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llvm/lib/CodeGen/Analysis.cpp

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//===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines several CodeGen-specific LLVM IR analysis utilties.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Analysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/DataLayout.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
using namespace llvm;
/// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
/// of insertvalue or extractvalue indices that identify a member, return
/// the linearized index of the start of the member.
///
unsigned llvm::ComputeLinearIndex(Type *Ty,
const unsigned *Indices,
const unsigned *IndicesEnd,
unsigned CurIndex) {
// Base case: We're done.
if (Indices && Indices == IndicesEnd)
return CurIndex;
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI) {
if (Indices && *Indices == unsigned(EI - EB))
return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
}
return CurIndex;
}
// Given an array type, recursively traverse the elements.
else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
if (Indices && *Indices == i)
return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
CurIndex = ComputeLinearIndex(EltTy, 0, 0, CurIndex);
}
return CurIndex;
}
// We haven't found the type we're looking for, so keep searching.
return CurIndex + 1;
}
/// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
/// EVTs that represent all the individual underlying
/// non-aggregate types that comprise it.
///
/// If Offsets is non-null, it points to a vector to be filled in
/// with the in-memory offsets of each of the individual values.
///
void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
SmallVectorImpl<EVT> &ValueVTs,
SmallVectorImpl<uint64_t> *Offsets,
uint64_t StartingOffset) {
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI)
ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
StartingOffset + SL->getElementOffset(EI - EB));
return;
}
// Given an array type, recursively traverse the elements.
if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
StartingOffset + i * EltSize);
return;
}
// Interpret void as zero return values.
if (Ty->isVoidTy())
return;
// Base case: we can get an EVT for this LLVM IR type.
ValueVTs.push_back(TLI.getValueType(Ty));
if (Offsets)
Offsets->push_back(StartingOffset);
}
/// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
V = V->stripPointerCasts();
GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
if (GV && GV->getName() == "llvm.eh.catch.all.value") {
assert(GV->hasInitializer() &&
"The EH catch-all value must have an initializer");
Value *Init = GV->getInitializer();
GV = dyn_cast<GlobalVariable>(Init);
if (!GV) V = cast<ConstantPointerNull>(Init);
}
assert((GV || isa<ConstantPointerNull>(V)) &&
"TypeInfo must be a global variable or NULL");
return GV;
}
/// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
/// processed uses a memory 'm' constraint.
bool
llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
const TargetLowering &TLI) {
for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
InlineAsm::ConstraintInfo &CI = CInfos[i];
for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
if (CType == TargetLowering::C_Memory)
return true;
}
// Indirect operand accesses access memory.
if (CI.isIndirect)
return true;
}
return false;
}
/// getFCmpCondCode - Return the ISD condition code corresponding to
/// the given LLVM IR floating-point condition code. This includes
/// consideration of global floating-point math flags.
///
ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
switch (Pred) {
case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
case FCmpInst::FCMP_OGT: return ISD::SETOGT;
case FCmpInst::FCMP_OGE: return ISD::SETOGE;
case FCmpInst::FCMP_OLT: return ISD::SETOLT;
case FCmpInst::FCMP_OLE: return ISD::SETOLE;
case FCmpInst::FCMP_ONE: return ISD::SETONE;
case FCmpInst::FCMP_ORD: return ISD::SETO;
case FCmpInst::FCMP_UNO: return ISD::SETUO;
case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
case FCmpInst::FCMP_UGT: return ISD::SETUGT;
case FCmpInst::FCMP_UGE: return ISD::SETUGE;
case FCmpInst::FCMP_ULT: return ISD::SETULT;
case FCmpInst::FCMP_ULE: return ISD::SETULE;
case FCmpInst::FCMP_UNE: return ISD::SETUNE;
case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
default: llvm_unreachable("Invalid FCmp predicate opcode!");
}
}
ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
switch (CC) {
case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
default: return CC;
}
}
/// getICmpCondCode - Return the ISD condition code corresponding to
/// the given LLVM IR integer condition code.
///
ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
switch (Pred) {
case ICmpInst::ICMP_EQ: return ISD::SETEQ;
case ICmpInst::ICMP_NE: return ISD::SETNE;
case ICmpInst::ICMP_SLE: return ISD::SETLE;
case ICmpInst::ICMP_ULE: return ISD::SETULE;
case ICmpInst::ICMP_SGE: return ISD::SETGE;
case ICmpInst::ICMP_UGE: return ISD::SETUGE;
case ICmpInst::ICMP_SLT: return ISD::SETLT;
case ICmpInst::ICMP_ULT: return ISD::SETULT;
case ICmpInst::ICMP_SGT: return ISD::SETGT;
case ICmpInst::ICMP_UGT: return ISD::SETUGT;
default:
llvm_unreachable("Invalid ICmp predicate opcode!");
}
}
/// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
/// through it (and any transitive noop operands to it) and return its input
/// value. This is used to determine if a tail call can be formed.
