InstructionCombining.cpp [plain text]
#define DEBUG_TYPE "instcombine"
#include "llvm/Transforms/Scalar.h"
#include "InstCombine.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include <algorithm>
#include <climits>
using namespace llvm;
using namespace llvm::PatternMatch;
STATISTIC(NumCombined , "Number of insts combined");
STATISTIC(NumConstProp, "Number of constant folds");
STATISTIC(NumDeadInst , "Number of dead inst eliminated");
STATISTIC(NumSunkInst , "Number of instructions sunk");
char InstCombiner::ID = 0;
static RegisterPass<InstCombiner>
X("instcombine", "Combine redundant instructions");
void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreservedID(LCSSAID);
AU.setPreservesCFG();
}
bool InstCombiner::ShouldChangeType(const Type *From, const Type *To) const {
assert(From->isIntegerTy() && To->isIntegerTy());
if (!TD) return false;
unsigned FromWidth = From->getPrimitiveSizeInBits();
unsigned ToWidth = To->getPrimitiveSizeInBits();
bool FromLegal = TD->isLegalInteger(FromWidth);
bool ToLegal = TD->isLegalInteger(ToWidth);
if (FromLegal && !ToLegal)
return false;
if (!FromLegal && !ToLegal && ToWidth > FromWidth)
return false;
return true;
}
bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
bool Changed = false;
if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
Changed = !I.swapOperands();
if (!I.isAssociative()) return Changed;
Instruction::BinaryOps Opcode = I.getOpcode();
if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
if (isa<Constant>(I.getOperand(1))) {
Constant *Folded = ConstantExpr::get(I.getOpcode(),
cast<Constant>(I.getOperand(1)),
cast<Constant>(Op->getOperand(1)));
I.setOperand(0, Op->getOperand(0));
I.setOperand(1, Folded);
return true;
}
if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)))
if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
Op->hasOneUse() && Op1->hasOneUse()) {
Constant *C1 = cast<Constant>(Op->getOperand(1));
Constant *C2 = cast<Constant>(Op1->getOperand(1));
Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
Instruction *New = BinaryOperator::Create(Opcode, Op->getOperand(0),
Op1->getOperand(0),
Op1->getName(), &I);
Worklist.Add(New);
I.setOperand(0, New);
I.setOperand(1, Folded);
return true;
}
}
return Changed;
}
Value *InstCombiner::dyn_castNegVal(Value *V) const {
if (BinaryOperator::isNeg(V))
return BinaryOperator::getNegArgument(V);
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantExpr::getNeg(C);
if (ConstantVector *C = dyn_cast<ConstantVector>(V))
if (C->getType()->getElementType()->isIntegerTy())
return ConstantExpr::getNeg(C);
return 0;
}
Value *InstCombiner::dyn_castFNegVal(Value *V) const {
if (BinaryOperator::isFNeg(V))
return BinaryOperator::getFNegArgument(V);
if (ConstantFP *C = dyn_cast<ConstantFP>(V))
return ConstantExpr::getFNeg(C);
if (ConstantVector *C = dyn_cast<ConstantVector>(V))
if (C->getType()->getElementType()->isFloatingPointTy())
return ConstantExpr::getFNeg(C);
return 0;
}
static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
InstCombiner *IC) {
if (CastInst *CI = dyn_cast<CastInst>(&I))
return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType());
bool ConstIsRHS = isa<Constant>(I.getOperand(1));
Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
if (Constant *SOC = dyn_cast<Constant>(SO)) {
if (ConstIsRHS)
return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
}
Value *Op0 = SO, *Op1 = ConstOperand;
if (!ConstIsRHS)
std::swap(Op0, Op1);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1,
SO->getName()+".op");
if (ICmpInst *CI = dyn_cast<ICmpInst>(&I))
return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
SO->getName()+".cmp");
if (FCmpInst *CI = dyn_cast<FCmpInst>(&I))
return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
SO->getName()+".cmp");
llvm_unreachable("Unknown binary instruction type!");
}
Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) {
if (!SI->hasOneUse()) return 0;
