (X == Op1)
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
if (X == Op0)
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1);
if (Op1I) {
Value *A, *B;
if (match(Op1I, m_Or(m_Value(A), m_Value(B)))) {
if (A == Op0) { // B^(B|A) == (A|B)^B
Op1I->swapOperands();
I.swapOperands();
std::swap(Op0, Op1);
} else if (B == Op0) { // B^(A|B) == (A|B)^B
I.swapOperands(); // Simplified below.
std::swap(Op0, Op1);
}
} else if (match(Op1I, m_Xor(m_Specific(Op0), m_Value(B)))) {
return ReplaceInstUsesWith(I, B); // A^(A^B) == B
} else if (match(Op1I, m_Xor(m_Value(A), m_Specific(Op0)))) {
return ReplaceInstUsesWith(I, A); // A^(B^A) == B
} else if (match(Op1I, m_And(m_Value(A), m_Value(B))) &&
Op1I->hasOneUse()){
if (A == Op0) { // A^(A&B) -> A^(B&A)
Op1I->swapOperands();
std::swap(A, B);
}
if (B == Op0) { // A^(B&A) -> (B&A)^A
I.swapOperands(); // Simplified below.
std::swap(Op0, Op1);
}
}
}
BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0);
if (Op0I) {
Value *A, *B;
if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
Op0I->hasOneUse()) {
if (A == Op1) // (B|A)^B == (A|B)^B
std::swap(A, B);
if (B == Op1) // (A|B)^B == A & ~B
return BinaryOperator::CreateAnd(A, Builder->CreateNot(Op1, "tmp"));
} else if (match(Op0I, m_Xor(m_Specific(Op1), m_Value(B)))) {
return ReplaceInstUsesWith(I, B); // (A^B)^A == B
} else if (match(Op0I, m_Xor(m_Value(A), m_Specific(Op1)))) {
return ReplaceInstUsesWith(I, A); // (B^A)^A == B
} else if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
Op0I->hasOneUse()){
if (A == Op1) // (A&B)^A -> (B&A)^A
std::swap(A, B);
if (B == Op1 && // (B&A)^A == ~B & A
!isa<ConstantInt>(Op1)) { // Canonical form is (B&C)^C
return BinaryOperator::CreateAnd(Builder->CreateNot(A, "tmp"), Op1);
}
}
}
// (X >> Z) ^ (Y >> Z) -> (X^Y) >> Z for all shifts.
if (Op0I && Op1I && Op0I->isShift() &&
Op0I->getOpcode() == Op1I->getOpcode() &&
Op0I->getOperand(1) == Op1I->getOperand(1) &&
(Op1I->hasOneUse() || Op1I->hasOneUse())) {
Value *NewOp =
Builder->CreateXor(Op0I->getOperand(0), Op1I->getOperand(0),
Op0I->getName());
return BinaryOperator::Create(Op1I->getOpcode(), NewOp,
Op1I->getOperand(1));
}
if (Op0I && Op1I) {
Value *A, *B, *C, *D;
// (A & B)^(A | B) -> A ^ B
if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
match(Op1I, m_Or(m_Value(C), m_Value(D)))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::CreateXor(A, B);
}
// (A | B)^(A & B) -> A ^ B
if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
match(Op1I, m_And(m_Value(C), m_Value(D)))) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::CreateXor(A, B);
}
// (A & B)^(C & D)
if ((Op0I->hasOneUse() || Op1I->hasOneUse()) &&
match(Op0I, m_And(m_Value(A), m_Value(B))) &&
match(Op1I, m_And(m_Value(C), m_Value(D)))) {
// (X & Y)^(X & Y) -> (Y^Z) & X
Value *X = 0, *Y = 0, *Z = 0;
if (A == C)
X = A, Y = B, Z = D;
else if (A == D)
X = A, Y = B, Z = C;
else if (B == C)
X = B, Y = A, Z = D;
else if (B == D)
X = B, Y = A, Z = C;
if (X) {
Value *NewOp = Builder->CreateXor(Y, Z, Op0->getName());
return BinaryOperator::CreateAnd(NewOp, X);
}
}
}
// (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)
if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
return R;
// fold (xor (cast A), (cast B)) -> (cast (xor A, B))
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (Op0C->getOpcode() == Op1C->getOpcode()) { // same cast kind?
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
I.getType(), TD) &&
ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
I.getType(), TD)) {
Value *NewOp = Builder->CreateXor(Op0C->getOperand(0),
Op1C->getOperand(0), I.getName());
return CastInst::Create(Op0C->getOpcode(), NewOp, I.getType());
}
}
}
return Changed ? &I : 0;
}
static ConstantInt *ExtractElement(Constant *V, Constant *Idx,
LLVMContext *Context) {
return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx));
}
static bool HasAddOverflow(ConstantInt *Result,
ConstantInt *In1, ConstantInt *In2,
bool IsSigned) {
if (IsSigned)
if (In2->getValue().isNegative())
return Result->getValue().sgt(In1->getValue());
else
return Result->getValue().slt(In1->getValue());
else
return Result->getValue().ult(In1->getValue());
}
/// AddWithOverflow - Compute Result = In1+In2, returning true if the result
/// overflowed for this type.
static bool AddWithOverflow(Constant *&Result, Constant *In1,
Constant *In2, LLVMContext *Context,
bool IsSigned = false) {
Result = ConstantExpr::getAdd(In1, In2);
if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
Constant *Idx = ConstantInt::get(Type::getInt32Ty(*Context), i);
if (HasAddOverflow(ExtractElement(Result, Idx, Context),
ExtractElement(In1, Idx, Context),
ExtractElement(In2, Idx, Context),
IsSigned))
return true;
}
return false;
}
return HasAddOverflow(cast<ConstantInt>(Result),
cast<ConstantInt>(In1), cast<ConstantInt>(In2),
IsSigned);
}
static bool HasSubOverflow(ConstantInt *Result,
ConstantInt *In1, ConstantInt *In2,
bool IsSigned) {
if (IsSigned)
if (In2->getValue().isNegative())
return Result->getValue().slt(In1->getValue());
else
return Result->getValue().sgt(In1->getValue());
else
return Result->getValue().ugt(In1->getValue());
}
/// SubWithOverflow - Compute Result = In1-In2, returning true if the result
/// overflowed for this type.
static bool SubWithOverflow(Constant *&Result, Constant *In1,
Constant *In2, LLVMContext *Context,
bool IsSigned = false) {
Result = ConstantExpr::getSub(In1, In2);
if (const VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
Constant *Idx = ConstantInt::get(Type::getInt32Ty(*Context), i);
if (HasSubOverflow(ExtractElement(Result, Idx, Context),
ExtractElement(In1, Idx, Context),
ExtractElement(In2, Idx, Context),
IsSigned))
return true;
}
return false;
}
return HasSubOverflow(cast<ConstantInt>(Result),
cast<ConstantInt>(In1), cast<ConstantInt>(In2),
IsSigned);
}
/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
/// code necessary to compute the offset from the base pointer (without adding
/// in the base pointer). Return the result as a signed integer of intptr size.
static Value *EmitGEPOffset(User *GEP, Instruction &I, InstCombiner &IC) {
TargetData &TD = *IC.getTargetData();
gep_type_iterator GTI = gep_type_begin(GEP);
const Type *IntPtrTy = TD.getIntPtrType(I.getContext());
Value *Result = Constant::getNullValue(IntPtrTy);
// Build a mask for high order bits.
unsigned IntPtrWidth = TD.getPointerSizeInBits();
uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
++i, ++GTI) {
Value *Op = *i;
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
if (OpC->isZero()) continue;
// Handle a struct index, which adds its field offset to the pointer.
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
Result = IC.Builder->CreateAdd(Result,
ConstantInt::get(IntPtrTy, Size),
GEP->getName()+".offs");
continue;
}
Constant *Scale = ConstantInt::get(IntPtrTy, Size);
Constant *OC =
ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
Scale = ConstantExpr::getMul(OC, Scale);
// Emit an add instruction.
Result = IC.Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
continue;
}
// Convert to correct type.
if (Op->getType() != IntPtrTy)
Op = IC.Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
if (Size != 1) {
Constant *Scale = ConstantInt::get(IntPtrTy, Size);
// We'll let instcombine(mul) convert this to a shl if possible.
Op = IC.Builder->CreateMul(Op, Scale, GEP->getName()+".idx");
}
// Emit an add instruction.
Result = IC.Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
}
return Result;
}
/// EvaluateGEPOffsetExpression - Return a value that can be used to compare
/// the *offset* implied by a GEP to zero. For example, if we have &A[i], we
/// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can
/// be complex, and scales are involved. The above expression would also be
/// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32).
/// This later form is less amenable to optimization though, and we are allowed
/// to generate the first by knowing that pointer arithmetic doesn't overflow.
///
/// If we can't emit an optimized form for this expression, this returns null.
///
static Value *EvaluateGEPOffsetExpression(User *GEP, Instruction &I,
InstCombiner &IC) {
TargetData &TD = *IC.getTargetData();
gep_type_iterator GTI = gep_type_begin(GEP);
// Check to see if this gep only has a single variable index. If so, and if
// any constant indices are a multiple of its scale, then we can compute this
// in terms of the scale of the variable index. For example, if the GEP
// implies an offset of "12 + i*4", then we can codegen this as "3 + i",
// because the expression will cross zero at the same point.
unsigned i, e = GEP->getNumOperands();
int64_t Offset = 0;
for (i = 1; i != e; ++i, ++GTI) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
// Compute the aggregate offset of constant indices.
if (CI->isZero()) continue;
// Handle a struct index, which adds its field offset to the pointer.
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
} else {
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
Offset += Size*CI->getSExtValue();
}
} else {
// Found our variable index.
break;
}
}
// If there are no variable indices, we must have a constant offset, just
// evaluate it the general way.
if (i == e) return 0;
Value *VariableIdx = GEP->getOperand(i);
// Determine the scale factor of the variable element. For example, this is
// 4 if the variable index is into an array of i32.
uint64_t VariableScale = TD.getTypeAllocSize(GTI.getIndexedType());
// Verify that there are no other variable indices. If so, emit the hard way.
for (++i, ++GTI; i != e; ++i, ++GTI) {
ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
if (!CI) return 0;
// Compute the aggregate offset of constant indices.
if (CI->isZero()) continue;
// Handle a struct index, which adds its field offset to the pointer.
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
} else {
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
Offset += Size*CI->getSExtValue();
}
}
// Okay, we know we have a single variable index, which must be a
// pointer/array/vector index. If there is no offset, life is simple, return
// the index.
unsigned IntPtrWidth = TD.getPointerSizeInBits();
if (Offset == 0) {
// Cast to intptrty in case a truncation occurs. If an extension is needed,
// we don't need to bother extending: the extension won't affect where the
// computation crosses zero.
if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth)
VariableIdx = new TruncInst(VariableIdx,
TD.getIntPtrType(VariableIdx->getContext()),
VariableIdx->getName(), &I);
return VariableIdx;
}
// Otherwise, there is an index. The computation we will do will be modulo
// the pointer size, so get it.
uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
Offset &= PtrSizeMask;
VariableScale &= PtrSizeMask;
// To do this transformation, any constant index must be a multiple of the
// variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
// but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
// multiple of the variable scale.
int64_t NewOffs = Offset / (int64_t)VariableScale;
if (Offset != NewOffs*(int64_t)VariableScale)
return 0;
// Okay, we can do this evaluation. Start by converting the index to intptr.
const Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
if (VariableIdx->getType() != IntPtrTy)
VariableIdx = CastInst::CreateIntegerCast(VariableIdx, IntPtrTy,
true /*SExt*/,
VariableIdx->getName(), &I);
Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
return BinaryOperator::CreateAdd(VariableIdx, OffsetVal, "offset", &I);
}
/// FoldGEPICmp - Fold comparisons between a GEP instruction and something
/// else. At this point we know that the GEP is on the LHS of the comparison.
Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
ICmpInst::Predicate Cond,
Instruction &I) {
// Look through bitcasts.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS))
RHS = BCI->getOperand(0);
Value *PtrBase = GEPLHS->getOperand(0);
if (TD && PtrBase == RHS && GEPLHS->isInBounds()) {
// ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
// This transformation (ignoring the base and scales) is valid because we
// know pointers can't overflow since the gep is inbounds. See if we can
// output an optimized form.
Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, I, *this);
// If not, synthesize the offset the hard way.
if (Offset == 0)
Offset = EmitGEPOffset(GEPLHS, I, *this);
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
Constant::getNullValue(Offset->getType()));
} else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
// If the base pointers are different, but the indices are the same, just
// compare the base pointer.
if (PtrBase != GEPRHS->getOperand(0)) {
bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
GEPRHS->getOperand(0)->getType();
if (IndicesTheSame)
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
IndicesTheSame = false;
break;
}
// If all indices are the same, just compare the base pointers.
if (IndicesTheSame)
return new ICmpInst(ICmpInst::getSignedPredicate(Cond),
GEPLHS->getOperand(0), GEPRHS->getOperand(0));
// Otherwise, the base pointers are different and the indices are
// different, bail out.
return 0;
}
// If one of the GEPs has all zero indices, recurse.
bool AllZeros = true;
for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPLHS->getOperand(i)) ||
!cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
AllZeros = false;
break;
}
if (AllZeros)
return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
ICmpInst::getSwappedPredicate(Cond), I);
// If the other GEP has all zero indices, recurse.
AllZeros = true;
for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPRHS->getOperand(i)) ||
!cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
AllZeros = false;
break;
}
if (AllZeros)
return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
// If the GEPs only differ by one index, compare it.
unsigned NumDifferences = 0; // Keep track of # differences.
unsigned DiffOperand = 0; // The operand that differs.
for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
// Irreconcilable differences.
NumDifferences = 2;
break;
} else {
if (NumDifferences++) break;
DiffOperand = i;
}
}
if (NumDifferences == 0) // SAME GEP?
return ReplaceInstUsesWith(I, // No comparison is needed here.
ConstantInt::get(Type::getInt1Ty(*Context),
ICmpInst::isTrueWhenEqual(Cond)));
else if (NumDifferences == 1) {
Value *LHSV = GEPLHS->getOperand(DiffOperand);
Value *RHSV = GEPRHS->getOperand(DiffOperand);
// Make sure we do a signed comparison here.
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
}
}
// Only lower this if the icmp is the only user of the GEP or if we expect
// the result to fold to a constant!
if (TD &&
(isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
(isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
// ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
Value *L = EmitGEPOffset(GEPLHS, I, *this);
Value *R = EmitGEPOffset(GEPRHS, I, *this);
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
}
}
return 0;
}
/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
///
Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
Instruction *LHSI,
Constant *RHSC) {
if (!isa<ConstantFP>(RHSC)) return 0;
const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
// Get the width of the mantissa. We don't want to hack on conversions that
// might lose information from the integer, e.g. "i64 -> float"
int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
if (MantissaWidth == -1) return 0; // Unknown.
// Check to see that the input is converted from an integer type that is small
// enough that preserves all bits. TODO: check here for "known" sign bits.
// This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits();
// If this is a uitofp instruction, we need an extra bit to hold the sign.
bool LHSUnsigned = isa<UIToFPInst>(LHSI);
if (LHSUnsigned)
++InputSize;
// If the conversion would lose info, don't hack on this.
if ((int)InputSize > MantissaWidth)
return 0;
// Otherwise, we can potentially simplify the comparison. We know that it
// will always come through as an integer value and we know the constant is
// not a NAN (it would have been previously simplified).
assert(!RHS.isNaN() && "NaN comparison not already folded!");
ICmpInst::Predicate Pred;
switch (I.getPredicate()) {
default: llvm_unreachable("Unexpected predicate!");
case FCmpInst::FCMP_UEQ:
case FCmpInst::FCMP_OEQ:
Pred = ICmpInst::ICMP_EQ;
break;
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_OGT:
Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
break;
case FCmpInst::FCMP_UGE:
case FCmpInst::FCMP_OGE:
Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
break;
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_OLT:
Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
break;
case FCmpInst::FCMP_ULE:
case FCmpInst::FCMP_OLE:
Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
break;
case FCmpInst::FCMP_UNE:
case FCmpInst::FCMP_ONE:
Pred = ICmpInst::ICMP_NE;
break;
case FCmpInst::FCMP_ORD:
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
case FCmpInst::FCMP_UNO:
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
}
const IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
// Now we know that the APFloat is a normal number, zero or inf.
// See if the FP constant is too large for the integer. For example,
// comparing an i8 to 300.0.
unsigned IntWidth = IntTy->getScalarSizeInBits();
if (!LHSUnsigned) {
// If the RHS value is > SignedMax, fold the comparison. This handles +INF
// and large values.
APFloat SMax(RHS.getSemantics(), APFloat::fcZero, false);
SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
APFloat::rmNearestTiesToEven);
if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
Pred == ICmpInst::ICMP_SLE)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
}
} else {
// If the RHS value is > UnsignedMax, fold the comparison. This handles
// +INF and large values.
APFloat UMax(RHS.getSemantics(), APFloat::fcZero, false);
UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
APFloat::rmNearestTiesToEven);
if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
Pred == ICmpInst::ICMP_ULE)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
}
}
if (!LHSUnsigned) {
// See if the RHS value is < SignedMin.
APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false);
SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
APFloat::rmNearestTiesToEven);
if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
Pred == ICmpInst::ICMP_SGE)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
}
}
// Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
// [0, UMAX], but it may still be fractional. See if it is fractional by
// casting the FP value to the integer value and back, checking for equality.
// Don't do this for zero, because -0.0 is not fractional.
Constant *RHSInt = LHSUnsigned
? ConstantExpr::getFPToUI(RHSC, IntTy)
: ConstantExpr::getFPToSI(RHSC, IntTy);
if (!RHS.isZero()) {
bool Equal = LHSUnsigned
? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
: ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
if (!Equal) {
// If we had a comparison against a fractional value, we have to adjust
// the compare predicate and sometimes the value. RHSC is rounded towards
// zero at this point.
switch (Pred) {
default: llvm_unreachable("Unexpected integer comparison!");
case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
case ICmpInst::ICMP_ULE:
// (float)int <= 4.4 --> int <= 4
// (float)int <= -4.4 --> false
if (RHS.isNegative())
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
case ICmpInst::ICMP_SLE:
// (float)int <= 4.4 --> int <= 4
// (float)int <= -4.4 --> int < -4
if (RHS.isNegative())
Pred = ICmpInst::ICMP_SLT;
break;
case ICmpInst::ICMP_ULT:
// (float)int < -4.4 --> false
// (float)int < 4.4 --> int <= 4
if (RHS.isNegative())
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
Pred = ICmpInst::ICMP_ULE;
break;
case ICmpInst::ICMP_SLT:
// (float)int < -4.4 --> int < -4
// (float)int < 4.4 --> int <= 4
if (!RHS.isNegative())
Pred = ICmpInst::ICMP_SLE;
break;
case ICmpInst::ICMP_UGT:
// (float)int > 4.4 --> int > 4
// (float)int > -4.4 --> true
if (RHS.isNegative())
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
break;
case ICmpInst::ICMP_SGT:
// (float)int > 4.4 --> int > 4
// (float)int > -4.4 --> int >= -4
if (RHS.isNegative())
Pred = ICmpInst::ICMP_SGE;
break;
case ICmpInst::ICMP_UGE:
// (float)int >= -4.4 --> true
// (float)int >= 4.4 --> int > 4
if (!RHS.isNegative())
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
Pred = ICmpInst::ICMP_UGT;
break;
case ICmpInst::ICMP_SGE:
// (float)int >= -4.4 --> int >= -4
// (float)int >= 4.4 --> int > 4
if (!RHS.isNegative())
Pred = ICmpInst::ICMP_SGT;
break;
}
}
}
// Lower this FP comparison into an appropriate integer version of the
// comparison.
return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
}
Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
bool Changed = SimplifyCompare(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// Fold trivial predicates.
if (I.getPredicate() == FCmpInst::FCMP_FALSE)
return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), 0));
if (I.getPredicate() == FCmpInst::FCMP_TRUE)
return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), 1));
// Simplify 'fcmp pred X, X'
if (Op0 == Op1) {
switch (I.getPredicate()) {
default: llvm_unreachable("Unknown predicate!");
case FCmpInst::FCMP_UEQ: // True if unordered or equal
case FCmpInst::FCMP_UGE: // True if unordered, greater than, or equal
case FCmpInst::FCMP_ULE: // True if unordered, less than, or equal
return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), 1));
case FCmpInst::FCMP_OGT: // True if ordered and greater than
case FCmpInst::FCMP_OLT: // True if ordered and less than
case FCmpInst::FCMP_ONE: // True if ordered and operands are unequal
return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), 0));
case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
case FCmpInst::FCMP_ULT: // True if unordered or less than
case FCmpInst::FCMP_UGT: // True if unordered or greater than
case FCmpInst::FCMP_UNE: // True if unordered or not equal
// Canonicalize these to be 'fcmp uno %X, 0.0'.
I.setPredicate(FCmpInst::FCMP_UNO);
I.setOperand(1, Constant::getNullValue(Op0->getType()));
return &I;
case FCmpInst::FCMP_ORD: // True if ordered (no nans)
case FCmpInst::FCMP_OEQ: // True if ordered and equal
case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
// Canonicalize these to be 'fcmp ord %X, 0.0'.
I.setPredicate(FCmpInst::FCMP_ORD);
I.setOperand(1, Constant::getNullValue(Op0->getType()));
return &I;
}
}
if (isa<UndefValue>(Op1)) // fcmp pred X, undef -> undef
return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
// Handle fcmp with constant RHS
if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
// If the constant is a nan, see if we can fold the comparison based on it.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
if (CFP->getValueAPF().isNaN()) {
if (FCmpInst::isOrdered(I.getPredicate())) // True if ordered and...
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
assert(FCmpInst::isUnordered(I.getPredicate()) &&
"Comparison must be either ordered or unordered!");
// True if unordered.
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
}
}
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::PHI:
// Only fold fcmp into the PHI if the phi and fcmp are in the same
// block. If in the same block, we're encouraging jump threading. If
// not, we are just pessimizing the code by making an i1 phi.
if (LHSI->getParent() == I.getParent())
if (Instruction *NV = FoldOpIntoPhi(I, true))
return NV;
break;
case Instruction::SIToFP:
case Instruction::UIToFP:
if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC))
return NV;
break;
case Instruction::Select:
// If either operand of the select is a constant, we can fold the
// comparison into the select arms, which will cause one to be
// constant folded and the select turned into a bitwise or.
Value *Op1 = 0, *Op2 = 0;
if (LHSI->hasOneUse()) {
if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
// Fold the known value into the constant operand.
Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
// Insert a new FCmp of the other select operand.
Op2 = Builder->CreateFCmp(I.getPredicate(),
LHSI->getOperand(2), RHSC, I.getName());
} else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
// Fold the known value into the constant operand.
Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
// Insert a new FCmp of the other select operand.
Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1),
RHSC, I.getName());
}
}
if (Op1)
return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
break;
}
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool Changed = SimplifyCompare(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
const Type *Ty = Op0->getType();
// icmp X, X
if (Op0 == Op1)
return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(),
I.isTrueWhenEqual()));
if (isa<UndefValue>(Op1)) // X icmp undef -> undef
return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
// icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
// addresses never equal each other! We already know that Op0 != Op1.
if ((isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0) ||
isa<ConstantPointerNull>(Op0)) &&
(isa<GlobalValue>(Op1) || isa<AllocaInst>(Op1) ||
isa<ConstantPointerNull>(Op1)))
return ReplaceInstUsesWith(I, ConstantInt::get(Type::getInt1Ty(*Context),
!I.isTrueWhenEqual()));
// icmp's with boolean values can always be turned into bitwise operations
if (Ty == Type::getInt1Ty(*Context)) {
switch (I.getPredicate()) {
default: llvm_unreachable("Invalid icmp instruction!");
case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B)
Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp");
return BinaryOperator::CreateNot(Xor);
}
case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B
return BinaryOperator::CreateXor(Op0, Op1);
case ICmpInst::ICMP_UGT:
std::swap(Op0, Op1); // Change icmp ugt -> icmp ult
// FALL THROUGH
case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B
Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
return BinaryOperator::CreateAnd(Not, Op1);
}
case ICmpInst::ICMP_SGT:
std::swap(Op0, Op1); // Change icmp sgt -> icmp slt
// FALL THROUGH
case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B
Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
return BinaryOperator::CreateAnd(Not, Op0);
}
case ICmpInst::ICMP_UGE:
std::swap(Op0, Op1); // Change icmp uge -> icmp ule
// FALL THROUGH
case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B
Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
return BinaryOperator::CreateOr(Not, Op1);
}
case ICmpInst::ICMP_SGE:
std::swap(Op0, Op1); // Change icmp sge -> icmp sle
// FALL THROUGH
case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B
Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
return BinaryOperator::CreateOr(Not, Op0);
}
}
}
unsigned BitWidth = 0;
if (TD)
BitWidth = TD->getTypeSizeInBits(Ty->getScalarType());
else if (Ty->isIntOrIntVector())
BitWidth = Ty->getScalarSizeInBits();
bool isSignBit = false;
// See if we are doing a comparison with a constant.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A = 0, *B = 0;
// (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
if (I.isEquality() && CI->isNullValue() &&
match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
// (icmp cond A B) if cond is equality
return new ICmpInst(I.getPredicate(), A, B);
}
// If we have an icmp le or icmp ge instruction, turn it into the
// appropriate icmp lt or icmp gt instruction. This allows us to rely on
// them being folded in the code below.
switch (I.getPredicate()) {
default: break;
case ICmpInst::ICMP_ULE:
if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return new ICmpInst(ICmpInst::ICMP_ULT, Op0,
AddOne(CI));
case ICmpInst::ICMP_SLE:
if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
AddOne(CI));
case ICmpInst::ICMP_UGE:
if (CI->isMinValue(false)) // A >=u MIN -> TRUE
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return new ICmpInst(ICmpInst::ICMP_UGT, Op0,
SubOne(CI));
case ICmpInst::ICMP_SGE:
if (CI->isMinValue(true)) // A >=s MIN -> TRUE
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
SubOne(CI));
}
// If this comparison is a normal comparison, it demands all
// bits, if it is a sign bit comparison, it only demands the sign bit.
bool UnusedBit;
isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
}
// See if we can fold the comparison based on range information we can get
// by checking whether bits are known to be zero or one in the input.
if (BitWidth != 0) {
APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0);
APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0);
if (SimplifyDemandedBits(I.getOperandUse(0),
isSignBit ? APInt::getSignBit(BitWidth)
: APInt::getAllOnesValue(BitWidth),
Op0KnownZero, Op0KnownOne, 0))
return &I;
if (SimplifyDemandedBits(I.getOperandUse(1),
APInt::getAllOnesValue(BitWidth),
Op1KnownZero, Op1KnownOne, 0))
return &I;
// Given the known and unknown bits, compute a range that the LHS could be
// in. Compute the Min, Max and RHS values based on the known bits. For the
// EQ and NE we use unsigned values.
APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
if (ICmpInst::isSignedPredicate(I.getPredicate())) {
ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
Op0Min, Op0Max);
ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
Op1Min, Op1Max);
} else {
ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
Op0Min, Op0Max);
ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
Op1Min, Op1Max);
}
// If Min and Max are known to be the same, then SimplifyDemandedBits
// figured out that the LHS is a constant. Just constant fold this now so
// that code below can assume that Min != Max.
if (!isa<Constant>(Op0) && Op0Min == Op0Max)
return new ICmpInst(I.getPredicate(),
ConstantInt::get(*Context, Op0Min), Op1);
if (!isa<Constant>(Op1) && Op1Min == Op1Max)
return new ICmpInst(I.getPredicate(), Op0,
ConstantInt::get(*Context, Op1Min));
// Based on the range information we know about the LHS, see if we can
// simplify this comparison. For example, (x&4) < 8 is always true.
switch (I.getPredicate()) {
default: llvm_unreachable("Unknown icmp opcode!");
case ICmpInst::ICMP_EQ:
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
case ICmpInst::ICMP_NE:
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
break;
case ICmpInst::ICMP_ULT:
if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
SubOne(CI));
// (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
if (CI->isMinValue(true))
return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
Constant::getAllOnesValue(Op0->getType()));
}
break;
case ICmpInst::ICMP_UGT:
if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
AddOne(CI));
// (x >u 2147483647) -> (x <s 0) -> true if sign bit set
if (CI->isMaxValue(true))
return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
Constant::getNullValue(Op0->getType()));
}
break;
case ICmpInst::ICMP_SLT:
if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
SubOne(CI));
}
break;
case ICmpInst::ICMP_SGT:
if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C
return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
AddOne(CI));
}
break;
case ICmpInst::ICMP_SGE:
assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
case ICmpInst::ICMP_SLE:
assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
case ICmpInst::ICMP_UGE:
assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
case ICmpInst::ICMP_ULE:
assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(*Context));
if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
return ReplaceInstUsesWith(I, ConstantInt::getFalse(*Context));
break;
}
// Turn a signed comparison into an unsigned one if both operands
// are known to have the same sign.
if (I.isSignedPredicate() &&
((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) ||
(Op0KnownOne.isNegative() && Op1KnownOne.isNegative())))
return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
}
// Test if the ICmpInst instruction is used exclusively by a select as
// part of a minimum or maximum operation. If so, refrain from doing
// any other folding. This helps out other analyses which understand
// non-obfuscated minimum and maximum idioms, such as ScalarEvolution
// and CodeGen. And in this case, at least one of the comparison
// operands has at least one user besides the compare (the select),
// which would often largely negate the benefit of folding anyway.
if (I.hasOneUse())
if (SelectInst *SI = dyn_cast<SelectInst>(*I.use_begin()))
if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
(SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
return 0;
// See if we are doing a comparison between a constant and an instruction that
// can be folded into the comparison.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
// Since the RHS is a ConstantInt (CI), if the left hand side is an
// instruction, see if that instruction also has constants so that the
// instruction can be folded into the icmp
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI))
return Res;
}
// Handle icmp with constant (but not simple integer constant) RHS
if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::GetElementPtr:
if (RHSC->isNullValue()) {
// icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
bool isAllZeros = true;
for (unsigned i = 1, e = LHSI->getNumOperands(); i != e; ++i)
if (!isa<Constant>(LHSI->getOperand(i)) ||
!cast<Constant>(LHSI->getOperand(i))->isNullValue()) {
isAllZeros = false;
break;
}
if (isAllZeros)
return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
Constant::getNullValue(LHSI->getOperand(0)->getType()));
}
break;
case Instruction::PHI:
// Only fold icmp into the PHI if the phi and icmp are in the same
// block. If in the same block, we're encouraging jump threading. If
// not, we are just pessimizing the code by making an i1 phi.
if (LHSI->getParent() == I.getParent())
if (Instruction *NV = FoldOpIntoPhi(I, true))
return NV;
break;
case Instruction::Select: {
// If either operand of the select is a constant, we can fold the
// comparison into the select arms, which will cause one to be
// constant folded and the select turned into a bitwise or.