///
static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
// If V is not an instruction, it can't be looked through.
const Instruction *I = dyn_cast<Instruction>(V);
if (I == 0 || !I->hasOneUse() || I->getNumOperands() == 0) return V;
Value *Op = I->getOperand(0);
// Look through truly no-op truncates.
if (isa<TruncInst>(I) &&
TLI.isTruncateFree(I->getOperand(0)->getType(), I->getType()))
return getNoopInput(I->getOperand(0), TLI);
// Look through truly no-op bitcasts.
if (isa<BitCastInst>(I)) {
// No type change at all.
if (Op->getType() == I->getType())
return getNoopInput(Op, TLI);
// Pointer to pointer cast.
if (Op->getType()->isPointerTy() && I->getType()->isPointerTy())
return getNoopInput(Op, TLI);
if (isa<VectorType>(Op->getType()) && isa<VectorType>(I->getType()) &&
TLI.isTypeLegal(EVT::getEVT(Op->getType())) &&
TLI.isTypeLegal(EVT::getEVT(I->getType())))
return getNoopInput(Op, TLI);
}
// Look through inttoptr.
if (isa<IntToPtrInst>(I) && !isa<VectorType>(I->getType())) {
// Make sure this isn't a truncating or extending cast. We could support
// this eventually, but don't bother for now.
if (TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(Op->getType())->getBitWidth())
return getNoopInput(Op, TLI);
}
// Look through ptrtoint.
if (isa<PtrToIntInst>(I) && !isa<VectorType>(I->getType())) {
// Make sure this isn't a truncating or extending cast. We could support
// this eventually, but don't bother for now.
if (TLI.getPointerTy().getSizeInBits() ==
cast<IntegerType>(I->getType())->getBitWidth())
return getNoopInput(Op, TLI);
}
// Otherwise it's not something we can look through.
return V;
}
/// Test if the given instruction is in a position to be optimized
/// with a tail-call. This roughly means that it's in a block with
/// a return and there's nothing that needs to be scheduled
/// between it and the return.
///
/// This function only tests target-independent requirements.
bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
const TargetLowering &TLI) {
const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
// The block must end in a return statement or unreachable.
//
// FIXME: Decline tailcall if it's not guaranteed and if the block ends in
// an unreachable, for now. The way tailcall optimization is currently
// implemented means it will add an epilogue followed by a jump. That is
// not profitable. Also, if the callee is a special function (e.g.
// longjmp on x86), it can end up causing miscompilation that has not
// been fully understood.
if (!Ret &&
(!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
!isa<UnreachableInst>(Term)))
return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(I))
for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
--BBI) {
if (&*BBI == I)
break;
// Debug info intrinsics do not get in the way of tail call optimization.
if (isa<DbgInfoIntrinsic>(BBI))
continue;
if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(BBI))
return false;
}
// If the block ends with a void return or unreachable, it doesn't matter
// what the call's return type is.
if (!Ret || Ret->getNumOperands() == 0) return true;
// If the return value is undef, it doesn't matter what the call's
// return type is.
if (isa<UndefValue>(Ret->getOperand(0))) return true;
// Conservatively require the attributes of the call to match those of
// the return. Ignore noalias because it doesn't affect the call sequence.
const Function *F = ExitBB->getParent();
Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
if (AttrBuilder(CalleeRetAttr).removeAttribute(Attributes::NoAlias) !=
AttrBuilder(CallerRetAttr).removeAttribute(Attributes::NoAlias))
return false;
// It's not safe to eliminate the sign / zero extension of the return value.
if (CallerRetAttr.hasAttribute(Attributes::ZExt) ||
CallerRetAttr.hasAttribute(Attributes::SExt))
return false;
// Otherwise, make sure the unmodified return value of I is the return value.
// We handle two cases: multiple return values + scalars.
Value *RetVal = Ret->getOperand(0);
if (!isa<InsertValueInst>(RetVal) || !isa<StructType>(RetVal->getType()))
// Handle scalars first.
return getNoopInput(Ret->getOperand(0), TLI) == I;
// If this is an aggregate return, look through the insert/extract values and
// see if each is transparent.
for (unsigned i = 0, e =cast<StructType>(RetVal->getType())->getNumElements();
i != e; ++i) {
const Value *InScalar = FindInsertedValue(RetVal, i);
if (InScalar == 0) return false;
InScalar = getNoopInput(InScalar, TLI);
// If the scalar value being inserted is an extractvalue of the right index
// from the call, then everything is good.
const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(InScalar);
if (EVI == 0 || EVI->getOperand(0) != I || EVI->getNumIndices() != 1 ||
EVI->getIndices()[0] != i)
return false;
}
return true;
}
bool llvm::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,
SDValue &Chain, const TargetLowering &TLI) {
const Function *F = DAG.getMachineFunction().getFunction();
// Conservatively require the attributes of the call to match those of
// the return. Ignore noalias because it doesn't affect the call sequence.
Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
if (AttrBuilder(CallerRetAttr)
.removeAttribute(Attributes::NoAlias).hasAttributes())
return false;
// It's not safe to eliminate the sign / zero extension of the return value.
if (CallerRetAttr.hasAttribute(Attributes::ZExt) ||
CallerRetAttr.hasAttribute(Attributes::SExt))
return false;
// Check if the only use is a function return node.
return TLI.isUsedByReturnOnly(Node, Chain);
}
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