mirror of
https://github.com/RPCS3/llvm.git
synced 2024-12-13 23:18:58 +00:00
46bdfb0e6b
to more accurately describe what it does. Expand its doxygen comment to describe what the backedge-taken count is and how it differs from the actual iteration count of the loop. Adjust names and comments in associated code accordingly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65382 91177308-0d34-0410-b5e6-96231b3b80d8
2700 lines
111 KiB
C++
2700 lines
111 KiB
C++
//===- LoopStrengthReduce.cpp - Strength Reduce GEPs in Loops -------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass performs a strength reduction on array references inside loops that
|
|
// have as one or more of their components the loop induction variable. This is
|
|
// accomplished by creating a new Value to hold the initial value of the array
|
|
// access for the first iteration, and then creating a new GEP instruction in
|
|
// the loop to increment the value by the appropriate amount.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "loop-reduce"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Constants.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/IntrinsicInst.h"
|
|
#include "llvm/Type.h"
|
|
#include "llvm/DerivedTypes.h"
|
|
#include "llvm/Analysis/Dominators.h"
|
|
#include "llvm/Analysis/LoopInfo.h"
|
|
#include "llvm/Analysis/LoopPass.h"
|
|
#include "llvm/Analysis/ScalarEvolutionExpander.h"
|
|
#include "llvm/Transforms/Utils/AddrModeMatcher.h"
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/Transforms/Utils/Local.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/Compiler.h"
|
|
#include "llvm/Support/CommandLine.h"
|
|
#include "llvm/Support/GetElementPtrTypeIterator.h"
|
|
#include "llvm/Target/TargetLowering.h"
|
|
#include <algorithm>
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumReduced , "Number of GEPs strength reduced");
|
|
STATISTIC(NumInserted, "Number of PHIs inserted");
|
|
STATISTIC(NumVariable, "Number of PHIs with variable strides");
|
|
STATISTIC(NumEliminated, "Number of strides eliminated");
|
|
STATISTIC(NumShadow, "Number of Shadow IVs optimized");
|
|
STATISTIC(NumImmSunk, "Number of common expr immediates sunk into uses");
|
|
|
|
static cl::opt<bool> EnableFullLSRMode("enable-full-lsr",
|
|
cl::init(false),
|
|
cl::Hidden);
|
|
|
|
namespace {
|
|
|
|
struct BasedUser;
|
|
|
|
/// IVStrideUse - Keep track of one use of a strided induction variable, where
|
|
/// the stride is stored externally. The Offset member keeps track of the
|
|
/// offset from the IV, User is the actual user of the operand, and
|
|
/// 'OperandValToReplace' is the operand of the User that is the use.
|
|
struct VISIBILITY_HIDDEN IVStrideUse {
|
|
SCEVHandle Offset;
|
|
Instruction *User;
|
|
Value *OperandValToReplace;
|
|
|
|
// isUseOfPostIncrementedValue - True if this should use the
|
|
// post-incremented version of this IV, not the preincremented version.
|
|
// This can only be set in special cases, such as the terminating setcc
|
|
// instruction for a loop or uses dominated by the loop.
|
|
bool isUseOfPostIncrementedValue;
|
|
|
|
IVStrideUse(const SCEVHandle &Offs, Instruction *U, Value *O)
|
|
: Offset(Offs), User(U), OperandValToReplace(O),
|
|
isUseOfPostIncrementedValue(false) {}
|
|
};
|
|
|
|
/// IVUsersOfOneStride - This structure keeps track of all instructions that
|
|
/// have an operand that is based on the trip count multiplied by some stride.
|
|
/// The stride for all of these users is common and kept external to this
|
|
/// structure.
|
|
struct VISIBILITY_HIDDEN IVUsersOfOneStride {
|
|
/// Users - Keep track of all of the users of this stride as well as the
|
|
/// initial value and the operand that uses the IV.
|
|
std::vector<IVStrideUse> Users;
|
|
|
|
void addUser(const SCEVHandle &Offset,Instruction *User, Value *Operand) {
|
|
Users.push_back(IVStrideUse(Offset, User, Operand));
|
|
}
|
|
};
|
|
|
|
/// IVInfo - This structure keeps track of one IV expression inserted during
|
|
/// StrengthReduceStridedIVUsers. It contains the stride, the common base, as
|
|
/// well as the PHI node and increment value created for rewrite.
|
|
struct VISIBILITY_HIDDEN IVExpr {
|
|
SCEVHandle Stride;
|
|
SCEVHandle Base;
|
|
PHINode *PHI;
|
|
Value *IncV;
|
|
|
|
IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
|
|
Value *incv)
|
|
: Stride(stride), Base(base), PHI(phi), IncV(incv) {}
|
|
};
|
|
|
|
/// IVsOfOneStride - This structure keeps track of all IV expression inserted
|
|
/// during StrengthReduceStridedIVUsers for a particular stride of the IV.
|
|
struct VISIBILITY_HIDDEN IVsOfOneStride {
|
|
std::vector<IVExpr> IVs;
|
|
|
|
void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI,
|
|
Value *IncV) {
|
|
IVs.push_back(IVExpr(Stride, Base, PHI, IncV));
|
|
}
|
|
};
|
|
|
|
class VISIBILITY_HIDDEN LoopStrengthReduce : public LoopPass {
|
|
LoopInfo *LI;
|
|
DominatorTree *DT;
|
|
ScalarEvolution *SE;
|
|
const TargetData *TD;
|
|
const Type *UIntPtrTy;
|
|
bool Changed;
|
|
|
|
/// IVUsesByStride - Keep track of all uses of induction variables that we
|
|
/// are interested in. The key of the map is the stride of the access.
|
|
std::map<SCEVHandle, IVUsersOfOneStride> IVUsesByStride;
|
|
|
|
/// IVsByStride - Keep track of all IVs that have been inserted for a
|
|
/// particular stride.
|
|
std::map<SCEVHandle, IVsOfOneStride> IVsByStride;
|
|
|
|
/// StrideOrder - An ordering of the keys in IVUsesByStride that is stable:
|
|
/// We use this to iterate over the IVUsesByStride collection without being
|
|
/// dependent on random ordering of pointers in the process.
|
|
SmallVector<SCEVHandle, 16> StrideOrder;
|
|
|
|
/// GEPlist - A list of the GEP's that have been remembered in the SCEV
|
|
/// data structures. SCEV does not know to update these when the operands
|
|
/// of the GEP are changed, which means we cannot leave them live across
|
|
/// loops.
|
|
SmallVector<GetElementPtrInst *, 16> GEPlist;
|
|
|
|
/// CastedValues - As we need to cast values to uintptr_t, this keeps track
|
|
/// of the casted version of each value. This is accessed by
|
|
/// getCastedVersionOf.
|
|
DenseMap<Value*, Value*> CastedPointers;
|
|
|
|
/// DeadInsts - Keep track of instructions we may have made dead, so that
|
|
/// we can remove them after we are done working.
|
|
SmallVector<Instruction*, 16> DeadInsts;
|
|
|
|
/// TLI - Keep a pointer of a TargetLowering to consult for determining
|
|
/// transformation profitability.
|
|
const TargetLowering *TLI;
|
|
|
|
public:
|
|
static char ID; // Pass ID, replacement for typeid
|
|
explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
|
|
LoopPass(&ID), TLI(tli) {
|
|
}
|
|
|
|
bool runOnLoop(Loop *L, LPPassManager &LPM);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
// We split critical edges, so we change the CFG. However, we do update
|
|
// many analyses if they are around.
|
|
AU.addPreservedID(LoopSimplifyID);
|
|
AU.addPreserved<LoopInfo>();
|
|
AU.addPreserved<DominanceFrontier>();
|
|
AU.addPreserved<DominatorTree>();
|
|
|
|
AU.addRequiredID(LoopSimplifyID);
|
|
AU.addRequired<LoopInfo>();
|
|
AU.addRequired<DominatorTree>();
|
|
AU.addRequired<TargetData>();
|
|
AU.addRequired<ScalarEvolution>();
|
|
AU.addPreserved<ScalarEvolution>();
|
|
}
|
|
|
|
/// getCastedVersionOf - Return the specified value casted to uintptr_t.
|
|
///
|
|
Value *getCastedVersionOf(Instruction::CastOps opcode, Value *V);
|
|
private:
|
|
bool AddUsersIfInteresting(Instruction *I, Loop *L,
|
|
SmallPtrSet<Instruction*,16> &Processed);
|
|
SCEVHandle GetExpressionSCEV(Instruction *E);
|
|
ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
|
|
IVStrideUse* &CondUse,
|
|
const SCEVHandle* &CondStride);
|
|
void OptimizeIndvars(Loop *L);
|
|
|
|
/// OptimizeShadowIV - If IV is used in a int-to-float cast
|
|
/// inside the loop then try to eliminate the cast opeation.
|
|
void OptimizeShadowIV(Loop *L);
|
|
|
|
/// OptimizeSMax - Rewrite the loop's terminating condition
|
|
/// if it uses an smax computation.
|
|
ICmpInst *OptimizeSMax(Loop *L, ICmpInst *Cond,
|
|
IVStrideUse* &CondUse);
|
|
|
|
bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
|
|
const SCEVHandle *&CondStride);
|
|
bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
|
|
SCEVHandle CheckForIVReuse(bool, bool, bool, const SCEVHandle&,
|
|
IVExpr&, const Type*,
|
|
const std::vector<BasedUser>& UsersToProcess);
|
|
bool ValidStride(bool, int64_t,
|
|
const std::vector<BasedUser>& UsersToProcess);
|
|
SCEVHandle CollectIVUsers(const SCEVHandle &Stride,
|
|
IVUsersOfOneStride &Uses,
|
|
Loop *L,
|
|
bool &AllUsesAreAddresses,
|
|
bool &AllUsesAreOutsideLoop,
|
|
std::vector<BasedUser> &UsersToProcess);
|
|
bool ShouldUseFullStrengthReductionMode(
|
|
const std::vector<BasedUser> &UsersToProcess,
|
|
const Loop *L,
|
|
bool AllUsesAreAddresses,
|
|
SCEVHandle Stride);
|
|
void PrepareToStrengthReduceFully(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
SCEVHandle Stride,
|
|
SCEVHandle CommonExprs,
|
|
const Loop *L,
|
|
SCEVExpander &PreheaderRewriter);
|
|
void PrepareToStrengthReduceFromSmallerStride(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
Value *CommonBaseV,
|
|
const IVExpr &ReuseIV,
|
|
Instruction *PreInsertPt);
|
|
void PrepareToStrengthReduceWithNewPhi(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
SCEVHandle Stride,
|
|
SCEVHandle CommonExprs,
|
|
Value *CommonBaseV,
|
|
const Loop *L,
|
|
SCEVExpander &PreheaderRewriter);
|
|
void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
|
|
IVUsersOfOneStride &Uses,
|
|
Loop *L, bool isOnlyStride);
|
|
void DeleteTriviallyDeadInstructions();
|
|
};
|
|
}
|
|
|
|
char LoopStrengthReduce::ID = 0;
|
|
static RegisterPass<LoopStrengthReduce>
|
|
X("loop-reduce", "Loop Strength Reduction");
|
|
|
|
Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
|
|
return new LoopStrengthReduce(TLI);
|
|
}
|
|
|
|
/// getCastedVersionOf - Return the specified value casted to uintptr_t. This
|
|
/// assumes that the Value* V is of integer or pointer type only.
|
|
///
|
|
Value *LoopStrengthReduce::getCastedVersionOf(Instruction::CastOps opcode,
|
|
Value *V) {
|
|
if (V->getType() == UIntPtrTy) return V;
|
|
if (Constant *CB = dyn_cast<Constant>(V))
|
|
return ConstantExpr::getCast(opcode, CB, UIntPtrTy);
|
|
|
|
Value *&New = CastedPointers[V];
|
|
if (New) return New;
|
|
|
|
New = SCEVExpander::InsertCastOfTo(opcode, V, UIntPtrTy);
|
|
DeadInsts.push_back(cast<Instruction>(New));
|
|
return New;
|
|
}
|
|
|
|
|
|
/// DeleteTriviallyDeadInstructions - If any of the instructions is the
|
|
/// specified set are trivially dead, delete them and see if this makes any of
|
|
/// their operands subsequently dead.
|
|
void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
|
|
if (DeadInsts.empty()) return;
|
|
|
|
// Sort the deadinsts list so that we can trivially eliminate duplicates as we
|
|
// go. The code below never adds a non-dead instruction to the worklist, but
|
|
// callers may not be so careful.
|
|
array_pod_sort(DeadInsts.begin(), DeadInsts.end());
|
|
|
|
// Drop duplicate instructions and those with uses.
|
|
for (unsigned i = 0, e = DeadInsts.size()-1; i < e; ++i) {
|
|
Instruction *I = DeadInsts[i];
|
|
if (!I->use_empty()) DeadInsts[i] = 0;
|
|
while (i != e && DeadInsts[i+1] == I)
|
|
DeadInsts[++i] = 0;
|
|
}
|
|
|
|
while (!DeadInsts.empty()) {
|
|
Instruction *I = DeadInsts.back();
|
|
DeadInsts.pop_back();
|
|
|
|
if (I == 0 || !isInstructionTriviallyDead(I))
|
|
continue;
|
|
|
|
SE->deleteValueFromRecords(I);
|
|
|
|
for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) {
|
|
if (Instruction *U = dyn_cast<Instruction>(*OI)) {
|
|
*OI = 0;
|
|
if (U->use_empty())
|
|
DeadInsts.push_back(U);
|
|
}
|
|
}
|
|
|
|
I->eraseFromParent();
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
|
|
/// GetExpressionSCEV - Compute and return the SCEV for the specified
|
|
/// instruction.
|
|
SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp) {
|
|
// Pointer to pointer bitcast instructions return the same value as their
|
|
// operand.
|
|
if (BitCastInst *BCI = dyn_cast<BitCastInst>(Exp)) {
|
|
if (SE->hasSCEV(BCI) || !isa<Instruction>(BCI->getOperand(0)))
|
|
return SE->getSCEV(BCI);
|
|
SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)));
|
|
SE->setSCEV(BCI, R);
|
|
return R;
|
|
}
|
|
|
|
// Scalar Evolutions doesn't know how to compute SCEV's for GEP instructions.
|
|
// If this is a GEP that SE doesn't know about, compute it now and insert it.
|
|
// If this is not a GEP, or if we have already done this computation, just let
|
|
// SE figure it out.
|
|
GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Exp);
|
|
if (!GEP || SE->hasSCEV(GEP))
|
|
return SE->getSCEV(Exp);
|
|
|
|
// Analyze all of the subscripts of this getelementptr instruction, looking
|
|
// for uses that are determined by the trip count of the loop. First, skip
|
|
// all operands the are not dependent on the IV.