Value *Op1 = 0, *Op2 = 0;
if (LHSI->hasOneUse()) {
if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
// Fold the known value into the constant operand.
Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
// Insert a new ICmp of the other select operand.
Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2),
RHSC, I.getName());
} else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
// Fold the known value into the constant operand.
Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
// Insert a new ICmp of the other select operand.
Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1),
RHSC, I.getName());
}
}
if (Op1)
return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
break;
}
case Instruction::Malloc:
// If we have (malloc != null), and if the malloc has a single use, we
// can assume it is successful and remove the malloc.
if (LHSI->hasOneUse() && isa<ConstantPointerNull>(RHSC)) {
Worklist.Add(LHSI);
return ReplaceInstUsesWith(I,
ConstantInt::get(Type::getInt1Ty(*Context),
!I.isTrueWhenEqual()));
}
break;
case Instruction::Call:
// If we have (malloc != null), and if the malloc has a single use, we
// can assume it is successful and remove the malloc.
if (isMalloc(LHSI) && LHSI->hasOneUse() &&
isa<ConstantPointerNull>(RHSC)) {
Worklist.Add(LHSI);
return ReplaceInstUsesWith(I,
ConstantInt::get(Type::getInt1Ty(*Context),
!I.isTrueWhenEqual()));
}
break;
}
}
// If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I))
return NI;
if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
if (Instruction *NI = FoldGEPICmp(GEP, Op0,
ICmpInst::getSwappedPredicate(I.getPredicate()), I))
return NI;
// Test to see if the operands of the icmp are casted versions of other
// values. If the ptr->ptr cast can be stripped off both arguments, we do so
// now.
if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
if (isa<PointerType>(Op0->getType()) &&
(isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
// We keep moving the cast from the left operand over to the right
// operand, where it can often be eliminated completely.
Op0 = CI->getOperand(0);
// If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
// so eliminate it as well.
if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
Op1 = CI2->getOperand(0);
// If Op1 is a constant, we can fold the cast into the constant.
if (Op0->getType() != Op1->getType()) {
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
} else {
// Otherwise, cast the RHS right before the icmp
Op1 = Builder->CreateBitCast(Op1, Op0->getType());
}
}
return new ICmpInst(I.getPredicate(), Op0, Op1);
}
}
if (isa<CastInst>(Op0)) {
// Handle the special case of: icmp (cast bool to X), <cst>
// This comes up when you have code like
// int X = A < B;
// if (X) ...
// For generality, we handle any zero-extension of any operand comparison
// with a constant or another cast from the same type.
if (isa<ConstantInt>(Op1) || isa<CastInst>(Op1))
if (Instruction *R = visitICmpInstWithCastAndCast(I))
return R;
}
// See if it's the same type of instruction on the left and right.
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
if (Op0I->getOpcode() == Op1I->getOpcode() && Op0I->hasOneUse() &&
Op1I->hasOneUse() && Op0I->getOperand(1) == Op1I->getOperand(1)) {
switch (Op0I->getOpcode()) {
default: break;
case Instruction::Add:
case Instruction::Sub:
case Instruction::Xor:
if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
return new ICmpInst(I.getPredicate(), Op0I->getOperand(0),
Op1I->getOperand(0));
// icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
if (CI->getValue().isSignBit()) {
ICmpInst::Predicate Pred = I.isSignedPredicate()
? I.getUnsignedPredicate()
: I.getSignedPredicate();
return new ICmpInst(Pred, Op0I->getOperand(0),
Op1I->getOperand(0));
}
if (CI->getValue().isMaxSignedValue()) {
ICmpInst::Predicate Pred = I.isSignedPredicate()
? I.getUnsignedPredicate()
: I.getSignedPredicate();
Pred = I.getSwappedPredicate(Pred);
return new ICmpInst(Pred, Op0I->getOperand(0),
Op1I->getOperand(0));
}
}
break;
case Instruction::Mul:
if (!I.isEquality())
break;
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
// a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
// Mask = -1 >> count-trailing-zeros(Cst).
if (!CI->isZero() && !CI->isOne()) {
const APInt &AP = CI->getValue();
ConstantInt *Mask = ConstantInt::get(*Context,
APInt::getLowBitsSet(AP.getBitWidth(),
AP.getBitWidth() -
AP.countTrailingZeros()));
Value *And1 = Builder->CreateAnd(Op0I->getOperand(0), Mask);
Value *And2 = Builder->CreateAnd(Op1I->getOperand(0), Mask);
return new ICmpInst(I.getPredicate(), And1, And2);
}
}
break;
}
}
}
}
// ~x < ~y --> y < x
{ Value *A, *B;
if (match(Op0, m_Not(m_Value(A))) &&
match(Op1, m_Not(m_Value(B))))
return new ICmpInst(I.getPredicate(), B, A);
}
if (I.isEquality()) {
Value *A, *B, *C, *D;
// -x == -y --> x == y
if (match(Op0, m_Neg(m_Value(A))) &&
match(Op1, m_Neg(m_Value(B))))
return new ICmpInst(I.getPredicate(), A, B);
if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
Value *OtherVal = A == Op1 ? B : A;
return new ICmpInst(I.getPredicate(), OtherVal,
Constant::getNullValue(A->getType()));
}
if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
// A^c1 == C^c2 --> A == C^(c1^c2)
ConstantInt *C1, *C2;
if (match(B, m_ConstantInt(C1)) &&
match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) {
Constant *NC =
ConstantInt::get(*Context, C1->getValue() ^ C2->getValue());
Value *Xor = Builder->CreateXor(C, NC, "tmp");
return new ICmpInst(I.getPredicate(), A, Xor);
}
// A^B == A^D -> B == D
if (A == C) return new ICmpInst(I.getPredicate(), B, D);
if (A == D) return new ICmpInst(I.getPredicate(), B, C);
if (B == C) return new ICmpInst(I.getPredicate(), A, D);
if (B == D) return new ICmpInst(I.getPredicate(), A, C);
}
}
if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
(A == Op0 || B == Op0)) {
// A == (A^B) -> B == 0
Value *OtherVal = A == Op0 ? B : A;
return new ICmpInst(I.getPredicate(), OtherVal,
Constant::getNullValue(A->getType()));
}
// (A-B) == A -> B == 0
if (match(Op0, m_Sub(m_Specific(Op1), m_Value(B))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));
// A == (A-B) -> B == 0
if (match(Op1, m_Sub(m_Specific(Op0), m_Value(B))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));
// (X&Z) == (Y&Z) -> (X^Y) & Z == 0
if (Op0->hasOneUse() && Op1->hasOneUse() &&
match(Op0, m_And(m_Value(A), m_Value(B))) &&
match(Op1, m_And(m_Value(C), m_Value(D)))) {
Value *X = 0, *Y = 0, *Z = 0;
if (A == C) {
X = B; Y = D; Z = A;
} else if (A == D) {
X = B; Y = C; Z = A;
} else if (B == C) {
X = A; Y = D; Z = B;
} else if (B == D) {
X = A; Y = C; Z = B;
}
if (X) { // Build (X^Y) & Z
Op1 = Builder->CreateXor(X, Y, "tmp");
Op1 = Builder->CreateAnd(Op1, Z, "tmp");
I.setOperand(0, Op1);
I.setOperand(1, Constant::getNullValue(Op1->getType()));
return &I;
}
}
}
return Changed ? &I : 0;
}
/// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS
/// and CmpRHS are both known to be integer constants.
Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS) {
ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1));
const APInt &CmpRHSV = CmpRHS->getValue();
// FIXME: If the operand types don't match the type of the divide
// then don't attempt this transform. The code below doesn't have the
// logic to deal with a signed divide and an unsigned compare (and
// vice versa). This is because (x /s C1) <s C2 produces different
// results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
// (x /u C1) <u C2. Simply casting the operands and result won't
// work. :( The if statement below tests that condition and bails
// if it finds it.
bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv;
if (!ICI.isEquality() && DivIsSigned != ICI.isSignedPredicate())
return 0;
if (DivRHS->isZero())
return 0; // The ProdOV computation fails on divide by zero.
if (DivIsSigned && DivRHS->isAllOnesValue())
return 0; // The overflow computation also screws up here
if (DivRHS->isOne())
return 0; // Not worth bothering, and eliminates some funny cases
// with INT_MIN.
// Compute Prod = CI * DivRHS. We are essentially solving an equation
// of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
// C2 (CI). By solving for X we can turn this into a range check
// instead of computing a divide.
Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS);
// Determine if the product overflows by seeing if the product is
// not equal to the divide. Make sure we do the same kind of divide
// as in the LHS instruction that we're folding.
bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
// Get the ICmp opcode
ICmpInst::Predicate Pred = ICI.getPredicate();
// Figure out the interval that is being checked. For example, a comparison
// like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
// Compute this interval based on the constants involved and the signedness of
// the compare/divide. This computes a half-open interval, keeping track of
// whether either value in the interval overflows. After analysis each
// overflow variable is set to 0 if it's corresponding bound variable is valid
// -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
int LoOverflow = 0, HiOverflow = 0;
Constant *LoBound = 0, *HiBound = 0;
if (!DivIsSigned) { // udiv
// e.g. X/5 op 3 --> [15, 20)
LoBound = Prod;
HiOverflow = LoOverflow = ProdOV;
if (!HiOverflow)
HiOverflow = AddWithOverflow(HiBound, LoBound, DivRHS, Context, false);
} else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0.
if (CmpRHSV == 0) { // (X / pos) op 0
// Can't overflow. e.g. X/2 op 0 --> [-1, 2)
LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
HiBound = DivRHS;
} else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos
LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
HiOverflow = LoOverflow = ProdOV;
if (!HiOverflow)
HiOverflow = AddWithOverflow(HiBound, Prod, DivRHS, Context, true);
} else { // (X / pos) op neg
// e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
HiBound = AddOne(Prod);
LoOverflow = HiOverflow = ProdOV ? -1 : 0;
if (!LoOverflow) {
ConstantInt* DivNeg =
cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, Context,
true) ? -1 : 0;
}
}
} else if (DivRHS->getValue().isNegative()) { // Divisor is < 0.
if (CmpRHSV == 0) { // (X / neg) op 0
// e.g. X/-5 op 0 --> [-4, 5)
LoBound = AddOne(DivRHS);
HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
if (HiBound == DivRHS) { // -INTMIN = INTMIN
HiOverflow = 1; // [INTMIN+1, overflow)
HiBound = 0; // e.g. X/INTMIN = 0 --> X > INTMIN
}
} else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos
// e.g. X/-5 op 3 --> [-19, -14)
HiBound = AddOne(Prod);
HiOverflow = LoOverflow = ProdOV ? -1 : 0;
if (!LoOverflow)
LoOverflow = AddWithOverflow(LoBound, HiBound,
DivRHS, Context, true) ? -1 : 0;
} else { // (X / neg) op neg
LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
LoOverflow = HiOverflow = ProdOV;
if (!HiOverflow)
HiOverflow = SubWithOverflow(HiBound, Prod, DivRHS, Context, true);
}
// Dividing by a negative swaps the condition. LT <-> GT
Pred = ICmpInst::getSwappedPredicate(Pred);
}
Value *X = DivI->getOperand(0);
switch (Pred) {
default: llvm_unreachable("Unhandled icmp opcode!");
case ICmpInst::ICMP_EQ:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned, true, ICI);
case ICmpInst::ICMP_NE:
if (LoOverflow && HiOverflow)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
else if (HiOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
ICmpInst::ICMP_ULT, X, LoBound);
else if (LoOverflow)
return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
ICmpInst::ICMP_UGE, X, HiBound);
else
return InsertRangeTest(X, LoBound, HiBound, DivIsSigned, false, ICI);
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT:
if (LoOverflow == +1) // Low bound is greater than input range.
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
if (LoOverflow == -1) // Low bound is less than input range.
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
return new ICmpInst(Pred, X, LoBound);
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
if (HiOverflow == +1) // High bound greater than input range.
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
else if (HiOverflow == -1) // High bound less than input range.
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
if (Pred == ICmpInst::ICMP_UGT)
return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
else
return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
}
}
/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
///
Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
Instruction *LHSI,
ConstantInt *RHS) {
const APInt &RHSV = RHS->getValue();
switch (LHSI->getOpcode()) {
case Instruction::Trunc:
if (ICI.isEquality() && LHSI->hasOneUse()) {
// Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
// of the high bits truncated out of x are known.
unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits();
APInt Mask(APInt::getHighBitsSet(SrcBits, SrcBits-DstBits));
APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
ComputeMaskedBits(LHSI->getOperand(0), Mask, KnownZero, KnownOne);
// If all the high bits are known, we can do this xform.
if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) {
// Pull in the high bits from known-ones set.
APInt NewRHS(RHS->getValue());
NewRHS.zext(SrcBits);
NewRHS |= KnownOne;
return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
ConstantInt::get(*Context, NewRHS));
}
}
break;
case Instruction::Xor: // (icmp pred (xor X, XorCST), CI)
if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// If this is a comparison that tests the signbit (X < 0) or (x > -1),
// fold the xor.
if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) ||
(ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) {
Value *CompareVal = LHSI->getOperand(0);
// If the sign bit of the XorCST is not set, there is no change to
// the operation, just stop using the Xor.
if (!XorCST->getValue().isNegative()) {
ICI.setOperand(0, CompareVal);
Worklist.Add(LHSI);
return &ICI;
}
// Was the old condition true if the operand is positive?
bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT;
// If so, the new one isn't.
isTrueIfPositive ^= true;
if (isTrueIfPositive)
return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal,
SubOne(RHS));
else
return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal,
AddOne(RHS));
}
if (LHSI->hasOneUse()) {
// (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit))
if (!ICI.isEquality() && XorCST->getValue().isSignBit()) {
const APInt &SignBit = XorCST->getValue();
ICmpInst::Predicate Pred = ICI.isSignedPredicate()
? ICI.getUnsignedPredicate()
: ICI.getSignedPredicate();
return new ICmpInst(Pred, LHSI->getOperand(0),
ConstantInt::get(*Context, RHSV ^ SignBit));
}
// (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A)
if (!ICI.isEquality() && XorCST->getValue().isMaxSignedValue()) {
const APInt &NotSignBit = XorCST->getValue();
ICmpInst::Predicate Pred = ICI.isSignedPredicate()
? ICI.getUnsignedPredicate()
: ICI.getSignedPredicate();
Pred = ICI.getSwappedPredicate(Pred);
return new ICmpInst(Pred, LHSI->getOperand(0),
ConstantInt::get(*Context, RHSV ^ NotSignBit));
}
}
}
break;
case Instruction::And: // (icmp pred (and X, AndCST), RHS)
if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
LHSI->getOperand(0)->hasOneUse()) {
ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
// If the LHS is an AND of a truncating cast, we can widen the
// and/compare to be the input width without changing the value
// produced, eliminating a cast.
if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) {
// We can do this transformation if either the AND constant does not
// have its sign bit set or if it is an equality comparison.
// Extending a relational comparison when we're checking the sign
// bit would not work.
if (Cast->hasOneUse() &&
(ICI.isEquality() ||
(AndCST->getValue().isNonNegative() && RHSV.isNonNegative()))) {
uint32_t BitWidth =
cast<IntegerType>(Cast->getOperand(0)->getType())->getBitWidth();
APInt NewCST = AndCST->getValue();
NewCST.zext(BitWidth);
APInt NewCI = RHSV;
NewCI.zext(BitWidth);
Value *NewAnd =
Builder->CreateAnd(Cast->getOperand(0),
ConstantInt::get(*Context, NewCST), LHSI->getName());
return new ICmpInst(ICI.getPredicate(), NewAnd,
ConstantInt::get(*Context, NewCI));
}
}
// If this is: (X >> C1) & C2 != C3 (where any shift and any compare
// could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
// happens a LOT in code produced by the C front-end, for bitfield
// access.
BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0));
if (Shift && !Shift->isShift())
Shift = 0;
ConstantInt *ShAmt;
ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0;
const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift.
const Type *AndTy = AndCST->getType(); // Type of the and.
// We can fold this as long as we can't shift unknown bits
// into the mask. This can only happen with signed shift
// rights, as they sign-extend.
if (ShAmt) {
bool CanFold = Shift->isLogicalShift();
if (!CanFold) {
// To test for the bad case of the signed shr, see if any
// of the bits shifted in could be tested after the mask.
uint32_t TyBits = Ty->getPrimitiveSizeInBits();
int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits);
uint32_t BitWidth = AndTy->getPrimitiveSizeInBits();
if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) &
AndCST->getValue()) == 0)
CanFold = true;
}
if (CanFold) {
Constant *NewCst;
if (Shift->getOpcode() == Instruction::Shl)
NewCst = ConstantExpr::getLShr(RHS, ShAmt);
else
NewCst = ConstantExpr::getShl(RHS, ShAmt);
// Check to see if we are shifting out any of the bits being
// compared.
if (ConstantExpr::get(Shift->getOpcode(),
NewCst, ShAmt) != RHS) {
// If we shifted bits out, the fold is not going to work out.
// As a special case, check to see if this means that the
// result is always true or false now.
if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
if (ICI.getPredicate() == ICmpInst::ICMP_NE)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
} else {
ICI.setOperand(1, NewCst);
Constant *NewAndCST;
if (Shift->getOpcode() == Instruction::Shl)
NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt);
else
NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
LHSI->setOperand(1, NewAndCST);
LHSI->setOperand(0, Shift->getOperand(0));
Worklist.Add(Shift); // Shift is dead.
return &ICI;
}
}
}
// Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is
// preferable because it allows the C<<Y expression to be hoisted out
// of a loop if Y is invariant and X is not.
if (Shift && Shift->hasOneUse() && RHSV == 0 &&
ICI.isEquality() && !Shift->isArithmeticShift() &&
!isa<Constant>(Shift->getOperand(0))) {
// Compute C << Y.
Value *NS;
if (Shift->getOpcode() == Instruction::LShr) {
NS = Builder->CreateShl(AndCST, Shift->getOperand(1), "tmp");
} else {
// Insert a logical shift.
NS = Builder->CreateLShr(AndCST, Shift->getOperand(1), "tmp");
}
// Compute X & (C << Y).
Value *NewAnd =
Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName());
ICI.setOperand(0, NewAnd);
return &ICI;
}
}
break;
case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI)
ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
if (!ShAmt) break;
uint32_t TypeBits = RHSV.getBitWidth();
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
if (ShAmt->uge(TypeBits))
break;
if (ICI.isEquality()) {
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
Constant *Comp =
ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt),
ShAmt);
if (Comp != RHS) {// Comparing against a bit that we know is zero.
bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
Constant *Cst = ConstantInt::get(Type::getInt1Ty(*Context), IsICMP_NE);
return ReplaceInstUsesWith(ICI, Cst);
}
if (LHSI->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
Constant *Mask =
ConstantInt::get(*Context, APInt::getLowBitsSet(TypeBits,
TypeBits-ShAmtVal));
Value *And =
Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask");
return new ICmpInst(ICI.getPredicate(), And,
ConstantInt::get(*Context, RHSV.lshr(ShAmtVal)));
}
}
// Otherwise, if this is a comparison of the sign bit, simplify to and/test.
bool TrueIfSigned = false;
if (LHSI->hasOneUse() &&
isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) {
// (X << 31) <s 0 --> (X&1) != 0
Constant *Mask = ConstantInt::get(*Context, APInt(TypeBits, 1) <<
(TypeBits-ShAmt->getZExtValue()-1));
Value *And =
Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask");
return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
And, Constant::getNullValue(And->getType()));
}
break;
}
case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
case Instruction::AShr: {
// Only handle equality comparisons of shift-by-constant.
ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
if (!ShAmt || !ICI.isEquality()) break;
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
// simplified.
uint32_t TypeBits = RHSV.getBitWidth();
if (ShAmt->uge(TypeBits))
break;
uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
// If we are comparing against bits always shifted out, the
// comparison cannot succeed.
APInt Comp = RHSV << ShAmtVal;
if (LHSI->getOpcode() == Instruction::LShr)
Comp = Comp.lshr(ShAmtVal);
else
Comp = Comp.ashr(ShAmtVal);
if (Comp != RHSV) { // Comparing against a bit that we know is zero.
bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
Constant *Cst = ConstantInt::get(Type::getInt1Ty(*Context), IsICMP_NE);
return ReplaceInstUsesWith(ICI, Cst);
}
// Otherwise, check to see if the bits shifted out are known to be zero.
// If so, we can compare against the unshifted value:
// (X & 4) >> 1 == 2 --> (X & 4) == 4.
if (LHSI->hasOneUse() &&
MaskedValueIsZero(LHSI->getOperand(0),
APInt::getLowBitsSet(Comp.getBitWidth(), ShAmtVal))) {
return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
ConstantExpr::getShl(RHS, ShAmt));
}
if (LHSI->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
Constant *Mask = ConstantInt::get(*Context, Val);
Value *And = Builder->CreateAnd(LHSI->getOperand(0),
Mask, LHSI->getName()+".mask");
return new ICmpInst(ICI.getPredicate(), And,
ConstantExpr::getShl(RHS, ShAmt));
}
break;
}
case Instruction::SDiv:
case Instruction::UDiv:
// Fold: icmp pred ([us]div X, C1), C2 -> range test
// Fold this div into the comparison, producing a range check.
// Determine, based on the divide type, what the range is being
// checked. If there is an overflow on the low or high side, remember
// it, otherwise compute the range [low, hi) bounding the new value.
// See: InsertRangeTest above for the kinds of replacements possible.
if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
DivRHS))
return R;
break;
case Instruction::Add:
// Fold: icmp pred (add, X, C1), C2
if (!ICI.isEquality()) {
ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1));
if (!LHSC) break;
const APInt &LHSV = LHSC->getValue();
ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV)
.subtract(LHSV);
if (ICI.isSignedPredicate()) {
if (CR.getLower().isSignBit()) {
return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0),
ConstantInt::get(*Context, CR.getUpper()));
} else if (CR.getUpper().isSignBit()) {
return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0),
ConstantInt::get(*Context, CR.getLower()));
}
} else {
if (CR.getLower().isMinValue()) {
return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0),
ConstantInt::get(*Context, CR.getUpper()));
} else if (CR.getUpper().isMinValue()) {
return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0),
ConstantInt::get(*Context, CR.getLower()));
}
}
}
break;
}
// Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
if (ICI.isEquality()) {
bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
// If the first operand is (add|sub|and|or|xor|rem) with a constant, and
// the second operand is a constant, simplify a bit.
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) {
switch (BO->getOpcode()) {
case Instruction::SRem:
// If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){
const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue();
if (V.sgt(APInt(V.getBitWidth(), 1)) && V.isPowerOf2()) {
Value *NewRem =
Builder->CreateURem(BO->getOperand(0), BO->getOperand(1),
BO->getName());
return new ICmpInst(ICI.getPredicate(), NewRem,
Constant::getNullValue(BO->getType()));
}
}
break;
case Instruction::Add:
// Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
if (BO->hasOneUse())
return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
ConstantExpr::getSub(RHS, BOp1C));
} else if (RHSV == 0) {
// Replace ((add A, B) != 0) with (A != -B) if A or B is
// efficiently invertible, or if the add has just this one use.
Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
if (Value *NegVal = dyn_castNegVal(BOp1))
return new ICmpInst(ICI.getPredicate(), BOp0, NegVal);
else if (Value *NegVal = dyn_castNegVal(BOp0))
return new ICmpInst(ICI.getPredicate(), NegVal, BOp1);
else if (BO->hasOneUse()) {
Value *Neg = Builder->CreateNeg(BOp1);
Neg->takeName(BO);
return new ICmpInst(ICI.getPredicate(), BOp0, Neg);
}
}
break;
case Instruction::Xor:
// For the xor case, we can xor two constants together, eliminating
// the explicit xor.
if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
ConstantExpr::getXor(RHS, BOC));
// FALLTHROUGH
case Instruction::Sub:
// Replace (([sub|xor] A, B) != 0) with (A != B)
if (RHSV == 0)
return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
BO->getOperand(1));
break;
case Instruction::Or:
// If bits are being or'd in that are not present in the constant we
// are comparing against, then the comparison could never succeed!
if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
Constant *NotCI = ConstantExpr::getNot(RHS);
if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
return ReplaceInstUsesWith(ICI,
ConstantInt::get(Type::getInt1Ty(*Context),
isICMP_NE));
}
break;
case Instruction::And:
if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
// If bits are being compared against that are and'd out, then the
// comparison can never succeed!
if ((RHSV & ~BOC->getValue()) != 0)
return ReplaceInstUsesWith(ICI,
ConstantInt::get(Type::getInt1Ty(*Context),
isICMP_NE));
// If we have ((X & C) == C), turn it into ((X & C) != 0).
if (RHS == BOC && RHSV.isPowerOf2())
return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ :
ICmpInst::ICMP_NE, LHSI,
Constant::getNullValue(RHS->getType()));
// Replace (and X, (1 << size(X)-1) != 0) with x s< 0
if (BOC->getValue().isSignBit()) {
Value *X = BO->getOperand(0);
Constant *Zero = Constant::getNullValue(X->getType());
ICmpInst::Predicate pred = isICMP_NE ?
ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
return new ICmpInst(pred, X, Zero);
}
// ((X & ~7) == 0) --> X < 8
if (RHSV == 0 && isHighOnes(BOC)) {
Value *X = BO->getOperand(0);
Constant *NegX = ConstantExpr::getNeg(BOC);
ICmpInst::Predicate pred = isICMP_NE ?
ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
return new ICmpInst(pred, X, NegX);
}
}
default: break;
}
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) {
// Handle icmp {eq|ne} <intrinsic>, intcst.
if (II->getIntrinsicID() == Intrinsic::bswap) {
Worklist.Add(II);
ICI.setOperand(0, II->getOperand(1));
ICI.setOperand(1, ConstantInt::get(*Context, RHSV.byteSwap()));
return &ICI;
}
}
}
return 0;
}
/// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst).
/// We only handle extending casts so far.
///
Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) {
const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0));
Value *LHSCIOp = LHSCI->getOperand(0);
const Type *SrcTy = LHSCIOp->getType();
const Type *DestTy = LHSCI->getType();
Value *RHSCIOp;
// Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
// integer type is the same size as the pointer type.
if (TD && LHSCI->getOpcode() == Instruction::PtrToInt &&
TD->getPointerSizeInBits() ==
cast<IntegerType>(DestTy)->getBitWidth()) {
Value *RHSOp = 0;
if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
} else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
RHSOp = RHSC->getOperand(0);
// If the pointer types don't match, insert a bitcast.
if (LHSCIOp->getType() != RHSOp->getType())
RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
}
if (RHSOp)
return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);
}
// The code below only handles extension cast instructions, so far.
// Enforce this.
if (LHSCI->getOpcode() != Instruction::ZExt &&
LHSCI->getOpcode() != Instruction::SExt)
return 0;
bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
bool isSignedCmp = ICI.isSignedPredicate();
if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) {
// Not an extension from the same type?
RHSCIOp = CI->getOperand(0);
if (RHSCIOp->getType() != LHSCIOp->getType())
return 0;
// If the signedness of the two casts doesn't agree (i.e. one is a sext
// and the other is a zext), then we can't handle this.
if (CI->getOpcode() != LHSCI->getOpcode())
return 0;
// Deal with equality cases early.
if (ICI.isEquality())
return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
// A signed comparison of sign extended values simplifies into a
// signed comparison.
if (isSignedCmp && isSignedExt)
return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
// The other three cases all fold into an unsigned comparison.
return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
}
// If we aren't dealing with a constant on the RHS, exit early
ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1));
if (!CI)
return 0;
// Compute the constant that would happen if we truncated to SrcTy then
// reextended to DestTy.
Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy);
Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(),
Res1, DestTy);
// If the re-extended constant didn't change...
if (Res2 == CI) {
// Make sure that sign of the Cmp and the sign of the Cast are the same.
// For example, we might have:
// %A = sext i16 %X to i32
// %B = icmp ugt i32 %A, 1330
// It is incorrect to transform this into
// %B = icmp ugt i16 %X, 1330
// because %A may have negative value.
//
// However, we allow this when the compare is EQ/NE, because they are
// signless.
if (isSignedExt == isSignedCmp || ICI.isEquality())
return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
return 0;
}
// The re-extended constant changed so the constant cannot be represented
// in the shorter type. Consequently, we cannot emit a simple comparison.
// First, handle some easy cases. We know the result cannot be equal at this
// point so handle the ICI.isEquality() cases
if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(*Context));
if (ICI.getPredicate() == ICmpInst::ICMP_NE)
return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(*Context));
// Evaluate the comparison for LT (we invert for GT below). LE and GE cases
// should have been folded away previously and not enter in here.