Value *TV = SI->getOperand(1);
Value *FV = SI->getOperand(2);
if (isa<Constant>(TV) || isa<Constant>(FV)) {
if (SI->getType()->isIntegerTy(1)) return 0;
Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this);
Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this);
return SelectInst::Create(SI->getCondition(), SelectTrueVal,
SelectFalseVal);
}
return 0;
}
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
bool AllowAggressive) {
AllowAggressive = false;
PHINode *PN = cast<PHINode>(I.getOperand(0));
unsigned NumPHIValues = PN->getNumIncomingValues();
if (NumPHIValues == 0 ||
(!PN->hasOneUse() && !AllowAggressive))
return 0;
BasicBlock *NonConstBB = 0;
for (unsigned i = 0; i != NumPHIValues; ++i)
if (!isa<Constant>(PN->getIncomingValue(i)) ||
isa<ConstantExpr>(PN->getIncomingValue(i))) {
if (NonConstBB) return 0; if (isa<PHINode>(PN->getIncomingValue(i))) return 0; NonConstBB = PN->getIncomingBlock(i);
if (NonConstBB == I.getParent())
return 0;
}
if (NonConstBB != 0 && !AllowAggressive) {
BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
if (!BI || !BI->isUnconditional()) return 0;
}
PHINode *NewPN = PHINode::Create(I.getType(), "");
NewPN->reserveOperandSpace(PN->getNumOperands()/2);
InsertNewInstBefore(NewPN, *PN);
NewPN->takeName(PN);
if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
Value *TrueV = SI->getTrueValue();
Value *FalseV = SI->getFalseValue();
BasicBlock *PhiTransBB = PN->getParent();
for (unsigned i = 0; i != NumPHIValues; ++i) {
BasicBlock *ThisBB = PN->getIncomingBlock(i);
Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB);
Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB);
Value *InV = 0;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
InV = SelectInst::Create(PN->getIncomingValue(i), TrueVInPred,
FalseVInPred,
"phitmp", NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, ThisBB);
}
} else if (I.getNumOperands() == 2) {
Constant *C = cast<Constant>(I.getOperand(1));
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV = 0;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
if (CmpInst *CI = dyn_cast<CmpInst>(&I))
InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C);
else
InV = ConstantExpr::get(I.getOpcode(), InC, C);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
InV = BinaryOperator::Create(BO->getOpcode(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else if (CmpInst *CI = dyn_cast<CmpInst>(&I))
InV = CmpInst::Create(CI->getOpcode(),
CI->getPredicate(),
PN->getIncomingValue(i), C, "phitmp",
NonConstBB->getTerminator());
else
llvm_unreachable("Unknown binop!");
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
} else {
CastInst *CI = cast<CastInst>(&I);
const Type *RetTy = CI->getType();
for (unsigned i = 0; i != NumPHIValues; ++i) {
Value *InV;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy);
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
InV = CastInst::Create(CI->getOpcode(), PN->getIncomingValue(i),
I.getType(), "phitmp",
NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
}
return ReplaceInstUsesWith(I, NewPN);
}
const Type *InstCombiner::FindElementAtOffset(const Type *Ty, int64_t Offset,
SmallVectorImpl<Value*> &NewIndices) {
if (!TD) return 0;
if (!Ty->isSized()) return 0;
const Type *IntPtrTy = TD->getIntPtrType(Ty->getContext());
int64_t FirstIdx = 0;
if (int64_t TySize = TD->getTypeAllocSize(Ty)) {
FirstIdx = Offset/TySize;
Offset -= FirstIdx*TySize;
if (Offset < 0) {
--FirstIdx;
Offset += TySize;
assert(Offset >= 0);
}
assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
}
NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
while (Offset) {
if (uint64_t(Offset*8) >= TD->getTypeSizeInBits(Ty))
return 0;
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TD->getStructLayout(STy);
assert(Offset < (int64_t)SL->getSizeInBytes() &&
"Offset must stay within the indexed type");
unsigned Elt = SL->getElementContainingOffset(Offset);
NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
Elt));
Offset -= SL->getElementOffset(Elt);
Ty = STy->getElementType(Elt);
} else if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
uint64_t EltSize = TD->getTypeAllocSize(AT->getElementType());
assert(EltSize && "Cannot index into a zero-sized array");
NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
Offset %= EltSize;
Ty = AT->getElementType();
} else {
return 0;
}
}
return Ty;
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD))
return ReplaceInstUsesWith(GEP, V);
Value *PtrOp = GEP.getOperand(0);
if (isa<UndefValue>(GEP.getOperand(0)))
return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
if (TD) {
bool MadeChange = false;
unsigned PtrSize = TD->getPointerSizeInBits();
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end();
I != E; ++I, ++GTI) {
if (!isa<SequentialType>(*GTI)) continue;
unsigned OpBits = cast<IntegerType>((*I)->getType())->getBitWidth();
if (OpBits == PtrSize)
continue;
*I = Builder->CreateIntCast(*I, TD->getIntPtrType(GEP.getContext()),true);
MadeChange = true;
}
if (MadeChange) return &GEP;
}
if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
if (GetElementPtrInst *SrcGEP =
dyn_cast<GetElementPtrInst>(Src->getOperand(0)))
if (SrcGEP->getNumOperands() == 2)
return 0;
SmallVector<Value*, 8> Indices;
bool EndsWithSequential = false;
for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
I != E; ++I)
EndsWithSequential = !(*I)->isStructTy();
if (EndsWithSequential) {
Value *Sum;
Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
Value *GO1 = GEP.getOperand(1);
if (SO1 == Constant::getNullValue(SO1->getType())) {
Sum = GO1;
} else if (GO1 == Constant::getNullValue(GO1->getType())) {
Sum = SO1;
} else {
if (SO1->getType() != GO1->getType())
return 0;
Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum");
}
if (Src->getNumOperands() == 2) {
GEP.setOperand(0, Src->getOperand(0));
GEP.setOperand(1, Sum);
return &GEP;
}
Indices.append(Src->op_begin()+1, Src->op_end()-1);
Indices.push_back(Sum);
Indices.append(GEP.op_begin()+2, GEP.op_end());
} else if (isa<Constant>(*GEP.idx_begin()) &&
cast<Constant>(*GEP.idx_begin())->isNullValue() &&
Src->getNumOperands() != 1) {
Indices.append(Src->op_begin()+1, Src->op_end());
Indices.append(GEP.idx_begin()+1, GEP.idx_end());
}
if (!Indices.empty())
return (GEP.isInBounds() && Src->isInBounds()) ?
GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices.begin(),
Indices.end(), GEP.getName()) :
GetElementPtrInst::Create(Src->getOperand(0), Indices.begin(),
Indices.end(), GEP.getName());
}
Value *StrippedPtr = PtrOp->stripPointerCasts();
if (StrippedPtr != PtrOp) {
const PointerType *StrippedPtrTy =cast<PointerType>(StrippedPtr->getType());
bool HasZeroPointerIndex = false;
if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isZero();
if (HasZeroPointerIndex) {
const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
if (const ArrayType *CATy =
dyn_cast<ArrayType>(CPTy->getElementType())) {
if (CATy->getElementType() == StrippedPtrTy->getElementType()) {
SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end());
GetElementPtrInst *Res =
GetElementPtrInst::Create(StrippedPtr, Idx.begin(),
Idx.end(), GEP.getName());
Res->setIsInBounds(GEP.isInBounds());
return Res;
}
if (const ArrayType *XATy =
dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){
if (CATy->getElementType() == XATy->getElementType()) {
GEP.setOperand(0, StrippedPtr);
return &GEP;
}
}
}
} else if (GEP.getNumOperands() == 2) {
const Type *SrcElTy = StrippedPtrTy->getElementType();
const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
if (TD && SrcElTy->isArrayTy() &&
TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
TD->getTypeAllocSize(ResElTy)) {
Value *Idx[2];
Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext()));
Idx[1] = GEP.getOperand(1);
Value *NewGEP = GEP.isInBounds() ?
Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()) :
Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName());
return new BitCastInst(NewGEP, GEP.getType());
}
if (TD && SrcElTy->isArrayTy() && ResElTy->isIntegerTy(8)) {
uint64_t ArrayEltSize =
TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType());
Value *NewIdx = 0;
ConstantInt *Scale = 0;
if (ArrayEltSize == 1) {
NewIdx = GEP.getOperand(1);
Scale = ConstantInt::get(cast<IntegerType>(NewIdx->getType()), 1);
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
NewIdx = ConstantInt::get(CI->getType(), 1);
Scale = CI;
} else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
if (Inst->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(Inst->getOperand(1))) {
ConstantInt *ShAmt = cast<ConstantInt>(Inst->getOperand(1));
uint32_t ShAmtVal = ShAmt->getLimitedValue(64);
Scale = ConstantInt::get(cast<IntegerType>(Inst->getType()),
1ULL << ShAmtVal);
NewIdx = Inst->getOperand(0);
} else if (Inst->getOpcode() == Instruction::Mul &&
isa<ConstantInt>(Inst->getOperand(1))) {
Scale = cast<ConstantInt>(Inst->getOperand(1));
NewIdx = Inst->getOperand(0);
}
}
if (ArrayEltSize && Scale && Scale->getSExtValue() >= 0LL &&
Scale->getZExtValue() % ArrayEltSize == 0) {
Scale = ConstantInt::get(Scale->getType(),
Scale->getZExtValue() / ArrayEltSize);
if (Scale->getZExtValue() != 1) {
Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(),
false );
NewIdx = Builder->CreateMul(NewIdx, C, "idxscale");
}
Value *Idx[2];
Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext()));
Idx[1] = NewIdx;
Value *NewGEP = GEP.isInBounds() ?
Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2,GEP.getName()):
Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName());
return new BitCastInst(NewGEP, GEP.getType());
}
}
}
}
if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
if (TD &&
!isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) {
ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP));
int64_t Offset = OffsetV->getSExtValue();
if (Offset == 0) {
if (isa<AllocaInst>(BCI->getOperand(0)) ||
isMalloc(BCI->getOperand(0))) {
if (Instruction *I = visitBitCast(*BCI)) {
if (I != BCI) {
I->takeName(BCI);
BCI->getParent()->getInstList().insert(BCI, I);
ReplaceInstUsesWith(*BCI, I);
}
return &GEP;
}
}
return new BitCastInst(BCI->getOperand(0), GEP.getType());
}
SmallVector<Value*, 8> NewIndices;
const Type *InTy =
cast<PointerType>(BCI->getOperand(0)->getType())->getElementType();
if (FindElementAtOffset(InTy, Offset, NewIndices)) {
Value *NGEP = GEP.isInBounds() ?
Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices.begin(),
NewIndices.end()) :
Builder->CreateGEP(BCI->getOperand(0), NewIndices.begin(),
NewIndices.end());
if (NGEP->getType() == GEP.getType())
return ReplaceInstUsesWith(GEP, NGEP);
NGEP->takeName(&GEP);
return new BitCastInst(NGEP, GEP.getType());
}
}
}
return 0;
}
Instruction *InstCombiner::visitFree(Instruction &FI) {
Value *Op = FI.getOperand(1);
if (isa<UndefValue>(Op)) {
new StoreInst(ConstantInt::getTrue(FI.getContext()),
UndefValue::get(Type::getInt1PtrTy(FI.getContext())), &FI);
return EraseInstFromFunction(FI);
}
if (isa<ConstantPointerNull>(Op))
return EraseInstFromFunction(FI);
if (isMalloc(Op)) {
if (CallInst* CI = extractMallocCallFromBitCast(Op)) {
if (Op->hasOneUse() && CI->hasOneUse()) {
EraseInstFromFunction(FI);
EraseInstFromFunction(*CI);
return EraseInstFromFunction(*cast<Instruction>(Op));
}
} else {
if (Op->hasOneUse()) {
EraseInstFromFunction(FI);
return EraseInstFromFunction(*cast<Instruction>(Op));
}
}
}
return 0;
}
Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
Value *X = 0;
BasicBlock *TrueDest;
BasicBlock *FalseDest;
if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
!isa<Constant>(X)) {
BI.setCondition(X);
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
return &BI;
}
FCmpInst::Predicate FPred; Value *Y;
if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)),
TrueDest, FalseDest)) &&
BI.getCondition()->hasOneUse())
if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE ||
FPred == FCmpInst::FCMP_OGE) {
FCmpInst *Cond = cast<FCmpInst>(BI.getCondition());
Cond->setPredicate(FCmpInst::getInversePredicate(FPred));
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
Worklist.Add(Cond);
return &BI;
}
ICmpInst::Predicate IPred;
if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)),
TrueDest, FalseDest)) &&
BI.getCondition()->hasOneUse())
if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE ||
IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE ||
IPred == ICmpInst::ICMP_SGE) {
ICmpInst *Cond = cast<ICmpInst>(BI.getCondition());
Cond->setPredicate(ICmpInst::getInversePredicate(IPred));
BI.setSuccessor(0, FalseDest);
BI.setSuccessor(1, TrueDest);
Worklist.Add(Cond);
return &BI;
}
return 0;
}
Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
Value *Cond = SI.getCondition();
if (Instruction *I = dyn_cast<Instruction>(Cond)) {
if (I->getOpcode() == Instruction::Add)
if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
SI.setOperand(i,
ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
AddRHS));
SI.setOperand(0, I->getOperand(0));
Worklist.Add(I);
return &SI;
}
}
return 0;
}
Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {
Value *Agg = EV.getAggregateOperand();
if (!EV.hasIndices())
return ReplaceInstUsesWith(EV, Agg);
if (Constant *C = dyn_cast<Constant>(Agg)) {
if (isa<UndefValue>(C))
return ReplaceInstUsesWith(EV, UndefValue::get(EV.getType()));
if (isa<ConstantAggregateZero>(C))
return ReplaceInstUsesWith(EV, Constant::getNullValue(EV.getType()));
if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) {
Value *V = C->getOperand(*EV.idx_begin());
if (EV.getNumIndices() > 1)
return ExtractValueInst::Create(V, EV.idx_begin() + 1, EV.idx_end());
else
return ReplaceInstUsesWith(EV, V);
}
return 0; }
if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
const unsigned *exti, *exte, *insi, *inse;
for (exti = EV.idx_begin(), insi = IV->idx_begin(),
exte = EV.idx_end(), inse = IV->idx_end();
exti != exte && insi != inse;
++exti, ++insi) {
if (*insi != *exti)
return ExtractValueInst::Create(IV->getAggregateOperand(),