|
|
|
|
// Build up the base expression. Insert an LLVM cast of the pointer to
|
|
// uintptr_t first.
|
|
SCEVHandle GEPVal = SE->getUnknown(
|
|
getCastedVersionOf(Instruction::PtrToInt, GEP->getOperand(0)));
|
|
|
|
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 this is a use of a recurrence that we can analyze, and it comes before
|
|
// Op does in the GEP operand list, we will handle this when we process this
|
|
// operand.
|
|
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
|
|
const StructLayout *SL = TD->getStructLayout(STy);
|
|
unsigned Idx = cast<ConstantInt>(*i)->getZExtValue();
|
|
uint64_t Offset = SL->getElementOffset(Idx);
|
|
GEPVal = SE->getAddExpr(GEPVal,
|
|
SE->getIntegerSCEV(Offset, UIntPtrTy));
|
|
} else {
|
|
unsigned GEPOpiBits =
|
|
(*i)->getType()->getPrimitiveSizeInBits();
|
|
unsigned IntPtrBits = UIntPtrTy->getPrimitiveSizeInBits();
|
|
Instruction::CastOps opcode = (GEPOpiBits < IntPtrBits ?
|
|
Instruction::SExt : (GEPOpiBits > IntPtrBits ? Instruction::Trunc :
|
|
Instruction::BitCast));
|
|
Value *OpVal = getCastedVersionOf(opcode, *i);
|
|
SCEVHandle Idx = SE->getSCEV(OpVal);
|
|
|
|
uint64_t TypeSize = TD->getTypePaddedSize(GTI.getIndexedType());
|
|
if (TypeSize != 1)
|
|
Idx = SE->getMulExpr(Idx,
|
|
SE->getConstant(ConstantInt::get(UIntPtrTy,
|
|
TypeSize)));
|
|
GEPVal = SE->getAddExpr(GEPVal, Idx);
|
|
}
|
|
}
|
|
|
|
SE->setSCEV(GEP, GEPVal);
|
|
GEPlist.push_back(GEP);
|
|
return GEPVal;
|
|
}
|
|
|
|
/// containsAddRecFromDifferentLoop - Determine whether expression S involves a
|
|
/// subexpression that is an AddRec from a loop other than L. An outer loop
|
|
/// of L is OK, but not an inner loop nor a disjoint loop.
|
|
static bool containsAddRecFromDifferentLoop(SCEVHandle S, Loop *L) {
|
|
// This is very common, put it first.
|
|
if (isa<SCEVConstant>(S))
|
|
return false;
|
|
if (SCEVCommutativeExpr *AE = dyn_cast<SCEVCommutativeExpr>(S)) {
|
|
for (unsigned int i=0; i< AE->getNumOperands(); i++)
|
|
if (containsAddRecFromDifferentLoop(AE->getOperand(i), L))
|
|
return true;
|
|
return false;
|
|
}
|
|
if (SCEVAddRecExpr *AE = dyn_cast<SCEVAddRecExpr>(S)) {
|
|
if (const Loop *newLoop = AE->getLoop()) {
|
|
if (newLoop == L)
|
|
return false;
|
|
// if newLoop is an outer loop of L, this is OK.
|
|
if (!LoopInfoBase<BasicBlock>::isNotAlreadyContainedIn(L, newLoop))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
if (SCEVUDivExpr *DE = dyn_cast<SCEVUDivExpr>(S))
|
|
return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
|
|
containsAddRecFromDifferentLoop(DE->getRHS(), L);
|
|
#if 0
|
|
// SCEVSDivExpr has been backed out temporarily, but will be back; we'll
|
|
// need this when it is.
|
|
if (SCEVSDivExpr *DE = dyn_cast<SCEVSDivExpr>(S))
|
|
return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
|
|
containsAddRecFromDifferentLoop(DE->getRHS(), L);
|
|
#endif
|
|
if (SCEVTruncateExpr *TE = dyn_cast<SCEVTruncateExpr>(S))
|
|
return containsAddRecFromDifferentLoop(TE->getOperand(), L);
|
|
if (SCEVZeroExtendExpr *ZE = dyn_cast<SCEVZeroExtendExpr>(S))
|
|
return containsAddRecFromDifferentLoop(ZE->getOperand(), L);
|
|
if (SCEVSignExtendExpr *SE = dyn_cast<SCEVSignExtendExpr>(S))
|
|
return containsAddRecFromDifferentLoop(SE->getOperand(), L);
|
|
return false;
|
|
}
|
|
|
|
/// getSCEVStartAndStride - Compute the start and stride of this expression,
|
|
/// returning false if the expression is not a start/stride pair, or true if it
|
|
/// is. The stride must be a loop invariant expression, but the start may be
|
|
/// a mix of loop invariant and loop variant expressions. The start cannot,
|
|
/// however, contain an AddRec from a different loop, unless that loop is an
|
|
/// outer loop of the current loop.
|
|
static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
|
|
SCEVHandle &Start, SCEVHandle &Stride,
|
|
ScalarEvolution *SE, DominatorTree *DT) {
|
|
SCEVHandle TheAddRec = Start; // Initialize to zero.
|
|
|
|
// If the outer level is an AddExpr, the operands are all start values except
|
|
// for a nested AddRecExpr.
|
|
if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
|
|
for (unsigned i = 0, e = AE->getNumOperands(); i != e; ++i)
|
|
if (SCEVAddRecExpr *AddRec =
|
|
dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
|
|
if (AddRec->getLoop() == L)
|
|
TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
|
|
else
|
|
return false; // Nested IV of some sort?
|
|
} else {
|
|
Start = SE->getAddExpr(Start, AE->getOperand(i));
|
|
}
|
|
|
|
} else if (isa<SCEVAddRecExpr>(SH)) {
|
|
TheAddRec = SH;
|
|
} else {
|
|
return false; // not analyzable.
|
|
}
|
|
|
|
SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
|
|
if (!AddRec || AddRec->getLoop() != L) return false;
|
|
|
|
// FIXME: Generalize to non-affine IV's.
|
|
if (!AddRec->isAffine()) return false;
|
|
|
|
// If Start contains an SCEVAddRecExpr from a different loop, other than an
|
|
// outer loop of the current loop, reject it. SCEV has no concept of
|
|
// operating on one loop at a time so don't confuse it with such expressions.
|
|
if (containsAddRecFromDifferentLoop(AddRec->getOperand(0), L))
|
|
return false;
|
|
|
|
Start = SE->getAddExpr(Start, AddRec->getOperand(0));
|
|
|
|
if (!isa<SCEVConstant>(AddRec->getOperand(1))) {
|
|
// If stride is an instruction, make sure it dominates the loop preheader.
|
|
// Otherwise we could end up with a use before def situation.
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
if (!AddRec->getOperand(1)->dominates(Preheader, DT))
|
|
return false;
|
|
|
|
DOUT << "[" << L->getHeader()->getName()
|
|
<< "] Variable stride: " << *AddRec << "\n";
|
|
}
|
|
|
|
Stride = AddRec->getOperand(1);
|
|
return true;
|
|
}
|
|
|
|
/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
|
|
/// and now we need to decide whether the user should use the preinc or post-inc
|
|
/// value. If this user should use the post-inc version of the IV, return true.
|
|
///
|
|
/// Choosing wrong here can break dominance properties (if we choose to use the
|
|
/// post-inc value when we cannot) or it can end up adding extra live-ranges to
|
|
/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
|
|
/// should use the post-inc value).
|
|
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
|
|
Loop *L, DominatorTree *DT, Pass *P,
|
|
SmallVectorImpl<Instruction*> &DeadInsts){
|
|
// If the user is in the loop, use the preinc value.
|
|
if (L->contains(User->getParent())) return false;
|
|
|
|
BasicBlock *LatchBlock = L->getLoopLatch();
|
|
|
|
// Ok, the user is outside of the loop. If it is dominated by the latch
|
|
// block, use the post-inc value.
|
|
if (DT->dominates(LatchBlock, User->getParent()))
|
|
return true;
|
|
|
|
// There is one case we have to be careful of: PHI nodes. These little guys
|
|
// can live in blocks that do not dominate the latch block, but (since their
|
|
// uses occur in the predecessor block, not the block the PHI lives in) should
|
|
// still use the post-inc value. Check for this case now.
|
|
PHINode *PN = dyn_cast<PHINode>(User);
|
|
if (!PN) return false; // not a phi, not dominated by latch block.
|
|
|
|
// Look at all of the uses of IV by the PHI node. If any use corresponds to
|
|
// a block that is not dominated by the latch block, give up and use the
|
|
// preincremented value.
|
|
unsigned NumUses = 0;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (PN->getIncomingValue(i) == IV) {
|
|
++NumUses;
|
|
if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
|
|
return false;
|
|
}
|
|
|
|
// Okay, all uses of IV by PN are in predecessor blocks that really are
|
|
// dominated by the latch block. Split the critical edges and use the
|
|
// post-incremented value.
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (PN->getIncomingValue(i) == IV) {
|
|
SplitCriticalEdge(PN->getIncomingBlock(i), PN->getParent(), P, false);
|
|
// Splitting the critical edge can reduce the number of entries in this
|
|
// PHI.
|
|
e = PN->getNumIncomingValues();
|
|
if (--NumUses == 0) break;
|
|
}
|
|
|
|
// PHI node might have become a constant value after SplitCriticalEdge.
|
|
DeadInsts.push_back(User);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// isAddressUse - Returns true if the specified instruction is using the
|
|
/// specified value as an address.
|
|
static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
|
|
bool isAddress = isa<LoadInst>(Inst);
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
if (SI->getOperand(1) == OperandVal)
|
|
isAddress = true;
|
|
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
|
|
// Addressing modes can also be folded into prefetches and a variety
|
|
// of intrinsics.
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::prefetch:
|
|
case Intrinsic::x86_sse2_loadu_dq:
|
|
case Intrinsic::x86_sse2_loadu_pd:
|
|
case Intrinsic::x86_sse_loadu_ps:
|
|
case Intrinsic::x86_sse_storeu_ps:
|
|
case Intrinsic::x86_sse2_storeu_pd:
|
|
case Intrinsic::x86_sse2_storeu_dq:
|
|
case Intrinsic::x86_sse2_storel_dq:
|
|
if (II->getOperand(1) == OperandVal)
|
|
isAddress = true;
|
|
break;
|
|
}
|
|
}
|
|
return isAddress;
|
|
}
|
|
|
|
/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
|
|
/// reducible SCEV, recursively add its users to the IVUsesByStride set and
|
|
/// return true. Otherwise, return false.
|
|
bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
|
|
SmallPtrSet<Instruction*,16> &Processed) {
|
|
if (!I->getType()->isInteger() && !isa<PointerType>(I->getType()))
|
|
return false; // Void and FP expressions cannot be reduced.
|
|
if (!Processed.insert(I))
|
|
return true; // Instruction already handled.
|
|
|
|
// Get the symbolic expression for this instruction.
|
|
SCEVHandle ISE = GetExpressionSCEV(I);
|
|
if (isa<SCEVCouldNotCompute>(ISE)) return false;
|
|
|
|
// Get the start and stride for this expression.
|
|
SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());
|
|
SCEVHandle Stride = Start;
|
|
if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE, DT))
|
|
return false; // Non-reducible symbolic expression, bail out.
|
|
|
|
std::vector<Instruction *> IUsers;
|
|
// Collect all I uses now because IVUseShouldUsePostIncValue may
|
|
// invalidate use_iterator.
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; ++UI)
|
|
IUsers.push_back(cast<Instruction>(*UI));
|
|
|
|
for (unsigned iused_index = 0, iused_size = IUsers.size();
|
|
iused_index != iused_size; ++iused_index) {
|
|
|
|
Instruction *User = IUsers[iused_index];
|
|
|
|
// Do not infinitely recurse on PHI nodes.
|
|
if (isa<PHINode>(User) && Processed.count(User))
|
|
continue;
|
|
|
|
// Descend recursively, but not into PHI nodes outside the current loop.
|
|
// It's important to see the entire expression outside the loop to get
|
|
// choices that depend on addressing mode use right, although we won't
|
|
// consider references ouside the loop in all cases.
|
|
// If User is already in Processed, we don't want to recurse into it again,
|
|
// but do want to record a second reference in the same instruction.
|
|
bool AddUserToIVUsers = false;
|
|
if (LI->getLoopFor(User->getParent()) != L) {
|
|
if (isa<PHINode>(User) || Processed.count(User) ||
|
|
!AddUsersIfInteresting(User, L, Processed)) {
|
|
DOUT << "FOUND USER in other loop: " << *User
|
|
<< " OF SCEV: " << *ISE << "\n";
|
|
AddUserToIVUsers = true;
|
|
}
|
|
} else if (Processed.count(User) ||
|
|
!AddUsersIfInteresting(User, L, Processed)) {
|
|
DOUT << "FOUND USER: " << *User
|
|
<< " OF SCEV: " << *ISE << "\n";
|
|
AddUserToIVUsers = true;
|
|
}
|
|
|
|
if (AddUserToIVUsers) {
|
|
IVUsersOfOneStride &StrideUses = IVUsesByStride[Stride];
|
|
if (StrideUses.Users.empty()) // First occurrence of this stride?
|
|
StrideOrder.push_back(Stride);
|
|
|
|
// Okay, we found a user that we cannot reduce. Analyze the instruction
|
|
// and decide what to do with it. If we are a use inside of the loop, use
|
|
// the value before incrementation, otherwise use it after incrementation.
|
|
if (IVUseShouldUsePostIncValue(User, I, L, DT, this, DeadInsts)) {
|
|
// The value used will be incremented by the stride more than we are
|
|
// expecting, so subtract this off.
|
|
SCEVHandle NewStart = SE->getMinusSCEV(Start, Stride);
|
|
StrideUses.addUser(NewStart, User, I);
|
|
StrideUses.Users.back().isUseOfPostIncrementedValue = true;
|
|
DOUT << " USING POSTINC SCEV, START=" << *NewStart<< "\n";
|
|
} else {
|
|
StrideUses.addUser(Start, User, I);
|
|
}
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
/// BasedUser - For a particular base value, keep information about how we've
|
|
/// partitioned the expression so far.
|
|
struct BasedUser {
|
|
/// SE - The current ScalarEvolution object.
|
|
ScalarEvolution *SE;
|
|
|
|
/// Base - The Base value for the PHI node that needs to be inserted for
|
|
/// this use. As the use is processed, information gets moved from this
|
|
/// field to the Imm field (below). BasedUser values are sorted by this
|
|
/// field.
|
|
SCEVHandle Base;
|
|
|
|
/// Inst - The instruction using the induction variable.
|
|
Instruction *Inst;
|
|
|
|
/// OperandValToReplace - The operand value of Inst to replace with the
|
|
/// EmittedBase.