Value *Result;
if (isSignedCmp) {
// We're performing a signed comparison.
if (cast<ConstantInt>(CI)->getValue().isNegative())
Result = ConstantInt::getFalse(*Context); // X < (small) --> false
else
Result = ConstantInt::getTrue(*Context); // X < (large) --> true
} else {
// We're performing an unsigned comparison.
if (isSignedExt) {
// We're performing an unsigned comp with a sign extended value.
// This is true if the input is >= 0. [aka >s -1]
Constant *NegOne = Constant::getAllOnesValue(SrcTy);
Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName());
} else {
// Unsigned extend & unsigned compare -> always true.
Result = ConstantInt::getTrue(*Context);
}
}
// Finally, return the value computed.
if (ICI.getPredicate() == ICmpInst::ICMP_ULT ||
ICI.getPredicate() == ICmpInst::ICMP_SLT)
return ReplaceInstUsesWith(ICI, Result);
assert((ICI.getPredicate()==ICmpInst::ICMP_UGT ||
ICI.getPredicate()==ICmpInst::ICMP_SGT) &&
"ICmp should be folded!");
if (Constant *CI = dyn_cast<Constant>(Result))
return ReplaceInstUsesWith(ICI, ConstantExpr::getNot(CI));
return BinaryOperator::CreateNot(Result);
}
Instruction *InstCombiner::visitShl(BinaryOperator &I) {
return commonShiftTransforms(I);
}
Instruction *InstCombiner::visitLShr(BinaryOperator &I) {
return commonShiftTransforms(I);
}
Instruction *InstCombiner::visitAShr(BinaryOperator &I) {
if (Instruction *R = commonShiftTransforms(I))
return R;
Value *Op0 = I.getOperand(0);
// ashr int -1, X = -1 (for any arithmetic shift rights of ~0)
if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
if (CSI->isAllOnesValue())
return ReplaceInstUsesWith(I, CSI);
// See if we can turn a signed shr into an unsigned shr.
if (MaskedValueIsZero(Op0,
APInt::getSignBit(I.getType()->getScalarSizeInBits())))
return BinaryOperator::CreateLShr(Op0, I.getOperand(1));
// Arithmetic shifting an all-sign-bit value is a no-op.
unsigned NumSignBits = ComputeNumSignBits(Op0);
if (NumSignBits == Op0->getType()->getScalarSizeInBits())
return ReplaceInstUsesWith(I, Op0);
return 0;
}
Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) {
assert(I.getOperand(1)->getType() == I.getOperand(0)->getType());
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// shl X, 0 == X and shr X, 0 == X
// shl 0, X == 0 and shr 0, X == 0
if (Op1 == Constant::getNullValue(Op1->getType()) ||
Op0 == Constant::getNullValue(Op0->getType()))
return ReplaceInstUsesWith(I, Op0);
if (isa<UndefValue>(Op0)) {
if (I.getOpcode() == Instruction::AShr) // undef >>s X -> undef
return ReplaceInstUsesWith(I, Op0);
else // undef << X -> 0, undef >>u X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
if (isa<UndefValue>(Op1)) {
if (I.getOpcode() == Instruction::AShr) // X >>s undef -> X
return ReplaceInstUsesWith(I, Op0);
else // X << undef, X >>u undef -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
}
// See if we can fold away this shift.
if (SimplifyDemandedInstructionBits(I))
return &I;
// Try to fold constant and into select arguments.
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (ConstantInt *CUI = dyn_cast<ConstantInt>(Op1))
if (Instruction *Res = FoldShiftByConstant(Op0, CUI, I))
return Res;
return 0;
}
Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
BinaryOperator &I) {
bool isLeftShift = I.getOpcode() == Instruction::Shl;
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint32_t TypeBits = Op0->getType()->getScalarSizeInBits();
// shl i32 X, 32 = 0 and srl i8 Y, 9 = 0, ... just don't eliminate
// a signed shift.
//
if (Op1->uge(TypeBits)) {
if (I.getOpcode() != Instruction::AShr)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
else {
I.setOperand(1, ConstantInt::get(I.getType(), TypeBits-1));
return &I;
}
}
// ((X*C1) << C2) == (X * (C1 << C2))
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
if (BO->getOpcode() == Instruction::Mul && isLeftShift)
if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
return BinaryOperator::CreateMul(BO->getOperand(0),
ConstantExpr::getShl(BOOp, Op1));
// Try to fold constant and into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// Fold shift2(trunc(shift1(x,c1)), c2) -> trunc(shift2(shift1(x,c1),c2))
if (TruncInst *TI = dyn_cast<TruncInst>(Op0)) {
Instruction *TrOp = dyn_cast<Instruction>(TI->getOperand(0));
// If 'shift2' is an ashr, we would have to get the sign bit into a funny
// place. Don't try to do this transformation in this case. Also, we
// require that the input operand is a shift-by-constant so that we have
// confidence that the shifts will get folded together. We could do this
// xform in more cases, but it is unlikely to be profitable.
if (TrOp && I.isLogicalShift() && TrOp->isShift() &&
isa<ConstantInt>(TrOp->getOperand(1))) {
// Okay, we'll do this xform. Make the shift of shift.
Constant *ShAmt = ConstantExpr::getZExt(Op1, TrOp->getType());
// (shift2 (shift1 & 0x00FF), c2)
Value *NSh = Builder->CreateBinOp(I.getOpcode(), TrOp, ShAmt,I.getName());
// For logical shifts, the truncation has the effect of making the high
// part of the register be zeros. Emulate this by inserting an AND to
// clear the top bits as needed. This 'and' will usually be zapped by
// other xforms later if dead.
unsigned SrcSize = TrOp->getType()->getScalarSizeInBits();
unsigned DstSize = TI->getType()->getScalarSizeInBits();
APInt MaskV(APInt::getLowBitsSet(SrcSize, DstSize));
// The mask we constructed says what the trunc would do if occurring
// between the shifts. We want to know the effect *after* the second
// shift. We know that it is a logical shift by a constant, so adjust the
// mask as appropriate.
if (I.getOpcode() == Instruction::Shl)
MaskV <<= Op1->getZExtValue();
else {
assert(I.getOpcode() == Instruction::LShr && "Unknown logical shift");
MaskV = MaskV.lshr(Op1->getZExtValue());
}
// shift1 & 0x00FF
Value *And = Builder->CreateAnd(NSh, ConstantInt::get(*Context, MaskV),
TI->getName());
// Return the value truncated to the interesting size.
return new TruncInst(And, I.getType());
}
}
if (Op0->hasOneUse()) {
if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) {
// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
Value *V1, *V2;
ConstantInt *CC;
switch (Op0BO->getOpcode()) {
default: break;
case Instruction::Add:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
// These operators commute.
// Turn (Y + (X >> C)) << C -> (X + (Y << C)) & (~0 << C)
if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
match(Op0BO->getOperand(1), m_Shr(m_Value(V1),
m_Specific(Op1)))) {
Value *YS = // (Y << C)
Builder->CreateShl(Op0BO->getOperand(0), Op1, Op0BO->getName());
// (X + (Y << C))
Value *X = Builder->CreateBinOp(Op0BO->getOpcode(), YS, V1,
Op0BO->getOperand(1)->getName());
uint32_t Op1Val = Op1->getLimitedValue(TypeBits);
return BinaryOperator::CreateAnd(X, ConstantInt::get(*Context,
APInt::getHighBitsSet(TypeBits, TypeBits-Op1Val)));
}
// Turn (Y + ((X >> C) & CC)) << C -> ((X & (CC << C)) + (Y << C))
Value *Op0BOOp1 = Op0BO->getOperand(1);
if (isLeftShift && Op0BOOp1->hasOneUse() &&
match(Op0BOOp1,
m_And(m_Shr(m_Value(V1), m_Specific(Op1)),
m_ConstantInt(CC))) &&
cast<BinaryOperator>(Op0BOOp1)->getOperand(0)->hasOneUse()) {
Value *YS = // (Y << C)
Builder->CreateShl(Op0BO->getOperand(0), Op1,
Op0BO->getName());
// X & (CC << C)
Value *XM = Builder->CreateAnd(V1, ConstantExpr::getShl(CC, Op1),
V1->getName()+".mask");
return BinaryOperator::Create(Op0BO->getOpcode(), YS, XM);
}
}
// FALL THROUGH.
case Instruction::Sub: {
// Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
match(Op0BO->getOperand(0), m_Shr(m_Value(V1),
m_Specific(Op1)))) {
Value *YS = // (Y << C)
Builder->CreateShl(Op0BO->getOperand(1), Op1, Op0BO->getName());
// (X + (Y << C))
Value *X = Builder->CreateBinOp(Op0BO->getOpcode(), V1, YS,
Op0BO->getOperand(0)->getName());
uint32_t Op1Val = Op1->getLimitedValue(TypeBits);
return BinaryOperator::CreateAnd(X, ConstantInt::get(*Context,
APInt::getHighBitsSet(TypeBits, TypeBits-Op1Val)));
}
// Turn (((X >> C)&CC) + Y) << C -> (X + (Y << C)) & (CC << C)
if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
match(Op0BO->getOperand(0),
m_And(m_Shr(m_Value(V1), m_Value(V2)),
m_ConstantInt(CC))) && V2 == Op1 &&
cast<BinaryOperator>(Op0BO->getOperand(0))
->getOperand(0)->hasOneUse()) {
Value *YS = // (Y << C)
Builder->CreateShl(Op0BO->getOperand(1), Op1, Op0BO->getName());
// X & (CC << C)
Value *XM = Builder->CreateAnd(V1, ConstantExpr::getShl(CC, Op1),
V1->getName()+".mask");
return BinaryOperator::Create(Op0BO->getOpcode(), XM, YS);
}
break;
}
}
// If the operand is an bitwise operator with a constant RHS, and the
// shift is the only use, we can pull it out of the shift.
if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
bool isValid = true; // Valid only for And, Or, Xor
bool highBitSet = false; // Transform if high bit of constant set?
switch (Op0BO->getOpcode()) {
default: isValid = false; break; // Do not perform transform!
case Instruction::Add:
isValid = isLeftShift;
break;
case Instruction::Or:
case Instruction::Xor:
highBitSet = false;
break;
case Instruction::And:
highBitSet = true;
break;
}
// If this is a signed shift right, and the high bit is modified
// by the logical operation, do not perform the transformation.
// The highBitSet boolean indicates the value of the high bit of
// the constant which would cause it to be modified for this
// operation.
//
if (isValid && I.getOpcode() == Instruction::AShr)
isValid = Op0C->getValue()[TypeBits-1] == highBitSet;
if (isValid) {
Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, Op1);
Value *NewShift =
Builder->CreateBinOp(I.getOpcode(), Op0BO->getOperand(0), Op1);
NewShift->takeName(Op0BO);
return BinaryOperator::Create(Op0BO->getOpcode(), NewShift,
NewRHS);
}
}
}
}
// Find out if this is a shift of a shift by a constant.
BinaryOperator *ShiftOp = dyn_cast<BinaryOperator>(Op0);
if (ShiftOp && !ShiftOp->isShift())
ShiftOp = 0;
if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) {
ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1));
uint32_t ShiftAmt1 = ShiftAmt1C->getLimitedValue(TypeBits);
uint32_t ShiftAmt2 = Op1->getLimitedValue(TypeBits);
assert(ShiftAmt2 != 0 && "Should have been simplified earlier");
if (ShiftAmt1 == 0) return 0; // Will be simplified in the future.
Value *X = ShiftOp->getOperand(0);
uint32_t AmtSum = ShiftAmt1+ShiftAmt2; // Fold into one big shift.
const IntegerType *Ty = cast<IntegerType>(I.getType());
// Check for (X << c1) << c2 and (X >> c1) >> c2
if (I.getOpcode() == ShiftOp->getOpcode()) {
// If this is oversized composite shift, then unsigned shifts get 0, ashr
// saturates.
if (AmtSum >= TypeBits) {
if (I.getOpcode() != Instruction::AShr)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
AmtSum = TypeBits-1; // Saturate to 31 for i32 ashr.
}
return BinaryOperator::Create(I.getOpcode(), X,
ConstantInt::get(Ty, AmtSum));
}
if (ShiftOp->getOpcode() == Instruction::LShr &&
I.getOpcode() == Instruction::AShr) {
if (AmtSum >= TypeBits)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// ((X >>u C1) >>s C2) -> (X >>u (C1+C2)) since C1 != 0.
return BinaryOperator::CreateLShr(X, ConstantInt::get(Ty, AmtSum));
}
if (ShiftOp->getOpcode() == Instruction::AShr &&
I.getOpcode() == Instruction::LShr) {
// ((X >>s C1) >>u C2) -> ((X >>s (C1+C2)) & mask) since C1 != 0.
if (AmtSum >= TypeBits)
AmtSum = TypeBits-1;
Value *Shift = Builder->CreateAShr(X, ConstantInt::get(Ty, AmtSum));
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::CreateAnd(Shift, ConstantInt::get(*Context, Mask));
}
// Okay, if we get here, one shift must be left, and the other shift must be
// right. See if the amounts are equal.
if (ShiftAmt1 == ShiftAmt2) {
// If we have ((X >>? C) << C), turn this into X & (-1 << C).
if (I.getOpcode() == Instruction::Shl) {
APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1));
return BinaryOperator::CreateAnd(X, ConstantInt::get(*Context, Mask));
}
// If we have ((X << C) >>u C), turn this into X & (-1 >>u C).
if (I.getOpcode() == Instruction::LShr) {
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt1));
return BinaryOperator::CreateAnd(X, ConstantInt::get(*Context, Mask));
}
// We can simplify ((X << C) >>s C) into a trunc + sext.
// NOTE: we could do this for any C, but that would make 'unusual' integer
// types. For now, just stick to ones well-supported by the code
// generators.
const Type *SExtType = 0;
switch (Ty->getBitWidth() - ShiftAmt1) {
case 1 :
case 8 :
case 16 :
case 32 :
case 64 :
case 128:
SExtType = IntegerType::get(*Context, Ty->getBitWidth() - ShiftAmt1);
break;
default: break;
}
if (SExtType)
return new SExtInst(Builder->CreateTrunc(X, SExtType, "sext"), Ty);
// Otherwise, we can't handle it yet.
} else if (ShiftAmt1 < ShiftAmt2) {
uint32_t ShiftDiff = ShiftAmt2-ShiftAmt1;
// (X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2)
if (I.getOpcode() == Instruction::Shl) {
assert(ShiftOp->getOpcode() == Instruction::LShr ||
ShiftOp->getOpcode() == Instruction::AShr);
Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff));
APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::CreateAnd(Shift,
ConstantInt::get(*Context, Mask));
}
// (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2)
if (I.getOpcode() == Instruction::LShr) {
assert(ShiftOp->getOpcode() == Instruction::Shl);
Value *Shift = Builder->CreateLShr(X, ConstantInt::get(Ty, ShiftDiff));
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::CreateAnd(Shift,
ConstantInt::get(*Context, Mask));
}
// We can't handle (X << C1) >>s C2, it shifts arbitrary bits in.
} else {
assert(ShiftAmt2 < ShiftAmt1);
uint32_t ShiftDiff = ShiftAmt1-ShiftAmt2;
// (X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2)
if (I.getOpcode() == Instruction::Shl) {
assert(ShiftOp->getOpcode() == Instruction::LShr ||
ShiftOp->getOpcode() == Instruction::AShr);
Value *Shift = Builder->CreateBinOp(ShiftOp->getOpcode(), X,
ConstantInt::get(Ty, ShiftDiff));
APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::CreateAnd(Shift,
ConstantInt::get(*Context, Mask));
}
// (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2)
if (I.getOpcode() == Instruction::LShr) {
assert(ShiftOp->getOpcode() == Instruction::Shl);
Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff));
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
return BinaryOperator::CreateAnd(Shift,
ConstantInt::get(*Context, Mask));
}
// We can't handle (X << C1) >>a C2, it shifts arbitrary bits in.
}
}
return 0;
}
/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
/// expression. If so, decompose it, returning some value X, such that Val is
/// X*Scale+Offset.
///
static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
int &Offset, LLVMContext *Context) {
assert(Val->getType() == Type::getInt32Ty(*Context) &&
"Unexpected allocation size type!");
if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
Offset = CI->getZExtValue();
Scale = 0;
return ConstantInt::get(Type::getInt32Ty(*Context), 0);
} else if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = 1U << RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'RHS'.
Scale = RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1,
// where C1 is divisible by C2.
unsigned SubScale;
Value *SubVal =
DecomposeSimpleLinearExpr(I->getOperand(0), SubScale,
Offset, Context);
Offset += RHS->getZExtValue();
Scale = SubScale;
return SubVal;
}
}
}
// Otherwise, we can't look past this.
Scale = 1;
Offset = 0;
return Val;
}
/// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
/// try to eliminate the cast by moving the type information into the alloc.
Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
AllocationInst &AI) {
const PointerType *PTy = cast<PointerType>(CI.getType());
BuilderTy AllocaBuilder(*Builder);
AllocaBuilder.SetInsertPoint(AI.getParent(), &AI);
// Remove any uses of AI that are dead.
assert(!CI.use_empty() && "Dead instructions should be removed earlier!");
for (Value::use_iterator UI = AI.use_begin(), E = AI.use_end(); UI != E; ) {
Instruction *User = cast<Instruction>(*UI++);
if (isInstructionTriviallyDead(User)) {
while (UI != E && *UI == User)
++UI; // If this instruction uses AI more than once, don't break UI.
++NumDeadInst;
DEBUG(errs() << "IC: DCE: " << *User << '\n');
EraseInstFromFunction(*User);
}
}
// This requires TargetData to get the alloca alignment and size information.
if (!TD) return 0;
// Get the type really allocated and the type casted to.
const Type *AllocElTy = AI.getAllocatedType();
const Type *CastElTy = PTy->getElementType();
if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy);
unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy);
if (CastElTyAlign < AllocElTyAlign) return 0;
// If the allocation has multiple uses, only promote it if we are strictly
// increasing the alignment of the resultant allocation. If we keep it the
// same, we open the door to infinite loops of various kinds. (A reference
// from a dbg.declare doesn't count as a use for this purpose.)
if (!AI.hasOneUse() && !hasOneUsePlusDeclare(&AI) &&
CastElTyAlign == AllocElTyAlign) return 0;
uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy);
uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy);
if (CastElTySize == 0 || AllocElTySize == 0) return 0;
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale;
int ArrayOffset;
Value *NumElements = // See if the array size is a decomposable linear expr.
DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale,
ArrayOffset, Context);
// If we can now satisfy the modulus, by using a non-1 scale, we really can
// do the xform.
if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
(AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
Value *Amt = 0;
if (Scale == 1) {
Amt = NumElements;
} else {
Amt = ConstantInt::get(Type::getInt32Ty(*Context), Scale);
// Insert before the alloca, not before the cast.
Amt = AllocaBuilder.CreateMul(Amt, NumElements, "tmp");
}
if (int Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
Value *Off = ConstantInt::get(Type::getInt32Ty(*Context), Offset, true);
Amt = AllocaBuilder.CreateAdd(Amt, Off, "tmp");
}
AllocationInst *New;
if (isa<MallocInst>(AI))
New = AllocaBuilder.CreateMalloc(CastElTy, Amt);
else
New = AllocaBuilder.CreateAlloca(CastElTy, Amt);
New->setAlignment(AI.getAlignment());
New->takeName(&AI);
// If the allocation has one real use plus a dbg.declare, just remove the
// declare.
if (DbgDeclareInst *DI = hasOneUsePlusDeclare(&AI)) {
EraseInstFromFunction(*DI);
}
// If the allocation has multiple real uses, insert a cast and change all
// things that used it to use the new cast. This will also hack on CI, but it
// will die soon.
else if (!AI.hasOneUse()) {
// New is the allocation instruction, pointer typed. AI is the original
// allocation instruction, also pointer typed. Thus, cast to use is BitCast.
Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
AI.replaceAllUsesWith(NewCast);
}
return ReplaceInstUsesWith(CI, New);
}
/// CanEvaluateInDifferentType - Return true if we can take the specified value
/// and return it as type Ty without inserting any new casts and without
/// changing the computed value. This is used by code that tries to decide
/// whether promoting or shrinking integer operations to wider or smaller types
/// will allow us to eliminate a truncate or extend.
///
/// This is a truncation operation if Ty is smaller than V->getType(), or an
/// extension operation if Ty is larger.
///
/// If CastOpc is a truncation, then Ty will be a type smaller than V. We
/// should return true if trunc(V) can be computed by computing V in the smaller
/// type. If V is an instruction, then trunc(inst(x,y)) can be computed as
/// inst(trunc(x),trunc(y)), which only makes sense if x and y can be
/// efficiently truncated.
///
/// If CastOpc is a sext or zext, we are asking if the low bits of the value can
/// bit computed in a larger type, which is then and'd or sext_in_reg'd to get
/// the final result.
bool InstCombiner::CanEvaluateInDifferentType(Value *V, const Type *Ty,
unsigned CastOpc,
int &NumCastsRemoved){
// We can always evaluate constants in another type.
if (isa<Constant>(V))
return true;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
const Type *OrigTy = V->getType();
// If this is an extension or truncate, we can often eliminate it.
if (isa<TruncInst>(I) || isa<ZExtInst>(I) || isa<SExtInst>(I)) {
// If this is a cast from the destination type, we can trivially eliminate
// it, and this will remove a cast overall.
if (I->getOperand(0)->getType() == Ty) {
// If the first operand is itself a cast, and is eliminable, do not count
// this as an eliminable cast. We would prefer to eliminate those two
// casts first.
if (!isa<CastInst>(I->getOperand(0)) && I->hasOneUse())
++NumCastsRemoved;
return true;
}
}
// We can't extend or shrink something that has multiple uses: doing so would
// require duplicating the instruction in general, which isn't profitable.
if (!I->hasOneUse()) return false;
unsigned Opc = I->getOpcode();
switch (Opc) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators can all arbitrarily be extended or truncated.
return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
NumCastsRemoved) &&
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
case Instruction::UDiv:
case Instruction::URem: {
// UDiv and URem can be truncated if all the truncated bits are zero.
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (BitWidth < OrigBitWidth) {
APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth);
if (MaskedValueIsZero(I->getOperand(0), Mask) &&
MaskedValueIsZero(I->getOperand(1), Mask)) {
return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
NumCastsRemoved) &&
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
}
}
break;
}
case Instruction::Shl:
// If we are truncating the result of this SHL, and if it's a shift of a
// constant amount, we can always perform a SHL in a smaller type.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (BitWidth < OrigTy->getScalarSizeInBits() &&
CI->getLimitedValue(BitWidth) < BitWidth)
return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
NumCastsRemoved);
}
break;
case Instruction::LShr:
// If this is a truncate of a logical shr, we can truncate it to a smaller
// lshr iff we know that the bits we would otherwise be shifting in are
// already zeros.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (BitWidth < OrigBitWidth &&
MaskedValueIsZero(I->getOperand(0),
APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) &&
CI->getLimitedValue(BitWidth) < BitWidth) {
return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
NumCastsRemoved);
}
}
break;
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::Trunc:
// If this is the same kind of case as our original (e.g. zext+zext), we
// can safely replace it. Note that replacing it does not reduce the number
// of casts in the input.
if (Opc == CastOpc)
return true;
// sext (zext ty1), ty2 -> zext ty2
if (CastOpc == Instruction::SExt && Opc == Instruction::ZExt)
return true;
break;
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
return CanEvaluateInDifferentType(SI->getTrueValue(), Ty, CastOpc,
NumCastsRemoved) &&
CanEvaluateInDifferentType(SI->getFalseValue(), Ty, CastOpc,
NumCastsRemoved);
}
case Instruction::PHI: {
// We can change a phi if we can change all operands.
PHINode *PN = cast<PHINode>(I);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (!CanEvaluateInDifferentType(PN->getIncomingValue(i), Ty, CastOpc,
NumCastsRemoved))
return false;
return true;
}
default:
// TODO: Can handle more cases here.
break;
}
return false;
}
/// EvaluateInDifferentType - Given an expression that
/// CanEvaluateInDifferentType returns true for, actually insert the code to
/// evaluate the expression.
Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
bool isSigned) {
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getIntegerCast(C, Ty,
isSigned /*Sext or ZExt*/);
// Otherwise, it must be an instruction.
Instruction *I = cast<Instruction>(V);
Instruction *Res = 0;
unsigned Opc = I->getOpcode();
switch (Opc) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::AShr:
case Instruction::LShr:
case Instruction::Shl:
case Instruction::UDiv:
case Instruction::URem: {
Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
break;
}
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
// If the source type of the cast is the type we're trying for then we can
// just return the source. There's no need to insert it because it is not
// new.
if (I->getOperand(0)->getType() == Ty)
return I->getOperand(0);
// Otherwise, must be the same type of cast, so just reinsert a new one.
Res = CastInst::Create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),
Ty);
break;
case Instruction::Select: {
Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
Res = SelectInst::Create(I->getOperand(0), True, False);
break;
}
case Instruction::PHI: {
PHINode *OPN = cast<PHINode>(I);
PHINode *NPN = PHINode::Create(Ty);
for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
NPN->addIncoming(V, OPN->getIncomingBlock(i));
}
Res = NPN;
break;
}
default:
// TODO: Can handle more cases here.
llvm_unreachable("Unreachable!");
break;
}
Res->takeName(I);
return InsertNewInstBefore(Res, *I);
}
/// @brief Implement the transforms common to all CastInst visitors.
Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
Value *Src = CI.getOperand(0);
// Many cases of "cast of a cast" are eliminable. If it's eliminable we just
// eliminate it now.
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
if (Instruction::CastOps opc =
isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) {
// The first cast (CSrc) is eliminable so we need to fix up or replace
// the second cast (CI). CSrc will then have a good chance of being dead.
return CastInst::Create(opc, CSrc->getOperand(0), CI.getType());
}
}
// If we are casting a select then fold the cast into the select
if (SelectInst *SI = dyn_cast<SelectInst>(Src))
if (Instruction *NV = FoldOpIntoSelect(CI, SI, this))
return NV;
// If we are casting a PHI then fold the cast into the PHI
if (isa<PHINode>(Src))
if (Instruction *NV = FoldOpIntoPhi(CI))
return NV;
return 0;
}
/// FindElementAtOffset - Given a type and a constant offset, determine whether
/// or not there is a sequence of GEP indices into the type that will land us at
/// the specified offset. If so, fill them into NewIndices and return the
/// resultant element type, otherwise return null.
static const Type *FindElementAtOffset(const Type *Ty, int64_t Offset,
SmallVectorImpl<Value*> &NewIndices,
const TargetData *TD,
LLVMContext *Context) {
if (!TD) return 0;
if (!Ty->isSized()) return 0;
// Start with the index over the outer type. Note that the type size
// might be zero (even if the offset isn't zero) if the indexed type
// is something like [0 x {int, int}]
const Type *IntPtrTy = TD->getIntPtrType(*Context);
int64_t FirstIdx = 0;
if (int64_t TySize = TD->getTypeAllocSize(Ty)) {
FirstIdx = Offset/TySize;
Offset -= FirstIdx*TySize;
// Handle hosts where % returns negative instead of values [0..TySize).
if (Offset < 0) {
--FirstIdx;
Offset += TySize;
assert(Offset >= 0);
}
assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
}
NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
// Index into the types. If we fail, set OrigBase to null.
while (Offset) {
// Indexing into tail padding between struct/array elements.
if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty))
return 0;
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TD->getStructLayout(STy);
assert(Offset < (int64_t)SL->getSizeInBytes() &&
"Offset must stay within the indexed type");
unsigned Elt = SL->getElementContainingOffset(Offset);
NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(*Context), Elt));
Offset -= SL->getElementOffset(Elt);
Ty = STy->getElementType(Elt);
} else if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType());
assert(EltSize && "Cannot index into a zero-sized array");
NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
Offset %= EltSize;
Ty = AT->getElementType();
} else {
// Otherwise, we can't index into the middle of this atomic type, bail.
return 0;
}
}
return Ty;
}
/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
Value *Src = CI.getOperand(0);
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
// If casting the result of a getelementptr instruction with no offset, turn
// this into a cast of the original pointer!
if (GEP->hasAllZeroIndices()) {
// Changing the cast operand is usually not a good idea but it is safe
// here because the pointer operand is being replaced with another
// pointer operand so the opcode doesn't need to change.
Worklist.Add(GEP);
CI.setOperand(0, GEP->getOperand(0));
return &CI;
}
// If the GEP has a single use, and the base pointer is a bitcast, and the
// GEP computes a constant offset, see if we can convert these three
// instructions into fewer. This typically happens with unions and other
// non-type-safe code.
if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0))) {
if (GEP->hasAllConstantIndices()) {
// We are guaranteed to get a constant from EmitGEPOffset.
ConstantInt *OffsetV =
cast<ConstantInt>(EmitGEPOffset(GEP, CI, *this));
int64_t Offset = OffsetV->getSExtValue();
// Get the base pointer input of the bitcast, and the type it points to.
Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
const Type *GEPIdxTy =
cast<PointerType>(OrigBase->getType())->getElementType();
SmallVector<Value*, 8> NewIndices;
if (FindElementAtOffset(GEPIdxTy, Offset, NewIndices, TD, Context)) {
// If we were able to index down into an element, create the GEP
// and bitcast the result. This eliminates one bitcast, potentially
// two.
Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ?
Builder->CreateInBoundsGEP(OrigBase,
NewIndices.begin(), NewIndices.end()) :
Builder->CreateGEP(OrigBase, NewIndices.begin(), NewIndices.end());
NGEP->takeName(GEP);
if (isa<BitCastInst>(CI))
return new BitCastInst(NGEP, CI.getType());
assert(isa<PtrToIntInst>(CI));
return new PtrToIntInst(NGEP, CI.getType());
}
}
}
}
return commonCastTransforms(CI);
}
/// isSafeIntegerType - Return true if this is a basic integer type, not a crazy
/// type like i42. We don't want to introduce operations on random non-legal
/// integer types where they don't already exist in the code. In the future,
/// we should consider making this based off target-data, so that 32-bit targets
/// won't get i64 operations etc.
static bool isSafeIntegerType(const Type *Ty) {
switch (Ty->getPrimitiveSizeInBits()) {
case 8:
case 16:
case 32:
case 64:
return true;
default:
return false;
}
}
/// commonIntCastTransforms - This function implements the common transforms
/// for trunc, zext, and sext.
Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
if (Instruction *Result = commonCastTransforms(CI))
return Result;
Value *Src = CI.getOperand(0);
const Type *SrcTy = Src->getType();
const Type *DestTy = CI.getType();
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
// See if we can simplify any instructions used by the LHS whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(CI))
return &CI;
// If the source isn't an instruction or has more than one use then we
// can't do anything more.
Instruction *SrcI = dyn_cast<Instruction>(Src);
if (!SrcI || !Src->hasOneUse())
return 0;
// Attempt to propagate the cast into the instruction for int->int casts.
int NumCastsRemoved = 0;
// Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
if ((isSafeIntegerType(DestTy->getScalarType()) ||
!isSafeIntegerType(SrcI->getType()->getScalarType())) &&
CanEvaluateInDifferentType(SrcI, DestTy,
CI.getOpcode(), NumCastsRemoved)) {
// If this cast is a truncate, evaluting in a different type always
// eliminates the cast, so it is always a win. If this is a zero-extension,
// we need to do an AND to maintain the clear top-part of the computation,
// so we require that the input have eliminated at least one cast. If this
// is a sign extension, we insert two new casts (to do the extension) so we
// require that two casts have been eliminated.
bool DoXForm = false;
bool JustReplace = false;
switch (CI.getOpcode()) {
default:
// All the others use floating point so we shouldn't actually
// get here because of the check above.
llvm_unreachable("Unknown cast type");
case Instruction::Trunc:
DoXForm = true;
break;
case Instruction::ZExt: {
DoXForm = NumCastsRemoved >= 1;
if (!DoXForm && 0) {
// If it's unnecessary to issue an AND to clear the high bits, it's
// always profitable to do this xform.
Value *TryRes = EvaluateInDifferentType(SrcI, DestTy, false);
APInt Mask(APInt::getBitsSet(DestBitSize, SrcBitSize, DestBitSize));
if (MaskedValueIsZero(TryRes, Mask))
return ReplaceInstUsesWith(CI, TryRes);
if (Instruction *TryI = dyn_cast<Instruction>(TryRes))
if (TryI->use_empty())
EraseInstFromFunction(*TryI);
}
break;
}
case Instruction::SExt: {
DoXForm = NumCastsRemoved >= 2;
if (!DoXForm && !isa<TruncInst>(SrcI) && 0) {
// If we do not have to emit the truncate + sext pair, then it's always
// profitable to do this xform.
//
// It's not safe to eliminate the trunc + sext pair if one of the
// eliminated cast is a truncate. e.g.
// t2 = trunc i32 t1 to i16
// t3 = sext i16 t2 to i32
// !=
// i32 t1
Value *TryRes = EvaluateInDifferentType(SrcI, DestTy, true);
unsigned NumSignBits = ComputeNumSignBits(TryRes);
if (NumSignBits > (DestBitSize - SrcBitSize))
return ReplaceInstUsesWith(CI, TryRes);
if (Instruction *TryI = dyn_cast<Instruction>(TryRes))
if (TryI->use_empty())
EraseInstFromFunction(*TryI);
}
break;
}
}
if (DoXForm) {
DEBUG(errs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid cast: " << CI);
Value *Res = EvaluateInDifferentType(SrcI, DestTy,
CI.getOpcode() == Instruction::SExt);
if (JustReplace)
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
assert(Res->getType() == DestTy);
switch (CI.getOpcode()) {
default: llvm_unreachable("Unknown cast type!");
case Instruction::Trunc:
// Just replace this cast with the result.
return ReplaceInstUsesWith(CI, Res);
case Instruction::ZExt: {
assert(SrcBitSize < DestBitSize && "Not a zext?");
// If the high bits are already zero, just replace this cast with the
// result.
APInt Mask(APInt::getBitsSet(DestBitSize, SrcBitSize, DestBitSize));
if (MaskedValueIsZero(Res, Mask))
return ReplaceInstUsesWith(CI, Res);
// We need to emit an AND to clear the high bits.
Constant *C = ConstantInt::get(*Context,
APInt::getLowBitsSet(DestBitSize, SrcBitSize));
return BinaryOperator::CreateAnd(Res, C);
}
case Instruction::SExt: {
// If the high bits are already filled with sign bit, just replace this
// cast with the result.
unsigned NumSignBits = ComputeNumSignBits(Res);
if (NumSignBits > (DestBitSize - SrcBitSize))
return ReplaceInstUsesWith(CI, Res);
// We need to emit a cast to truncate, then a cast to sext.
return new SExtInst(Builder->CreateTrunc(Res, Src->getType()), DestTy);
}
}
}
}
Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
switch (SrcI->getOpcode()) {
case Instruction::Add:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// If we are discarding information, rewrite.
if (DestBitSize < SrcBitSize && DestBitSize != 1) {
// Don't insert two casts unless at least one can be eliminated.
if (!ValueRequiresCast(CI.getOpcode(), Op1, DestTy, TD) ||
!ValueRequiresCast(CI.getOpcode(), Op0, DestTy, TD)) {
Value *Op0c = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
Value *Op1c = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
return BinaryOperator::Create(
cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
}
}
// cast (xor bool X, true) to int --> xor (cast bool X to int), 1
if (isa<ZExtInst>(CI) && SrcBitSize == 1 &&
SrcI->getOpcode() == Instruction::Xor &&
Op1 == ConstantInt::getTrue(*Context) &&
(!Op0->hasOneUse() || !isa<CmpInst>(Op0))) {
Value *New = Builder->CreateZExt(Op0, DestTy, Op0->getName());
return BinaryOperator::CreateXor(New,
ConstantInt::get(CI.getType(), 1));
}
break;
case Instruction::Shl: {
// Canonicalize trunc inside shl, if we can.
ConstantInt *CI = dyn_cast<ConstantInt>(Op1);
if (CI && DestBitSize < SrcBitSize &&
CI->getLimitedValue(DestBitSize) < DestBitSize) {
Value *Op0c = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
Value *Op1c = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
return BinaryOperator::CreateShl(Op0c, Op1c);
}
break;
}
}
return 0;
}
Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
if (Instruction *Result = commonIntCastTransforms(CI))
return Result;
Value *Src = CI.getOperand(0);
const Type *Ty = CI.getType();
uint32_t DestBitWidth = Ty->getScalarSizeInBits();
uint32_t SrcBitWidth = Src->getType()->getScalarSizeInBits();
// Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0)
if (DestBitWidth == 1) {
Constant *One = ConstantInt::get(Src->getType(), 1);
Src = Builder->CreateAnd(Src, One, "tmp");
Value *Zero = Constant::getNullValue(Src->getType());
return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
}
// Optimize trunc(lshr(), c) to pull the shift through the truncate.
ConstantInt *ShAmtV = 0;
Value *ShiftOp = 0;
if (Src->hasOneUse() &&
match(Src, m_LShr(m_Value(ShiftOp), m_ConstantInt(ShAmtV)))) {
uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
// Get a mask for the bits shifting in.
APInt Mask(APInt::getLowBitsSet(SrcBitWidth, ShAmt).shl(DestBitWidth));
if (MaskedValueIsZero(ShiftOp, Mask)) {
if (ShAmt >= DestBitWidth) // All zeros.
return ReplaceInstUsesWith(CI, Constant::getNullValue(Ty));
// Okay, we can shrink this. Truncate the input, then return a new
// shift.
Value *V1 = Builder->CreateTrunc(ShiftOp, Ty, ShiftOp->getName());
Value *V2 = ConstantExpr::getTrunc(ShAmtV, Ty);
return BinaryOperator::CreateLShr(V1, V2);
}
}
return 0;
}
/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations
/// in order to eliminate the icmp.
Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// to an integer, then shift the bit to the appropriate place and then
// cast to integer to avoid the comparison.
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
const APInt &Op1CV = Op1C->getValue();
// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
// zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
(ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) {
if (!DoXform) return ICI;
Value *In = ICI->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getScalarSizeInBits()-1);
In = Builder->CreateLShr(In, Sh, In->getName()+".lobit");
if (In->getType() != CI.getType())
In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/, "tmp");
if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
Constant *One = ConstantInt::get(In->getType(), 1);
In = Builder->CreateXor(In, One, In->getName()+".not");
}
return ReplaceInstUsesWith(CI, In);
}
// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
// zext (X == 1) to i32 --> X iff X has only the low bit set.
// zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 0) to i32 --> X iff X has only the low bit set.
// zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
// zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
// This only works for EQ and NE
ICI->isEquality()) {
// If Op1C some other power of two, convert:
uint32_t BitWidth = Op1C->getType()->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
APInt TypeMask(APInt::getAllOnesValue(BitWidth));
ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne);
APInt KnownZeroMask(~KnownZero);
if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
if (!DoXform) return ICI;
bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
// (X&4) == 2 --> false
// (X&4) != 2 --> true
Constant *Res = ConstantInt::get(Type::getInt1Ty(*Context), isNE);
Res = ConstantExpr::getZExt(Res, CI.getType());
return ReplaceInstUsesWith(CI, Res);
}
uint32_t ShiftAmt = KnownZeroMask.logBase2();
Value *In = ICI->getOperand(0);
if (ShiftAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt),
In->getName()+".lobit");
}
if ((Op1CV != 0) == isNE) { // Toggle the low bit.
Constant *One = ConstantInt::get(In->getType(), 1);
In = Builder->CreateXor(In, One, "tmp");
}
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
else
return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/);
}
}
}
return 0;
}
Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
// If one of the common conversion will work ..
if (Instruction *Result = commonIntCastTransforms(CI))
return Result;
Value *Src = CI.getOperand(0);
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
// types and if the sizes are just right we can convert this into a logical
// 'and' which will be much cheaper than the pair of casts.
if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
// Get the sizes of the types involved. We know that the intermediate type
// will be smaller than A or C, but don't know the relation between A and C.
Value *A = CSrc->getOperand(0);
unsigned SrcSize = A->getType()->getScalarSizeInBits();
unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
unsigned DstSize = CI.getType()->getScalarSizeInBits();
// If we're actually extending zero bits, then if
// SrcSize < DstSize: zext(a & mask)
// SrcSize == DstSize: a & mask
// SrcSize > DstSize: trunc(a) & mask
if (SrcSize < DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask");
return new ZExtInst(And, CI.getType());
}
if (SrcSize == DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(),
AndValue));
}
if (SrcSize > DstSize) {
Value *Trunc = Builder->CreateTrunc(A, CI.getType(), "tmp");
APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
return BinaryOperator::CreateAnd(Trunc,
ConstantInt::get(Trunc->getType(),
AndValue));
}
}
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
return transformZExtICmp(ICI, CI);
BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src);
if (SrcI && SrcI->getOpcode() == Instruction::Or) {
// zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one
// of the (zext icmp) will be transformed.
ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0));
ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1));
if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() &&
(transformZExtICmp(LHS, CI, false) ||
transformZExtICmp(RHS, CI, false))) {
Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName());
Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName());
return BinaryOperator::Create(Instruction::Or, LCast, RCast);
}
}
// zext(trunc(t) & C) -> (t & zext(C)).
if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse())
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) {
Value *TI0 = TI->getOperand(0);
if (TI0->getType() == CI.getType())
return
BinaryOperator::CreateAnd(TI0,
ConstantExpr::getZExt(C, CI.getType()));
}
// zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)).
if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse())
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0)))
if (And->getOpcode() == Instruction::And && And->hasOneUse() &&
And->getOperand(1) == C)
if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) {
Value *TI0 = TI->getOperand(0);
if (TI0->getType() == CI.getType()) {
Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
Value *NewAnd = Builder->CreateAnd(TI0, ZC, "tmp");
return BinaryOperator::CreateXor(NewAnd, ZC);
}
}
return 0;
}
Instruction *InstCombiner::visitSExt(SExtInst &CI) {
if (Instruction *I = commonIntCastTransforms(CI))
return I;
Value *Src = CI.getOperand(0);
// Canonicalize sign-extend from i1 to a select.
if (Src->getType() == Type::getInt1Ty(*Context))
return SelectInst::Create(Src,
Constant::getAllOnesValue(CI.getType()),
Constant::getNullValue(CI.getType()));
// See if the value being truncated is already sign extended. If so, just
// eliminate the trunc/sext pair.
if (Operator::getOpcode(Src) == Instruction::Trunc) {
Value *Op = cast<User>(Src)->getOperand(0);
unsigned OpBits = Op->getType()->getScalarSizeInBits();
unsigned MidBits = Src->getType()->getScalarSizeInBits();
unsigned DestBits = CI.getType()->getScalarSizeInBits();
unsigned NumSignBits = ComputeNumSignBits(Op);
if (OpBits == DestBits) {
// Op is i32, Mid is i8, and Dest is i32. If Op has more than 24 sign
// bits, it is already ready.
if (NumSignBits > DestBits-MidBits)
return ReplaceInstUsesWith(CI, Op);
} else if (OpBits < DestBits) {
// Op is i32, Mid is i8, and Dest is i64. If Op has more than 24 sign
// bits, just sext from i32.
if (NumSignBits > OpBits-MidBits)
return new SExtInst(Op, CI.getType(), "tmp");
} else {
// Op is i64, Mid is i8, and Dest is i32. If Op has more than 56 sign
// bits, just truncate to i32.
if (NumSignBits > OpBits-MidBits)
return new TruncInst(Op, CI.getType(), "tmp");
}
}
// If the input is a shl/ashr pair of a same constant, then this is a sign
// extension from a smaller value. If we could trust arbitrary bitwidth
// integers, we could turn this into a truncate to the smaller bit and then
// use a sext for the whole extension. Since we don't, look deeper and check
// for a truncate. If the source and dest are the same type, eliminate the
// trunc and extend and just do shifts. For example, turn:
// %a = trunc i32 %i to i8
// %b = shl i8 %a, 6
// %c = ashr i8 %b, 6
// %d = sext i8 %c to i32
// into:
// %a = shl i32 %i, 30
// %d = ashr i32 %a, 30
Value *A = 0;
ConstantInt *BA = 0, *CA = 0;
if (match(Src, m_AShr(m_Shl(m_Value(A), m_ConstantInt(BA)),
m_ConstantInt(CA))) &&
BA == CA && isa<TruncInst>(A)) {
Value *I = cast<TruncInst>(A)->getOperand(0);
if (I->getType() == CI.getType()) {
unsigned MidSize = Src->getType()->getScalarSizeInBits();
unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
I = Builder->CreateShl(I, ShAmtV, CI.getName());
return BinaryOperator::CreateAShr(I, ShAmtV);
}
}
return 0;
}
/// FitsInFPType - Return a Constant* for the specified FP constant if it fits
/// in the specified FP type without changing its value.
static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem,
LLVMContext *Context) {
bool losesInfo;
APFloat F = CFP->getValueAPF();
(void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo);
if (!losesInfo)
return ConstantFP::get(*Context, F);
return 0;
}
/// LookThroughFPExtensions - If this is an fp extension instruction, look
/// through it until we get the source value.
static Value *LookThroughFPExtensions(Value *V, LLVMContext *Context) {
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::FPExt)
return LookThroughFPExtensions(I->getOperand(0), Context);
// If this value is a constant, return the constant in the smallest FP type
// that can accurately represent it. This allows us to turn
// (float)((double)X+2.0) into x+2.0f.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
if (CFP->getType() == Type::getPPC_FP128Ty(*Context))
return V; // No constant folding of this.
// See if the value can be truncated to float and then reextended.
if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle, Context))
return V;
if (CFP->getType() == Type::getDoubleTy(*Context))
return V; // Won't shrink.
if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble, Context))
return V;
// Don't try to shrink to various long double types.
}
return V;
}
Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
if (Instruction *I = commonCastTransforms(CI))
return I;
// If we have fptrunc(fadd (fpextend x), (fpextend y)), where x and y are
// smaller than the destination type, we can eliminate the truncate by doing
// the add as the smaller type. This applies to fadd/fsub/fmul/fdiv as well as
// many builtins (sqrt, etc).
BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0));
if (OpI && OpI->hasOneUse()) {
switch (OpI->getOpcode()) {
default: break;
case Instruction::FAdd:
case Instruction::FSub:
case Instruction::FMul:
case Instruction::FDiv:
case Instruction::FRem:
const Type *SrcTy = OpI->getType();
Value *LHSTrunc = LookThroughFPExtensions(OpI->getOperand(0), Context);
Value *RHSTrunc = LookThroughFPExtensions(OpI->getOperand(1), Context);
if (LHSTrunc->getType() != SrcTy &&
RHSTrunc->getType() != SrcTy) {
unsigned DstSize = CI.getType()->getScalarSizeInBits();
// If the source types were both smaller than the destination type of
// the cast, do this xform.
if (LHSTrunc->getType()->getScalarSizeInBits() <= DstSize &&
RHSTrunc->getType()->getScalarSizeInBits() <= DstSize) {
LHSTrunc = Builder->CreateFPExt(LHSTrunc, CI.getType());
RHSTrunc = Builder->CreateFPExt(RHSTrunc, CI.getType());
return BinaryOperator::Create(OpI->getOpcode(), LHSTrunc, RHSTrunc);
}
}
break;
}
}
return 0;
}
Instruction *InstCombiner::visitFPExt(CastInst &CI) {
return commonCastTransforms(CI);
}
Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) {
Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
if (OpI == 0)
return commonCastTransforms(FI);
// fptoui(uitofp(X)) --> X
// fptoui(sitofp(X)) --> X
// This is safe if the intermediate type has enough bits in its mantissa to
// accurately represent all values of X. For example, do not do this with
// i64->float->i64. This is also safe for sitofp case, because any negative
// 'X' value would cause an undefined result for the fptoui.
if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
OpI->getOperand(0)->getType() == FI.getType() &&
(int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */
OpI->getType()->getFPMantissaWidth())
return ReplaceInstUsesWith(FI, OpI->getOperand(0));
return commonCastTransforms(FI);
}
Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) {
Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
if (OpI == 0)
return commonCastTransforms(FI);
// fptosi(sitofp(X)) --> X
// fptosi(uitofp(X)) --> X
// This is safe if the intermediate type has enough bits in its mantissa to
// accurately represent all values of X. For example, do not do this with
// i64->float->i64. This is also safe for sitofp case, because any negative
// 'X' value would cause an undefined result for the fptoui.
if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
OpI->getOperand(0)->getType() == FI.getType() &&
(int)FI.getType()->getScalarSizeInBits() <=
OpI->getType()->getFPMantissaWidth())
return ReplaceInstUsesWith(FI, OpI->getOperand(0));
return commonCastTransforms(FI);
}
Instruction *InstCombiner::visitUIToFP(CastInst &CI) {
return commonCastTransforms(CI);
}
Instruction *InstCombiner::visitSIToFP(CastInst &CI) {
return commonCastTransforms(CI);
}
Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) {
// If the destination integer type is smaller than the intptr_t type for
// this target, do a ptrtoint to intptr_t then do a trunc. This allows the
// trunc to be exposed to other transforms. Don't do this for extending
// ptrtoint's, because we don't know if the target sign or zero extends its
// pointers.
if (TD &&
CI.getType()->getScalarSizeInBits() < TD->getPointerSizeInBits()) {
Value *P = Builder->CreatePtrToInt(CI.getOperand(0),
TD->getIntPtrType(CI.getContext()),
"tmp");
return new TruncInst(P, CI.getType());
}
return commonPointerCastTransforms(CI);
}
Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
// If the source integer type is larger than the intptr_t type for
// this target, do a trunc to the intptr_t type, then inttoptr of it. This
// allows the trunc to be exposed to other transforms. Don't do this for
// extending inttoptr's, because we don't know if the target sign or zero
// extends to pointers.
if (TD && CI.getOperand(0)->getType()->getScalarSizeInBits() >
TD->getPointerSizeInBits()) {
Value *P = Builder->CreateTrunc(CI.getOperand(0),
TD->getIntPtrType(CI.getContext()), "tmp");
return new IntToPtrInst(P, CI.getType());
}
if (Instruction *I = commonCastTransforms(CI))
return I;
return 0;
}
Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
// If the operands are integer typed then apply the integer transforms,
// otherwise just apply the common ones.
Value *Src = CI.getOperand(0);
const Type *SrcTy = Src->getType();
const Type *DestTy = CI.getType();
if (isa<PointerType>(SrcTy)) {
if (Instruction *I = commonPointerCastTransforms(CI))
return I;
} else {
if (Instruction *Result = commonCastTransforms(CI))
return Result;
}
// Get rid of casts from one type to the same type. These are useless and can
// be replaced by the operand.
if (DestTy == Src->getType())
return ReplaceInstUsesWith(CI, Src);
if (const PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
const PointerType *SrcPTy = cast<PointerType>(SrcTy);
const Type *DstElTy = DstPTy->getElementType();
const Type *SrcElTy = SrcPTy->getElementType();
// If the address spaces don't match, don't eliminate the bitcast, which is
// required for changing types.
if (SrcPTy->getAddressSpace() != DstPTy->getAddressSpace())
return 0;
// If we are casting a alloca to a pointer to a type of the same
// size, rewrite the allocation instruction to allocate the "right" type.
// There is no need to modify malloc calls because it is their bitcast that
// needs to be cleaned up.
if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
return V;
// If the source and destination are pointers, and this cast is equivalent
// to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
// This can enhance SROA and other transforms that want type-safe pointers.
Constant *ZeroUInt = Constant::getNullValue(Type::getInt32Ty(*Context));
unsigned NumZeros = 0;
while (SrcElTy != DstElTy &&
isa<CompositeType>(SrcElTy) && !isa<PointerType>(SrcElTy) &&
SrcElTy->getNumContainedTypes() /* not "{}" */) {
SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt);
++NumZeros;
}
// If we found a path from the src to dest, create the getelementptr now.
if (SrcElTy == DstElTy) {
SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt);
return GetElementPtrInst::CreateInBounds(Src, Idxs.begin(), Idxs.end(), "",
((Instruction*) NULL));
}
}
if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
if (DestVTy->getNumElements() == 1) {
if (!isa<VectorType>(SrcTy)) {
Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType());
return InsertElementInst::Create(UndefValue::get(DestTy), Elem,
Constant::getNullValue(Type::getInt32Ty(*Context)));
}
// FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast)
}
}
if (const VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) {
if (SrcVTy->getNumElements() == 1) {
if (!isa<VectorType>(DestTy)) {
Value *Elem =
Builder->CreateExtractElement(Src,
Constant::getNullValue(Type::getInt32Ty(*Context)));
return CastInst::Create(Instruction::BitCast, Elem, DestTy);
}
}
}
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) {
if (SVI->hasOneUse()) {
// Okay, we have (bitconvert (shuffle ..)). Check to see if this is
// a bitconvert to a vector with the same # elts.
if (isa<VectorType>(DestTy) &&
cast<VectorType>(DestTy)->getNumElements() ==
SVI->getType()->getNumElements() &&
SVI->getType()->getNumElements() ==
cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements()) {
CastInst *Tmp;
// If either of the operands is a cast from CI.getType(), then
// evaluating the shuffle in the casted destination's type will allow
// us to eliminate at least one cast.
if (((Tmp = dyn_cast<CastInst>(SVI->getOperand(0))) &&
Tmp->getOperand(0)->getType() == DestTy) ||
((Tmp = dyn_cast<CastInst>(SVI->getOperand(1))) &&
Tmp->getOperand(0)->getType() == DestTy)) {
Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy);
Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy);
// Return a new shuffle vector. Use the same element ID's, as we
// know the vector types match #elts.
return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2));
}
}
}
}
return 0;
}
/// GetSelectFoldableOperands - We want to turn code that looks like this:
/// %C = or %A, %B
/// %D = select %cond, %C, %A
/// into:
/// %C = select %cond, %B, 0
/// %D = or %A, %C
///
/// Assuming that the specified instruction is an operand to the select, return
/// a bitmask indicating which operands of this instruction are foldable if they
/// equal the other incoming value of the select.
///
static unsigned GetSelectFoldableOperands(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
return 3; // Can fold through either operand.
case Instruction::Sub: // Can only fold on the amount subtracted.
case Instruction::Shl: // Can only fold on the shift amount.
case Instruction::LShr:
case Instruction::AShr:
return 1;
default:
return 0; // Cannot fold
}
}
/// GetSelectFoldableConstant - For the same transformation as the previous
/// function, return the identity constant that goes into the select.
static Constant *GetSelectFoldableConstant(Instruction *I,
LLVMContext *Context) {
switch (I->getOpcode()) {
default: llvm_unreachable("This cannot happen!");
case Instruction::Add:
case Instruction::Sub:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
return Constant::getNullValue(I->getType());
case Instruction::And:
return Constant::getAllOnesValue(I->getType());
case Instruction::Mul:
return ConstantInt::get(I->getType(), 1);
}
}
/// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
/// have the same opcode and only one use each. Try to simplify this.
Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI) {
if (TI->getNumOperands() == 1) {
// If this is a non-volatile load or a cast from the same type,
// merge.
if (TI->isCast()) {
if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
return 0;
} else {
return 0; // unknown unary op.
}
// Fold this by inserting a select from the input values.
SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0),
FI->getOperand(0), SI.getName()+".v");
InsertNewInstBefore(NewSI, SI);
return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
TI->getType());
}
// Only handle binary operators here.
if (!isa<BinaryOperator>(TI))
return 0;
// Figure out if the operations have any operands in common.
Value *MatchOp, *OtherOpT, *OtherOpF;
bool MatchIsOpZero;
if (TI->getOperand(0) == FI->getOperand(0)) {
MatchOp = TI->getOperand(0);
OtherOpT = TI->getOperand(1);
OtherOpF = FI->getOperand(1);
MatchIsOpZero = true;
} else if (TI->getOperand(1) == FI->getOperand(1)) {
MatchOp = TI->getOperand(1);
OtherOpT = TI->getOperand(0);
OtherOpF = FI->getOperand(0);
MatchIsOpZero = false;
} else if (!TI->isCommutative()) {
return 0;
} else if (TI->getOperand(0) == FI->getOperand(1)) {
MatchOp = TI->getOperand(0);
OtherOpT = TI->getOperand(1);
OtherOpF = FI->getOperand(0);
MatchIsOpZero = true;
} else if (TI->getOperand(1) == FI->getOperand(0)) {
MatchOp = TI->getOperand(1);
OtherOpT = TI->getOperand(0);
OtherOpF = FI->getOperand(1);
MatchIsOpZero = true;
} else {
return 0;
}
// If we reach here, they do have operations in common.
SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT,
OtherOpF, SI.getName()+".v");
InsertNewInstBefore(NewSI, SI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
if (MatchIsOpZero)
return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
else
return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
}
llvm_unreachable("Shouldn't get here");
return 0;
}
static bool isSelect01(Constant *C1, Constant *C2) {
ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
if (!C1I)
return false;
ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
if (!C2I)
return false;
return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne());
}
/// FoldSelectIntoOp - Try fold the select into one of the operands to
/// facilitate further optimization.
Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
Value *FalseVal) {
// See the comment above GetSelectFoldableOperands for a description of the
// transformation we are doing here.
if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
!isa<Constant>(FalseVal)) {
if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
unsigned OpToFold = 0;
if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
OpToFold = 1;
} else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
OpToFold = 2;
}
if (OpToFold) {
Constant *C = GetSelectFoldableConstant(TVI, Context);
Value *OOp = TVI->getOperand(2-OpToFold);
// Avoid creating select between 2 constants unless it's selecting
// between 0 and 1.
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
InsertNewInstBefore(NewSel, SI);
NewSel->takeName(TVI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
llvm_unreachable("Unknown instruction!!");
}
}
}
}
}
if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
!isa<Constant>(TrueVal)) {
if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
unsigned OpToFold = 0;
if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
OpToFold = 1;
} else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
OpToFold = 2;
}
if (OpToFold) {
Constant *C = GetSelectFoldableConstant(FVI, Context);
Value *OOp = FVI->getOperand(2-OpToFold);
// Avoid creating select between 2 constants unless it's selecting
// between 0 and 1.
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
InsertNewInstBefore(NewSel, SI);
NewSel->takeName(FVI);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
llvm_unreachable("Unknown instruction!!");
}
}
}
}
}
return 0;
}
/// visitSelectInstWithICmp - Visit a SelectInst that has an
/// ICmpInst as its first operand.