EV.idx_begin(), EV.idx_end());
}
if (exti == exte && insi == inse)
return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand());
if (exti == exte) {
Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(),
EV.idx_begin(), EV.idx_end());
return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
insi, inse);
}
if (insi == inse)
return ExtractValueInst::Create(IV->getInsertedValueOperand(),
exti, exte);
}
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) {
if (II->hasOneUse()) {
switch (II->getIntrinsicID()) {
case Intrinsic::uadd_with_overflow:
case Intrinsic::sadd_with_overflow:
if (*EV.idx_begin() == 0) { Value *LHS = II->getOperand(1), *RHS = II->getOperand(2);
II->replaceAllUsesWith(UndefValue::get(II->getType()));
EraseInstFromFunction(*II);
return BinaryOperator::CreateAdd(LHS, RHS);
}
break;
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow:
if (*EV.idx_begin() == 0) { Value *LHS = II->getOperand(1), *RHS = II->getOperand(2);
II->replaceAllUsesWith(UndefValue::get(II->getType()));
EraseInstFromFunction(*II);
return BinaryOperator::CreateSub(LHS, RHS);
}
break;
case Intrinsic::umul_with_overflow:
case Intrinsic::smul_with_overflow:
if (*EV.idx_begin() == 0) { Value *LHS = II->getOperand(1), *RHS = II->getOperand(2);
II->replaceAllUsesWith(UndefValue::get(II->getType()));
EraseInstFromFunction(*II);
return BinaryOperator::CreateMul(LHS, RHS);
}
break;
default:
break;
}
}
}
return 0;
}
static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
assert(I->hasOneUse() && "Invariants didn't hold!");
if (isa<PHINode>(I) || I->mayHaveSideEffects() || isa<TerminatorInst>(I))
return false;
if (isa<AllocaInst>(I) && I->getParent() ==
&DestBlock->getParent()->getEntryBlock())
return false;
if (I->mayReadFromMemory()) {
for (BasicBlock::iterator Scan = I, E = I->getParent()->end();
Scan != E; ++Scan)
if (Scan->mayWriteToMemory())
return false;
}
BasicBlock::iterator InsertPos = DestBlock->getFirstNonPHI();
I->moveBefore(InsertPos);
++NumSunkInst;
return true;
}
static bool AddReachableCodeToWorklist(BasicBlock *BB,
SmallPtrSet<BasicBlock*, 64> &Visited,
InstCombiner &IC,
const TargetData *TD) {
bool MadeIRChange = false;
SmallVector<BasicBlock*, 256> Worklist;
Worklist.push_back(BB);
std::vector<Instruction*> InstrsForInstCombineWorklist;
InstrsForInstCombineWorklist.reserve(128);
SmallPtrSet<ConstantExpr*, 64> FoldedConstants;
do {
BB = Worklist.pop_back_val();
if (!Visited.insert(BB)) continue;
for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
Instruction *Inst = BBI++;
if (isInstructionTriviallyDead(Inst)) {
++NumDeadInst;
DEBUG(errs() << "IC: DCE: " << *Inst << '\n');
Inst->eraseFromParent();
continue;
}
if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0)))
if (Constant *C = ConstantFoldInstruction(Inst, TD)) {
DEBUG(errs() << "IC: ConstFold to: " << *C << " from: "
<< *Inst << '\n');
Inst->replaceAllUsesWith(C);
++NumConstProp;
Inst->eraseFromParent();
continue;
}
if (TD) {
for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end();
i != e; ++i) {
ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
if (CE == 0) continue;
if (!FoldedConstants.insert(CE))
continue;
Constant *NewC = ConstantFoldConstantExpression(CE, TD);
if (NewC && NewC != CE) {
*i = NewC;
MadeIRChange = true;
}
}
}
InstrsForInstCombineWorklist.push_back(Inst);
}
TerminatorInst *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
Worklist.push_back(ReachableBB);
continue;
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i)
if (SI->getCaseValue(i) == Cond) {
BasicBlock *ReachableBB = SI->getSuccessor(i);