|
|
Value *OperandValToReplace;
|
|
|
|
/// Imm - The immediate value that should be added to the base immediately
|
|
/// before Inst, because it will be folded into the imm field of the
|
|
/// instruction. This is also sometimes used for loop-variant values that
|
|
/// must be added inside the loop.
|
|
SCEVHandle Imm;
|
|
|
|
/// Phi - The induction variable that performs the striding that
|
|
/// should be used for this user.
|
|
Value *Phi;
|
|
|
|
/// IncV - The post-incremented value of Phi.
|
|
Value *IncV;
|
|
|
|
// isUseOfPostIncrementedValue - True if this should use the
|
|
// post-incremented version of this IV, not the preincremented version.
|
|
// This can only be set in special cases, such as the terminating setcc
|
|
// instruction for a loop and uses outside the loop that are dominated by
|
|
// the loop.
|
|
bool isUseOfPostIncrementedValue;
|
|
|
|
BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
|
|
: SE(se), Base(IVSU.Offset), Inst(IVSU.User),
|
|
OperandValToReplace(IVSU.OperandValToReplace),
|
|
Imm(SE->getIntegerSCEV(0, Base->getType())),
|
|
isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue) {}
|
|
|
|
// Once we rewrite the code to insert the new IVs we want, update the
|
|
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
|
|
// to it.
|
|
void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
|
|
Instruction *InsertPt,
|
|
SCEVExpander &Rewriter, Loop *L, Pass *P,
|
|
SmallVectorImpl<Instruction*> &DeadInsts);
|
|
|
|
Value *InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
|
|
SCEVExpander &Rewriter,
|
|
Instruction *IP, Loop *L);
|
|
void dump() const;
|
|
};
|
|
}
|
|
|
|
void BasedUser::dump() const {
|
|
cerr << " Base=" << *Base;
|
|
cerr << " Imm=" << *Imm;
|
|
cerr << " Inst: " << *Inst;
|
|
}
|
|
|
|
Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
|
|
SCEVExpander &Rewriter,
|
|
Instruction *IP, Loop *L) {
|
|
// Figure out where we *really* want to insert this code. In particular, if
|
|
// the user is inside of a loop that is nested inside of L, we really don't
|
|
// want to insert this expression before the user, we'd rather pull it out as
|
|
// many loops as possible.
|
|
LoopInfo &LI = Rewriter.getLoopInfo();
|
|
Instruction *BaseInsertPt = IP;
|
|
|
|
// Figure out the most-nested loop that IP is in.
|
|
Loop *InsertLoop = LI.getLoopFor(IP->getParent());
|
|
|
|
// If InsertLoop is not L, and InsertLoop is nested inside of L, figure out
|
|
// the preheader of the outer-most loop where NewBase is not loop invariant.
|
|
if (L->contains(IP->getParent()))
|
|
while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
|
|
BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
|
|
InsertLoop = InsertLoop->getParentLoop();
|
|
}
|
|
|
|
Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
|
|
|
|
// If there is no immediate value, skip the next part.
|
|
if (Imm->isZero())
|
|
return Base;
|
|
|
|
// If we are inserting the base and imm values in the same block, make sure to
|
|
// adjust the IP position if insertion reused a result.
|
|
if (IP == BaseInsertPt)
|
|
IP = Rewriter.getInsertionPoint();
|
|
|
|
// Always emit the immediate (if non-zero) into the same block as the user.
|
|
SCEVHandle NewValSCEV = SE->getAddExpr(SE->getUnknown(Base), Imm);
|
|
return Rewriter.expandCodeFor(NewValSCEV, IP);
|
|
|
|
}
|
|
|
|
|
|
// Once we rewrite the code to insert the new IVs we want, update the
|
|
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
|
|
// to it. NewBasePt is the last instruction which contributes to the
|
|
// value of NewBase in the case that it's a diffferent instruction from
|
|
// the PHI that NewBase is computed from, or null otherwise.
|
|
//
|
|
void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
|
|
Instruction *NewBasePt,
|
|
SCEVExpander &Rewriter, Loop *L, Pass *P,
|
|
SmallVectorImpl<Instruction*> &DeadInsts){
|
|
if (!isa<PHINode>(Inst)) {
|
|
// By default, insert code at the user instruction.
|
|
BasicBlock::iterator InsertPt = Inst;
|
|
|
|
// However, if the Operand is itself an instruction, the (potentially
|
|
// complex) inserted code may be shared by many users. Because of this, we
|
|
// want to emit code for the computation of the operand right before its old
|
|
// computation. This is usually safe, because we obviously used to use the
|
|
// computation when it was computed in its current block. However, in some
|
|
// cases (e.g. use of a post-incremented induction variable) the NewBase
|
|
// value will be pinned to live somewhere after the original computation.
|
|
// In this case, we have to back off.
|
|
//
|
|
// If this is a use outside the loop (which means after, since it is based
|
|
// on a loop indvar) we use the post-incremented value, so that we don't
|
|
// artificially make the preinc value live out the bottom of the loop.
|
|
if (!isUseOfPostIncrementedValue && L->contains(Inst->getParent())) {
|
|
if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
|
|
InsertPt = NewBasePt;
|
|
++InsertPt;
|
|
} else if (Instruction *OpInst
|
|
= dyn_cast<Instruction>(OperandValToReplace)) {
|
|
InsertPt = OpInst;
|
|
while (isa<PHINode>(InsertPt)) ++InsertPt;
|
|
}
|
|
}
|
|
Value *NewVal = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
|
|
// Adjust the type back to match the Inst. Note that we can't use InsertPt
|
|
// here because the SCEVExpander may have inserted the instructions after
|
|
// that point, in its efforts to avoid inserting redundant expressions.
|
|
if (isa<PointerType>(OperandValToReplace->getType())) {
|
|
NewVal = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
|
|
NewVal,
|
|
OperandValToReplace->getType());
|
|
}
|
|
// Replace the use of the operand Value with the new Phi we just created.
|
|
Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
|
|
|
|
DOUT << " Replacing with ";
|
|
DEBUG(WriteAsOperand(*DOUT, NewVal, /*PrintType=*/false));
|
|
DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
|
|
return;
|
|
}
|
|
|
|
// PHI nodes are more complex. We have to insert one copy of the NewBase+Imm
|
|
// expression into each operand block that uses it. Note that PHI nodes can
|
|
// have multiple entries for the same predecessor. We use a map to make sure
|
|
// that a PHI node only has a single Value* for each predecessor (which also
|
|
// prevents us from inserting duplicate code in some blocks).
|
|
DenseMap<BasicBlock*, Value*> InsertedCode;
|
|
PHINode *PN = cast<PHINode>(Inst);
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
if (PN->getIncomingValue(i) == OperandValToReplace) {
|
|
// If the original expression is outside the loop, put the replacement
|
|
// code in the same place as the original expression,
|
|
// which need not be an immediate predecessor of this PHI. This way we
|
|
// need only one copy of it even if it is referenced multiple times in
|
|
// the PHI. We don't do this when the original expression is inside the
|
|
// loop because multiple copies sometimes do useful sinking of code in
|
|
// that case(?).
|
|
Instruction *OldLoc = dyn_cast<Instruction>(OperandValToReplace);
|
|
if (L->contains(OldLoc->getParent())) {
|
|
// If this is a critical edge, split the edge so that we do not insert
|
|
// the code on all predecessor/successor paths. We do this unless this
|
|
// is the canonical backedge for this loop, as this can make some
|
|
// inserted code be in an illegal position.
|
|
BasicBlock *PHIPred = PN->getIncomingBlock(i);
|
|
if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
|
|
(PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
|
|
|
|
// First step, split the critical edge.
|
|
SplitCriticalEdge(PHIPred, PN->getParent(), P, false);
|
|
|
|
// Next step: move the basic block. In particular, if the PHI node
|
|
// is outside of the loop, and PredTI is in the loop, we want to
|
|
// move the block to be immediately before the PHI block, not
|
|
// immediately after PredTI.
|
|
if (L->contains(PHIPred) && !L->contains(PN->getParent())) {
|
|
BasicBlock *NewBB = PN->getIncomingBlock(i);
|
|
NewBB->moveBefore(PN->getParent());
|
|
}
|
|
|
|
// Splitting the edge can reduce the number of PHI entries we have.
|
|
e = PN->getNumIncomingValues();
|
|
}
|
|
}
|
|
Value *&Code = InsertedCode[PN->getIncomingBlock(i)];
|
|
if (!Code) {
|
|
// Insert the code into the end of the predecessor block.
|
|
Instruction *InsertPt = (L->contains(OldLoc->getParent())) ?
|
|
PN->getIncomingBlock(i)->getTerminator() :
|
|
OldLoc->getParent()->getTerminator();
|
|
Code = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
|
|
|
|
// Adjust the type back to match the PHI. Note that we can't use
|
|
// InsertPt here because the SCEVExpander may have inserted its
|
|
// instructions after that point, in its efforts to avoid inserting
|
|
// redundant expressions.
|
|
if (isa<PointerType>(PN->getType())) {
|
|
Code = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
|
|
Code,
|
|
PN->getType());
|
|
}
|
|
|
|
DOUT << " Changing PHI use to ";
|
|
DEBUG(WriteAsOperand(*DOUT, Code, /*PrintType=*/false));
|
|
DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
|
|
}
|
|
|
|
// Replace the use of the operand Value with the new Phi we just created.
|
|
PN->setIncomingValue(i, Code);
|
|
Rewriter.clear();
|
|
}
|
|
}
|
|
|
|
// PHI node might have become a constant value after SplitCriticalEdge.
|
|
DeadInsts.push_back(Inst);
|
|
}
|
|
|
|
|
|
/// fitsInAddressMode - Return true if V can be subsumed within an addressing
|
|
/// mode, and does not need to be put in a register first.
|
|
static bool fitsInAddressMode(const SCEVHandle &V, const Type *UseTy,
|
|
const TargetLowering *TLI, bool HasBaseReg) {
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
|
|
int64_t VC = SC->getValue()->getSExtValue();
|
|
if (TLI) {
|
|
TargetLowering::AddrMode AM;
|
|
AM.BaseOffs = VC;
|
|
AM.HasBaseReg = HasBaseReg;
|
|
return TLI->isLegalAddressingMode(AM, UseTy);
|
|
} else {
|
|
// Defaults to PPC. PPC allows a sign-extended 16-bit immediate field.
|
|
return (VC > -(1 << 16) && VC < (1 << 16)-1);
|
|
}
|
|
}
|
|
|
|
if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
|
|
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(SU->getValue()))
|
|
if (TLI && CE->getOpcode() == Instruction::PtrToInt) {
|
|
Constant *Op0 = CE->getOperand(0);
|
|
if (GlobalValue *GV = dyn_cast<GlobalValue>(Op0)) {
|
|
TargetLowering::AddrMode AM;
|
|
AM.BaseGV = GV;
|
|
AM.HasBaseReg = HasBaseReg;
|
|
return TLI->isLegalAddressingMode(AM, UseTy);
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// MoveLoopVariantsToImmediateField - Move any subexpressions from Val that are
|
|
/// loop varying to the Imm operand.
|
|
static void MoveLoopVariantsToImmediateField(SCEVHandle &Val, SCEVHandle &Imm,
|
|
Loop *L, ScalarEvolution *SE) {
|
|
if (Val->isLoopInvariant(L)) return; // Nothing to do.
|
|
|
|
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
|
|
std::vector<SCEVHandle> NewOps;
|
|
NewOps.reserve(SAE->getNumOperands());
|
|
|
|
for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
|
|
if (!SAE->getOperand(i)->isLoopInvariant(L)) {
|
|
// If this is a loop-variant expression, it must stay in the immediate
|
|
// field of the expression.
|
|
Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
|
|
} else {
|
|
NewOps.push_back(SAE->getOperand(i));
|
|
}
|
|
|
|
if (NewOps.empty())
|
|
Val = SE->getIntegerSCEV(0, Val->getType());
|
|
else
|
|
Val = SE->getAddExpr(NewOps);
|
|
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
|
|
// Try to pull immediates out of the start value of nested addrec's.
|
|
SCEVHandle Start = SARE->getStart();
|
|
MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
|
|
|
|
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
|
|
Ops[0] = Start;
|
|
Val = SE->getAddRecExpr(Ops, SARE->getLoop());
|
|
} else {
|
|
// Otherwise, all of Val is variant, move the whole thing over.
|
|
Imm = SE->getAddExpr(Imm, Val);
|
|
Val = SE->getIntegerSCEV(0, Val->getType());
|
|
}
|
|
}
|
|
|
|
|
|
/// MoveImmediateValues - Look at Val, and pull out any additions of constants
|
|
/// that can fit into the immediate field of instructions in the target.
|
|
/// Accumulate these immediate values into the Imm value.
|
|
static void MoveImmediateValues(const TargetLowering *TLI,
|
|
const Type *UseTy,
|
|
SCEVHandle &Val, SCEVHandle &Imm,
|
|
bool isAddress, Loop *L,
|
|
ScalarEvolution *SE) {
|
|
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
|
|
std::vector<SCEVHandle> NewOps;
|
|
NewOps.reserve(SAE->getNumOperands());
|
|
|
|
for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
|
|
SCEVHandle NewOp = SAE->getOperand(i);
|
|
MoveImmediateValues(TLI, UseTy, NewOp, Imm, isAddress, L, SE);
|
|
|
|
if (!NewOp->isLoopInvariant(L)) {
|
|
// If this is a loop-variant expression, it must stay in the immediate
|
|
// field of the expression.
|
|
Imm = SE->getAddExpr(Imm, NewOp);
|
|
} else {
|
|
NewOps.push_back(NewOp);
|
|
}
|
|
}
|
|
|
|
if (NewOps.empty())
|
|
Val = SE->getIntegerSCEV(0, Val->getType());
|
|
else
|
|
Val = SE->getAddExpr(NewOps);
|
|
return;
|
|
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
|
|
// Try to pull immediates out of the start value of nested addrec's.
|
|
SCEVHandle Start = SARE->getStart();
|
|
MoveImmediateValues(TLI, UseTy, Start, Imm, isAddress, L, SE);
|
|
|
|
if (Start != SARE->getStart()) {
|
|
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
|
|
Ops[0] = Start;
|
|
Val = SE->getAddRecExpr(Ops, SARE->getLoop());
|
|
}
|
|
return;
|
|
} else if (SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
|
|
// Transform "8 * (4 + v)" -> "32 + 8*V" if "32" fits in the immed field.
|
|
if (isAddress && fitsInAddressMode(SME->getOperand(0), UseTy, TLI, false) &&
|
|
SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
|
|
|
|
SCEVHandle SubImm = SE->getIntegerSCEV(0, Val->getType());
|
|
SCEVHandle NewOp = SME->getOperand(1);
|
|
MoveImmediateValues(TLI, UseTy, NewOp, SubImm, isAddress, L, SE);
|
|
|
|
// If we extracted something out of the subexpressions, see if we can
|
|
// simplify this!