///
Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
ICmpInst *ICI) {
bool Changed = false;
ICmpInst::Predicate Pred = ICI->getPredicate();
Value *CmpLHS = ICI->getOperand(0);
Value *CmpRHS = ICI->getOperand(1);
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
// Check cases where the comparison is with a constant that
// can be adjusted to fit the min/max idiom. We may edit ICI in
// place here, so make sure the select is the only user.
if (ICI->hasOneUse())
if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
switch (Pred) {
default: break;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT: {
// X < MIN ? T : F --> F
if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
return ReplaceInstUsesWith(SI, FalseVal);
// X < C ? X : C-1 --> X > C-1 ? C-1 : X
Constant *AdjustedRHS = SubOne(CI);
if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
(CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
Pred = ICmpInst::getSwappedPredicate(Pred);
CmpRHS = AdjustedRHS;
std::swap(FalseVal, TrueVal);
ICI->setPredicate(Pred);
ICI->setOperand(1, CmpRHS);
SI.setOperand(1, TrueVal);
SI.setOperand(2, FalseVal);
Changed = true;
}
break;
}
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT: {
// X > MAX ? T : F --> F
if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
return ReplaceInstUsesWith(SI, FalseVal);
// X > C ? X : C+1 --> X < C+1 ? C+1 : X
Constant *AdjustedRHS = AddOne(CI);
if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
(CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
Pred = ICmpInst::getSwappedPredicate(Pred);
CmpRHS = AdjustedRHS;
std::swap(FalseVal, TrueVal);
ICI->setPredicate(Pred);
ICI->setOperand(1, CmpRHS);
SI.setOperand(1, TrueVal);
SI.setOperand(2, FalseVal);
Changed = true;
}
break;
}
}
// (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed
// (x >s -1) ? -1 : 0 -> ashr x, 31 -> all ones if not signed
CmpInst::Predicate Pred = CmpInst::BAD_ICMP_PREDICATE;
if (match(TrueVal, m_ConstantInt<-1>()) &&
match(FalseVal, m_ConstantInt<0>()))
Pred = ICI->getPredicate();
else if (match(TrueVal, m_ConstantInt<0>()) &&
match(FalseVal, m_ConstantInt<-1>()))
Pred = CmpInst::getInversePredicate(ICI->getPredicate());
if (Pred != CmpInst::BAD_ICMP_PREDICATE) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// to an integer, then shift the bit to the appropriate place and then
// cast to integer to avoid the comparison.
const APInt &Op1CV = CI->getValue();
// sext (x <s 0) to i32 --> x>>s31 true if signbit set.
// sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear.
if ((Pred == ICmpInst::ICMP_SLT && Op1CV == 0) ||
(Pred == ICmpInst::ICMP_SGT && Op1CV.isAllOnesValue())) {
Value *In = ICI->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getScalarSizeInBits()-1);
In = InsertNewInstBefore(BinaryOperator::CreateAShr(In, Sh,
In->getName()+".lobit"),
*ICI);
if (In->getType() != SI.getType())
In = CastInst::CreateIntegerCast(In, SI.getType(),
true/*SExt*/, "tmp", ICI);
if (Pred == ICmpInst::ICMP_SGT)
In = InsertNewInstBefore(BinaryOperator::CreateNot(In,
In->getName()+".not"), *ICI);
return ReplaceInstUsesWith(SI, In);
}
}
}
if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
// Transform (X == Y) ? X : Y -> Y
if (Pred == ICmpInst::ICMP_EQ)
return ReplaceInstUsesWith(SI, FalseVal);
// Transform (X != Y) ? X : Y -> X
if (Pred == ICmpInst::ICMP_NE)
return ReplaceInstUsesWith(SI, TrueVal);
/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
} else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
// Transform (X == Y) ? Y : X -> X
if (Pred == ICmpInst::ICMP_EQ)
return ReplaceInstUsesWith(SI, FalseVal);
// Transform (X != Y) ? Y : X -> Y
if (Pred == ICmpInst::ICMP_NE)
return ReplaceInstUsesWith(SI, TrueVal);
/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
}
/// NOTE: if we wanted to, this is where to detect integer ABS
return Changed ? &SI : 0;
}
/// isDefinedInBB - Return true if the value is an instruction defined in the
/// specified basicblock.
static bool isDefinedInBB(const Value *V, const BasicBlock *BB) {
const Instruction *I = dyn_cast<Instruction>(V);
return I != 0 && I->getParent() == BB;
}
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
// select true, X, Y -> X
// select false, X, Y -> Y
if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
// select C, X, X -> X
if (TrueVal == FalseVal)
return ReplaceInstUsesWith(SI, TrueVal);
if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
return ReplaceInstUsesWith(SI, FalseVal);
if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
return ReplaceInstUsesWith(SI, TrueVal);
if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
if (isa<Constant>(TrueVal))
return ReplaceInstUsesWith(SI, TrueVal);
else
return ReplaceInstUsesWith(SI, FalseVal);
}
if (SI.getType() == Type::getInt1Ty(*Context)) {
if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
if (C->getZExtValue()) {
// Change: A = select B, true, C --> A = or B, C
return BinaryOperator::CreateOr(CondVal, FalseVal);
} else {
// Change: A = select B, false, C --> A = and !B, C
Value *NotCond =
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
"not."+CondVal->getName()), SI);
return BinaryOperator::CreateAnd(NotCond, FalseVal);
}
} else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
if (C->getZExtValue() == false) {
// Change: A = select B, C, false --> A = and B, C
return BinaryOperator::CreateAnd(CondVal, TrueVal);
} else {
// Change: A = select B, C, true --> A = or !B, C
Value *NotCond =
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
"not."+CondVal->getName()), SI);
return BinaryOperator::CreateOr(NotCond, TrueVal);
}
}
// select a, b, a -> a&b
// select a, a, b -> a|b
if (CondVal == TrueVal)
return BinaryOperator::CreateOr(CondVal, FalseVal);
else if (CondVal == FalseVal)
return BinaryOperator::CreateAnd(CondVal, TrueVal);
}
// Selecting between two integer constants?
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
// select C, 1, 0 -> zext C to int
if (FalseValC->isZero() && TrueValC->getValue() == 1) {
return CastInst::Create(Instruction::ZExt, CondVal, SI.getType());
} else if (TrueValC->isZero() && FalseValC->getValue() == 1) {
// select C, 0, 1 -> zext !C to int
Value *NotCond =
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
"not."+CondVal->getName()), SI);
return CastInst::Create(Instruction::ZExt, NotCond, SI.getType());
}
if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
// If one of the constants is zero (we know they can't both be) and we
// have an icmp instruction with zero, and we have an 'and' with the
// non-constant value, eliminate this whole mess. This corresponds to
// cases like this: ((X & 27) ? 27 : 0)
if (TrueValC->isZero() || FalseValC->isZero())
if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
cast<Constant>(IC->getOperand(1))->isNullValue())
if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
if (ICA->getOpcode() == Instruction::And &&
isa<ConstantInt>(ICA->getOperand(1)) &&
(ICA->getOperand(1) == TrueValC ||
ICA->getOperand(1) == FalseValC) &&
isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
// Okay, now we know that everything is set up, we just don't
// know whether we have a icmp_ne or icmp_eq and whether the
// true or false val is the zero.
bool ShouldNotVal = !TrueValC->isZero();
ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
Value *V = ICA;
if (ShouldNotVal)
V = InsertNewInstBefore(BinaryOperator::Create(
Instruction::Xor, V, ICA->getOperand(1)), SI);
return ReplaceInstUsesWith(SI, V);
}
}
}
// See if we are selecting two values based on a comparison of the two values.
if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
// Transform (X == Y) ? X : Y -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
// This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? X : Y -> X
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
return ReplaceInstUsesWith(SI, TrueVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
// Transform (X == Y) ? Y : X -> X
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
// This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? Y : X -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
return ReplaceInstUsesWith(SI, TrueVal);
// NOTE: if we wanted to, this is where to detect MIN/MAX
}
// NOTE: if we wanted to, this is where to detect ABS
}
// See if we are selecting two values based on a comparison of the two values.
if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
return Result;
if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
if (TI->hasOneUse() && FI->hasOneUse()) {
Instruction *AddOp = 0, *SubOp = 0;
// Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
if (TI->getOpcode() == FI->getOpcode())
if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
return IV;
// Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
// even legal for FP.
if ((TI->getOpcode() == Instruction::Sub &&
FI->getOpcode() == Instruction::Add) ||
(TI->getOpcode() == Instruction::FSub &&
FI->getOpcode() == Instruction::FAdd)) {
AddOp = FI; SubOp = TI;
} else if ((FI->getOpcode() == Instruction::Sub &&
TI->getOpcode() == Instruction::Add) ||
(FI->getOpcode() == Instruction::FSub &&
TI->getOpcode() == Instruction::FAdd)) {
AddOp = TI; SubOp = FI;
}
if (AddOp) {
Value *OtherAddOp = 0;
if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
OtherAddOp = AddOp->getOperand(1);
} else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
OtherAddOp = AddOp->getOperand(0);
}
if (OtherAddOp) {
// So at this point we know we have (Y -> OtherAddOp):
// select C, (add X, Y), (sub X, Z)
Value *NegVal; // Compute -Z
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
NegVal = ConstantExpr::getNeg(C);
} else {
NegVal = InsertNewInstBefore(
BinaryOperator::CreateNeg(SubOp->getOperand(1),
"tmp"), SI);
}
Value *NewTrueOp = OtherAddOp;
Value *NewFalseOp = NegVal;
if (AddOp != TI)
std::swap(NewTrueOp, NewFalseOp);
Instruction *NewSel =
SelectInst::Create(CondVal, NewTrueOp,
NewFalseOp, SI.getName() + ".p");
NewSel = InsertNewInstBefore(NewSel, SI);
return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
}
}
}
// See if we can fold the select into one of our operands.
if (SI.getType()->isInteger()) {
Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal);
if (FoldI)
return FoldI;
}
// See if we can fold the select into a phi node. The true/false values have
// to be live in the predecessor blocks. If they are instructions in SI's
// block, we can't map to the predecessor.
if (isa<PHINode>(SI.getCondition()) &&
(!isDefinedInBB(SI.getTrueValue(), SI.getParent()) ||
isa<PHINode>(SI.getTrueValue())) &&
(!isDefinedInBB(SI.getFalseValue(), SI.getParent()) ||
isa<PHINode>(SI.getFalseValue())))
if (Instruction *NV = FoldOpIntoPhi(SI))
return NV;
if (BinaryOperator::isNot(CondVal)) {
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
SI.setOperand(1, FalseVal);
SI.setOperand(2, TrueVal);
return &SI;
}
return 0;
}
/// EnforceKnownAlignment - If the specified pointer points to an object that
/// we control, modify the object's alignment to PrefAlign. This isn't
/// often possible though. If alignment is important, a more reliable approach
/// is to simply align all global variables and allocation instructions to
/// their preferred alignment from the beginning.
///
static unsigned EnforceKnownAlignment(Value *V,
unsigned Align, unsigned PrefAlign) {
User *U = dyn_cast<User>(V);
if (!U) return Align;
switch (Operator::getOpcode(U)) {
default: break;
case Instruction::BitCast:
return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
case Instruction::GetElementPtr: {
// If all indexes are zero, it is just the alignment of the base pointer.
bool AllZeroOperands = true;
for (User::op_iterator i = U->op_begin() + 1, e = U->op_end(); i != e; ++i)
if (!isa<Constant>(*i) ||
!cast<Constant>(*i)->isNullValue()) {
AllZeroOperands = false;
break;
}
if (AllZeroOperands) {
// Treat this like a bitcast.
return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
}
break;
}
}
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
// If there is a large requested alignment and we can, bump up the alignment
// of the global.
if (!GV->isDeclaration()) {
if (GV->getAlignment() >= PrefAlign)
Align = GV->getAlignment();
else {
GV->setAlignment(PrefAlign);
Align = PrefAlign;
}
}
} else if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
// If there is a requested alignment and if this is an alloca, round up.
if (AI->getAlignment() >= PrefAlign)
Align = AI->getAlignment();
else {
AI->setAlignment(PrefAlign);
Align = PrefAlign;
}
}
return Align;
}
/// GetOrEnforceKnownAlignment - If the specified pointer has an alignment that
/// we can determine, return it, otherwise return 0. If PrefAlign is specified,
/// and it is more than the alignment of the ultimate object, see if we can
/// increase the alignment of the ultimate object, making this check succeed.
unsigned InstCombiner::GetOrEnforceKnownAlignment(Value *V,
unsigned PrefAlign) {
unsigned BitWidth = TD ? TD->getTypeSizeInBits(V->getType()) :
sizeof(PrefAlign) * CHAR_BIT;
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
ComputeMaskedBits(V, Mask, KnownZero, KnownOne);
unsigned TrailZ = KnownZero.countTrailingOnes();
unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
if (PrefAlign > Align)
Align = EnforceKnownAlignment(V, Align, PrefAlign);
// We don't need to make any adjustment.
return Align;
}
Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getOperand(1));
unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2));
unsigned MinAlign = std::min(DstAlign, SrcAlign);
unsigned CopyAlign = MI->getAlignment();
if (CopyAlign < MinAlign) {
MI->setAlignment(ConstantInt::get(MI->getAlignmentType(),
MinAlign, false));
return MI;
}
// If MemCpyInst length is 1/2/4/8 bytes then replace memcpy with
// load/store.
ConstantInt *MemOpLength = dyn_cast<ConstantInt>(MI->getOperand(3));
if (MemOpLength == 0) return 0;
// Source and destination pointer types are always "i8*" for intrinsic. See
// if the size is something we can handle with a single primitive load/store.
// A single load+store correctly handles overlapping memory in the memmove
// case.
unsigned Size = MemOpLength->getZExtValue();
if (Size == 0) return MI; // Delete this mem transfer.
if (Size > 8 || (Size&(Size-1)))
return 0; // If not 1/2/4/8 bytes, exit.
// Use an integer load+store unless we can find something better.
Type *NewPtrTy =
PointerType::getUnqual(IntegerType::get(*Context, Size<<3));
// Memcpy forces the use of i8* for the source and destination. That means
// that if you're using memcpy to move one double around, you'll get a cast
// from double* to i8*. We'd much rather use a double load+store rather than
// an i64 load+store, here because this improves the odds that the source or
// dest address will be promotable. See if we can find a better type than the
// integer datatype.
if (Value *Op = getBitCastOperand(MI->getOperand(1))) {
const Type *SrcETy = cast<PointerType>(Op->getType())->getElementType();
if (TD && SrcETy->isSized() && TD->getTypeStoreSize(SrcETy) == Size) {
// The SrcETy might be something like {{{double}}} or [1 x double]. Rip
// down through these levels if so.
while (!SrcETy->isSingleValueType()) {
if (const StructType *STy = dyn_cast<StructType>(SrcETy)) {
if (STy->getNumElements() == 1)
SrcETy = STy->getElementType(0);
else
break;
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(SrcETy)) {
if (ATy->getNumElements() == 1)
SrcETy = ATy->getElementType();
else
break;
} else
break;
}
if (SrcETy->isSingleValueType())
NewPtrTy = PointerType::getUnqual(SrcETy);
}
}
// If the memcpy/memmove provides better alignment info than we can
// infer, use it.
SrcAlign = std::max(SrcAlign, CopyAlign);
DstAlign = std::max(DstAlign, CopyAlign);
Value *Src = Builder->CreateBitCast(MI->getOperand(2), NewPtrTy);
Value *Dest = Builder->CreateBitCast(MI->getOperand(1), NewPtrTy);
Instruction *L = new LoadInst(Src, "tmp", false, SrcAlign);
InsertNewInstBefore(L, *MI);
InsertNewInstBefore(new StoreInst(L, Dest, false, DstAlign), *MI);
// Set the size of the copy to 0, it will be deleted on the next iteration.
MI->setOperand(3, Constant::getNullValue(MemOpLength->getType()));
return MI;
}
Instruction *InstCombiner::SimplifyMemSet(MemSetInst *MI) {
unsigned Alignment = GetOrEnforceKnownAlignment(MI->getDest());
if (MI->getAlignment() < Alignment) {
MI->setAlignment(ConstantInt::get(MI->getAlignmentType(),
Alignment, false));
return MI;
}
// Extract the length and alignment and fill if they are constant.
ConstantInt *LenC = dyn_cast<ConstantInt>(MI->getLength());
ConstantInt *FillC = dyn_cast<ConstantInt>(MI->getValue());
if (!LenC || !FillC || FillC->getType() != Type::getInt8Ty(*Context))
return 0;
uint64_t Len = LenC->getZExtValue();
Alignment = MI->getAlignment();
// If the length is zero, this is a no-op
if (Len == 0) return MI; // memset(d,c,0,a) -> noop
// memset(s,c,n) -> store s, c (for n=1,2,4,8)
if (Len <= 8 && isPowerOf2_32((uint32_t)Len)) {
const Type *ITy = IntegerType::get(*Context, Len*8); // n=1 -> i8.
Value *Dest = MI->getDest();
Dest = Builder->CreateBitCast(Dest, PointerType::getUnqual(ITy));
// Alignment 0 is identity for alignment 1 for memset, but not store.
if (Alignment == 0) Alignment = 1;
// Extract the fill value and store.
uint64_t Fill = FillC->getZExtValue()*0x0101010101010101ULL;
InsertNewInstBefore(new StoreInst(ConstantInt::get(ITy, Fill),
Dest, false, Alignment), *MI);
// Set the size of the copy to 0, it will be deleted on the next iteration.
MI->setLength(Constant::getNullValue(LenC->getType()));
return MI;
}
return 0;
}
/// visitCallInst - CallInst simplification. This mostly only handles folding
/// of intrinsic instructions. For normal calls, it allows visitCallSite to do
/// the heavy lifting.
///
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// If the caller function is nounwind, mark the call as nounwind, even if the
// callee isn't.
if (CI.getParent()->getParent()->doesNotThrow() &&
!CI.doesNotThrow()) {
CI.setDoesNotThrow();
return &CI;
}
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
if (!II) return visitCallSite(&CI);
// Intrinsics cannot occur in an invoke, so handle them here instead of in
// visitCallSite.
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(II)) {
bool Changed = false;
// memmove/cpy/set of zero bytes is a noop.
if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
if (CI->getZExtValue() == 1) {
// Replace the instruction with just byte operations. We would
// transform other cases to loads/stores, but we don't know if
// alignment is sufficient.
}
}
// If we have a memmove and the source operation is a constant global,
// then the source and dest pointers can't alias, so we can change this
// into a call to memcpy.
if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) {
if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
if (GVSrc->isConstant()) {
Module *M = CI.getParent()->getParent()->getParent();
Intrinsic::ID MemCpyID = Intrinsic::memcpy;
const Type *Tys[1];
Tys[0] = CI.getOperand(3)->getType();
CI.setOperand(0,
Intrinsic::getDeclaration(M, MemCpyID, Tys, 1));
Changed = true;
}
// memmove(x,x,size) -> noop.
if (MMI->getSource() == MMI->getDest())
return EraseInstFromFunction(CI);
}
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (isa<MemTransferInst>(MI)) {
if (Instruction *I = SimplifyMemTransfer(MI))
return I;
} else if (MemSetInst *MSI = dyn_cast<MemSetInst>(MI)) {
if (Instruction *I = SimplifyMemSet(MSI))
return I;
}
if (Changed) return II;
}
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::bswap:
// bswap(bswap(x)) -> x
if (IntrinsicInst *Operand = dyn_cast<IntrinsicInst>(II->getOperand(1)))
if (Operand->getIntrinsicID() == Intrinsic::bswap)
return ReplaceInstUsesWith(CI, Operand->getOperand(1));
break;
case Intrinsic::ppc_altivec_lvx:
case Intrinsic::ppc_altivec_lvxl:
case Intrinsic::x86_sse_loadu_ps:
case Intrinsic::x86_sse2_loadu_pd:
case Intrinsic::x86_sse2_loadu_dq:
// Turn PPC lvx -> load if the pointer is known aligned.
// Turn X86 loadups -> load if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(1), 16) >= 16) {
Value *Ptr = Builder->CreateBitCast(II->getOperand(1),
PointerType::getUnqual(II->getType()));
return new LoadInst(Ptr);
}
break;
case Intrinsic::ppc_altivec_stvx:
case Intrinsic::ppc_altivec_stvxl:
// Turn stvx -> store if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(2), 16) >= 16) {
const Type *OpPtrTy =
PointerType::getUnqual(II->getOperand(1)->getType());
Value *Ptr = Builder->CreateBitCast(II->getOperand(2), OpPtrTy);
return new StoreInst(II->getOperand(1), Ptr);
}
break;
case Intrinsic::x86_sse_storeu_ps:
case Intrinsic::x86_sse2_storeu_pd:
case Intrinsic::x86_sse2_storeu_dq:
// Turn X86 storeu -> store if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(1), 16) >= 16) {
const Type *OpPtrTy =
PointerType::getUnqual(II->getOperand(2)->getType());
Value *Ptr = Builder->CreateBitCast(II->getOperand(1), OpPtrTy);
return new StoreInst(II->getOperand(2), Ptr);
}
break;
case Intrinsic::x86_sse_cvttss2si: {
// These intrinsics only demands the 0th element of its input vector. If
// we can simplify the input based on that, do so now.
unsigned VWidth =
cast<VectorType>(II->getOperand(1)->getType())->getNumElements();
APInt DemandedElts(VWidth, 1);
APInt UndefElts(VWidth, 0);
if (Value *V = SimplifyDemandedVectorElts(II->getOperand(1), DemandedElts,
UndefElts)) {
II->setOperand(1, V);
return II;
}
break;
}
case Intrinsic::ppc_altivec_vperm:
// Turn vperm(V1,V2,mask) -> shuffle(V1,V2,mask) if mask is a constant.
if (ConstantVector *Mask = dyn_cast<ConstantVector>(II->getOperand(3))) {
assert(Mask->getNumOperands() == 16 && "Bad type for intrinsic!");
// Check that all of the elements are integer constants or undefs.
bool AllEltsOk = true;
for (unsigned i = 0; i != 16; ++i) {
if (!isa<ConstantInt>(Mask->getOperand(i)) &&
!isa<UndefValue>(Mask->getOperand(i))) {
AllEltsOk = false;
break;
}
}
if (AllEltsOk) {
// Cast the input vectors to byte vectors.
Value *Op0 = Builder->CreateBitCast(II->getOperand(1), Mask->getType());
Value *Op1 = Builder->CreateBitCast(II->getOperand(2), Mask->getType());
Value *Result = UndefValue::get(Op0->getType());
// Only extract each element once.
Value *ExtractedElts[32];
memset(ExtractedElts, 0, sizeof(ExtractedElts));
for (unsigned i = 0; i != 16; ++i) {
if (isa<UndefValue>(Mask->getOperand(i)))
continue;
unsigned Idx=cast<ConstantInt>(Mask->getOperand(i))->getZExtValue();
Idx &= 31; // Match the hardware behavior.
if (ExtractedElts[Idx] == 0) {
ExtractedElts[Idx] =
Builder->CreateExtractElement(Idx < 16 ? Op0 : Op1,
ConstantInt::get(Type::getInt32Ty(*Context), Idx&15, false),
"tmp");
}
// Insert this value into the result vector.
Result = Builder->CreateInsertElement(Result, ExtractedElts[Idx],
ConstantInt::get(Type::getInt32Ty(*Context), i, false),
"tmp");
}
return CastInst::Create(Instruction::BitCast, Result, CI.getType());
}
}
break;
case Intrinsic::stackrestore: {
// If the save is right next to the restore, remove the restore. This can
// happen when variable allocas are DCE'd.
if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getOperand(1))) {
if (SS->getIntrinsicID() == Intrinsic::stacksave) {
BasicBlock::iterator BI = SS;
if (&*++BI == II)
return EraseInstFromFunction(CI);
}
}
// Scan down this block to see if there is another stack restore in the
// same block without an intervening call/alloca.
BasicBlock::iterator BI = II;
TerminatorInst *TI = II->getParent()->getTerminator();
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI) || isMalloc(BI)) {
CannotRemove = true;
break;
}
if (CallInst *BCI = dyn_cast<CallInst>(BI)) {
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BCI)) {
// If there is a stackrestore below this one, remove this one.
if (II->getIntrinsicID() == Intrinsic::stackrestore)
return EraseInstFromFunction(CI);
// Otherwise, ignore the intrinsic.
} else {
// If we found a non-intrinsic call, we can't remove the stack
// restore.
CannotRemove = true;
break;
}
}
}
// If the stack restore is in a return/unwind block and if there are no
// allocas or calls between the restore and the return, nuke the restore.
if (!CannotRemove && (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)))
return EraseInstFromFunction(CI);
break;
}
}
return visitCallSite(II);
}
// InvokeInst simplification
//
Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
return visitCallSite(&II);
}
/// isSafeToEliminateVarargsCast - If this cast does not affect the value
/// passed through the varargs area, we can eliminate the use of the cast.
static bool isSafeToEliminateVarargsCast(const CallSite CS,
const CastInst * const CI,
const TargetData * const TD,
const int ix) {
if (!CI->isLosslessCast())
return false;
// The size of ByVal arguments is derived from the type, so we
// can't change to a type with a different size. If the size were
// passed explicitly we could avoid this check.
if (!CS.paramHasAttr(ix, Attribute::ByVal))
return true;
const Type* SrcTy =
cast<PointerType>(CI->getOperand(0)->getType())->getElementType();
const Type* DstTy = cast<PointerType>(CI->getType())->getElementType();
if (!SrcTy->isSized() || !DstTy->isSized())
return false;
if (!TD || TD->getTypeAllocSize(SrcTy) != TD->getTypeAllocSize(DstTy))
return false;
return true;
}
// visitCallSite - Improvements for call and invoke instructions.
//
Instruction *InstCombiner::visitCallSite(CallSite CS) {
bool Changed = false;
// If the callee is a constexpr cast of a function, attempt to move the cast
// to the arguments of the call/invoke.
if (transformConstExprCastCall(CS)) return 0;
Value *Callee = CS.getCalledValue();
if (Function *CalleeF = dyn_cast<Function>(Callee))
if (CalleeF->getCallingConv() != CS.getCallingConv()) {
Instruction *OldCall = CS.getInstruction();
// If the call and callee calling conventions don't match, this call must
// be unreachable, as the call is undefined.
new StoreInst(ConstantInt::getTrue(*Context),
UndefValue::get(Type::getInt1PtrTy(*Context)),
OldCall);
if (!OldCall->use_empty())
OldCall->replaceAllUsesWith(UndefValue::get(OldCall->getType()));
if (isa<CallInst>(OldCall)) // Not worth removing an invoke here.
return EraseInstFromFunction(*OldCall);
return 0;
}
if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
// This instruction is not reachable, just remove it. We insert a store to
// undef so that we know that this code is not reachable, despite the fact
// that we can't modify the CFG here.
new StoreInst(ConstantInt::getTrue(*Context),
UndefValue::get(Type::getInt1PtrTy(*Context)),
CS.getInstruction());
if (!CS.getInstruction()->use_empty())
CS.getInstruction()->
replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
// Don't break the CFG, insert a dummy cond branch.
BranchInst::Create(II->getNormalDest(), II->getUnwindDest(),
ConstantInt::getTrue(*Context), II);
}
return EraseInstFromFunction(*CS.getInstruction());
}
if (BitCastInst *BC = dyn_cast<BitCastInst>(Callee))
if (IntrinsicInst *In = dyn_cast<IntrinsicInst>(BC->getOperand(0)))
if (In->getIntrinsicID() == Intrinsic::init_trampoline)
return transformCallThroughTrampoline(CS);
const PointerType *PTy = cast<PointerType>(Callee->getType());
const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
if (FTy->isVarArg()) {
int ix = FTy->getNumParams() + (isa<InvokeInst>(Callee) ? 3 : 1);
// See if we can optimize any arguments passed through the varargs area of
// the call.
for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
E = CS.arg_end(); I != E; ++I, ++ix) {
CastInst *CI = dyn_cast<CastInst>(*I);
if (CI && isSafeToEliminateVarargsCast(CS, CI, TD, ix)) {
*I = CI->getOperand(0);
Changed = true;
}
}
}
if (isa<InlineAsm>(Callee) && !CS.doesNotThrow()) {
// Inline asm calls cannot throw - mark them 'nounwind'.
CS.setDoesNotThrow();
Changed = true;
}
return Changed ? CS.getInstruction() : 0;
}
// transformConstExprCastCall - If the callee is a constexpr cast of a function,
// attempt to move the cast to the arguments of the call/invoke.
//
bool InstCombiner::transformConstExprCastCall(CallSite CS) {
if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
if (CE->getOpcode() != Instruction::BitCast ||
!isa<Function>(CE->getOperand(0)))
return false;
Function *Callee = cast<Function>(CE->getOperand(0));
Instruction *Caller = CS.getInstruction();
const AttrListPtr &CallerPAL = CS.getAttributes();
// Okay, this is a cast from a function to a different type. Unless doing so
// would cause a type conversion of one of our arguments, change this call to
// be a direct call with arguments casted to the appropriate types.
//
const FunctionType *FT = Callee->getFunctionType();
const Type *OldRetTy = Caller->getType();
const Type *NewRetTy = FT->getReturnType();
if (isa<StructType>(NewRetTy))
return false; // TODO: Handle multiple return values.
// Check to see if we are changing the return type...
if (OldRetTy != NewRetTy) {
if (Callee->isDeclaration() &&
// Conversion is ok if changing from one pointer type to another or from
// a pointer to an integer of the same size.
!((isa<PointerType>(OldRetTy) || !TD ||
OldRetTy == TD->getIntPtrType(Caller->getContext())) &&
(isa<PointerType>(NewRetTy) || !TD ||
NewRetTy == TD->getIntPtrType(Caller->getContext()))))
return false; // Cannot transform this return value.
if (!Caller->use_empty() &&
// void -> non-void is handled specially
NewRetTy != Type::getVoidTy(*Context) && !CastInst::isCastable(NewRetTy, OldRetTy))
return false; // Cannot transform this return value.
if (!CallerPAL.isEmpty() && !Caller->use_empty()) {
Attributes RAttrs = CallerPAL.getRetAttributes();
if (RAttrs & Attribute::typeIncompatible(NewRetTy))
return false; // Attribute not compatible with transformed value.
}
// If the callsite is an invoke instruction, and the return value is used by
// a PHI node in a successor, we cannot change the return type of the call
// because there is no place to put the cast instruction (without breaking
// the critical edge). Bail out in this case.
if (!Caller->use_empty())
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
UI != E; ++UI)
if (PHINode *PN = dyn_cast<PHINode>(*UI))
if (PN->getParent() == II->getNormalDest() ||
PN->getParent() == II->getUnwindDest())
return false;
}
unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
CallSite::arg_iterator AI = CS.arg_begin();
for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
const Type *ParamTy = FT->getParamType(i);
const Type *ActTy = (*AI)->getType();
if (!CastInst::isCastable(ActTy, ParamTy))
return false; // Cannot transform this parameter value.
if (CallerPAL.getParamAttributes(i + 1)
& Attribute::typeIncompatible(ParamTy))
return false; // Attribute not compatible with transformed value.