Worklist.push_back(ReachableBB);
continue;
}
Worklist.push_back(SI->getSuccessor(0));
continue;
}
}
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
Worklist.push_back(TI->getSuccessor(i));
} while (!Worklist.empty());
IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
InstrsForInstCombineWorklist.size());
return MadeIRChange;
}
bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
MadeIRChange = false;
DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
<< F.getNameStr() << "\n");
{
SmallPtrSet<BasicBlock*, 64> Visited;
MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, TD);
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (!Visited.count(BB)) {
Instruction *Term = BB->getTerminator();
while (Term != BB->begin()) { BasicBlock::iterator I = Term; --I;
DEBUG(errs() << "IC: DCE: " << *I << '\n');
if (!isa<DbgInfoIntrinsic>(I)) {
++NumDeadInst;
MadeIRChange = true;
}
if (!I->getType()->isVoidTy())
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
}
}
while (!Worklist.isEmpty()) {
Instruction *I = Worklist.RemoveOne();
if (I == 0) continue;
if (isInstructionTriviallyDead(I)) {
DEBUG(errs() << "IC: DCE: " << *I << '\n');
EraseInstFromFunction(*I);
++NumDeadInst;
MadeIRChange = true;
continue;
}
if (!I->use_empty() && isa<Constant>(I->getOperand(0)))
if (Constant *C = ConstantFoldInstruction(I, TD)) {
DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n');
ReplaceInstUsesWith(*I, C);
++NumConstProp;
EraseInstFromFunction(*I);
MadeIRChange = true;
continue;
}
if (I->hasOneUse()) {
BasicBlock *BB = I->getParent();
Instruction *UserInst = cast<Instruction>(I->use_back());
BasicBlock *UserParent;
if (PHINode *PN = dyn_cast<PHINode>(UserInst))
UserParent = PN->getIncomingBlock(I->use_begin().getUse());
else
UserParent = UserInst->getParent();
if (UserParent != BB) {
bool UserIsSuccessor = false;
for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
if (*SI == UserParent) {
UserIsSuccessor = true;
break;
}
if (UserIsSuccessor && UserParent->getSinglePredecessor())
MadeIRChange |= TryToSinkInstruction(I, UserParent);
}
}
Builder->SetInsertPoint(I->getParent(), I);
#ifndef NDEBUG
std::string OrigI;
#endif
DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str(););
DEBUG(errs() << "IC: Visiting: " << OrigI << '\n');
if (Instruction *Result = visit(*I)) {
++NumCombined;
if (Result != I) {
DEBUG(errs() << "IC: Old = " << *I << '\n'
<< " New = " << *Result << '\n');
I->replaceAllUsesWith(Result);
Worklist.Add(Result);
Worklist.AddUsersToWorkList(*Result);
Result->takeName(I);
BasicBlock *InstParent = I->getParent();
BasicBlock::iterator InsertPos = I;
if (!isa<PHINode>(Result)) while (isa<PHINode>(InsertPos)) ++InsertPos;
InstParent->getInstList().insert(InsertPos, Result);
EraseInstFromFunction(*I);
} else {
#ifndef NDEBUG
DEBUG(errs() << "IC: Mod = " << OrigI << '\n'
<< " New = " << *I << '\n');
#endif
if (isInstructionTriviallyDead(I)) {
EraseInstFromFunction(*I);
} else {
Worklist.Add(I);
Worklist.AddUsersToWorkList(*I);
}
}
MadeIRChange = true;
}
}
Worklist.Zap();
return MadeIRChange;
}
bool InstCombiner::runOnFunction(Function &F) {
MustPreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
TD = getAnalysisIfAvailable<TargetData>();
IRBuilder<true, TargetFolder, InstCombineIRInserter>
TheBuilder(F.getContext(), TargetFolder(TD),
InstCombineIRInserter(Worklist));
Builder = &TheBuilder;
bool EverMadeChange = false;
unsigned Iteration = 0;
while (DoOneIteration(F, Iteration++))
EverMadeChange = true;
Builder = 0;
return EverMadeChange;
}
FunctionPass *llvm::createInstructionCombiningPass() {
return new InstCombiner();
}