|
|
if (NewOp != SME->getOperand(1)) {
|
|
// Scale SubImm up by "8". If the result is a target constant, we are
|
|
// good.
|
|
SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
|
|
if (fitsInAddressMode(SubImm, UseTy, TLI, false)) {
|
|
// Accumulate the immediate.
|
|
Imm = SE->getAddExpr(Imm, SubImm);
|
|
|
|
// Update what is left of 'Val'.
|
|
Val = SE->getMulExpr(SME->getOperand(0), NewOp);
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Loop-variant expressions must stay in the immediate field of the
|
|
// expression.
|
|
if ((isAddress && fitsInAddressMode(Val, UseTy, TLI, false)) ||
|
|
!Val->isLoopInvariant(L)) {
|
|
Imm = SE->getAddExpr(Imm, Val);
|
|
Val = SE->getIntegerSCEV(0, Val->getType());
|
|
return;
|
|
}
|
|
|
|
// Otherwise, no immediates to move.
|
|
}
|
|
|
|
static void MoveImmediateValues(const TargetLowering *TLI,
|
|
Instruction *User,
|
|
SCEVHandle &Val, SCEVHandle &Imm,
|
|
bool isAddress, Loop *L,
|
|
ScalarEvolution *SE) {
|
|
const Type *UseTy = User->getType();
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(User))
|
|
UseTy = SI->getOperand(0)->getType();
|
|
MoveImmediateValues(TLI, UseTy, Val, Imm, isAddress, L, SE);
|
|
}
|
|
|
|
/// SeparateSubExprs - Decompose Expr into all of the subexpressions that are
|
|
/// added together. This is used to reassociate common addition subexprs
|
|
/// together for maximal sharing when rewriting bases.
|
|
static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
|
|
SCEVHandle Expr,
|
|
ScalarEvolution *SE) {
|
|
if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
|
|
for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
|
|
SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
|
|
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
|
|
SCEVHandle Zero = SE->getIntegerSCEV(0, Expr->getType());
|
|
if (SARE->getOperand(0) == Zero) {
|
|
SubExprs.push_back(Expr);
|
|
} else {
|
|
// Compute the addrec with zero as its base.
|
|
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
|
|
Ops[0] = Zero; // Start with zero base.
|
|
SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
|
|
|
|
|
|
SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
|
|
}
|
|
} else if (!Expr->isZero()) {
|
|
// Do not add zero.
|
|
SubExprs.push_back(Expr);
|
|
}
|
|
}
|
|
|
|
// This is logically local to the following function, but C++ says we have
|
|
// to make it file scope.
|
|
struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
|
|
|
|
/// RemoveCommonExpressionsFromUseBases - Look through all of the Bases of all
|
|
/// the Uses, removing any common subexpressions, except that if all such
|
|
/// subexpressions can be folded into an addressing mode for all uses inside
|
|
/// the loop (this case is referred to as "free" in comments herein) we do
|
|
/// not remove anything. This looks for things like (a+b+c) and
|
|
/// (a+c+d) and computes the common (a+c) subexpression. The common expression
|
|
/// is *removed* from the Bases and returned.
|
|
static SCEVHandle
|
|
RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
|
|
ScalarEvolution *SE, Loop *L,
|
|
const TargetLowering *TLI) {
|
|
unsigned NumUses = Uses.size();
|
|
|
|
// Only one use? This is a very common case, so we handle it specially and
|
|
// cheaply.
|
|
SCEVHandle Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
|
|
SCEVHandle Result = Zero;
|
|
SCEVHandle FreeResult = Zero;
|
|
if (NumUses == 1) {
|
|
// If the use is inside the loop, use its base, regardless of what it is:
|
|
// it is clearly shared across all the IV's. If the use is outside the loop
|
|
// (which means after it) we don't want to factor anything *into* the loop,
|
|
// so just use 0 as the base.
|
|
if (L->contains(Uses[0].Inst->getParent()))
|
|
std::swap(Result, Uses[0].Base);
|
|
return Result;
|
|
}
|
|
|
|
// To find common subexpressions, count how many of Uses use each expression.
|
|
// If any subexpressions are used Uses.size() times, they are common.
|
|
// Also track whether all uses of each expression can be moved into an
|
|
// an addressing mode "for free"; such expressions are left within the loop.
|
|
// struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
|
|
std::map<SCEVHandle, SubExprUseData> SubExpressionUseData;
|
|
|
|
// UniqueSubExprs - Keep track of all of the subexpressions we see in the
|
|
// order we see them.
|
|
std::vector<SCEVHandle> UniqueSubExprs;
|
|
|
|
std::vector<SCEVHandle> SubExprs;
|
|
unsigned NumUsesInsideLoop = 0;
|
|
for (unsigned i = 0; i != NumUses; ++i) {
|
|
// If the user is outside the loop, just ignore it for base computation.
|
|
// Since the user is outside the loop, it must be *after* the loop (if it
|
|
// were before, it could not be based on the loop IV). We don't want users
|
|
// after the loop to affect base computation of values *inside* the loop,
|
|
// because we can always add their offsets to the result IV after the loop
|
|
// is done, ensuring we get good code inside the loop.
|
|
if (!L->contains(Uses[i].Inst->getParent()))
|
|
continue;
|
|
NumUsesInsideLoop++;
|
|
|
|
// If the base is zero (which is common), return zero now, there are no
|
|
// CSEs we can find.
|
|
if (Uses[i].Base == Zero) return Zero;
|
|
|
|
// If this use is as an address we may be able to put CSEs in the addressing
|
|
// mode rather than hoisting them.
|
|
bool isAddrUse = isAddressUse(Uses[i].Inst, Uses[i].OperandValToReplace);
|
|
// We may need the UseTy below, but only when isAddrUse, so compute it
|
|
// only in that case.
|
|
const Type *UseTy = 0;
|
|
if (isAddrUse) {
|
|
UseTy = Uses[i].Inst->getType();
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Uses[i].Inst))
|
|
UseTy = SI->getOperand(0)->getType();
|
|
}
|
|
|
|
// Split the expression into subexprs.
|
|
SeparateSubExprs(SubExprs, Uses[i].Base, SE);
|
|
// Add one to SubExpressionUseData.Count for each subexpr present, and
|
|
// if the subexpr is not a valid immediate within an addressing mode use,
|
|
// set SubExpressionUseData.notAllUsesAreFree. We definitely want to
|
|
// hoist these out of the loop (if they are common to all uses).
|
|
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
|
|
if (++SubExpressionUseData[SubExprs[j]].Count == 1)
|
|
UniqueSubExprs.push_back(SubExprs[j]);
|
|
if (!isAddrUse || !fitsInAddressMode(SubExprs[j], UseTy, TLI, false))
|
|
SubExpressionUseData[SubExprs[j]].notAllUsesAreFree = true;
|
|
}
|
|
SubExprs.clear();
|
|
}
|
|
|
|
// Now that we know how many times each is used, build Result. Iterate over
|
|
// UniqueSubexprs so that we have a stable ordering.
|
|
for (unsigned i = 0, e = UniqueSubExprs.size(); i != e; ++i) {
|
|
std::map<SCEVHandle, SubExprUseData>::iterator I =
|
|
SubExpressionUseData.find(UniqueSubExprs[i]);
|
|
assert(I != SubExpressionUseData.end() && "Entry not found?");
|
|
if (I->second.Count == NumUsesInsideLoop) { // Found CSE!
|
|
if (I->second.notAllUsesAreFree)
|
|
Result = SE->getAddExpr(Result, I->first);
|
|
else
|
|
FreeResult = SE->getAddExpr(FreeResult, I->first);
|
|
} else
|
|
// Remove non-cse's from SubExpressionUseData.
|
|
SubExpressionUseData.erase(I);
|
|
}
|
|
|
|
if (FreeResult != Zero) {
|
|
// We have some subexpressions that can be subsumed into addressing
|
|
// modes in every use inside the loop. However, it's possible that
|
|
// there are so many of them that the combined FreeResult cannot
|
|
// be subsumed, or that the target cannot handle both a FreeResult
|
|
// and a Result in the same instruction (for example because it would
|
|
// require too many registers). Check this.
|
|
for (unsigned i=0; i<NumUses; ++i) {
|
|
if (!L->contains(Uses[i].Inst->getParent()))
|
|
continue;
|
|
// We know this is an addressing mode use; if there are any uses that
|
|
// are not, FreeResult would be Zero.
|
|
const Type *UseTy = Uses[i].Inst->getType();
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Uses[i].Inst))
|
|
UseTy = SI->getOperand(0)->getType();
|
|
if (!fitsInAddressMode(FreeResult, UseTy, TLI, Result!=Zero)) {
|
|
// FIXME: could split up FreeResult into pieces here, some hoisted
|
|
// and some not. There is no obvious advantage to this.
|
|
Result = SE->getAddExpr(Result, FreeResult);
|
|
FreeResult = Zero;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// If we found no CSE's, return now.
|
|
if (Result == Zero) return Result;
|
|
|
|
// If we still have a FreeResult, remove its subexpressions from
|
|
// SubExpressionUseData. This means they will remain in the use Bases.
|
|
if (FreeResult != Zero) {
|
|
SeparateSubExprs(SubExprs, FreeResult, SE);
|
|
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
|
|
std::map<SCEVHandle, SubExprUseData>::iterator I =
|
|
SubExpressionUseData.find(SubExprs[j]);
|
|
SubExpressionUseData.erase(I);
|
|
}
|
|
SubExprs.clear();
|
|
}
|
|
|
|
// Otherwise, remove all of the CSE's we found from each of the base values.
|
|
for (unsigned i = 0; i != NumUses; ++i) {
|
|
// Uses outside the loop don't necessarily include the common base, but
|
|
// the final IV value coming into those uses does. Instead of trying to
|
|
// remove the pieces of the common base, which might not be there,
|
|
// subtract off the base to compensate for this.
|
|
if (!L->contains(Uses[i].Inst->getParent())) {
|
|
Uses[i].Base = SE->getMinusSCEV(Uses[i].Base, Result);
|
|
continue;
|
|
}
|
|
|
|
// Split the expression into subexprs.
|
|
SeparateSubExprs(SubExprs, Uses[i].Base, SE);
|
|
|
|
// Remove any common subexpressions.
|
|
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
|
|
if (SubExpressionUseData.count(SubExprs[j])) {
|
|
SubExprs.erase(SubExprs.begin()+j);
|
|
--j; --e;
|
|
}
|
|
|
|
// Finally, add the non-shared expressions together.
|
|
if (SubExprs.empty())
|
|
Uses[i].Base = Zero;
|
|
else
|
|
Uses[i].Base = SE->getAddExpr(SubExprs);
|
|
SubExprs.clear();
|
|
}
|
|
|
|
return Result;
|
|
}
|
|
|
|
/// ValidStride - Check whether the given Scale is valid for all loads and
|
|
/// stores in UsersToProcess.
|
|
///
|
|
bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
|
|
int64_t Scale,
|
|
const std::vector<BasedUser>& UsersToProcess) {
|
|
if (!TLI)
|
|
return true;
|
|
|
|
for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
|
|
// If this is a load or other access, pass the type of the access in.
|
|
const Type *AccessTy = Type::VoidTy;
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst))
|
|
AccessTy = SI->getOperand(0)->getType();
|
|
else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
|
|
AccessTy = LI->getType();
|
|
else if (isa<PHINode>(UsersToProcess[i].Inst))
|
|
continue;
|
|
|
|
TargetLowering::AddrMode AM;
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
|
|
AM.BaseOffs = SC->getValue()->getSExtValue();
|
|
AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
|
|
AM.Scale = Scale;
|
|
|
|
// If load[imm+r*scale] is illegal, bail out.
|
|
if (!TLI->isLegalAddressingMode(AM, AccessTy))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// RequiresTypeConversion - Returns true if converting Ty1 to Ty2 is not
|
|
/// a nop.
|
|
bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
|
|
const Type *Ty2) {
|
|
if (Ty1 == Ty2)
|
|
return false;
|
|
if (Ty1->canLosslesslyBitCastTo(Ty2))
|
|
return false;
|
|
if (TLI && TLI->isTruncateFree(Ty1, Ty2))
|
|
return false;
|
|
if (isa<PointerType>(Ty2) && Ty1->canLosslesslyBitCastTo(UIntPtrTy))
|
|
return false;
|
|
if (isa<PointerType>(Ty1) && Ty2->canLosslesslyBitCastTo(UIntPtrTy))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
/// CheckForIVReuse - Returns the multiple if the stride is the multiple
|
|
/// of a previous stride and it is a legal value for the target addressing
|
|
/// mode scale component and optional base reg. This allows the users of
|
|
/// this stride to be rewritten as prev iv * factor. It returns 0 if no
|
|
/// reuse is possible. Factors can be negative on same targets, e.g. ARM.
|
|
///
|
|
/// If all uses are outside the loop, we don't require that all multiplies
|
|
/// be folded into the addressing mode, nor even that the factor be constant;
|
|
/// a multiply (executed once) outside the loop is better than another IV
|
|
/// within. Well, usually.
|
|
SCEVHandle LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
|
|
bool AllUsesAreAddresses,
|
|
bool AllUsesAreOutsideLoop,
|
|
const SCEVHandle &Stride,
|
|
IVExpr &IV, const Type *Ty,
|
|
const std::vector<BasedUser>& UsersToProcess) {
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
|
|
int64_t SInt = SC->getValue()->getSExtValue();
|
|
for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
|
|
++NewStride) {
|
|
std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
|
|
IVsByStride.find(StrideOrder[NewStride]);
|
|
if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
|
|
continue;
|
|
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
|
|
if (SI->first != Stride &&
|
|
(unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0))
|
|
continue;
|
|
int64_t Scale = SInt / SSInt;
|
|
// Check that this stride is valid for all the types used for loads and
|
|
// stores; if it can be used for some and not others, we might as well use
|
|
// the original stride everywhere, since we have to create the IV for it
|
|
// anyway. If the scale is 1, then we don't need to worry about folding
|
|
// multiplications.
|
|
if (Scale == 1 ||
|
|
(AllUsesAreAddresses &&
|
|
ValidStride(HasBaseReg, Scale, UsersToProcess)))
|
|
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
|
|
IE = SI->second.IVs.end(); II != IE; ++II)
|
|
// FIXME: Only handle base == 0 for now.
|
|
// Only reuse previous IV if it would not require a type conversion.
|
|
if (II->Base->isZero() &&
|
|
!RequiresTypeConversion(II->Base->getType(), Ty)) {
|
|
IV = *II;
|
|
return SE->getIntegerSCEV(Scale, Stride->getType());
|
|
}
|
|
}
|
|
} else if (AllUsesAreOutsideLoop) {
|
|
// Accept nonconstant strides here; it is really really right to substitute
|
|
// an existing IV if we can.