// Converting from one pointer type to another or between a pointer and an
// integer of the same size is safe even if we do not have a body.
bool isConvertible = ActTy == ParamTy ||
(TD && ((isa<PointerType>(ParamTy) ||
ParamTy == TD->getIntPtrType(Caller->getContext())) &&
(isa<PointerType>(ActTy) ||
ActTy == TD->getIntPtrType(Caller->getContext()))));
if (Callee->isDeclaration() && !isConvertible) return false;
}
if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
Callee->isDeclaration())
return false; // Do not delete arguments unless we have a function body.
if (FT->getNumParams() < NumActualArgs && FT->isVarArg() &&
!CallerPAL.isEmpty())
// In this case we have more arguments than the new function type, but we
// won't be dropping them. Check that these extra arguments have attributes
// that are compatible with being a vararg call argument.
for (unsigned i = CallerPAL.getNumSlots(); i; --i) {
if (CallerPAL.getSlot(i - 1).Index <= FT->getNumParams())
break;
Attributes PAttrs = CallerPAL.getSlot(i - 1).Attrs;
if (PAttrs & Attribute::VarArgsIncompatible)
return false;
}
// Okay, we decided that this is a safe thing to do: go ahead and start
// inserting cast instructions as necessary...
std::vector<Value*> Args;
Args.reserve(NumActualArgs);
SmallVector<AttributeWithIndex, 8> attrVec;
attrVec.reserve(NumCommonArgs);
// Get any return attributes.
Attributes RAttrs = CallerPAL.getRetAttributes();
// If the return value is not being used, the type may not be compatible
// with the existing attributes. Wipe out any problematic attributes.
RAttrs &= ~Attribute::typeIncompatible(NewRetTy);
// Add the new return attributes.
if (RAttrs)
attrVec.push_back(AttributeWithIndex::get(0, RAttrs));
AI = CS.arg_begin();
for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
const Type *ParamTy = FT->getParamType(i);
if ((*AI)->getType() == ParamTy) {
Args.push_back(*AI);
} else {
Instruction::CastOps opcode = CastInst::getCastOpcode(*AI,
false, ParamTy, false);
Args.push_back(Builder->CreateCast(opcode, *AI, ParamTy, "tmp"));
}
// Add any parameter attributes.
if (Attributes PAttrs = CallerPAL.getParamAttributes(i + 1))
attrVec.push_back(AttributeWithIndex::get(i + 1, PAttrs));
}
// If the function takes more arguments than the call was taking, add them
// now.
for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
Args.push_back(Constant::getNullValue(FT->getParamType(i)));
// If we are removing arguments to the function, emit an obnoxious warning.
if (FT->getNumParams() < NumActualArgs) {
if (!FT->isVarArg()) {
errs() << "WARNING: While resolving call to function '"
<< Callee->getName() << "' arguments were dropped!\n";
} else {
// Add all of the arguments in their promoted form to the arg list.
for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
const Type *PTy = getPromotedType((*AI)->getType());
if (PTy != (*AI)->getType()) {
// Must promote to pass through va_arg area!
Instruction::CastOps opcode =
CastInst::getCastOpcode(*AI, false, PTy, false);
Args.push_back(Builder->CreateCast(opcode, *AI, PTy, "tmp"));
} else {
Args.push_back(*AI);
}
// Add any parameter attributes.
if (Attributes PAttrs = CallerPAL.getParamAttributes(i + 1))
attrVec.push_back(AttributeWithIndex::get(i + 1, PAttrs));
}
}
}
if (Attributes FnAttrs = CallerPAL.getFnAttributes())
attrVec.push_back(AttributeWithIndex::get(~0, FnAttrs));
if (NewRetTy == Type::getVoidTy(*Context))
Caller->setName(""); // Void type should not have a name.
const AttrListPtr &NewCallerPAL = AttrListPtr::get(attrVec.begin(),
attrVec.end());
Instruction *NC;
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
NC = InvokeInst::Create(Callee, II->getNormalDest(), II->getUnwindDest(),
Args.begin(), Args.end(),
Caller->getName(), Caller);
cast<InvokeInst>(NC)->setCallingConv(II->getCallingConv());
cast<InvokeInst>(NC)->setAttributes(NewCallerPAL);
} else {
NC = CallInst::Create(Callee, Args.begin(), Args.end(),
Caller->getName(), Caller);
CallInst *CI = cast<CallInst>(Caller);
if (CI->isTailCall())
cast<CallInst>(NC)->setTailCall();
cast<CallInst>(NC)->setCallingConv(CI->getCallingConv());
cast<CallInst>(NC)->setAttributes(NewCallerPAL);
}
// Insert a cast of the return type as necessary.
Value *NV = NC;
if (OldRetTy != NV->getType() && !Caller->use_empty()) {
if (NV->getType() != Type::getVoidTy(*Context)) {
Instruction::CastOps opcode = CastInst::getCastOpcode(NC, false,
OldRetTy, false);
NV = NC = CastInst::Create(opcode, NC, OldRetTy, "tmp");
// If this is an invoke instruction, we should insert it after the first
// non-phi, instruction in the normal successor block.
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
BasicBlock::iterator I = II->getNormalDest()->getFirstNonPHI();
InsertNewInstBefore(NC, *I);
} else {
// Otherwise, it's a call, just insert cast right after the call instr
InsertNewInstBefore(NC, *Caller);
}
Worklist.AddUsersToWorkList(*Caller);
} else {
NV = UndefValue::get(Caller->getType());
}
}
if (!Caller->use_empty())
Caller->replaceAllUsesWith(NV);
EraseInstFromFunction(*Caller);
return true;
}
// transformCallThroughTrampoline - Turn a call to a function created by the
// init_trampoline intrinsic into a direct call to the underlying function.
//
Instruction *InstCombiner::transformCallThroughTrampoline(CallSite CS) {
Value *Callee = CS.getCalledValue();
const PointerType *PTy = cast<PointerType>(Callee->getType());
const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
const AttrListPtr &Attrs = CS.getAttributes();
// If the call already has the 'nest' attribute somewhere then give up -
// otherwise 'nest' would occur twice after splicing in the chain.
if (Attrs.hasAttrSomewhere(Attribute::Nest))
return 0;
IntrinsicInst *Tramp =
cast<IntrinsicInst>(cast<BitCastInst>(Callee)->getOperand(0));
Function *NestF = cast<Function>(Tramp->getOperand(2)->stripPointerCasts());
const PointerType *NestFPTy = cast<PointerType>(NestF->getType());
const FunctionType *NestFTy = cast<FunctionType>(NestFPTy->getElementType());
const AttrListPtr &NestAttrs = NestF->getAttributes();
if (!NestAttrs.isEmpty()) {
unsigned NestIdx = 1;
const Type *NestTy = 0;
Attributes NestAttr = Attribute::None;
// Look for a parameter marked with the 'nest' attribute.
for (FunctionType::param_iterator I = NestFTy->param_begin(),
E = NestFTy->param_end(); I != E; ++NestIdx, ++I)
if (NestAttrs.paramHasAttr(NestIdx, Attribute::Nest)) {
// Record the parameter type and any other attributes.
NestTy = *I;
NestAttr = NestAttrs.getParamAttributes(NestIdx);
break;
}
if (NestTy) {
Instruction *Caller = CS.getInstruction();
std::vector<Value*> NewArgs;
NewArgs.reserve(unsigned(CS.arg_end()-CS.arg_begin())+1);
SmallVector<AttributeWithIndex, 8> NewAttrs;
NewAttrs.reserve(Attrs.getNumSlots() + 1);
// Insert the nest argument into the call argument list, which may
// mean appending it. Likewise for attributes.
// Add any result attributes.
if (Attributes Attr = Attrs.getRetAttributes())
NewAttrs.push_back(AttributeWithIndex::get(0, Attr));
{
unsigned Idx = 1;
CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
do {
if (Idx == NestIdx) {
// Add the chain argument and attributes.
Value *NestVal = Tramp->getOperand(3);
if (NestVal->getType() != NestTy)
NestVal = new BitCastInst(NestVal, NestTy, "nest", Caller);
NewArgs.push_back(NestVal);
NewAttrs.push_back(AttributeWithIndex::get(NestIdx, NestAttr));
}
if (I == E)
break;
// Add the original argument and attributes.
NewArgs.push_back(*I);
if (Attributes Attr = Attrs.getParamAttributes(Idx))
NewAttrs.push_back
(AttributeWithIndex::get(Idx + (Idx >= NestIdx), Attr));
++Idx, ++I;
} while (1);
}
// Add any function attributes.
if (Attributes Attr = Attrs.getFnAttributes())
NewAttrs.push_back(AttributeWithIndex::get(~0, Attr));
// The trampoline may have been bitcast to a bogus type (FTy).
// Handle this by synthesizing a new function type, equal to FTy
// with the chain parameter inserted.
std::vector<const Type*> NewTypes;
NewTypes.reserve(FTy->getNumParams()+1);
// Insert the chain's type into the list of parameter types, which may
// mean appending it.
{
unsigned Idx = 1;
FunctionType::param_iterator I = FTy->param_begin(),
E = FTy->param_end();
do {
if (Idx == NestIdx)
// Add the chain's type.
NewTypes.push_back(NestTy);
if (I == E)
break;
// Add the original type.
NewTypes.push_back(*I);
++Idx, ++I;
} while (1);
}
// Replace the trampoline call with a direct call. Let the generic
// code sort out any function type mismatches.
FunctionType *NewFTy = FunctionType::get(FTy->getReturnType(), NewTypes,
FTy->isVarArg());
Constant *NewCallee =
NestF->getType() == PointerType::getUnqual(NewFTy) ?
NestF : ConstantExpr::getBitCast(NestF,
PointerType::getUnqual(NewFTy));
const AttrListPtr &NewPAL = AttrListPtr::get(NewAttrs.begin(),
NewAttrs.end());
Instruction *NewCaller;
if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
NewCaller = InvokeInst::Create(NewCallee,
II->getNormalDest(), II->getUnwindDest(),
NewArgs.begin(), NewArgs.end(),
Caller->getName(), Caller);
cast<InvokeInst>(NewCaller)->setCallingConv(II->getCallingConv());
cast<InvokeInst>(NewCaller)->setAttributes(NewPAL);
} else {
NewCaller = CallInst::Create(NewCallee, NewArgs.begin(), NewArgs.end(),
Caller->getName(), Caller);
if (cast<CallInst>(Caller)->isTailCall())
cast<CallInst>(NewCaller)->setTailCall();
cast<CallInst>(NewCaller)->
setCallingConv(cast<CallInst>(Caller)->getCallingConv());
cast<CallInst>(NewCaller)->setAttributes(NewPAL);
}
if (Caller->getType() != Type::getVoidTy(*Context) && !Caller->use_empty())
Caller->replaceAllUsesWith(NewCaller);
Caller->eraseFromParent();
Worklist.Remove(Caller);
return 0;
}
}
// Replace the trampoline call with a direct call. Since there is no 'nest'
// parameter, there is no need to adjust the argument list. Let the generic
// code sort out any function type mismatches.
Constant *NewCallee =
NestF->getType() == PTy ? NestF :
ConstantExpr::getBitCast(NestF, PTy);
CS.setCalledFunction(NewCallee);
return CS.getInstruction();
}
/// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(a,c)]
/// and if a/b/c and the add's all have a single use, turn this into a phi
/// and a single binop.
Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
assert(isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst));
unsigned Opc = FirstInst->getOpcode();
Value *LHSVal = FirstInst->getOperand(0);
Value *RHSVal = FirstInst->getOperand(1);
const Type *LHSType = LHSVal->getType();
const Type *RHSType = RHSVal->getType();
// Scan to see if all operands are the same opcode, and all have one use.
for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
if (!I || I->getOpcode() != Opc || !I->hasOneUse() ||
// Verify type of the LHS matches so we don't fold cmp's of different
// types or GEP's with different index types.
I->getOperand(0)->getType() != LHSType ||
I->getOperand(1)->getType() != RHSType)
return 0;
// If they are CmpInst instructions, check their predicates
if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
if (cast<CmpInst>(I)->getPredicate() !=
cast<CmpInst>(FirstInst)->getPredicate())
return 0;
// Keep track of which operand needs a phi node.
if (I->getOperand(0) != LHSVal) LHSVal = 0;
if (I->getOperand(1) != RHSVal) RHSVal = 0;
}
// If both LHS and RHS would need a PHI, don't do this transformation,
// because it would increase the number of PHIs entering the block,
// which leads to higher register pressure. This is especially
// bad when the PHIs are in the header of a loop.
if (!LHSVal && !RHSVal)
return 0;
// Otherwise, this is safe to transform!
Value *InLHS = FirstInst->getOperand(0);
Value *InRHS = FirstInst->getOperand(1);
PHINode *NewLHS = 0, *NewRHS = 0;
if (LHSVal == 0) {
NewLHS = PHINode::Create(LHSType,
FirstInst->getOperand(0)->getName() + ".pn");
NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
InsertNewInstBefore(NewLHS, PN);
LHSVal = NewLHS;
}
if (RHSVal == 0) {
NewRHS = PHINode::Create(RHSType,
FirstInst->getOperand(1)->getName() + ".pn");
NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
NewRHS->addIncoming(InRHS, PN.getIncomingBlock(0));
InsertNewInstBefore(NewRHS, PN);
RHSVal = NewRHS;
}
// Add all operands to the new PHIs.
if (NewLHS || NewRHS) {
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
Instruction *InInst = cast<Instruction>(PN.getIncomingValue(i));
if (NewLHS) {
Value *NewInLHS = InInst->getOperand(0);
NewLHS->addIncoming(NewInLHS, PN.getIncomingBlock(i));
}
if (NewRHS) {
Value *NewInRHS = InInst->getOperand(1);
NewRHS->addIncoming(NewInRHS, PN.getIncomingBlock(i));
}
}
}
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::Create(BinOp->getOpcode(), LHSVal, RHSVal);
CmpInst *CIOp = cast<CmpInst>(FirstInst);
return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
LHSVal, RHSVal);
}
Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
GetElementPtrInst *FirstInst =cast<GetElementPtrInst>(PN.getIncomingValue(0));
SmallVector<Value*, 16> FixedOperands(FirstInst->op_begin(),
FirstInst->op_end());
// This is true if all GEP bases are allocas and if all indices into them are
// constants.
bool AllBasePointersAreAllocas = true;
// We don't want to replace this phi if the replacement would require
// more than one phi, which leads to higher register pressure. This is
// especially bad when the PHIs are in the header of a loop.
bool NeededPhi = false;
// Scan to see if all operands are the same opcode, and all have one use.
for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
GetElementPtrInst *GEP= dyn_cast<GetElementPtrInst>(PN.getIncomingValue(i));
if (!GEP || !GEP->hasOneUse() || GEP->getType() != FirstInst->getType() ||
GEP->getNumOperands() != FirstInst->getNumOperands())
return 0;
// Keep track of whether or not all GEPs are of alloca pointers.
if (AllBasePointersAreAllocas &&
(!isa<AllocaInst>(GEP->getOperand(0)) ||
!GEP->hasAllConstantIndices()))
AllBasePointersAreAllocas = false;
// Compare the operand lists.
for (unsigned op = 0, e = FirstInst->getNumOperands(); op != e; ++op) {
if (FirstInst->getOperand(op) == GEP->getOperand(op))
continue;
// Don't merge two GEPs when two operands differ (introducing phi nodes)
// if one of the PHIs has a constant for the index. The index may be
// substantially cheaper to compute for the constants, so making it a
// variable index could pessimize the path. This also handles the case
// for struct indices, which must always be constant.
if (isa<ConstantInt>(FirstInst->getOperand(op)) ||
isa<ConstantInt>(GEP->getOperand(op)))
return 0;
if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType())
return 0;
// If we already needed a PHI for an earlier operand, and another operand
// also requires a PHI, we'd be introducing more PHIs than we're
// eliminating, which increases register pressure on entry to the PHI's
// block.
if (NeededPhi)
return 0;
FixedOperands[op] = 0; // Needs a PHI.
NeededPhi = true;
}
}
// If all of the base pointers of the PHI'd GEPs are from allocas, don't
// bother doing this transformation. At best, this will just save a bit of
// offset calculation, but all the predecessors will have to materialize the
// stack address into a register anyway. We'd actually rather *clone* the
// load up into the predecessors so that we have a load of a gep of an alloca,
// which can usually all be folded into the load.
if (AllBasePointersAreAllocas)
return 0;
// Otherwise, this is safe to transform. Insert PHI nodes for each operand
// that is variable.
SmallVector<PHINode*, 16> OperandPhis(FixedOperands.size());
bool HasAnyPHIs = false;
for (unsigned i = 0, e = FixedOperands.size(); i != e; ++i) {
if (FixedOperands[i]) continue; // operand doesn't need a phi.
Value *FirstOp = FirstInst->getOperand(i);
PHINode *NewPN = PHINode::Create(FirstOp->getType(),
FirstOp->getName()+".pn");
InsertNewInstBefore(NewPN, PN);
NewPN->reserveOperandSpace(e);
NewPN->addIncoming(FirstOp, PN.getIncomingBlock(0));
OperandPhis[i] = NewPN;
FixedOperands[i] = NewPN;
HasAnyPHIs = true;
}
// Add all operands to the new PHIs.
if (HasAnyPHIs) {
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
GetElementPtrInst *InGEP =cast<GetElementPtrInst>(PN.getIncomingValue(i));
BasicBlock *InBB = PN.getIncomingBlock(i);
for (unsigned op = 0, e = OperandPhis.size(); op != e; ++op)
if (PHINode *OpPhi = OperandPhis[op])
OpPhi->addIncoming(InGEP->getOperand(op), InBB);
}
}
Value *Base = FixedOperands[0];
return cast<GEPOperator>(FirstInst)->isInBounds() ?
GetElementPtrInst::CreateInBounds(Base, FixedOperands.begin()+1,
FixedOperands.end()) :
GetElementPtrInst::Create(Base, FixedOperands.begin()+1,
FixedOperands.end());
}
/// isSafeAndProfitableToSinkLoad - Return true if we know that it is safe to
/// sink the load out of the block that defines it. This means that it must be
/// obvious the value of the load is not changed from the point of the load to
/// the end of the block it is in.
///
/// Finally, it is safe, but not profitable, to sink a load targetting a
/// non-address-taken alloca. Doing so will cause us to not promote the alloca
/// to a register.
static bool isSafeAndProfitableToSinkLoad(LoadInst *L) {
BasicBlock::iterator BBI = L, E = L->getParent()->end();
for (++BBI; BBI != E; ++BBI)
if (BBI->mayWriteToMemory())
return false;
// Check for non-address taken alloca. If not address-taken already, it isn't
// profitable to do this xform.
if (AllocaInst *AI = dyn_cast<AllocaInst>(L->getOperand(0))) {
bool isAddressTaken = false;
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI) {
if (isa<LoadInst>(UI)) continue;
if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
// If storing TO the alloca, then the address isn't taken.
if (SI->getOperand(1) == AI) continue;
}
isAddressTaken = true;
break;
}
if (!isAddressTaken && AI->isStaticAlloca())
return false;
}
// If this load is a load from a GEP with a constant offset from an alloca,
// then we don't want to sink it. In its present form, it will be
// load [constant stack offset]. Sinking it will cause us to have to
// materialize the stack addresses in each predecessor in a register only to
// do a shared load from register in the successor.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(L->getOperand(0)))
if (AllocaInst *AI = dyn_cast<AllocaInst>(GEP->getOperand(0)))
if (AI->isStaticAlloca() && GEP->hasAllConstantIndices())
return false;
return true;
}
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
// inputs, and do the operation once, to the result of the PHI.
Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
// Scan the instruction, looking for input operations that can be folded away.
// If all input operands to the phi are the same instruction (e.g. a cast from
// the same type or "+42") we can pull the operation through the PHI, reducing
// code size and simplifying code.
Constant *ConstantOp = 0;
const Type *CastSrcTy = 0;
bool isVolatile = false;
if (isa<CastInst>(FirstInst)) {
CastSrcTy = FirstInst->getOperand(0)->getType();
} else if (isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst)) {
// Can fold binop, compare or shift here if the RHS is a constant,
// otherwise call FoldPHIArgBinOpIntoPHI.
ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
if (ConstantOp == 0)
return FoldPHIArgBinOpIntoPHI(PN);
} else if (LoadInst *LI = dyn_cast<LoadInst>(FirstInst)) {
isVolatile = LI->isVolatile();
// We can't sink the load if the loaded value could be modified between the
// load and the PHI.
if (LI->getParent() != PN.getIncomingBlock(0) ||
!isSafeAndProfitableToSinkLoad(LI))
return 0;
// If the PHI is of volatile loads and the load block has multiple
// successors, sinking it would remove a load of the volatile value from
// the path through the other successor.
if (isVolatile &&
LI->getParent()->getTerminator()->getNumSuccessors() != 1)
return 0;
} else if (isa<GetElementPtrInst>(FirstInst)) {
return FoldPHIArgGEPIntoPHI(PN);
} else {
return 0; // Cannot fold this operation.
}
// Check to see if all arguments are the same operation.
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
if (!isa<Instruction>(PN.getIncomingValue(i))) return 0;
Instruction *I = cast<Instruction>(PN.getIncomingValue(i));
if (!I->hasOneUse() || !I->isSameOperationAs(FirstInst))
return 0;
if (CastSrcTy) {
if (I->getOperand(0)->getType() != CastSrcTy)
return 0; // Cast operation must match.
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// We can't sink the load if the loaded value could be modified between
// the load and the PHI.
if (LI->isVolatile() != isVolatile ||
LI->getParent() != PN.getIncomingBlock(i) ||
!isSafeAndProfitableToSinkLoad(LI))
return 0;
// If the PHI is of volatile loads and the load block has multiple
// successors, sinking it would remove a load of the volatile value from
// the path through the other successor.
if (isVolatile &&
LI->getParent()->getTerminator()->getNumSuccessors() != 1)
return 0;
} else if (I->getOperand(1) != ConstantOp) {
return 0;
}
}
// Okay, they are all the same operation. Create a new PHI node of the
// correct type, and PHI together all of the LHS's of the instructions.
PHINode *NewPN = PHINode::Create(FirstInst->getOperand(0)->getType(),
PN.getName()+".in");
NewPN->reserveOperandSpace(PN.getNumOperands()/2);
Value *InVal = FirstInst->getOperand(0);
NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
// Add all operands to the new PHI.
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
if (NewInVal != InVal)
InVal = 0;
NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
}
Value *PhiVal;
if (InVal) {
// The new PHI unions all of the same values together. This is really
// common, so we handle it intelligently here for compile-time speed.
PhiVal = InVal;
delete NewPN;
} else {
InsertNewInstBefore(NewPN, PN);
PhiVal = NewPN;
}
// Insert and return the new operation.
if (CastInst* FirstCI = dyn_cast<CastInst>(FirstInst))
return CastInst::Create(FirstCI->getOpcode(), PhiVal, PN.getType());
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::Create(BinOp->getOpcode(), PhiVal, ConstantOp);
if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
return CmpInst::Create(CIOp->getOpcode(), CIOp->getPredicate(),
PhiVal, ConstantOp);
assert(isa<LoadInst>(FirstInst) && "Unknown operation");
// If this was a volatile load that we are merging, make sure to loop through
// and mark all the input loads as non-volatile. If we don't do this, we will
// insert a new volatile load and the old ones will not be deletable.
if (isVolatile)
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
cast<LoadInst>(PN.getIncomingValue(i))->setVolatile(false);
return new LoadInst(PhiVal, "", isVolatile);
}
/// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
/// that is dead.
static bool DeadPHICycle(PHINode *PN,
SmallPtrSet<PHINode*, 16> &PotentiallyDeadPHIs) {
if (PN->use_empty()) return true;
if (!PN->hasOneUse()) return false;
// Remember this node, and if we find the cycle, return.
if (!PotentiallyDeadPHIs.insert(PN))
return true;
// Don't scan crazily complex things.
if (PotentiallyDeadPHIs.size() == 16)
return false;
if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
return DeadPHICycle(PU, PotentiallyDeadPHIs);
return false;
}
/// PHIsEqualValue - Return true if this phi node is always equal to
/// NonPhiInVal. This happens with mutually cyclic phi nodes like:
/// z = some value; x = phi (y, z); y = phi (x, z)
static bool PHIsEqualValue(PHINode *PN, Value *NonPhiInVal,
SmallPtrSet<PHINode*, 16> &ValueEqualPHIs) {
// See if we already saw this PHI node.
if (!ValueEqualPHIs.insert(PN))
return true;
// Don't scan crazily complex things.
if (ValueEqualPHIs.size() == 16)
return false;
// Scan the operands to see if they are either phi nodes or are equal to
// the value.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *Op = PN->getIncomingValue(i);
if (PHINode *OpPN = dyn_cast<PHINode>(Op)) {
if (!PHIsEqualValue(OpPN, NonPhiInVal, ValueEqualPHIs))
return false;
} else if (Op != NonPhiInVal)
return false;
}
return true;
}
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// If LCSSA is around, don't mess with Phi nodes
if (MustPreserveLCSSA) return 0;
if (Value *V = PN.hasConstantValue())
return ReplaceInstUsesWith(PN, V);
// If all PHI operands are the same operation, pull them through the PHI,
// reducing code size.
if (isa<Instruction>(PN.getIncomingValue(0)) &&
isa<Instruction>(PN.getIncomingValue(1)) &&
cast<Instruction>(PN.getIncomingValue(0))->getOpcode() ==
cast<Instruction>(PN.getIncomingValue(1))->getOpcode() &&
// FIXME: The hasOneUse check will fail for PHIs that use the value more
// than themselves more than once.
PN.getIncomingValue(0)->hasOneUse())
if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
return Result;
// If this is a trivial cycle in the PHI node graph, remove it. Basically, if
// this PHI only has a single use (a PHI), and if that PHI only has one use (a
// PHI)... break the cycle.
if (PN.hasOneUse()) {
Instruction *PHIUser = cast<Instruction>(PN.use_back());
if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) {
SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs;
PotentiallyDeadPHIs.insert(&PN);
if (DeadPHICycle(PU, PotentiallyDeadPHIs))
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
}
// If this phi has a single use, and if that use just computes a value for
// the next iteration of a loop, delete the phi. This occurs with unused
// induction variables, e.g. "for (int j = 0; ; ++j);". Detecting this
// common case here is good because the only other things that catch this
// are induction variable analysis (sometimes) and ADCE, which is only run
// late.
if (PHIUser->hasOneUse() &&
(isa<BinaryOperator>(PHIUser) || isa<GetElementPtrInst>(PHIUser)) &&
PHIUser->use_back() == &PN) {
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
}
}
// We sometimes end up with phi cycles that non-obviously end up being the
// same value, for example:
// z = some value; x = phi (y, z); y = phi (x, z)
// where the phi nodes don't necessarily need to be in the same block. Do a
// quick check to see if the PHI node only contains a single non-phi value, if
// so, scan to see if the phi cycle is actually equal to that value.
{
unsigned InValNo = 0, NumOperandVals = PN.getNumIncomingValues();
// Scan for the first non-phi operand.
while (InValNo != NumOperandVals &&
isa<PHINode>(PN.getIncomingValue(InValNo)))
++InValNo;
if (InValNo != NumOperandVals) {
Value *NonPhiInVal = PN.getOperand(InValNo);
// Scan the rest of the operands to see if there are any conflicts, if so
// there is no need to recursively scan other phis.
for (++InValNo; InValNo != NumOperandVals; ++InValNo) {
Value *OpVal = PN.getIncomingValue(InValNo);
if (OpVal != NonPhiInVal && !isa<PHINode>(OpVal))
break;
}
// If we scanned over all operands, then we have one unique value plus
// phi values. Scan PHI nodes to see if they all merge in each other or
// the value.
if (InValNo == NumOperandVals) {
SmallPtrSet<PHINode*, 16> ValueEqualPHIs;
if (PHIsEqualValue(&PN, NonPhiInVal, ValueEqualPHIs))
return ReplaceInstUsesWith(PN, NonPhiInVal);
}
}
}
return 0;
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
// Eliminate 'getelementptr %P, i32 0' and 'getelementptr %P', they are noops.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, PtrOp);
if (isa<UndefValue>(GEP.getOperand(0)))
return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, PtrOp);
// Eliminate unneeded casts for indices.
if (TD) {
bool MadeChange = false;
unsigned PtrSize = TD->getPointerSizeInBits();
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end();
I != E; ++I, ++GTI) {
if (!isa<SequentialType>(*GTI)) continue;
// If we are using a wider index than needed for this platform, shrink it
// to what we need. If narrower, sign-extend it to what we need. This
// explicit cast can make subsequent optimizations more obvious.
unsigned OpBits = cast<IntegerType>((*I)->getType())->getBitWidth();
if (OpBits == PtrSize)
continue;
*I = Builder->CreateIntCast(*I, TD->getIntPtrType(GEP.getContext()),true);
MadeChange = true;
}
if (MadeChange) return &GEP;
}
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
//
if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
// Note that if our source is a gep chain itself that we wait for that
// chain to be resolved before we perform this transformation. This
// avoids us creating a TON of code in some cases.
//
if (GetElementPtrInst *SrcGEP =
dyn_cast<GetElementPtrInst>(Src->getOperand(0)))
if (SrcGEP->getNumOperands() == 2)
return 0; // Wait until our source is folded to completion.