|
|
for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
|
|
++NewStride) {
|
|
std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
|
|
IVsByStride.find(StrideOrder[NewStride]);
|
|
if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
|
|
continue;
|
|
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
|
|
if (SI->first != Stride && SSInt != 1)
|
|
continue;
|
|
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
|
|
IE = SI->second.IVs.end(); II != IE; ++II)
|
|
// Accept nonzero base here.
|
|
// Only reuse previous IV if it would not require a type conversion.
|
|
if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
|
|
IV = *II;
|
|
return Stride;
|
|
}
|
|
}
|
|
// Special case, old IV is -1*x and this one is x. Can treat this one as
|
|
// -1*old.
|
|
for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
|
|
++NewStride) {
|
|
std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
|
|
IVsByStride.find(StrideOrder[NewStride]);
|
|
if (SI == IVsByStride.end())
|
|
continue;
|
|
if (SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(SI->first))
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(ME->getOperand(0)))
|
|
if (Stride == ME->getOperand(1) &&
|
|
SC->getValue()->getSExtValue() == -1LL)
|
|
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
|
|
IE = SI->second.IVs.end(); II != IE; ++II)
|
|
// Accept nonzero base here.
|
|
// Only reuse previous IV if it would not require type conversion.
|
|
if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
|
|
IV = *II;
|
|
return SE->getIntegerSCEV(-1LL, Stride->getType());
|
|
}
|
|
}
|
|
}
|
|
return SE->getIntegerSCEV(0, Stride->getType());
|
|
}
|
|
|
|
/// PartitionByIsUseOfPostIncrementedValue - Simple boolean predicate that
|
|
/// returns true if Val's isUseOfPostIncrementedValue is true.
|
|
static bool PartitionByIsUseOfPostIncrementedValue(const BasedUser &Val) {
|
|
return Val.isUseOfPostIncrementedValue;
|
|
}
|
|
|
|
/// isNonConstantNegative - Return true if the specified scev is negated, but
|
|
/// not a constant.
|
|
static bool isNonConstantNegative(const SCEVHandle &Expr) {
|
|
SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
|
|
if (!Mul) return false;
|
|
|
|
// If there is a constant factor, it will be first.
|
|
SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
|
|
if (!SC) return false;
|
|
|
|
// Return true if the value is negative, this matches things like (-42 * V).
|
|
return SC->getValue()->getValue().isNegative();
|
|
}
|
|
|
|
// CollectIVUsers - Transform our list of users and offsets to a bit more
|
|
// complex table. In this new vector, each 'BasedUser' contains 'Base', the base
|
|
// of the strided accesses, as well as the old information from Uses. We
|
|
// progressively move information from the Base field to the Imm field, until
|
|
// we eventually have the full access expression to rewrite the use.
|
|
SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
|
|
IVUsersOfOneStride &Uses,
|
|
Loop *L,
|
|
bool &AllUsesAreAddresses,
|
|
bool &AllUsesAreOutsideLoop,
|
|
std::vector<BasedUser> &UsersToProcess) {
|
|
UsersToProcess.reserve(Uses.Users.size());
|
|
for (unsigned i = 0, e = Uses.Users.size(); i != e; ++i) {
|
|
UsersToProcess.push_back(BasedUser(Uses.Users[i], SE));
|
|
|
|
// Move any loop variant operands from the offset field to the immediate
|
|
// field of the use, so that we don't try to use something before it is
|
|
// computed.
|
|
MoveLoopVariantsToImmediateField(UsersToProcess.back().Base,
|
|
UsersToProcess.back().Imm, L, SE);
|
|
assert(UsersToProcess.back().Base->isLoopInvariant(L) &&
|
|
"Base value is not loop invariant!");
|
|
}
|
|
|
|
// We now have a whole bunch of uses of like-strided induction variables, but
|
|
// they might all have different bases. We want to emit one PHI node for this
|
|
// stride which we fold as many common expressions (between the IVs) into as
|
|
// possible. Start by identifying the common expressions in the base values
|
|
// for the strides (e.g. if we have "A+C+B" and "A+B+D" as our bases, find
|
|
// "A+B"), emit it to the preheader, then remove the expression from the
|
|
// UsersToProcess base values.
|
|
SCEVHandle CommonExprs =
|
|
RemoveCommonExpressionsFromUseBases(UsersToProcess, SE, L, TLI);
|
|
|
|
// Next, figure out what we can represent in the immediate fields of
|
|
// instructions. If we can represent anything there, move it to the imm
|
|
// fields of the BasedUsers. We do this so that it increases the commonality
|
|
// of the remaining uses.
|
|
unsigned NumPHI = 0;
|
|
bool HasAddress = false;
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
|
|
// If the user is not in the current loop, this means it is using the exit
|
|
// value of the IV. Do not put anything in the base, make sure it's all in
|
|
// the immediate field to allow as much factoring as possible.
|
|
if (!L->contains(UsersToProcess[i].Inst->getParent())) {
|
|
UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
|
|
UsersToProcess[i].Base);
|
|
UsersToProcess[i].Base =
|
|
SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
|
|
} else {
|
|
// Not all uses are outside the loop.
|
|
AllUsesAreOutsideLoop = false;
|
|
|
|
// Addressing modes can be folded into loads and stores. Be careful that
|
|
// the store is through the expression, not of the expression though.
|
|
bool isPHI = false;
|
|
bool isAddress = isAddressUse(UsersToProcess[i].Inst,
|
|
UsersToProcess[i].OperandValToReplace);
|
|
if (isa<PHINode>(UsersToProcess[i].Inst)) {
|
|
isPHI = true;
|
|
++NumPHI;
|
|
}
|
|
|
|
if (isAddress)
|
|
HasAddress = true;
|
|
|
|
// If this use isn't an address, then not all uses are addresses.
|
|
if (!isAddress && !isPHI)
|
|
AllUsesAreAddresses = false;
|
|
|
|
MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
|
|
UsersToProcess[i].Imm, isAddress, L, SE);
|
|
}
|
|
}
|
|
|
|
// If one of the use is a PHI node and all other uses are addresses, still
|
|
// allow iv reuse. Essentially we are trading one constant multiplication
|
|
// for one fewer iv.
|
|
if (NumPHI > 1)
|
|
AllUsesAreAddresses = false;
|
|
|
|
// There are no in-loop address uses.
|
|
if (AllUsesAreAddresses && (!HasAddress && !AllUsesAreOutsideLoop))
|
|
AllUsesAreAddresses = false;
|
|
|
|
return CommonExprs;
|
|
}
|
|
|
|
/// ShouldUseFullStrengthReductionMode - Test whether full strength-reduction
|
|
/// is valid and profitable for the given set of users of a stride. In
|
|
/// full strength-reduction mode, all addresses at the current stride are
|
|
/// strength-reduced all the way down to pointer arithmetic.
|
|
///
|
|
bool LoopStrengthReduce::ShouldUseFullStrengthReductionMode(
|
|
const std::vector<BasedUser> &UsersToProcess,
|
|
const Loop *L,
|
|
bool AllUsesAreAddresses,
|
|
SCEVHandle Stride) {
|
|
if (!EnableFullLSRMode)
|
|
return false;
|
|
|
|
// The heuristics below aim to avoid increasing register pressure, but
|
|
// fully strength-reducing all the addresses increases the number of
|
|
// add instructions, so don't do this when optimizing for size.
|
|
// TODO: If the loop is large, the savings due to simpler addresses
|
|
// may oughtweight the costs of the extra increment instructions.
|
|
if (L->getHeader()->getParent()->hasFnAttr(Attribute::OptimizeForSize))
|
|
return false;
|
|
|
|
// TODO: For now, don't do full strength reduction if there could
|
|
// potentially be greater-stride multiples of the current stride
|
|
// which could reuse the current stride IV.
|
|
if (StrideOrder.back() != Stride)
|
|
return false;
|
|
|
|
// Iterate through the uses to find conditions that automatically rule out
|
|
// full-lsr mode.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
|
|
SCEV *Base = UsersToProcess[i].Base;
|
|
SCEV *Imm = UsersToProcess[i].Imm;
|
|
// If any users have a loop-variant component, they can't be fully
|
|
// strength-reduced.
|
|
if (Imm && !Imm->isLoopInvariant(L))
|
|
return false;
|
|
// If there are to users with the same base and the difference between
|
|
// the two Imm values can't be folded into the address, full
|
|
// strength reduction would increase register pressure.
|
|
do {
|
|
SCEV *CurImm = UsersToProcess[i].Imm;
|
|
if ((CurImm || Imm) && CurImm != Imm) {
|
|
if (!CurImm) CurImm = SE->getIntegerSCEV(0, Stride->getType());
|
|
if (!Imm) Imm = SE->getIntegerSCEV(0, Stride->getType());
|
|
const Instruction *Inst = UsersToProcess[i].Inst;
|
|
const Type *UseTy = Inst->getType();
|
|
if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
|
|
UseTy = SI->getOperand(0)->getType();
|
|
SCEVHandle Diff = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
|
|
if (!Diff->isZero() &&
|
|
(!AllUsesAreAddresses ||
|
|
!fitsInAddressMode(Diff, UseTy, TLI, /*HasBaseReg=*/true)))
|
|
return false;
|
|
}
|
|
} while (++i != e && Base == UsersToProcess[i].Base);
|
|
}
|
|
|
|
// If there's exactly one user in this stride, fully strength-reducing it
|
|
// won't increase register pressure. If it's starting from a non-zero base,
|
|
// it'll be simpler this way.
|
|
if (UsersToProcess.size() == 1 && !UsersToProcess[0].Base->isZero())
|
|
return true;
|
|
|
|
// Otherwise, if there are any users in this stride that don't require
|
|
// a register for their base, full strength-reduction will increase
|
|
// register pressure.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
|
|
if (UsersToProcess[i].Base->isZero())
|
|
return false;
|
|
|
|
// Otherwise, go for it.
|
|
return true;
|
|
}
|
|
|
|
/// InsertAffinePhi Create and insert a PHI node for an induction variable
|
|
/// with the specified start and step values in the specified loop.
|
|
///
|
|
/// If NegateStride is true, the stride should be negated by using a
|
|
/// subtract instead of an add.
|
|
///
|
|
/// Return the created phi node, and return the step instruction by
|
|
/// reference in IncV.
|
|
///
|
|
static PHINode *InsertAffinePhi(SCEVHandle Start, SCEVHandle Step,
|
|
const Loop *L,
|
|
SCEVExpander &Rewriter,
|
|
Value *&IncV) {
|
|
assert(Start->isLoopInvariant(L) && "New PHI start is not loop invariant!");
|
|
assert(Step->isLoopInvariant(L) && "New PHI stride is not loop invariant!");
|
|
|
|
BasicBlock *Header = L->getHeader();
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
|
|
PHINode *PN = PHINode::Create(Start->getType(), "lsr.iv", Header->begin());
|
|
PN->addIncoming(Rewriter.expandCodeFor(Start, Preheader->getTerminator()),
|
|
Preheader);
|
|
|
|
pred_iterator HPI = pred_begin(Header);
|
|
assert(HPI != pred_end(Header) && "Loop with zero preds???");
|
|
if (!L->contains(*HPI)) ++HPI;
|
|
assert(HPI != pred_end(Header) && L->contains(*HPI) &&
|
|
"No backedge in loop?");
|
|
|
|
// If the stride is negative, insert a sub instead of an add for the
|
|
// increment.
|
|
bool isNegative = isNonConstantNegative(Step);
|
|
SCEVHandle IncAmount = Step;
|
|
if (isNegative)
|
|
IncAmount = Rewriter.SE.getNegativeSCEV(Step);
|
|
|
|
// Insert an add instruction right before the terminator corresponding
|
|
// to the back-edge.
|
|
Value *StepV = Rewriter.expandCodeFor(IncAmount, Preheader->getTerminator());
|
|
if (isNegative) {
|
|
IncV = BinaryOperator::CreateSub(PN, StepV, "lsr.iv.next",
|
|
(*HPI)->getTerminator());
|
|
} else {
|
|
IncV = BinaryOperator::CreateAdd(PN, StepV, "lsr.iv.next",
|
|
(*HPI)->getTerminator());
|
|
}
|
|
if (!isa<ConstantInt>(StepV)) ++NumVariable;
|
|
|
|
pred_iterator PI = pred_begin(Header);
|
|
if (*PI == L->getLoopPreheader())
|
|
++PI;
|
|
PN->addIncoming(IncV, *PI);
|
|
|
|
++NumInserted;
|
|
return PN;
|
|
}
|
|
|
|
static void SortUsersToProcess(std::vector<BasedUser> &UsersToProcess) {
|
|
// We want to emit code for users inside the loop first. To do this, we
|
|
// rearrange BasedUser so that the entries at the end have
|
|
// isUseOfPostIncrementedValue = false, because we pop off the end of the
|
|
// vector (so we handle them first).
|
|
std::partition(UsersToProcess.begin(), UsersToProcess.end(),
|
|
PartitionByIsUseOfPostIncrementedValue);
|
|
|
|
// Sort this by base, so that things with the same base are handled
|
|
// together. By partitioning first and stable-sorting later, we are
|
|
// guaranteed that within each base we will pop off users from within the
|
|
// loop before users outside of the loop with a particular base.
|
|
//
|
|
// We would like to use stable_sort here, but we can't. The problem is that
|
|
// SCEVHandle's don't have a deterministic ordering w.r.t to each other, so
|
|
// we don't have anything to do a '<' comparison on. Because we think the
|
|
// number of uses is small, do a horrible bubble sort which just relies on
|
|
// ==.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
|
|
// Get a base value.
|
|
SCEVHandle Base = UsersToProcess[i].Base;
|
|
|
|
// Compact everything with this base to be consecutive with this one.
|
|
for (unsigned j = i+1; j != e; ++j) {
|
|
if (UsersToProcess[j].Base == Base) {
|
|
std::swap(UsersToProcess[i+1], UsersToProcess[j]);
|
|
++i;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// PrepareToStrengthReduceFully - Prepare to fully strength-reduce
|
|
/// UsersToProcess, meaning lowering addresses all the way down to direct
|
|
/// pointer arithmetic.
|
|
///
|
|
void
|
|
LoopStrengthReduce::PrepareToStrengthReduceFully(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
SCEVHandle Stride,
|
|
SCEVHandle CommonExprs,
|
|
const Loop *L,
|
|
SCEVExpander &PreheaderRewriter) {
|
|
DOUT << " Fully reducing all users\n";
|
|
|
|
// Rewrite the UsersToProcess records, creating a separate PHI for each
|
|
// unique Base value.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
|
|
// TODO: The uses are grouped by base, but not sorted. We arbitrarily
|
|
// pick the first Imm value here to start with, and adjust it for the
|
|
// other uses.