SmallVector<Value*, 8> Indices;
// Find out whether the last index in the source GEP is a sequential idx.
bool EndsWithSequential = false;
for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
I != E; ++I)
EndsWithSequential = !isa<StructType>(*I);
// Can we combine the two pointer arithmetics offsets?
if (EndsWithSequential) {
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
Value *Sum;
Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
Value *GO1 = GEP.getOperand(1);
if (SO1 == Constant::getNullValue(SO1->getType())) {
Sum = GO1;
} else if (GO1 == Constant::getNullValue(GO1->getType())) {
Sum = SO1;
} else {
// If they aren't the same type, then the input hasn't been processed
// by the loop above yet (which canonicalizes sequential index types to
// intptr_t). Just avoid transforming this until the input has been
// normalized.
if (SO1->getType() != GO1->getType())
return 0;
Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum");
}
// Update the GEP in place if possible.
if (Src->getNumOperands() == 2) {
GEP.setOperand(0, Src->getOperand(0));
GEP.setOperand(1, Sum);
return &GEP;
}
Indices.append(Src->op_begin()+1, Src->op_end()-1);
Indices.push_back(Sum);
Indices.append(GEP.op_begin()+2, GEP.op_end());
} else if (isa<Constant>(*GEP.idx_begin()) &&
cast<Constant>(*GEP.idx_begin())->isNullValue() &&
Src->getNumOperands() != 1) {
// Otherwise we can do the fold if the first index of the GEP is a zero
Indices.append(Src->op_begin()+1, Src->op_end());
Indices.append(GEP.idx_begin()+1, GEP.idx_end());
}
if (!Indices.empty())
return (cast<GEPOperator>(&GEP)->isInBounds() &&
Src->isInBounds()) ?
GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices.begin(),
Indices.end(), GEP.getName()) :
GetElementPtrInst::Create(Src->getOperand(0), Indices.begin(),
Indices.end(), GEP.getName());
}
// Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
if (Value *X = getBitCastOperand(PtrOp)) {
assert(isa<PointerType>(X->getType()) && "Must be cast from pointer");
// If the input bitcast is actually "bitcast(bitcast(x))", then we don't
// want to change the gep until the bitcasts are eliminated.
if (getBitCastOperand(X)) {
Worklist.AddValue(PtrOp);
return 0;
}
// Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
// into : GEP [10 x i8]* X, i32 0, ...
//
// Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ...
// into : GEP i8* X, ...
//
// This occurs when the program declares an array extern like "int X[];"
if (HasZeroPointerIndex) {
const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
const PointerType *XTy = cast<PointerType>(X->getType());
if (const ArrayType *CATy =
dyn_cast<ArrayType>(CPTy->getElementType())) {
// GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ?
if (CATy->getElementType() == XTy->getElementType()) {
// -> GEP i8* X, ...
SmallVector<Value*, 8> Indices(GEP.idx_begin()+1, GEP.idx_end());
return cast<GEPOperator>(&GEP)->isInBounds() ?
GetElementPtrInst::CreateInBounds(X, Indices.begin(), Indices.end(),
GEP.getName()) :
GetElementPtrInst::Create(X, Indices.begin(), Indices.end(),
GEP.getName());
}
if (const ArrayType *XATy = dyn_cast<ArrayType>(XTy->getElementType())){
// GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ?
if (CATy->getElementType() == XATy->getElementType()) {
// -> GEP [10 x i8]* X, i32 0, ...
// At this point, we know that the cast source type is a pointer
// to an array of the same type as the destination pointer
// array. Because the array type is never stepped over (there
// is a leading zero) we can fold the cast into this GEP.
GEP.setOperand(0, X);
return &GEP;
}
}
}
} else if (GEP.getNumOperands() == 2) {
// Transform things like:
// %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V
// into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast
const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
if (TD && isa<ArrayType>(SrcElTy) &&
TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
TD->getTypeAllocSize(ResElTy)) {
Value *Idx[2];
Idx[0] = Constant::getNullValue(Type::getInt32Ty(*Context));
Idx[1] = GEP.getOperand(1);
Value *NewGEP = cast<GEPOperator>(&GEP)->isInBounds() ?
Builder->CreateInBoundsGEP(X, Idx, Idx + 2, GEP.getName()) :
Builder->CreateGEP(X, Idx, Idx + 2, GEP.getName());
// V and GEP are both pointer types --> BitCast
return new BitCastInst(NewGEP, GEP.getType());
}
// Transform things like:
// getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp
// (where tmp = 8*tmp2) into:
// getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast
if (TD && isa<ArrayType>(SrcElTy) && ResElTy == Type::getInt8Ty(*Context)) {
uint64_t ArrayEltSize =
TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType());
// Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We
// allow either a mul, shift, or constant here.
Value *NewIdx = 0;
ConstantInt *Scale = 0;
if (ArrayEltSize == 1) {
NewIdx = GEP.getOperand(1);
Scale = ConstantInt::get(cast<IntegerType>(NewIdx->getType()), 1);
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
NewIdx = ConstantInt::get(CI->getType(), 1);
Scale = CI;
} else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
if (Inst->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(Inst->getOperand(1))) {
ConstantInt *ShAmt = cast<ConstantInt>(Inst->getOperand(1));
uint32_t ShAmtVal = ShAmt->getLimitedValue(64);
Scale = ConstantInt::get(cast<IntegerType>(Inst->getType()),
1ULL << ShAmtVal);
NewIdx = Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::Mul &&
isa<ConstantInt>(Inst->getOperand(1))) {
Scale = cast<ConstantInt>(Inst->getOperand(1));
NewIdx = Inst->getOperand(0);
}
}
// If the index will be to exactly the right offset with the scale taken
// out, perform the transformation. Note, we don't know whether Scale is
// signed or not. We'll use unsigned version of division/modulo
// operation after making sure Scale doesn't have the sign bit set.
if (ArrayEltSize && Scale && Scale->getSExtValue() >= 0LL &&
Scale->getZExtValue() % ArrayEltSize == 0) {
Scale = ConstantInt::get(Scale->getType(),
Scale->getZExtValue() / ArrayEltSize);
if (Scale->getZExtValue() != 1) {
Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(),
false /*ZExt*/);
NewIdx = Builder->CreateMul(NewIdx, C, "idxscale");
}
// Insert the new GEP instruction.
Value *Idx[2];
Idx[0] = Constant::getNullValue(Type::getInt32Ty(*Context));
Idx[1] = NewIdx;
Value *NewGEP = cast<GEPOperator>(&GEP)->isInBounds() ?
Builder->CreateInBoundsGEP(X, Idx, Idx + 2, GEP.getName()) :
Builder->CreateGEP(X, Idx, Idx + 2, GEP.getName());
// The NewGEP must be pointer typed, so must the old one -> BitCast
return new BitCastInst(NewGEP, GEP.getType());
}
}
}
}
/// See if we can simplify:
/// X = bitcast A* to B*
/// Y = gep X, <...constant indices...>
/// into a gep of the original struct. This is important for SROA and alias
/// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
if (TD &&
!isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) {
// Determine how much the GEP moves the pointer. We are guaranteed to get
// a constant back from EmitGEPOffset.
ConstantInt *OffsetV =
cast<ConstantInt>(EmitGEPOffset(&GEP, GEP, *this));
int64_t Offset = OffsetV->getSExtValue();
// If this GEP instruction doesn't move the pointer, just replace the GEP
// with a bitcast of the real input to the dest type.
if (Offset == 0) {
// If the bitcast is of an allocation, and the allocation will be
// converted to match the type of the cast, don't touch this.
if (isa<AllocationInst>(BCI->getOperand(0)) ||
isMalloc(BCI->getOperand(0))) {
// See if the bitcast simplifies, if so, don't nuke this GEP yet.
if (Instruction *I = visitBitCast(*BCI)) {
if (I != BCI) {
I->takeName(BCI);
BCI->getParent()->getInstList().insert(BCI, I);
ReplaceInstUsesWith(*BCI, I);
}
return &GEP;
}
}
return new BitCastInst(BCI->getOperand(0), GEP.getType());
}
// Otherwise, if the offset is non-zero, we need to find out if there is a
// field at Offset in 'A's type. If so, we can pull the cast through the
// GEP.
SmallVector<Value*, 8> NewIndices;
const Type *InTy =
cast<PointerType>(BCI->getOperand(0)->getType())->getElementType();
if (FindElementAtOffset(InTy, Offset, NewIndices, TD, Context)) {
Value *NGEP = cast<GEPOperator>(&GEP)->isInBounds() ?
Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices.begin(),
NewIndices.end()) :
Builder->CreateGEP(BCI->getOperand(0), NewIndices.begin(),
NewIndices.end());
if (NGEP->getType() == GEP.getType())
return ReplaceInstUsesWith(GEP, NGEP);
NGEP->takeName(&GEP);
return new BitCastInst(NGEP, GEP.getType());
}
}
}
return 0;
}
Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
// Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
if (AI.isArrayAllocation()) { // Check C != 1
if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
const Type *NewTy =
ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
AllocationInst *New = 0;
// Create and insert the replacement instruction...
if (isa<MallocInst>(AI))
New = Builder->CreateMalloc(NewTy, 0, AI.getName());
else {
assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
New = Builder->CreateAlloca(NewTy, 0, AI.getName());
}
New->setAlignment(AI.getAlignment());
// Scan to the end of the allocation instructions, to skip over a block of
// allocas if possible...also skip interleaved debug info
//
BasicBlock::iterator It = New;
while (isa<AllocationInst>(*It) || isa<DbgInfoIntrinsic>(*It)) ++It;
// Now that I is pointing to the first non-allocation-inst in the block,
// insert our getelementptr instruction...
//
Value *NullIdx = Constant::getNullValue(Type::getInt32Ty(*Context));
Value *Idx[2];
Idx[0] = NullIdx;
Idx[1] = NullIdx;
Value *V = GetElementPtrInst::CreateInBounds(New, Idx, Idx + 2,
New->getName()+".sub", It);
// Now make everything use the getelementptr instead of the original
// allocation.
return ReplaceInstUsesWith(AI, V);
} else if (isa<UndefValue>(AI.getArraySize())) {
return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
}
}
if (TD && isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized()) {
// If alloca'ing a zero byte object, replace the alloca with a null pointer.
// Note that we only do this for alloca's, because malloc should allocate
// and return a unique pointer, even for a zero byte allocation.
if (TD->getTypeAllocSize(AI.getAllocatedType()) == 0)
return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
// If the alignment is 0 (unspecified), assign it the preferred alignment.
if (AI.getAlignment() == 0)
AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType()));
}
return 0;
}
Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
Value *Op = FI.getOperand(0);
// free undef -> unreachable.
if (isa<UndefValue>(Op)) {
// Insert a new store to null because we cannot modify the CFG here.
new StoreInst(ConstantInt::getTrue(*Context),
UndefValue::get(Type::getInt1PtrTy(*Context)), &FI);
return EraseInstFromFunction(FI);
}
// If we have 'free null' delete the instruction. This can happen in stl code
// when lots of inlining happens.
if (isa<ConstantPointerNull>(Op))
return EraseInstFromFunction(FI);
// Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
if (BitCastInst *CI = dyn_cast<BitCastInst>(Op)) {
FI.setOperand(0, CI->getOperand(0));
return &FI;
}
// Change free (gep X, 0,0,0,0) into free(X)
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
if (GEPI->hasAllZeroIndices()) {
Worklist.Add(GEPI);
FI.setOperand(0, GEPI->getOperand(0));
return &FI;
}
}
// Change free(malloc) into nothing, if the malloc has a single use.
if (MallocInst *MI = dyn_cast<MallocInst>(Op))
if (MI->hasOneUse()) {
EraseInstFromFunction(FI);
return EraseInstFromFunction(*MI);
}
if (isMalloc(Op)) {
if (CallInst* CI = extractMallocCallFromBitCast(Op)) {
if (Op->hasOneUse() && CI->hasOneUse()) {
EraseInstFromFunction(FI);
EraseInstFromFunction(*CI);
return EraseInstFromFunction(*cast<Instruction>(Op));
}
} else {
// Op is a call to malloc
if (Op->hasOneUse()) {
EraseInstFromFunction(FI);
return EraseInstFromFunction(*cast<Instruction>(Op));
}
}
}
return 0;
}
/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible.
static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI,
const TargetData *TD) {
User *CI = cast<User>(LI.getOperand(0));
Value *CastOp = CI->getOperand(0);
LLVMContext *Context = IC.getContext();
if (TD) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(CI)) {
// Instead of loading constant c string, use corresponding integer value
// directly if string length is small enough.
std::string Str;
if (GetConstantStringInfo(CE->getOperand(0), Str) && !Str.empty()) {
unsigned len = Str.length();
const Type *Ty = cast<PointerType>(CE->getType())->getElementType();
unsigned numBits = Ty->getPrimitiveSizeInBits();
// Replace LI with immediate integer store.
if ((numBits >> 3) == len + 1) {
APInt StrVal(numBits, 0);
APInt SingleChar(numBits, 0);
if (TD->isLittleEndian()) {
for (signed i = len-1; i >= 0; i--) {
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
StrVal = (StrVal << 8) | SingleChar;
}
} else {
for (unsigned i = 0; i < len; i++) {
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
StrVal = (StrVal << 8) | SingleChar;
}
// Append NULL at the end.
SingleChar = 0;
StrVal = (StrVal << 8) | SingleChar;
}
Value *NL = ConstantInt::get(*Context, StrVal);
return IC.ReplaceInstUsesWith(LI, NL);
}
}
}
}
const PointerType *DestTy = cast<PointerType>(CI->getType());
const Type *DestPTy = DestTy->getElementType();
if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
// If the address spaces don't match, don't eliminate the cast.
if (DestTy->getAddressSpace() != SrcTy->getAddressSpace())
return 0;
const Type *SrcPTy = SrcTy->getElementType();
if (DestPTy->isInteger() || isa<PointerType>(DestPTy) ||
isa<VectorType>(DestPTy)) {
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
if (Constant *CSrc = dyn_cast<Constant>(CastOp))
if (ASrcTy->getNumElements() != 0) {
Value *Idxs[2];
Idxs[0] = Idxs[1] = Constant::getNullValue(Type::getInt32Ty(*Context));
CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs, 2);
SrcTy = cast<PointerType>(CastOp->getType());
SrcPTy = SrcTy->getElementType();
}
if (IC.getTargetData() &&
(SrcPTy->isInteger() || isa<PointerType>(SrcPTy) ||
isa<VectorType>(SrcPTy)) &&
// Do not allow turning this into a load of an integer, which is then
// casted to a pointer, this pessimizes pointer analysis a lot.
(isa<PointerType>(SrcPTy) == isa<PointerType>(LI.getType())) &&
IC.getTargetData()->getTypeSizeInBits(SrcPTy) ==
IC.getTargetData()->getTypeSizeInBits(DestPTy)) {
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the load, cast
// the result of the loaded value.
Value *NewLoad =
IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName());
// Now cast the result of the load.
return new BitCastInst(NewLoad, LI.getType());
}
}
}
return 0;
}
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
// Attempt to improve the alignment.
if (TD) {
unsigned KnownAlign =
GetOrEnforceKnownAlignment(Op, TD->getPrefTypeAlignment(LI.getType()));
if (KnownAlign >
(LI.getAlignment() == 0 ? TD->getABITypeAlignment(LI.getType()) :
LI.getAlignment()))
LI.setAlignment(KnownAlign);
}
// load (cast X) --> cast (load X) iff safe.
if (isa<CastInst>(Op))
if (Instruction *Res = InstCombineLoadCast(*this, LI, TD))
return Res;
// None of the following transforms are legal for volatile loads.
if (LI.isVolatile()) return 0;
// Do really simple store-to-load forwarding and load CSE, to catch cases
// where there are several consequtive memory accesses to the same location,
// separated by a few arithmetic operations.
BasicBlock::iterator BBI = &LI;
if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
return ReplaceInstUsesWith(LI, AvailableVal);
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
const Value *GEPI0 = GEPI->getOperand(0);
// TODO: Consider a target hook for valid address spaces for this xform.
if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
}
if (Constant *C = dyn_cast<Constant>(Op)) {
// load null/undef -> undef
// TODO: Consider a target hook for valid address spaces for this xform.
if (isa<UndefValue>(C) ||
(C->isNullValue() && LI.getPointerAddressSpace() == 0)) {
// Insert a new store to null instruction before the load to indicate that
// this code is not reachable. We do this instead of inserting an
// unreachable instruction directly because we cannot modify the CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
// Instcombine load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
return ReplaceInstUsesWith(LI, GV->getInitializer());
// Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
if (CE->getOperand(0)->isNullValue()) {
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
} else if (CE->isCast()) {
if (Instruction *Res = InstCombineLoadCast(*this, LI, TD))
return Res;
}
}
}
// If this load comes from anywhere in a constant global, and if the global
// is all undef or zero, we know what it loads.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op->getUnderlyingObject())){
if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
if (GV->getInitializer()->isNullValue())
return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
else if (isa<UndefValue>(GV->getInitializer()))
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
}
if (Op->hasOneUse()) {
// Change select and PHI nodes to select values instead of addresses: this
// helps alias analysis out a lot, allows many others simplifications, and
// exposes redundancy in the code.
//
// Note that we cannot do the transformation unless we know that the
// introduced loads cannot trap! Something like this is valid as long as
// the condition is always false: load (select bool %C, int* null, int* %G),
// but it would not be valid if we transformed it to load from null
// unconditionally.
//
if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
// load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
Value *V1 = Builder->CreateLoad(SI->getOperand(1),
SI->getOperand(1)->getName()+".val");
Value *V2 = Builder->CreateLoad(SI->getOperand(2),
SI->getOperand(2)->getName()+".val");
return SelectInst::Create(SI->getCondition(), V1, V2);
}
// load (select (cond, null, P)) -> load P
if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
if (C->isNullValue()) {
LI.setOperand(0, SI->getOperand(2));
return &LI;
}
// load (select (cond, P, null)) -> load P
if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
if (C->isNullValue()) {
LI.setOperand(0, SI->getOperand(1));
return &LI;
}
}
}
return 0;
}
/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P
/// when possible. This makes it generally easy to do alias analysis and/or
/// SROA/mem2reg of the memory object.
static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
User *CI = cast<User>(SI.getOperand(1));
Value *CastOp = CI->getOperand(0);
const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType());
if (SrcTy == 0) return 0;
const Type *SrcPTy = SrcTy->getElementType();
if (!DestPTy->isInteger() && !isa<PointerType>(DestPTy))
return 0;
/// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep"
/// to its first element. This allows us to handle things like:
/// store i32 xxx, (bitcast {foo*, float}* %P to i32*)
/// on 32-bit hosts.
SmallVector<Value*, 4> NewGEPIndices;
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
if (isa<ArrayType>(SrcPTy) || isa<StructType>(SrcPTy)) {
// Index through pointer.
Constant *Zero = Constant::getNullValue(Type::getInt32Ty(*IC.getContext()));
NewGEPIndices.push_back(Zero);
while (1) {
if (const StructType *STy = dyn_cast<StructType>(SrcPTy)) {
if (!STy->getNumElements()) /* Struct can be empty {} */
break;
NewGEPIndices.push_back(Zero);
SrcPTy = STy->getElementType(0);
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) {
NewGEPIndices.push_back(Zero);
SrcPTy = ATy->getElementType();
} else {
break;
}
}
SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace());
}
if (!SrcPTy->isInteger() && !isa<PointerType>(SrcPTy))
return 0;
// If the pointers point into different address spaces or if they point to
// values with different sizes, we can't do the transformation.
if (!IC.getTargetData() ||
SrcTy->getAddressSpace() !=
cast<PointerType>(CI->getType())->getAddressSpace() ||
IC.getTargetData()->getTypeSizeInBits(SrcPTy) !=
IC.getTargetData()->getTypeSizeInBits(DestPTy))
return 0;
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before
// the store, cast the value to be stored.
Value *NewCast;
Value *SIOp0 = SI.getOperand(0);
Instruction::CastOps opcode = Instruction::BitCast;
const Type* CastSrcTy = SIOp0->getType();
const Type* CastDstTy = SrcPTy;
if (isa<PointerType>(CastDstTy)) {
if (CastSrcTy->isInteger())
opcode = Instruction::IntToPtr;
} else if (isa<IntegerType>(CastDstTy)) {
if (isa<PointerType>(SIOp0->getType()))
opcode = Instruction::PtrToInt;
}
// SIOp0 is a pointer to aggregate and this is a store to the first field,
// emit a GEP to index into its first field.
if (!NewGEPIndices.empty())
CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices.begin(),
NewGEPIndices.end());
NewCast = IC.Builder->CreateCast(opcode, SIOp0, CastDstTy,
SIOp0->getName()+".c");
return new StoreInst(NewCast, CastOp);
}
/// equivalentAddressValues - Test if A and B will obviously have the same
/// value. This includes recognizing that %t0 and %t1 will have the same
/// value in code like this:
/// %t0 = getelementptr \@a, 0, 3
/// store i32 0, i32* %t0
/// %t1 = getelementptr \@a, 0, 3
/// %t2 = load i32* %t1
///
static bool equivalentAddressValues(Value *A, Value *B) {
// Test if the values are trivially equivalent.
if (A == B) return true;
// Test if the values come form identical arithmetic instructions.
// This uses isIdenticalToWhenDefined instead of isIdenticalTo because
// its only used to compare two uses within the same basic block, which
// means that they'll always either have the same value or one of them
// will have an undefined value.
if (isa<BinaryOperator>(A) ||
isa<CastInst>(A) ||
isa<PHINode>(A) ||
isa<GetElementPtrInst>(A))
if (Instruction *BI = dyn_cast<Instruction>(B))
if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
return true;
// Otherwise they may not be equivalent.
return false;
}
// If this instruction has two uses, one of which is a llvm.dbg.declare,
// return the llvm.dbg.declare.
DbgDeclareInst *InstCombiner::hasOneUsePlusDeclare(Value *V) {
if (!V->hasNUses(2))
return 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
UI != E; ++UI) {
if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI))
return DI;
if (isa<BitCastInst>(UI) && UI->hasOneUse()) {
if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI->use_begin()))
return DI;
}
}
return 0;
}
Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
Value *Val = SI.getOperand(0);
Value *Ptr = SI.getOperand(1);
if (isa<UndefValue>(Ptr)) { // store X, undef -> noop (even if volatile)
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// If the RHS is an alloca with a single use, zapify the store, making the
// alloca dead.
// If the RHS is an alloca with a two uses, the other one being a
// llvm.dbg.declare, zapify the store and the declare, making the
// alloca dead. We must do this to prevent declare's from affecting
// codegen.
if (!SI.isVolatile()) {
if (Ptr->hasOneUse()) {
if (isa<AllocaInst>(Ptr)) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
if (isa<AllocaInst>(GEP->getOperand(0))) {
if (GEP->getOperand(0)->hasOneUse()) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
if (DbgDeclareInst *DI = hasOneUsePlusDeclare(GEP->getOperand(0))) {
EraseInstFromFunction(*DI);
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
}
}
}
if (DbgDeclareInst *DI = hasOneUsePlusDeclare(Ptr)) {
EraseInstFromFunction(*DI);
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
}
// Attempt to improve the alignment.
if (TD) {
unsigned KnownAlign =
GetOrEnforceKnownAlignment(Ptr, TD->getPrefTypeAlignment(Val->getType()));
if (KnownAlign >
(SI.getAlignment() == 0 ? TD->getABITypeAlignment(Val->getType()) :
SI.getAlignment()))
SI.setAlignment(KnownAlign);
}
// Do really simple DSE, to catch cases where there are several consecutive
// stores to the same location, separated by a few arithmetic operations. This
// situation often occurs with bitfield accesses.
BasicBlock::iterator BBI = &SI;
for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts;
--ScanInsts) {
--BBI;
// Don't count debug info directives, lest they affect codegen,
// and we skip pointer-to-pointer bitcasts, which are NOPs.
// It is necessary for correctness to skip those that feed into a
// llvm.dbg.declare, as these are not present when debugging is off.
if (isa<DbgInfoIntrinsic>(BBI) ||
(isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType()))) {
ScanInsts++;
continue;
}
if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
// Prev store isn't volatile, and stores to the same location?
if (!PrevSI->isVolatile() &&equivalentAddressValues(PrevSI->getOperand(1),
SI.getOperand(1))) {
++NumDeadStore;
++BBI;
EraseInstFromFunction(*PrevSI);
continue;
}
break;
}
// If this is a load, we have to stop. However, if the loaded value is from
// the pointer we're loading and is producing the pointer we're storing,
// then *this* store is dead (X = load P; store X -> P).
if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) &&
!SI.isVolatile()) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// Otherwise, this is a load from some other location. Stores before it
// may not be dead.
break;
}
// Don't skip over loads or things that can modify memory.
if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory())
break;
}
if (SI.isVolatile()) return 0; // Don't hack volatile stores.
// store X, null -> turns into 'unreachable' in SimplifyCFG
if (isa<ConstantPointerNull>(Ptr) && SI.getPointerAddressSpace() == 0) {
if (!isa<UndefValue>(Val)) {
SI.setOperand(0, UndefValue::get(Val->getType()));
if (Instruction *U = dyn_cast<Instruction>(Val))
Worklist.Add(U); // Dropped a use.
++NumCombined;
}
return 0; // Do not modify these!
}
// store undef, Ptr -> noop
if (isa<UndefValue>(Val)) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;
}
// If the pointer destination is a cast, see if we can fold the cast into the
// source instead.
if (isa<CastInst>(Ptr))
if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->isCast())
if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res;
// If this store is the last instruction in the basic block (possibly
// excepting debug info instructions and the pointer bitcasts that feed
// into them), and if the block ends with an unconditional branch, try
// to move it to the successor block.
BBI = &SI;
do {
++BBI;
} while (isa<DbgInfoIntrinsic>(BBI) ||
(isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType())));
if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
if (BI->isUnconditional())
if (SimplifyStoreAtEndOfBlock(SI))
return 0; // xform done!
return 0;
}
/// SimplifyStoreAtEndOfBlock - Turn things like:
/// if () { *P = v1; } else { *P = v2 }
/// into a phi node with a store in the successor.
///
/// Simplify things like:
/// *P = v1; if () { *P = v2; }
/// into a phi node with a store in the successor.
///
bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
BasicBlock *StoreBB = SI.getParent();
// Check to see if the successor block has exactly two incoming edges. If
// so, see if the other predecessor contains a store to the same location.
// if so, insert a PHI node (if needed) and move the stores down.
BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0);
// Determine whether Dest has exactly two predecessors and, if so, compute
// the other predecessor.
pred_iterator PI = pred_begin(DestBB);
BasicBlock *OtherBB = 0;
if (*PI != StoreBB)
OtherBB = *PI;
++PI;
if (PI == pred_end(DestBB))
return false;
if (*PI != StoreBB) {
if (OtherBB)
return false;
OtherBB = *PI;
}
if (++PI != pred_end(DestBB))
return false;
// Bail out if all the relevant blocks aren't distinct (this can happen,
// for example, if SI is in an infinite loop)
if (StoreBB == DestBB || OtherBB == DestBB)
return false;
// Verify that the other block ends in a branch and is not otherwise empty.
BasicBlock::iterator BBI = OtherBB->getTerminator();
BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
if (!OtherBr || BBI == OtherBB->begin())
return false;
// If the other block ends in an unconditional branch, check for the 'if then
// else' case. there is an instruction before the branch.
StoreInst *OtherStore = 0;
if (OtherBr->isUnconditional()) {
--BBI;
// Skip over debugging info.
while (isa<DbgInfoIntrinsic>(BBI) ||
(isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType()))) {
if (BBI==OtherBB->begin())
return false;
--BBI;
}
// If this isn't a store, or isn't a store to the same location, bail out.
OtherStore = dyn_cast<StoreInst>(BBI);
if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1))
return false;
} else {
// Otherwise, the other block ended with a conditional branch. If one of the
// destinations is StoreBB, then we have the if/then case.
if (OtherBr->getSuccessor(0) != StoreBB &&
OtherBr->getSuccessor(1) != StoreBB)
return false;
// Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
// if/then triangle. See if there is a store to the same ptr as SI that
// lives in OtherBB.
for (;; --BBI) {
// Check to see if we find the matching store.
if ((OtherStore = dyn_cast<StoreInst>(BBI))) {
if (OtherStore->getOperand(1) != SI.getOperand(1))
return false;
break;
}
// If we find something that may be using or overwriting the stored
// value, or if we run out of instructions, we can't do the xform.
if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() ||
BBI == OtherBB->begin())
return false;
}
// In order to eliminate the store in OtherBr, we have to
// make sure nothing reads or overwrites the stored value in
// StoreBB.
for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
// FIXME: This should really be AA driven.
if (I->mayReadFromMemory() || I->mayWriteToMemory())
return false;
}
}
// Insert a PHI node now if we need it.
Value *MergedVal = OtherStore->getOperand(0);
if (MergedVal != SI.getOperand(0)) {
PHINode *PN = PHINode::Create(MergedVal->getType(), "storemerge");
PN->reserveOperandSpace(2);
PN->addIncoming(SI.getOperand(0), SI.getParent());
PN->addIncoming(OtherStore->getOperand(0), OtherBB);
MergedVal = InsertNewInstBefore(PN, DestBB->front());
}
// Advance to a place where it is safe to insert the new store and
// insert it.
BBI = DestBB->getFirstNonPHI();
InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
OtherStore->isVolatile()), *BBI);
// Nuke the old stores.
EraseInstFromFunction(SI);
EraseInstFromFunction(*OtherStore);
++NumCombined;
return true;
}
Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
// Change br (not X), label True, label False to: br X, label False, True
Value *X = 0;
BasicBlock *TrueDest;
BasicBlock *FalseDest;
if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
!isa<Constant>(X)) {
// Swap Destinations and condition...
BI.setCondition(X);
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
return &BI;
}
// Cannonicalize fcmp_one -> fcmp_oeq
FCmpInst::Predicate FPred; Value *Y;
if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)),
TrueDest, FalseDest)) &&
BI.getCondition()->hasOneUse())
if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE ||
FPred == FCmpInst::FCMP_OGE) {
FCmpInst *Cond = cast<FCmpInst>(BI.getCondition());
Cond->setPredicate(FCmpInst::getInversePredicate(FPred));
// Swap Destinations and condition.