|
|
SCEVHandle Imm = UsersToProcess[i].Imm;
|
|
SCEVHandle Base = UsersToProcess[i].Base;
|
|
SCEVHandle Start = SE->getAddExpr(CommonExprs, Base, Imm);
|
|
Value *IncV;
|
|
PHINode *Phi = InsertAffinePhi(Start, Stride, L,
|
|
PreheaderRewriter,
|
|
IncV);
|
|
// Loop over all the users with the same base.
|
|
do {
|
|
UsersToProcess[i].Base = SE->getIntegerSCEV(0, Stride->getType());
|
|
UsersToProcess[i].Imm = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
|
|
UsersToProcess[i].Phi = Phi;
|
|
UsersToProcess[i].IncV = IncV;
|
|
assert(UsersToProcess[i].Imm->isLoopInvariant(L) &&
|
|
"ShouldUseFullStrengthReductionMode should reject this!");
|
|
} while (++i != e && Base == UsersToProcess[i].Base);
|
|
}
|
|
}
|
|
|
|
/// PrepareToStrengthReduceWithNewPhi - Insert a new induction variable for the
|
|
/// given users to share.
|
|
///
|
|
void
|
|
LoopStrengthReduce::PrepareToStrengthReduceWithNewPhi(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
SCEVHandle Stride,
|
|
SCEVHandle CommonExprs,
|
|
Value *CommonBaseV,
|
|
const Loop *L,
|
|
SCEVExpander &PreheaderRewriter) {
|
|
DOUT << " Inserting new PHI:\n";
|
|
|
|
Value *IncV;
|
|
PHINode *Phi = InsertAffinePhi(SE->getUnknown(CommonBaseV),
|
|
Stride, L,
|
|
PreheaderRewriter,
|
|
IncV);
|
|
|
|
// Remember this in case a later stride is multiple of this.
|
|
IVsByStride[Stride].addIV(Stride, CommonExprs, Phi, IncV);
|
|
|
|
// All the users will share this new IV.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
|
|
UsersToProcess[i].Phi = Phi;
|
|
UsersToProcess[i].IncV = IncV;
|
|
}
|
|
|
|
DOUT << " IV=";
|
|
DEBUG(WriteAsOperand(*DOUT, Phi, /*PrintType=*/false));
|
|
DOUT << ", INC=";
|
|
DEBUG(WriteAsOperand(*DOUT, IncV, /*PrintType=*/false));
|
|
DOUT << "\n";
|
|
}
|
|
|
|
/// PrepareToStrengthReduceWithNewPhi - Prepare for the given users to reuse
|
|
/// an induction variable with a stride that is a factor of the current
|
|
/// induction variable.
|
|
///
|
|
void
|
|
LoopStrengthReduce::PrepareToStrengthReduceFromSmallerStride(
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
Value *CommonBaseV,
|
|
const IVExpr &ReuseIV,
|
|
Instruction *PreInsertPt) {
|
|
DOUT << " Rewriting in terms of existing IV of STRIDE " << *ReuseIV.Stride
|
|
<< " and BASE " << *ReuseIV.Base << "\n";
|
|
|
|
// All the users will share the reused IV.
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
|
|
UsersToProcess[i].Phi = ReuseIV.PHI;
|
|
UsersToProcess[i].IncV = ReuseIV.IncV;
|
|
}
|
|
|
|
Constant *C = dyn_cast<Constant>(CommonBaseV);
|
|
if (C &&
|
|
(!C->isNullValue() &&
|
|
!fitsInAddressMode(SE->getUnknown(CommonBaseV), CommonBaseV->getType(),
|
|
TLI, false)))
|
|
// We want the common base emitted into the preheader! This is just
|
|
// using cast as a copy so BitCast (no-op cast) is appropriate
|
|
CommonBaseV = new BitCastInst(CommonBaseV, CommonBaseV->getType(),
|
|
"commonbase", PreInsertPt);
|
|
}
|
|
|
|
static bool IsImmFoldedIntoAddrMode(GlobalValue *GV, int64_t Offset,
|
|
const Type *ReplacedTy,
|
|
std::vector<BasedUser> &UsersToProcess,
|
|
const TargetLowering *TLI) {
|
|
SmallVector<Instruction*, 16> AddrModeInsts;
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
|
|
if (UsersToProcess[i].isUseOfPostIncrementedValue)
|
|
continue;
|
|
ExtAddrMode AddrMode =
|
|
AddressingModeMatcher::Match(UsersToProcess[i].OperandValToReplace,
|
|
ReplacedTy, UsersToProcess[i].Inst,
|
|
AddrModeInsts, *TLI);
|
|
if (GV && GV != AddrMode.BaseGV)
|
|
return false;
|
|
if (Offset && !AddrMode.BaseOffs)
|
|
// FIXME: How to accurate check it's immediate offset is folded.
|
|
return false;
|
|
AddrModeInsts.clear();
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
|
|
/// stride of IV. All of the users may have different starting values, and this
|
|
/// may not be the only stride (we know it is if isOnlyStride is true).
|
|
void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
|
|
IVUsersOfOneStride &Uses,
|
|
Loop *L,
|
|
bool isOnlyStride) {
|
|
// If all the users are moved to another stride, then there is nothing to do.
|
|
if (Uses.Users.empty())
|
|
return;
|
|
|
|
// Keep track if every use in UsersToProcess is an address. If they all are,
|
|
// we may be able to rewrite the entire collection of them in terms of a
|
|
// smaller-stride IV.
|
|
bool AllUsesAreAddresses = true;
|
|
|
|
// Keep track if every use of a single stride is outside the loop. If so,
|
|
// we want to be more aggressive about reusing a smaller-stride IV; a
|
|
// multiply outside the loop is better than another IV inside. Well, usually.
|
|
bool AllUsesAreOutsideLoop = true;
|
|
|
|
// Transform our list of users and offsets to a bit more complex table. In
|
|
// this new vector, each 'BasedUser' contains 'Base' the base of the
|
|
// strided accessas well as the old information from Uses. We progressively
|
|
// move information from the Base field to the Imm field, until we eventually
|
|
// have the full access expression to rewrite the use.
|
|
std::vector<BasedUser> UsersToProcess;
|
|
SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
|
|
AllUsesAreOutsideLoop,
|
|
UsersToProcess);
|
|
|
|
// Sort the UsersToProcess array so that users with common bases are
|
|
// next to each other.
|
|
SortUsersToProcess(UsersToProcess);
|
|
|
|
// If we managed to find some expressions in common, we'll need to carry
|
|
// their value in a register and add it in for each use. This will take up
|
|
// a register operand, which potentially restricts what stride values are
|
|
// valid.
|
|
bool HaveCommonExprs = !CommonExprs->isZero();
|
|
|
|
const Type *ReplacedTy = CommonExprs->getType();
|
|
|
|
// If all uses are addresses, consider sinking the immediate part of the
|
|
// common expression back into uses if they can fit in the immediate fields.
|
|
if (TLI && HaveCommonExprs && AllUsesAreAddresses) {
|
|
SCEVHandle NewCommon = CommonExprs;
|
|
SCEVHandle Imm = SE->getIntegerSCEV(0, ReplacedTy);
|
|
MoveImmediateValues(TLI, ReplacedTy, NewCommon, Imm, true, L, SE);
|
|
if (!Imm->isZero()) {
|
|
bool DoSink = true;
|
|
|
|
// If the immediate part of the common expression is a GV, check if it's
|
|
// possible to fold it into the target addressing mode.
|
|
GlobalValue *GV = 0;
|
|
if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(Imm)) {
|
|
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(SU->getValue()))
|
|
if (CE->getOpcode() == Instruction::PtrToInt)
|
|
GV = dyn_cast<GlobalValue>(CE->getOperand(0));
|
|
}
|
|
int64_t Offset = 0;
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
|
|
Offset = SC->getValue()->getSExtValue();
|
|
if (GV || Offset)
|
|
DoSink = IsImmFoldedIntoAddrMode(GV, Offset, ReplacedTy,
|
|
UsersToProcess, TLI);
|
|
|
|
if (DoSink) {
|
|
DOUT << " Sinking " << *Imm << " back down into uses\n";
|
|
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
|
|
UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm, Imm);
|
|
CommonExprs = NewCommon;
|
|
HaveCommonExprs = !CommonExprs->isZero();
|
|
++NumImmSunk;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Now that we know what we need to do, insert the PHI node itself.
|
|
//
|
|
DOUT << "LSR: Examining IVs of TYPE " << *ReplacedTy << " of STRIDE "
|
|
<< *Stride << ":\n"
|
|
<< " Common base: " << *CommonExprs << "\n";
|
|
|
|
SCEVExpander Rewriter(*SE, *LI);
|
|
SCEVExpander PreheaderRewriter(*SE, *LI);
|
|
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
Instruction *PreInsertPt = Preheader->getTerminator();
|
|
BasicBlock *LatchBlock = L->getLoopLatch();
|
|
|
|
Value *CommonBaseV = ConstantInt::get(ReplacedTy, 0);
|
|
|
|
SCEVHandle RewriteFactor = SE->getIntegerSCEV(0, ReplacedTy);
|
|
IVExpr ReuseIV(SE->getIntegerSCEV(0, Type::Int32Ty),
|
|
SE->getIntegerSCEV(0, Type::Int32Ty),
|
|
0, 0);
|
|
|
|
/// Choose a strength-reduction strategy and prepare for it by creating
|
|
/// the necessary PHIs and adjusting the bookkeeping.
|
|
if (ShouldUseFullStrengthReductionMode(UsersToProcess, L,
|
|
AllUsesAreAddresses, Stride)) {
|
|
PrepareToStrengthReduceFully(UsersToProcess, Stride, CommonExprs, L,
|
|
PreheaderRewriter);
|
|
} else {
|
|
// Emit the initial base value into the loop preheader.
|
|
CommonBaseV = PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt);
|
|
|
|
// If all uses are addresses, check if it is possible to reuse an IV with a
|
|
// stride that is a factor of this stride. And that the multiple is a number
|
|
// that can be encoded in the scale field of the target addressing mode. And
|
|
// that we will have a valid instruction after this substition, including
|
|
// the immediate field, if any.
|
|
RewriteFactor = CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
|
|
AllUsesAreOutsideLoop,
|
|
Stride, ReuseIV, CommonExprs->getType(),
|
|
UsersToProcess);
|
|
if (isa<SCEVConstant>(RewriteFactor) &&
|
|
cast<SCEVConstant>(RewriteFactor)->isZero())
|
|
PrepareToStrengthReduceWithNewPhi(UsersToProcess, Stride, CommonExprs,
|
|
CommonBaseV, L, PreheaderRewriter);
|
|
else
|
|
PrepareToStrengthReduceFromSmallerStride(UsersToProcess, CommonBaseV,
|
|
ReuseIV, PreInsertPt);
|
|
}
|
|
|
|
// Process all the users now, replacing their strided uses with
|
|
// strength-reduced forms. This outer loop handles all bases, the inner
|
|
// loop handles all users of a particular base.
|
|
while (!UsersToProcess.empty()) {
|
|
SCEVHandle Base = UsersToProcess.back().Base;
|
|
Instruction *Inst = UsersToProcess.back().Inst;
|
|
|
|
// Emit the code for Base into the preheader.
|
|
Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt);
|
|
|
|
DOUT << " Examining uses with BASE ";
|
|
DEBUG(WriteAsOperand(*DOUT, BaseV, /*PrintType=*/false));
|
|
DOUT << ":\n";
|
|
|
|
// If BaseV is a constant other than 0, make sure that it gets inserted into
|
|
// the preheader, instead of being forward substituted into the uses. We do
|
|
// this by forcing a BitCast (noop cast) to be inserted into the preheader
|
|
// in this case.
|
|
if (Constant *C = dyn_cast<Constant>(BaseV)) {
|
|
if (!C->isNullValue() && !fitsInAddressMode(Base, ReplacedTy,
|
|
TLI, false)) {
|
|
// We want this constant emitted into the preheader! This is just
|
|
// using cast as a copy so BitCast (no-op cast) is appropriate
|
|
BaseV = new BitCastInst(BaseV, BaseV->getType(), "preheaderinsert",
|
|
PreInsertPt);
|
|
}
|
|
}
|
|
|
|
// Emit the code to add the immediate offset to the Phi value, just before
|
|
// the instructions that we identified as using this stride and base.
|
|
do {
|
|
// FIXME: Use emitted users to emit other users.
|
|
BasedUser &User = UsersToProcess.back();
|
|
|
|
DOUT << " Examining use ";
|
|
DEBUG(WriteAsOperand(*DOUT, UsersToProcess.back().OperandValToReplace,
|
|
/*PrintType=*/false));
|
|
DOUT << " in Inst: " << *Inst;
|
|
|
|
// If this instruction wants to use the post-incremented value, move it
|
|
// after the post-inc and use its value instead of the PHI.
|
|
Value *RewriteOp = User.Phi;
|
|
if (User.isUseOfPostIncrementedValue) {
|
|
RewriteOp = User.IncV;
|
|
|
|
// If this user is in the loop, make sure it is the last thing in the
|
|
// loop to ensure it is dominated by the increment.
|
|
if (L->contains(User.Inst->getParent()))
|
|
User.Inst->moveBefore(LatchBlock->getTerminator());
|
|
}
|
|
if (RewriteOp->getType() != ReplacedTy) {
|
|
Instruction::CastOps opcode = Instruction::Trunc;
|
|
if (ReplacedTy->getPrimitiveSizeInBits() ==
|
|
RewriteOp->getType()->getPrimitiveSizeInBits())
|
|
opcode = Instruction::BitCast;
|
|
RewriteOp = SCEVExpander::InsertCastOfTo(opcode, RewriteOp, ReplacedTy);
|
|
}
|
|
|
|
SCEVHandle RewriteExpr = SE->getUnknown(RewriteOp);
|
|
|
|
// If we had to insert new instructions for RewriteOp, we have to
|
|
// consider that they may not have been able to end up immediately
|
|
// next to RewriteOp, because non-PHI instructions may never precede
|
|
// PHI instructions in a block. In this case, remember where the last
|
|
// instruction was inserted so that if we're replacing a different
|
|
// PHI node, we can use the later point to expand the final
|
|
// RewriteExpr.
|
|
Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
|
|
if (RewriteOp == User.Phi) NewBasePt = 0;
|
|
|
|
// Clear the SCEVExpander's expression map so that we are guaranteed
|
|
// to have the code emitted where we expect it.
|
|
Rewriter.clear();
|
|
|
|
// If we are reusing the iv, then it must be multiplied by a constant
|
|
// factor to take advantage of the addressing mode scale component.
|
|
if (!isa<SCEVConstant>(RewriteFactor) ||
|
|
!cast<SCEVConstant>(RewriteFactor)->isZero()) {
|
|
// If we're reusing an IV with a nonzero base (currently this happens
|
|
// only when all reuses are outside the loop) subtract that base here.