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
Worklist.Add(Cond);
return &BI;
}
// Cannonicalize icmp_ne -> icmp_eq
ICmpInst::Predicate IPred;
if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)),
TrueDest, FalseDest)) &&
BI.getCondition()->hasOneUse())
if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE ||
IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE ||
IPred == ICmpInst::ICMP_SGE) {
ICmpInst *Cond = cast<ICmpInst>(BI.getCondition());
Cond->setPredicate(ICmpInst::getInversePredicate(IPred));
// Swap Destinations and condition.
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
Worklist.Add(Cond);
return &BI;
}
return 0;
}
Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
Value *Cond = SI.getCondition();
if (Instruction *I = dyn_cast<Instruction>(Cond)) {
if (I->getOpcode() == Instruction::Add)
if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
// change 'switch (X+4) case 1:' into 'switch (X) case -3'
for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
SI.setOperand(i,
ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
AddRHS));
SI.setOperand(0, I->getOperand(0));
Worklist.Add(I);
return &SI;
}
}
return 0;
}
Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {
Value *Agg = EV.getAggregateOperand();
if (!EV.hasIndices())
return ReplaceInstUsesWith(EV, Agg);
if (Constant *C = dyn_cast<Constant>(Agg)) {
if (isa<UndefValue>(C))
return ReplaceInstUsesWith(EV, UndefValue::get(EV.getType()));
if (isa<ConstantAggregateZero>(C))
return ReplaceInstUsesWith(EV, Constant::getNullValue(EV.getType()));
if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) {
// Extract the element indexed by the first index out of the constant
Value *V = C->getOperand(*EV.idx_begin());
if (EV.getNumIndices() > 1)
// Extract the remaining indices out of the constant indexed by the
// first index
return ExtractValueInst::Create(V, EV.idx_begin() + 1, EV.idx_end());
else
return ReplaceInstUsesWith(EV, V);
}
return 0; // Can't handle other constants
}
if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
// We're extracting from an insertvalue instruction, compare the indices
const unsigned *exti, *exte, *insi, *inse;
for (exti = EV.idx_begin(), insi = IV->idx_begin(),
exte = EV.idx_end(), inse = IV->idx_end();
exti != exte && insi != inse;
++exti, ++insi) {
if (*insi != *exti)
// The insert and extract both reference distinctly different elements.
// This means the extract is not influenced by the insert, and we can
// replace the aggregate operand of the extract with the aggregate
// operand of the insert. i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 0
// with
// %E = extractvalue { i32, { i32 } } %A, 0
return ExtractValueInst::Create(IV->getAggregateOperand(),
EV.idx_begin(), EV.idx_end());
}
if (exti == exte && insi == inse)
// Both iterators are at the end: Index lists are identical. Replace
// %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %C = extractvalue { i32, { i32 } } %B, 1, 0
// with "i32 42"
return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand());
if (exti == exte) {
// The extract list is a prefix of the insert list. i.e. replace
// %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %E = extractvalue { i32, { i32 } } %I, 1
// with
// %X = extractvalue { i32, { i32 } } %A, 1
// %E = insertvalue { i32 } %X, i32 42, 0
// by switching the order of the insert and extract (though the
// insertvalue should be left in, since it may have other uses).
Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(),
EV.idx_begin(), EV.idx_end());
return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
insi, inse);
}
if (insi == inse)
// The insert list is a prefix of the extract list
// We can simply remove the common indices from the extract and make it
// operate on the inserted value instead of the insertvalue result.
// i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 1, 0
// with
// %E extractvalue { i32 } { i32 42 }, 0
return ExtractValueInst::Create(IV->getInsertedValueOperand(),
exti, exte);
}
// Can't simplify extracts from other values. Note that nested extracts are
// already simplified implicitely by the above (extract ( extract (insert) )
// will be translated into extract ( insert ( extract ) ) first and then just
// the value inserted, if appropriate).
return 0;
}
/// CheapToScalarize - Return true if the value is cheaper to scalarize than it
/// is to leave as a vector operation.
static bool CheapToScalarize(Value *V, bool isConstant) {
if (isa<ConstantAggregateZero>(V))
return true;
if (ConstantVector *C = dyn_cast<ConstantVector>(V)) {
if (isConstant) return true;
// If all elts are the same, we can extract.
Constant *Op0 = C->getOperand(0);
for (unsigned i = 1; i < C->getNumOperands(); ++i)
if (C->getOperand(i) != Op0)
return false;
return true;
}
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
// Insert element gets simplified to the inserted element or is deleted if
// this is constant idx extract element and its a constant idx insertelt.
if (I->getOpcode() == Instruction::InsertElement && isConstant &&
isa<ConstantInt>(I->getOperand(2)))
return true;
if (I->getOpcode() == Instruction::Load && I->hasOneUse())
return true;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
if (BO->hasOneUse() &&
(CheapToScalarize(BO->getOperand(0), isConstant) ||
CheapToScalarize(BO->getOperand(1), isConstant)))
return true;
if (CmpInst *CI = dyn_cast<CmpInst>(I))
if (CI->hasOneUse() &&
(CheapToScalarize(CI->getOperand(0), isConstant) ||
CheapToScalarize(CI->getOperand(1), isConstant)))
return true;
return false;
}
/// Read and decode a shufflevector mask.
///
/// It turns undef elements into values that are larger than the number of
/// elements in the input.
static std::vector<unsigned> getShuffleMask(const ShuffleVectorInst *SVI) {
unsigned NElts = SVI->getType()->getNumElements();
if (isa<ConstantAggregateZero>(SVI->getOperand(2)))
return std::vector<unsigned>(NElts, 0);
if (isa<UndefValue>(SVI->getOperand(2)))
return std::vector<unsigned>(NElts, 2*NElts);
std::vector<unsigned> Result;
const ConstantVector *CP = cast<ConstantVector>(SVI->getOperand(2));
for (User::const_op_iterator i = CP->op_begin(), e = CP->op_end(); i!=e; ++i)
if (isa<UndefValue>(*i))
Result.push_back(NElts*2); // undef -> 8
else
Result.push_back(cast<ConstantInt>(*i)->getZExtValue());
return Result;
}
/// FindScalarElement - Given a vector and an element number, see if the scalar
/// value is already around as a register, for example if it were inserted then
/// extracted from the vector.
static Value *FindScalarElement(Value *V, unsigned EltNo,
LLVMContext *Context) {
assert(isa<VectorType>(V->getType()) && "Not looking at a vector?");
const VectorType *PTy = cast<VectorType>(V->getType());
unsigned Width = PTy->getNumElements();
if (EltNo >= Width) // Out of range access.
return UndefValue::get(PTy->getElementType());
if (isa<UndefValue>(V))
return UndefValue::get(PTy->getElementType());
else if (isa<ConstantAggregateZero>(V))
return Constant::getNullValue(PTy->getElementType());
else if (ConstantVector *CP = dyn_cast<ConstantVector>(V))
return CP->getOperand(EltNo);
else if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
// If this is an insert to a variable element, we don't know what it is.
if (!isa<ConstantInt>(III->getOperand(2)))
return 0;
unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
// If this is an insert to the element we are looking for, return the
// inserted value.
if (EltNo == IIElt)
return III->getOperand(1);
// Otherwise, the insertelement doesn't modify the value, recurse on its
// vector input.
return FindScalarElement(III->getOperand(0), EltNo, Context);
} else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
unsigned LHSWidth =
cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements();
unsigned InEl = getShuffleMask(SVI)[EltNo];
if (InEl < LHSWidth)
return FindScalarElement(SVI->getOperand(0), InEl, Context);
else if (InEl < LHSWidth*2)
return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth, Context);
else
return UndefValue::get(PTy->getElementType());
}
// Otherwise, we don't know.
return 0;
}
Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
// If vector val is undef, replace extract with scalar undef.
if (isa<UndefValue>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
// If vector val is constant 0, replace extract with scalar 0.
if (isa<ConstantAggregateZero>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, Constant::getNullValue(EI.getType()));
if (ConstantVector *C = dyn_cast<ConstantVector>(EI.getOperand(0))) {
// If vector val is constant with all elements the same, replace EI with
// that element. When the elements are not identical, we cannot replace yet
// (we do that below, but only when the index is constant).
Constant *op0 = C->getOperand(0);
for (unsigned i = 1; i != C->getNumOperands(); ++i)
if (C->getOperand(i) != op0) {
op0 = 0;
break;
}
if (op0)
return ReplaceInstUsesWith(EI, op0);
}
// If extracting a specified index from the vector, see if we can recursively
// find a previously computed scalar that was inserted into the vector.
if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) {
unsigned IndexVal = IdxC->getZExtValue();
unsigned VectorWidth = EI.getVectorOperandType()->getNumElements();
// If this is extracting an invalid index, turn this into undef, to avoid
// crashing the code below.
if (IndexVal >= VectorWidth)
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
// This instruction only demands the single element from the input vector.
// If the input vector has a single use, simplify it based on this use
// property.
if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) {
APInt UndefElts(VectorWidth, 0);
APInt DemandedMask(VectorWidth, 1 << IndexVal);
if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0),
DemandedMask, UndefElts)) {
EI.setOperand(0, V);
return &EI;
}
}
if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal, Context))
return ReplaceInstUsesWith(EI, Elt);
// If the this extractelement is directly using a bitcast from a vector of
// the same number of elements, see if we can find the source element from
// it. In this case, we will end up needing to bitcast the scalars.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(EI.getOperand(0))) {
if (const VectorType *VT =
dyn_cast<VectorType>(BCI->getOperand(0)->getType()))
if (VT->getNumElements() == VectorWidth)
if (Value *Elt = FindScalarElement(BCI->getOperand(0),
IndexVal, Context))
return new BitCastInst(Elt, EI.getType());
}
}
if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
// Push extractelement into predecessor operation if legal and
// profitable to do so
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
if (I->hasOneUse() &&
CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) {
Value *newEI0 =
Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
EI.getName()+".lhs");
Value *newEI1 =
Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
EI.getName()+".rhs");
return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
}
} else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
// Extracting the inserted element?
if (IE->getOperand(2) == EI.getOperand(1))
return ReplaceInstUsesWith(EI, IE->getOperand(1));
// If the inserted and extracted elements are constants, they must not
// be the same value, extract from the pre-inserted value instead.
if (isa<Constant>(IE->getOperand(2)) && isa<Constant>(EI.getOperand(1))) {
Worklist.AddValue(EI.getOperand(0));
EI.setOperand(0, IE->getOperand(0));
return &EI;
}
} else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) {
// If this is extracting an element from a shufflevector, figure out where
// it came from and extract from the appropriate input element instead.
if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) {
unsigned SrcIdx = getShuffleMask(SVI)[Elt->getZExtValue()];
Value *Src;
unsigned LHSWidth =
cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements();
if (SrcIdx < LHSWidth)
Src = SVI->getOperand(0);
else if (SrcIdx < LHSWidth*2) {
SrcIdx -= LHSWidth;
Src = SVI->getOperand(1);
} else {
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
}
return ExtractElementInst::Create(Src,
ConstantInt::get(Type::getInt32Ty(*Context), SrcIdx,
false));
}
}
// FIXME: Canonicalize extractelement(bitcast) -> bitcast(extractelement)
}
return 0;
}
/// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns
/// elements from either LHS or RHS, return the shuffle mask and true.
/// Otherwise, return false.
static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
std::vector<Constant*> &Mask,
LLVMContext *Context) {
assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() &&
"Invalid CollectSingleShuffleElements");
unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
if (isa<UndefValue>(V)) {
Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(*Context)));
return true;
} else if (V == LHS) {
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::getInt32Ty(*Context), i));
return true;
} else if (V == RHS) {
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::getInt32Ty(*Context), i+NumElts));
return true;
} else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
// If this is an insert of an extract from some other vector, include it.
Value *VecOp = IEI->getOperand(0);
Value *ScalarOp = IEI->getOperand(1);
Value *IdxOp = IEI->getOperand(2);
if (!isa<ConstantInt>(IdxOp))
return false;
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector.
// Okay, we can handle this if the vector we are insertinting into is
// transitively ok.
if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask, Context)) {
// If so, update the mask to reflect the inserted undef.
Mask[InsertedIdx] = UndefValue::get(Type::getInt32Ty(*Context));
return true;
}
} else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){
if (isa<ConstantInt>(EI->getOperand(1)) &&
EI->getOperand(0)->getType() == V->getType()) {
unsigned ExtractedIdx =
cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
// This must be extracting from either LHS or RHS.
if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) {
// Okay, we can handle this if the vector we are insertinting into is
// transitively ok.
if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask, Context)) {
// If so, update the mask to reflect the inserted value.
if (EI->getOperand(0) == LHS) {
Mask[InsertedIdx % NumElts] =
ConstantInt::get(Type::getInt32Ty(*Context), ExtractedIdx);
} else {
assert(EI->getOperand(0) == RHS);
Mask[InsertedIdx % NumElts] =
ConstantInt::get(Type::getInt32Ty(*Context), ExtractedIdx+NumElts);
}
return true;
}
}
}
}
}
// TODO: Handle shufflevector here!
return false;
}
/// CollectShuffleElements - We are building a shuffle of V, using RHS as the
/// RHS of the shuffle instruction, if it is not null. Return a shuffle mask
/// that computes V and the LHS value of the shuffle.
static Value *CollectShuffleElements(Value *V, std::vector<Constant*> &Mask,
Value *&RHS, LLVMContext *Context) {
assert(isa<VectorType>(V->getType()) &&
(RHS == 0 || V->getType() == RHS->getType()) &&
"Invalid shuffle!");
unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
if (isa<UndefValue>(V)) {
Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(*Context)));
return V;
} else if (isa<ConstantAggregateZero>(V)) {
Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(*Context), 0));
return V;
} else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
// If this is an insert of an extract from some other vector, include it.
Value *VecOp = IEI->getOperand(0);
Value *ScalarOp = IEI->getOperand(1);
Value *IdxOp = IEI->getOperand(2);
if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
EI->getOperand(0)->getType() == V->getType()) {
unsigned ExtractedIdx =
cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
// Either the extracted from or inserted into vector must be RHSVec,
// otherwise we'd end up with a shuffle of three inputs.
if (EI->getOperand(0) == RHS || RHS == 0) {
RHS = EI->getOperand(0);
Value *V = CollectShuffleElements(VecOp, Mask, RHS, Context);
Mask[InsertedIdx % NumElts] =
ConstantInt::get(Type::getInt32Ty(*Context), NumElts+ExtractedIdx);
return V;
}
if (VecOp == RHS) {
Value *V = CollectShuffleElements(EI->getOperand(0), Mask,
RHS, Context);
// Everything but the extracted element is replaced with the RHS.
for (unsigned i = 0; i != NumElts; ++i) {
if (i != InsertedIdx)
Mask[i] = ConstantInt::get(Type::getInt32Ty(*Context), NumElts+i);
}
return V;
}
// If this insertelement is a chain that comes from exactly these two
// vectors, return the vector and the effective shuffle.
if (CollectSingleShuffleElements(IEI, EI->getOperand(0), RHS, Mask,
Context))
return EI->getOperand(0);
}
}
}
// TODO: Handle shufflevector here!
// Otherwise, can't do anything fancy. Return an identity vector.
for (unsigned i = 0; i != NumElts; ++i)
Mask.push_back(ConstantInt::get(Type::getInt32Ty(*Context), i));
return V;
}
Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
Value *VecOp = IE.getOperand(0);
Value *ScalarOp = IE.getOperand(1);
Value *IdxOp = IE.getOperand(2);
// Inserting an undef or into an undefined place, remove this.
if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp))
ReplaceInstUsesWith(IE, VecOp);
// If the inserted element was extracted from some other vector, and if the
// indexes are constant, try to turn this into a shufflevector operation.
if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
EI->getOperand(0)->getType() == IE.getType()) {
unsigned NumVectorElts = IE.getType()->getNumElements();
unsigned ExtractedIdx =
cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
if (ExtractedIdx >= NumVectorElts) // Out of range extract.
return ReplaceInstUsesWith(IE, VecOp);
if (InsertedIdx >= NumVectorElts) // Out of range insert.
return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType()));
// If we are extracting a value from a vector, then inserting it right
// back into the same place, just use the input vector.
if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx)
return ReplaceInstUsesWith(IE, VecOp);
// If this insertelement isn't used by some other insertelement, turn it
// (and any insertelements it points to), into one big shuffle.
if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) {
std::vector<Constant*> Mask;
Value *RHS = 0;
Value *LHS = CollectShuffleElements(&IE, Mask, RHS, Context);
if (RHS == 0) RHS = UndefValue::get(LHS->getType());
// We now have a shuffle of LHS, RHS, Mask.
return new ShuffleVectorInst(LHS, RHS,
ConstantVector::get(Mask));
}
}
}
unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements();
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts))
return &IE;
return 0;
}
Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
Value *LHS = SVI.getOperand(0);
Value *RHS = SVI.getOperand(1);
std::vector<unsigned> Mask = getShuffleMask(&SVI);
bool MadeChange = false;
// Undefined shuffle mask -> undefined value.
if (isa<UndefValue>(SVI.getOperand(2)))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
if (VWidth != cast<VectorType>(LHS->getType())->getNumElements())
return 0;
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
LHS = SVI.getOperand(0);
RHS = SVI.getOperand(1);
MadeChange = true;
}
// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
if (LHS == RHS || isa<UndefValue>(LHS)) {
if (isa<UndefValue>(LHS) && LHS == RHS) {
// shuffle(undef,undef,mask) -> undef.
return ReplaceInstUsesWith(SVI, LHS);
}
// Remap any references to RHS to use LHS.
std::vector<Constant*> Elts;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= 2*e)
Elts.push_back(UndefValue::get(Type::getInt32Ty(*Context)));
else {
if ((Mask[i] >= e && isa<UndefValue>(RHS)) ||
(Mask[i] < e && isa<UndefValue>(LHS))) {
Mask[i] = 2*e; // Turn into undef.
Elts.push_back(UndefValue::get(Type::getInt32Ty(*Context)));
} else {
Mask[i] = Mask[i] % e; // Force to LHS.
Elts.push_back(ConstantInt::get(Type::getInt32Ty(*Context), Mask[i]));
}
}
}
SVI.setOperand(0, SVI.getOperand(1));
SVI.setOperand(1, UndefValue::get(RHS->getType()));
SVI.setOperand(2, ConstantVector::get(Elts));
LHS = SVI.getOperand(0);
RHS = SVI.getOperand(1);
MadeChange = true;
}
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
bool isLHSID = true, isRHSID = true;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= e*2) continue; // Ignore undef values.
// Is this an identity shuffle of the LHS value?
isLHSID &= (Mask[i] == i);
// Is this an identity shuffle of the RHS value?
isRHSID &= (Mask[i]-e == i);
}
// Eliminate identity shuffles.
if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
// If the LHS is a shufflevector itself, see if we can combine it with this
// one without producing an unusual shuffle. Here we are really conservative:
// we are absolutely afraid of producing a shuffle mask not in the input
// program, because the code gen may not be smart enough to turn a merged
// shuffle into two specific shuffles: it may produce worse code. As such,
// we only merge two shuffles if the result is one of the two input shuffle
// masks. In this case, merging the shuffles just removes one instruction,
// which we know is safe. This is good for things like turning:
// (splat(splat)) -> splat.
if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
if (isa<UndefValue>(RHS)) {
std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
std::vector<unsigned> NewMask;
for (unsigned i = 0, e = Mask.size(); i != e; ++i)
if (Mask[i] >= 2*e)
NewMask.push_back(2*e);
else
NewMask.push_back(LHSMask[Mask[i]]);
// If the result mask is equal to the src shuffle or this shuffle mask, do
// the replacement.
if (NewMask == LHSMask || NewMask == Mask) {
unsigned LHSInNElts =
cast<VectorType>(LHSSVI->getOperand(0)->getType())->getNumElements();
std::vector<Constant*> Elts;
for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
if (NewMask[i] >= LHSInNElts*2) {
Elts.push_back(UndefValue::get(Type::getInt32Ty(*Context)));
} else {
Elts.push_back(ConstantInt::get(Type::getInt32Ty(*Context), NewMask[i]));
}
}
return new ShuffleVectorInst(LHSSVI->getOperand(0),
LHSSVI->getOperand(1),
ConstantVector::get(Elts));
}
}
}
return MadeChange ? &SVI : 0;
}
/// TryToSinkInstruction - Try to move the specified instruction from its
/// current block into the beginning of DestBlock, which can only happen if it's
/// safe to move the instruction past all of the instructions between it and the
/// end of its block.
static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
assert(I->hasOneUse() && "Invariants didn't hold!");
// Cannot move control-flow-involving, volatile loads, vaarg, etc.
if (isa<PHINode>(I) || I->mayHaveSideEffects() || isa<TerminatorInst>(I))
return false;
// Do not sink alloca instructions out of the entry block.
if (isa<AllocaInst>(I) && I->getParent() ==
&DestBlock->getParent()->getEntryBlock())
return false;
// We can only sink load instructions if there is nothing between the load and
// the end of block that could change the value.
if (I->mayReadFromMemory()) {
for (BasicBlock::iterator Scan = I, E = I->getParent()->end();
Scan != E; ++Scan)
if (Scan->mayWriteToMemory())
return false;
}
BasicBlock::iterator InsertPos = DestBlock->getFirstNonPHI();
CopyPrecedingStopPoint(I, InsertPos);
I->moveBefore(InsertPos);
++NumSunkInst;
return true;
}
/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
/// all reachable code to the worklist.
///
/// This has a couple of tricks to make the code faster and more powerful. In
/// particular, we constant fold and DCE instructions as we go, to avoid adding
/// them to the worklist (this significantly speeds up instcombine on code where
/// many instructions are dead or constant). Additionally, if we find a branch
/// whose condition is a known constant, we only visit the reachable successors.
///
static void AddReachableCodeToWorklist(BasicBlock *BB,
SmallPtrSet<BasicBlock*, 64> &Visited,
InstCombiner &IC,
const TargetData *TD) {
SmallVector<BasicBlock*, 256> Worklist;
Worklist.push_back(BB);
std::vector<Instruction*> InstrsForInstCombineWorklist;
InstrsForInstCombineWorklist.reserve(128);
while (!Worklist.empty()) {
BB = Worklist.back();
Worklist.pop_back();
// We have now visited this block! If we've already been here, ignore it.
if (!Visited.insert(BB)) continue;
DbgInfoIntrinsic *DBI_Prev = NULL;
for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
Instruction *Inst = BBI++;
// DCE instruction if trivially dead.
if (isInstructionTriviallyDead(Inst)) {
++NumDeadInst;
DEBUG(errs() << "IC: DCE: " << *Inst << '\n');
Inst->eraseFromParent();
continue;
}
// ConstantProp instruction if trivially constant.
if (Constant *C = ConstantFoldInstruction(Inst, BB->getContext(), TD)) {
DEBUG(errs() << "IC: ConstFold to: " << *C << " from: "
<< *Inst << '\n');
Inst->replaceAllUsesWith(C);
++NumConstProp;
Inst->eraseFromParent();
continue;
}
// If there are two consecutive llvm.dbg.stoppoint calls then
// it is likely that the optimizer deleted code in between these
// two intrinsics.
DbgInfoIntrinsic *DBI_Next = dyn_cast<DbgInfoIntrinsic>(Inst);
if (DBI_Next) {
if (DBI_Prev
&& DBI_Prev->getIntrinsicID() == llvm::Intrinsic::dbg_stoppoint
&& DBI_Next->getIntrinsicID() == llvm::Intrinsic::dbg_stoppoint) {
IC.Worklist.Remove(DBI_Prev);
DBI_Prev->eraseFromParent();
}
DBI_Prev = DBI_Next;
} else {
DBI_Prev = 0;
}
InstrsForInstCombineWorklist.push_back(Inst);
}
// Recursively visit successors. If this is a branch or switch on a
// constant, only visit the reachable successor.
TerminatorInst *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
Worklist.push_back(ReachableBB);
continue;
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
// See if this is an explicit destination.
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i)
if (SI->getCaseValue(i) == Cond) {
BasicBlock *ReachableBB = SI->getSuccessor(i);
Worklist.push_back(ReachableBB);
continue;
}
// Otherwise it is the default destination.
Worklist.push_back(SI->getSuccessor(0));
continue;
}
}
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
Worklist.push_back(TI->getSuccessor(i));
}
// Once we've found all of the instructions to add to instcombine's worklist,
// add them in reverse order. This way instcombine will visit from the top
// of the function down. This jives well with the way that it adds all uses
// of instructions to the worklist after doing a transformation, thus avoiding
// some N^2 behavior in pathological cases.
IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
InstrsForInstCombineWorklist.size());
}
bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
MadeIRChange = false;
TD = getAnalysisIfAvailable<TargetData>();
DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
<< F.getNameStr() << "\n");
{
// Do a depth-first traversal of the function, populate the worklist with
// the reachable instructions. Ignore blocks that are not reachable. Keep
// track of which blocks we visit.
SmallPtrSet<BasicBlock*, 64> Visited;
AddReachableCodeToWorklist(F.begin(), Visited, *this, TD);
// Do a quick scan over the function. If we find any blocks that are
// unreachable, remove any instructions inside of them. This prevents
// the instcombine code from having to deal with some bad special cases.
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (!Visited.count(BB)) {
Instruction *Term = BB->getTerminator();
while (Term != BB->begin()) { // Remove instrs bottom-up
BasicBlock::iterator I = Term; --I;
DEBUG(errs() << "IC: DCE: " << *I << '\n');
// A debug intrinsic shouldn't force another iteration if we weren't
// going to do one without it.
if (!isa<DbgInfoIntrinsic>(I)) {
++NumDeadInst;
MadeIRChange = true;
}
if (!I->use_empty())
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
}
}
while (!Worklist.isEmpty()) {
Instruction *I = Worklist.RemoveOne();
if (I == 0) continue; // skip null values.
// Check to see if we can DCE the instruction.
if (isInstructionTriviallyDead(I)) {
DEBUG(errs() << "IC: DCE: " << *I << '\n');
EraseInstFromFunction(*I);
++NumDeadInst;
MadeIRChange = true;
continue;
}
// Instruction isn't dead, see if we can constant propagate it.
if (Constant *C = ConstantFoldInstruction(I, F.getContext(), TD)) {
DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n');
// Add operands to the worklist.
ReplaceInstUsesWith(*I, C);
++NumConstProp;
EraseInstFromFunction(*I);
MadeIRChange = true;
continue;
}
if (TD) {
// See if we can constant fold its operands.
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(i))
if (Constant *NewC = ConstantFoldConstantExpression(CE,
F.getContext(), TD))
if (NewC != CE) {
*i = NewC;
MadeIRChange = true;
}
}
// See if we can trivially sink this instruction to a successor basic block.
if (I->hasOneUse()) {
BasicBlock *BB = I->getParent();
BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
if (UserParent != BB) {
bool UserIsSuccessor = false;
// See if the user is one of our successors.
for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
if (*SI == UserParent) {
UserIsSuccessor = true;
break;
}
// If the user is one of our immediate successors, and if that successor
// only has us as a predecessors (we'd have to split the critical edge
// otherwise), we can keep going.
if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
next(pred_begin(UserParent)) == pred_end(UserParent))
// Okay, the CFG is simple enough, try to sink this instruction.
MadeIRChange |= TryToSinkInstruction(I, UserParent);
}
}
// Now that we have an instruction, try combining it to simplify it.
Builder->SetInsertPoint(I->getParent(), I);
#ifndef NDEBUG
std::string OrigI;
#endif
DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str(););
DEBUG(errs() << "IC: Visiting: " << OrigI << '\n');
if (Instruction *Result = visit(*I)) {
++NumCombined;
// Should we replace the old instruction with a new one?
if (Result != I) {
DEBUG(errs() << "IC: Old = " << *I << '\n'
<< " New = " << *Result << '\n');
// Everything uses the new instruction now.
I->replaceAllUsesWith(Result);
// Push the new instruction and any users onto the worklist.
Worklist.Add(Result);
Worklist.AddUsersToWorkList(*Result);
// Move the name to the new instruction first.
Result->takeName(I);
// Insert the new instruction into the basic block...
BasicBlock *InstParent = I->getParent();
BasicBlock::iterator InsertPos = I;
if (!isa<PHINode>(Result)) // If combining a PHI, don't insert
while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
++InsertPos;
InstParent->getInstList().insert(InsertPos, Result);
EraseInstFromFunction(*I);
} else {
#ifndef NDEBUG
DEBUG(errs() << "IC: Mod = " << OrigI << '\n'
<< " New = " << *I << '\n');
#endif
// If the instruction was modified, it's possible that it is now dead.
// if so, remove it.
if (isInstructionTriviallyDead(I)) {
EraseInstFromFunction(*I);
} else {
Worklist.Add(I);
Worklist.AddUsersToWorkList(*I);
}
}
MadeIRChange = true;
}
}
Worklist.Zap();
return MadeIRChange;
}
bool InstCombiner::runOnFunction(Function &F) {
MustPreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
Context = &F.getContext();
/// Builder - This is an IRBuilder that automatically inserts new
/// instructions into the worklist when they are created.
IRBuilder<true, ConstantFolder, InstCombineIRInserter>
TheBuilder(F.getContext(), ConstantFolder(F.getContext()),
InstCombineIRInserter(Worklist));
Builder = &TheBuilder;
bool EverMadeChange = false;
// Iterate while there is work to do.
unsigned Iteration = 0;
while (DoOneIteration(F, Iteration++))
EverMadeChange = true;
Builder = 0;
return EverMadeChange;
}
FunctionPass *llvm::createInstructionCombiningPass() {
return new InstCombiner();
}
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