|
|
// The base has been used to initialize the PHI node but we don't want
|
|
// it here.
|
|
if (!ReuseIV.Base->isZero()) {
|
|
SCEVHandle typedBase = ReuseIV.Base;
|
|
if (RewriteExpr->getType()->getPrimitiveSizeInBits() !=
|
|
ReuseIV.Base->getType()->getPrimitiveSizeInBits()) {
|
|
// It's possible the original IV is a larger type than the new IV,
|
|
// in which case we have to truncate the Base. We checked in
|
|
// RequiresTypeConversion that this is valid.
|
|
assert (RewriteExpr->getType()->getPrimitiveSizeInBits() <
|
|
ReuseIV.Base->getType()->getPrimitiveSizeInBits() &&
|
|
"Unexpected lengthening conversion!");
|
|
typedBase = SE->getTruncateExpr(ReuseIV.Base,
|
|
RewriteExpr->getType());
|
|
}
|
|
RewriteExpr = SE->getMinusSCEV(RewriteExpr, typedBase);
|
|
}
|
|
|
|
// Multiply old variable, with base removed, by new scale factor.
|
|
RewriteExpr = SE->getMulExpr(RewriteFactor,
|
|
RewriteExpr);
|
|
|
|
// The common base is emitted in the loop preheader. But since we
|
|
// are reusing an IV, it has not been used to initialize the PHI node.
|
|
// Add it to the expression used to rewrite the uses.
|
|
// When this use is outside the loop, we earlier subtracted the
|
|
// common base, and are adding it back here. Use the same expression
|
|
// as before, rather than CommonBaseV, so DAGCombiner will zap it.
|
|
if (!isa<ConstantInt>(CommonBaseV) ||
|
|
!cast<ConstantInt>(CommonBaseV)->isZero()) {
|
|
if (L->contains(User.Inst->getParent()))
|
|
RewriteExpr = SE->getAddExpr(RewriteExpr,
|
|
SE->getUnknown(CommonBaseV));
|
|
else
|
|
RewriteExpr = SE->getAddExpr(RewriteExpr, CommonExprs);
|
|
}
|
|
}
|
|
|
|
// Now that we know what we need to do, insert code before User for the
|
|
// immediate and any loop-variant expressions.
|
|
if (!isa<ConstantInt>(BaseV) || !cast<ConstantInt>(BaseV)->isZero())
|
|
// Add BaseV to the PHI value if needed.
|
|
RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
|
|
|
|
User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
|
|
Rewriter, L, this,
|
|
DeadInsts);
|
|
|
|
// Mark old value we replaced as possibly dead, so that it is eliminated
|
|
// if we just replaced the last use of that value.
|
|
DeadInsts.push_back(cast<Instruction>(User.OperandValToReplace));
|
|
|
|
UsersToProcess.pop_back();
|
|
++NumReduced;
|
|
|
|
// If there are any more users to process with the same base, process them
|
|
// now. We sorted by base above, so we just have to check the last elt.
|
|
} while (!UsersToProcess.empty() && UsersToProcess.back().Base == Base);
|
|
// TODO: Next, find out which base index is the most common, pull it out.
|
|
}
|
|
|
|
// IMPORTANT TODO: Figure out how to partition the IV's with this stride, but
|
|
// different starting values, into different PHIs.
|
|
}
|
|
|
|
/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
|
|
/// set the IV user and stride information and return true, otherwise return
|
|
/// false.
|
|
bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
|
|
const SCEVHandle *&CondStride) {
|
|
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e && !CondUse;
|
|
++Stride) {
|
|
std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
|
|
IVUsesByStride.find(StrideOrder[Stride]);
|
|
assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
|
|
|
|
for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
|
|
E = SI->second.Users.end(); UI != E; ++UI)
|
|
if (UI->User == Cond) {
|
|
// NOTE: we could handle setcc instructions with multiple uses here, but
|
|
// InstCombine does it as well for simple uses, it's not clear that it
|
|
// occurs enough in real life to handle.
|
|
CondUse = &*UI;
|
|
CondStride = &SI->first;
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
namespace {
|
|
// Constant strides come first which in turns are sorted by their absolute
|
|
// values. If absolute values are the same, then positive strides comes first.
|
|
// e.g.
|
|
// 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
|
|
struct StrideCompare {
|
|
bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
|
|
SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
|
|
SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
|
|
if (LHSC && RHSC) {
|
|
int64_t LV = LHSC->getValue()->getSExtValue();
|
|
int64_t RV = RHSC->getValue()->getSExtValue();
|
|
uint64_t ALV = (LV < 0) ? -LV : LV;
|
|
uint64_t ARV = (RV < 0) ? -RV : RV;
|
|
if (ALV == ARV) {
|
|
if (LV != RV)
|
|
return LV > RV;
|
|
} else {
|
|
return ALV < ARV;
|
|
}
|
|
|
|
// If it's the same value but different type, sort by bit width so
|
|
// that we emit larger induction variables before smaller
|
|
// ones, letting the smaller be re-written in terms of larger ones.
|
|
return RHS->getBitWidth() < LHS->getBitWidth();
|
|
}
|
|
return LHSC && !RHSC;
|
|
}
|
|
};
|
|
}
|
|
|
|
/// ChangeCompareStride - If a loop termination compare instruction is the
|
|
/// only use of its stride, and the compaison is against a constant value,
|
|
/// try eliminate the stride by moving the compare instruction to another
|
|
/// stride and change its constant operand accordingly. e.g.
|
|
///
|
|
/// loop:
|
|
/// ...
|
|
/// v1 = v1 + 3
|
|
/// v2 = v2 + 1
|
|
/// if (v2 < 10) goto loop
|
|
/// =>
|
|
/// loop:
|
|
/// ...
|
|
/// v1 = v1 + 3
|
|
/// if (v1 < 30) goto loop
|
|
ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
|
|
IVStrideUse* &CondUse,
|
|
const SCEVHandle* &CondStride) {
|
|
if (StrideOrder.size() < 2 ||
|
|
IVUsesByStride[*CondStride].Users.size() != 1)
|
|
return Cond;
|
|
const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
|
|
if (!SC) return Cond;
|
|
|
|
ICmpInst::Predicate Predicate = Cond->getPredicate();
|
|
int64_t CmpSSInt = SC->getValue()->getSExtValue();
|
|
unsigned BitWidth = (*CondStride)->getBitWidth();
|
|
uint64_t SignBit = 1ULL << (BitWidth-1);
|
|
const Type *CmpTy = Cond->getOperand(0)->getType();
|
|
const Type *NewCmpTy = NULL;
|
|
unsigned TyBits = CmpTy->getPrimitiveSizeInBits();
|
|
unsigned NewTyBits = 0;
|
|
SCEVHandle *NewStride = NULL;
|
|
Value *NewCmpLHS = NULL;
|
|
Value *NewCmpRHS = NULL;
|
|
int64_t Scale = 1;
|
|
SCEVHandle NewOffset = SE->getIntegerSCEV(0, UIntPtrTy);
|
|
std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
|
|
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1))) {
|
|
int64_t CmpVal = C->getValue().getSExtValue();
|
|
|
|
// Check stride constant and the comparision constant signs to detect
|
|
// overflow.
|
|
if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
|
|
return Cond;
|
|
|
|
// Look for a suitable stride / iv as replacement.
|
|
for (unsigned i = 0, e = StrideOrder.size(); i != e; ++i) {
|
|
std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
|
|
IVUsesByStride.find(StrideOrder[i]);
|
|
if (!isa<SCEVConstant>(SI->first))
|
|
continue;
|
|
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
|
|
if (abs(SSInt) <= abs(CmpSSInt) || (SSInt % CmpSSInt) != 0)
|
|
continue;
|
|
|
|
Scale = SSInt / CmpSSInt;
|
|
int64_t NewCmpVal = CmpVal * Scale;
|
|
APInt Mul = APInt(BitWidth, NewCmpVal);
|
|
// Check for overflow.
|
|
if (Mul.getSExtValue() != NewCmpVal)
|
|
continue;
|
|
|
|
// Watch out for overflow.
|
|
if (ICmpInst::isSignedPredicate(Predicate) &&
|
|
(CmpVal & SignBit) != (NewCmpVal & SignBit))
|
|
continue;
|
|
|
|
if (NewCmpVal == CmpVal)
|
|
continue;
|
|
// Pick the best iv to use trying to avoid a cast.
|
|
NewCmpLHS = NULL;
|
|
for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
|
|
E = SI->second.Users.end(); UI != E; ++UI) {
|
|
NewCmpLHS = UI->OperandValToReplace;
|
|
if (NewCmpLHS->getType() == CmpTy)
|
|
break;
|
|
}
|
|
if (!NewCmpLHS)
|
|
continue;
|
|
|
|
NewCmpTy = NewCmpLHS->getType();
|
|
NewTyBits = isa<PointerType>(NewCmpTy)
|
|
? UIntPtrTy->getPrimitiveSizeInBits()
|
|
: NewCmpTy->getPrimitiveSizeInBits();
|
|
if (RequiresTypeConversion(NewCmpTy, CmpTy)) {
|
|
// Check if it is possible to rewrite it using
|
|
// an iv / stride of a smaller integer type.
|
|
bool TruncOk = false;
|
|
if (NewCmpTy->isInteger()) {
|
|
unsigned Bits = NewTyBits;
|
|
if (ICmpInst::isSignedPredicate(Predicate))
|
|
--Bits;
|
|
uint64_t Mask = (1ULL << Bits) - 1;
|
|
if (((uint64_t)NewCmpVal & Mask) == (uint64_t)NewCmpVal)
|
|
TruncOk = true;
|
|
}
|
|
if (!TruncOk)
|
|
continue;
|
|
}
|
|
|
|
// Don't rewrite if use offset is non-constant and the new type is
|
|
// of a different type.
|
|
// FIXME: too conservative?
|
|
if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->Offset))
|
|
continue;
|
|
|
|
bool AllUsesAreAddresses = true;
|
|
bool AllUsesAreOutsideLoop = true;
|
|
std::vector<BasedUser> UsersToProcess;
|
|
SCEVHandle CommonExprs = CollectIVUsers(SI->first, SI->second, L,
|
|
AllUsesAreAddresses,
|
|
AllUsesAreOutsideLoop,
|
|
UsersToProcess);
|
|
// Avoid rewriting the compare instruction with an iv of new stride
|
|
// if it's likely the new stride uses will be rewritten using the
|
|
// stride of the compare instruction.
|
|
if (AllUsesAreAddresses &&
|
|
ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess))
|
|
continue;
|
|
|
|
// If scale is negative, use swapped predicate unless it's testing
|
|
// for equality.
|
|
if (Scale < 0 && !Cond->isEquality())
|
|
Predicate = ICmpInst::getSwappedPredicate(Predicate);
|
|
|
|
NewStride = &StrideOrder[i];
|
|
if (!isa<PointerType>(NewCmpTy))
|
|
NewCmpRHS = ConstantInt::get(NewCmpTy, NewCmpVal);
|
|
else {
|
|
NewCmpRHS = ConstantInt::get(UIntPtrTy, NewCmpVal);
|
|
NewCmpRHS = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
|
|
NewCmpRHS, NewCmpTy);
|
|
}
|
|
NewOffset = TyBits == NewTyBits
|
|
? SE->getMulExpr(CondUse->Offset,
|
|
SE->getConstant(ConstantInt::get(CmpTy, Scale)))
|
|
: SE->getConstant(ConstantInt::get(NewCmpTy,
|
|
cast<SCEVConstant>(CondUse->Offset)->getValue()->getSExtValue()*Scale));
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Forgo this transformation if it the increment happens to be
|
|
// unfortunately positioned after the condition, and the condition
|
|
// has multiple uses which prevent it from being moved immediately
|
|
// before the branch. See
|
|
// test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
|
|
// for an example of this situation.
|
|
if (!Cond->hasOneUse()) {
|
|
for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
|
|
I != E; ++I)
|
|
if (I == NewCmpLHS)
|
|
return Cond;
|
|
}
|
|
|
|
if (NewCmpRHS) {
|
|
// Create a new compare instruction using new stride / iv.
|
|
ICmpInst *OldCond = Cond;
|
|
// Insert new compare instruction.
|
|
Cond = new ICmpInst(Predicate, NewCmpLHS, NewCmpRHS,
|
|
L->getHeader()->getName() + ".termcond",
|
|
OldCond);
|
|
|
|
// Remove the old compare instruction. The old indvar is probably dead too.
|
|
DeadInsts.push_back(cast<Instruction>(CondUse->OperandValToReplace));
|
|
SE->deleteValueFromRecords(OldCond);
|
|
OldCond->replaceAllUsesWith(Cond);
|
|
OldCond->eraseFromParent();
|
|
|
|
IVUsesByStride[*CondStride].Users.pop_back();
|
|
IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewCmpLHS);
|
|
CondUse = &IVUsesByStride[*NewStride].Users.back();
|
|
CondStride = NewStride;
|
|
++NumEliminated;
|
|
}
|
|
|
|
return Cond;
|
|
}
|
|
|
|
/// OptimizeSMax - Rewrite the loop's terminating condition if it uses
|
|
/// an smax computation.
|
|
///
|
|
/// This is a narrow solution to a specific, but acute, problem. For loops
|
|
/// like this:
|
|
///
|
|
/// i = 0;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i < n);
|
|
///
|
|
/// where the comparison is signed, the trip count isn't just 'n', because
|
|
/// 'n' could be negative. And unfortunately this can come up even for loops
|
|
/// where the user didn't use a C do-while loop. For example, seemingly
|
|
/// well-behaved top-test loops will commonly be lowered like this:
|
|
//
|
|
/// if (n > 0) {
|
|
/// i = 0;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i < n);
|
|
/// }
|
|
///
|
|
/// and then it's possible for subsequent optimization to obscure the if
|
|
/// test in such a way that indvars can't find it.
|
|
///
|
|
/// When indvars can't find the if test in loops like this, it creates a
|
|
/// signed-max expression, which allows it to give the loop a canonical
|
|
/// induction variable:
|
|
///
|
|
/// i = 0;
|
|
/// smax = n < 1 ? 1 : n;
|
|
/// do {
|
|
/// p[i] = 0.0;
|
|
/// } while (++i != smax);
|
|
///
|
|
/// Canonical induction variables are necessary because the loop passes
|
|
/// are designed around them. The most obvious example of this is the
|
|
/// LoopInfo analysis, which doesn't remember trip count values. It
|
|
/// expects to be able to rediscover the trip count each time it is
|
|
/// needed, and it does this using a simple analyis that only succeeds if
|
|
/// the loop has a canonical induction variable.
|
|
///
|
|
/// However, when it comes time to generate code, the maximum operation
|
|
/// can be quite costly, especially if it's inside of an outer loop.
|
|
///
|
|
/// This function solves this problem by detecting this type of loop and
|
|
/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
|
|
/// the instructions for the maximum computation.
|
|
///
|
|
ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
|
|
IVStrideUse* &CondUse) {
|
|
// Check that the loop matches the pattern we're looking for.
|
|
if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
|
|
Cond->getPredicate() != CmpInst::ICMP_NE)
|
|
return Cond;
|
|
|
|
SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
|
|
if (!Sel || !Sel->hasOneUse()) return Cond;
|
|
|
|
SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
|
|
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
|
|
return Cond;
|
|
SCEVHandle One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType());
|
|
|
|
// Add one to the backedge-taken count to get the trip count.
|
|
SCEVHandle IterationCount = SE->getAddExpr(BackedgeTakenCount, One);
|
|
|
|
// Check for a max calculation that matches the pattern.
|
|
SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(IterationCount);
|
|
if (!SMax || SMax != SE->getSCEV(Sel)) return Cond;
|
|
|
|
SCEVHandle SMaxLHS = SMax->getOperand(0);
|
|
SCEVHandle SMaxRHS = SMax->getOperand(1);
|
|
if (!SMaxLHS || SMaxLHS != One) return Cond;
|
|
|
|
// Check the relevant induction variable for conformance to
|
|
// the pattern.
|
|
SCEVHandle IV = SE->getSCEV(Cond->getOperand(0));
|
|
SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
|
|
if (!AR || !AR->isAffine() ||
|
|
AR->getStart() != One ||
|
|
AR->getStepRecurrence(*SE) != One)
|
|
return Cond;
|
|
|
|
// Check the right operand of the select, and remember it, as it will
|
|
// be used in the new comparison instruction.
|
|
Value *NewRHS = 0;
|
|
if (SE->getSCEV(Sel->getOperand(1)) == SMaxRHS)
|
|
NewRHS = Sel->getOperand(1);
|
|
else if (SE->getSCEV(Sel->getOperand(2)) == SMaxRHS)
|
|
NewRHS = Sel->getOperand(2);
|
|
if (!NewRHS) return Cond;
|
|
|
|
// Ok, everything looks ok to change the condition into an SLT or SGE and
|
|
// delete the max calculation.
|
|
ICmpInst *NewCond =
|
|
new ICmpInst(Cond->getPredicate() == CmpInst::ICMP_NE ?
|
|
CmpInst::ICMP_SLT :
|
|
CmpInst::ICMP_SGE,
|
|
Cond->getOperand(0), NewRHS, "scmp", Cond);
|
|
|
|
// Delete the max calculation instructions.
|
|
SE->deleteValueFromRecords(Cond);
|
|
Cond->replaceAllUsesWith(NewCond);
|
|
Cond->eraseFromParent();
|
|
Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
|
|
SE->deleteValueFromRecords(Sel);
|
|
Sel->eraseFromParent();
|
|
if (Cmp->use_empty()) {
|
|
SE->deleteValueFromRecords(Cmp);
|
|
Cmp->eraseFromParent();
|
|
}
|
|
CondUse->User = NewCond;
|
|
return NewCond;
|
|
}
|
|
|
|
/// OptimizeShadowIV - If IV is used in a int-to-float cast
|
|
/// inside the loop then try to eliminate the cast opeation.
|
|
void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
|
|
|
|
SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
|
|
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
|
|
return;
|
|
|
|
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
|
|
++Stride) {
|
|
std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
|
|
IVUsesByStride.find(StrideOrder[Stride]);
|
|
assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
|
|
if (!isa<SCEVConstant>(SI->first))
|
|
continue;
|
|
|
|
for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
|
|
E = SI->second.Users.end(); UI != E; /* empty */) {
|
|
std::vector<IVStrideUse>::iterator CandidateUI = UI;
|
|
++UI;
|
|
Instruction *ShadowUse = CandidateUI->User;
|
|
const Type *DestTy = NULL;
|
|
|
|
/* If shadow use is a int->float cast then insert a second IV
|
|
to eliminate this cast.
|
|
|
|
for (unsigned i = 0; i < n; ++i)
|
|
foo((double)i);
|
|
|
|
is transformed into
|
|
|
|
double d = 0.0;
|
|
for (unsigned i = 0; i < n; ++i, ++d)
|
|
foo(d);
|
|
*/
|
|
if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User))
|
|
DestTy = UCast->getDestTy();
|
|
else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User))
|
|
DestTy = SCast->getDestTy();
|
|
if (!DestTy) continue;
|
|
|
|
if (TLI) {
|
|
/* If target does not support DestTy natively then do not apply
|
|
this transformation. */
|
|
MVT DVT = TLI->getValueType(DestTy);
|
|
if (!TLI->isTypeLegal(DVT)) continue;
|
|
}
|
|
|
|
PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
|
|
if (!PH) continue;
|
|
if (PH->getNumIncomingValues() != 2) continue;
|
|
|
|
const Type *SrcTy = PH->getType();
|
|
int Mantissa = DestTy->getFPMantissaWidth();
|
|
if (Mantissa == -1) continue;
|
|
if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa)
|
|
continue;
|
|
|
|
unsigned Entry, Latch;
|
|
if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
|
|
Entry = 0;
|
|
Latch = 1;
|
|
} else {
|
|
Entry = 1;
|
|
Latch = 0;
|
|
}
|
|
|
|
ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
|
|
if (!Init) continue;
|
|
ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
|
|
|
|
BinaryOperator *Incr =
|
|
dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
|
|
if (!Incr) continue;
|
|
if (Incr->getOpcode() != Instruction::Add
|
|
&& Incr->getOpcode() != Instruction::Sub)
|
|
continue;
|
|
|
|
/* Initialize new IV, double d = 0.0 in above example. */
|
|
ConstantInt *C = NULL;
|
|
if (Incr->getOperand(0) == PH)
|
|
C = dyn_cast<ConstantInt>(Incr->getOperand(1));
|
|
else if (Incr->getOperand(1) == PH)
|
|
C = dyn_cast<ConstantInt>(Incr->getOperand(0));
|
|
else
|
|
continue;
|
|
|
|
if (!C) continue;
|
|
|
|
/* Add new PHINode. */
|
|
PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
|
|
|
|
/* create new increment. '++d' in above example. */
|
|
ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
|
|
BinaryOperator *NewIncr =
|
|
BinaryOperator::Create(Incr->getOpcode(),
|
|
NewPH, CFP, "IV.S.next.", Incr);
|
|
|
|
NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
|
|
NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
|
|
|
|
/* Remove cast operation */
|
|
SE->deleteValueFromRecords(ShadowUse);
|
|
ShadowUse->replaceAllUsesWith(NewPH);
|
|
ShadowUse->eraseFromParent();
|
|
SI->second.Users.erase(CandidateUI);
|
|
NumShadow++;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
|
|
// uses in the loop, look to see if we can eliminate some, in favor of using
|
|
// common indvars for the different uses.
|
|
void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
|
|
// TODO: implement optzns here.
|
|
|
|
OptimizeShadowIV(L);
|
|
|
|
// Finally, get the terminating condition for the loop if possible. If we
|
|
// can, we want to change it to use a post-incremented version of its
|
|
// induction variable, to allow coalescing the live ranges for the IV into
|
|
// one register value.
|
|
PHINode *SomePHI = cast<PHINode>(L->getHeader()->begin());
|
|
BasicBlock *Preheader = L->getLoopPreheader();
|
|
BasicBlock *LatchBlock =
|
|
SomePHI->getIncomingBlock(SomePHI->getIncomingBlock(0) == Preheader);
|
|
BranchInst *TermBr = dyn_cast<BranchInst>(LatchBlock->getTerminator());
|
|
if (!TermBr || TermBr->isUnconditional() ||
|
|
!isa<ICmpInst>(TermBr->getCondition()))
|
|
return;
|
|
ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
|
|
|
|
// Search IVUsesByStride to find Cond's IVUse if there is one.
|
|
IVStrideUse *CondUse = 0;
|
|
const SCEVHandle *CondStride = 0;
|
|
|
|
if (!FindIVUserForCond(Cond, CondUse, CondStride))
|
|
return; // setcc doesn't use the IV.
|
|
|
|
// If the trip count is computed in terms of an smax (due to ScalarEvolution
|
|
// being unable to find a sufficient guard, for example), change the loop
|
|
// comparison to use SLT instead of NE.
|
|
Cond = OptimizeSMax(L, Cond, CondUse);
|
|
|
|
// If possible, change stride and operands of the compare instruction to
|
|
// eliminate one stride.
|
|
Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
|
|
|
|
// It's possible for the setcc instruction to be anywhere in the loop, and
|
|
// possible for it to have multiple users. If it is not immediately before
|
|
// the latch block branch, move it.
|
|
if (&*++BasicBlock::iterator(Cond) != (Instruction*)TermBr) {
|
|
if (Cond->hasOneUse()) { // Condition has a single use, just move it.
|
|
Cond->moveBefore(TermBr);
|
|
} else {
|
|
// Otherwise, clone the terminating condition and insert into the loopend.
|
|
Cond = cast<ICmpInst>(Cond->clone());
|
|
Cond->setName(L->getHeader()->getName() + ".termcond");
|
|
LatchBlock->getInstList().insert(TermBr, Cond);
|
|
|
|
// Clone the IVUse, as the old use still exists!
|
|
IVUsesByStride[*CondStride].addUser(CondUse->Offset, Cond,
|
|
CondUse->OperandValToReplace);
|
|
CondUse = &IVUsesByStride[*CondStride].Users.back();
|
|
}
|
|
}
|
|
|
|
// If we get to here, we know that we can transform the setcc instruction to
|
|
// use the post-incremented version of the IV, allowing us to coalesce the
|
|
// live ranges for the IV correctly.
|
|
CondUse->Offset = SE->getMinusSCEV(CondUse->Offset, *CondStride);
|
|
CondUse->isUseOfPostIncrementedValue = true;
|
|
Changed = true;
|
|
}
|
|
|
|
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
|
|
|
|
LI = &getAnalysis<LoopInfo>();
|
|
DT = &getAnalysis<DominatorTree>();
|
|
SE = &getAnalysis<ScalarEvolution>();
|
|
TD = &getAnalysis<TargetData>();
|
|
UIntPtrTy = TD->getIntPtrType();
|
|
Changed = false;
|
|
|
|
// Find all uses of induction variables in this loop, and categorize
|
|
// them by stride. Start by finding all of the PHI nodes in the header for
|
|
// this loop. If they are induction variables, inspect their uses.
|
|
SmallPtrSet<Instruction*,16> Processed; // Don't reprocess instructions.
|
|
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
|
|
AddUsersIfInteresting(I, L, Processed);
|
|
|
|
if (!IVUsesByStride.empty()) {
|
|
// Optimize induction variables. Some indvar uses can be transformed to use
|
|
// strides that will be needed for other purposes. A common example of this
|
|
// is the exit test for the loop, which can often be rewritten to use the
|
|
// computation of some other indvar to decide when to terminate the loop.
|
|
OptimizeIndvars(L);
|
|
|
|
// FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
|
|
// doing computation in byte values, promote to 32-bit values if safe.
|
|
|
|
// FIXME: Attempt to reuse values across multiple IV's. In particular, we
|
|
// could have something like "for(i) { foo(i*8); bar(i*16) }", which should
|
|
// be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
|
|
// Need to be careful that IV's are all the same type. Only works for
|
|
// intptr_t indvars.
|
|
|
|
// If we only have one stride, we can more aggressively eliminate some
|
|
// things.
|
|
bool HasOneStride = IVUsesByStride.size() == 1;
|
|
|
|
#ifndef NDEBUG
|
|
DOUT << "\nLSR on \"" << L->getHeader()->getParent()->getNameStart()
|
|
<< "\" ";
|
|
DEBUG(L->dump());
|
|
#endif
|
|
|
|
// IVsByStride keeps IVs for one particular loop.
|
|
assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
|
|
|
|
// Sort the StrideOrder so we process larger strides first.
|
|
std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
|
|
|
|
// Note: this processes each stride/type pair individually. All users
|
|
// passed into StrengthReduceStridedIVUsers have the same type AND stride.
|
|
// Also, note that we iterate over IVUsesByStride indirectly by using
|
|
// StrideOrder. This extra layer of indirection makes the ordering of
|
|
// strides deterministic - not dependent on map order.
|
|
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
|
|
std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
|
|
IVUsesByStride.find(StrideOrder[Stride]);
|
|
assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
|
|
StrengthReduceStridedIVUsers(SI->first, SI->second, L, HasOneStride);
|
|
}
|
|
}
|
|
|
|
// We're done analyzing this loop; release all the state we built up for it.
|
|
CastedPointers.clear();
|
|
IVUsesByStride.clear();
|
|
IVsByStride.clear();
|
|
StrideOrder.clear();
|
|
for (unsigned i=0; i<GEPlist.size(); i++)
|
|
SE->deleteValueFromRecords(GEPlist[i]);
|
|
GEPlist.clear();
|
|
|
|
// Clean up after ourselves
|
|
if (!DeadInsts.empty()) {
|
|
DeleteTriviallyDeadInstructions();
|
|
|
|
BasicBlock::iterator I = L->getHeader()->begin();
|
|
while (PHINode *PN = dyn_cast<PHINode>(I++)) {
|
|
// At this point, we know that we have killed one or more IV users.
|
|
// It is worth checking to see if the cannonical indvar is also
|
|
// dead, so that we can remove it as well.
|
|
//
|
|
// We can remove a PHI if it is on a cycle in the def-use graph
|
|
// where each node in the cycle has degree one, i.e. only one use,
|
|
// and is an instruction with no side effects.
|
|
//
|
|
// FIXME: this needs to eliminate an induction variable even if it's being
|
|
// compared against some value to decide loop termination.
|
|
if (!PN->hasOneUse())
|
|
continue;
|
|
|
|
SmallPtrSet<PHINode *, 4> PHIs;
|
|
for (Instruction *J = dyn_cast<Instruction>(*PN->use_begin());
|
|
J && J->hasOneUse() && !J->mayWriteToMemory();
|
|
J = dyn_cast<Instruction>(*J->use_begin())) {
|
|
// If we find the original PHI, we've discovered a cycle.
|
|
if (J == PN) {
|
|
// Break the cycle and mark the PHI for deletion.
|
|
SE->deleteValueFromRecords(PN);
|
|
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
|
|
DeadInsts.push_back(PN);
|
|
Changed = true;
|
|
break;
|
|
}
|
|
// If we find a PHI more than once, we're on a cycle that
|
|
// won't prove fruitful.
|
|
if (isa<PHINode>(J) && !PHIs.insert(cast<PHINode>(J)))
|
|
break;
|
|
}
|
|
}
|
|
DeleteTriviallyDeadInstructions();
|
|
}
|
|
return Changed;
|
|
}
|