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Implement PR1345 and Transforms/InstCombine/bitcast-gep.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36521 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-28 00:57:34 +00:00
parent 947780b1f9
commit 9bc1464094
1 changed files with 104 additions and 28 deletions
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132
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4358,15 +4358,27 @@ static Value *EmitGEPOffset(User *GEP, Instruction &I, InstCombiner &IC) {
}
} else {
// Convert to correct type.
Op = IC.InsertNewInstBefore(CastInst::createSExtOrBitCast(Op, IntPtrTy,
Op->getName()+".c"), I);
if (Size != 1)
// We'll let instcombine(mul) convert this to a shl if possible.
Op = IC.InsertNewInstBefore(BinaryOperator::createMul(Op, Scale,
if (Op->getType() != IntPtrTy) {
if (Constant *OpC = dyn_cast<Constant>(Op))
Op = ConstantExpr::getSExt(OpC, IntPtrTy);
else
Op = IC.InsertNewInstBefore(new SExtInst(Op, IntPtrTy,
Op->getName()+".c"), I);
}
if (Size != 1) {
if (Constant *OpC = dyn_cast<Constant>(Op))
Op = ConstantExpr::getMul(OpC, Scale);
else // We'll let instcombine(mul) convert this to a shl if possible.
Op = IC.InsertNewInstBefore(BinaryOperator::createMul(Op, Scale,
GEP->getName()+".idx"), I);
}
// Emit an add instruction.
Result = IC.InsertNewInstBefore(BinaryOperator::createAdd(Op, Result,
if (isa<Constant>(Op) && isa<Constant>(Result))
Result = ConstantExpr::getAdd(cast<Constant>(Op),
cast<Constant>(Result));
else
Result = IC.InsertNewInstBefore(BinaryOperator::createAdd(Op, Result,
GEP->getName()+".offs"), I);
}
}
@ -6343,17 +6355,96 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
Value *Src = CI.getOperand(0);
// If casting the result of a getelementptr instruction with no offset, turn
// this into a cast of the original pointer!
//
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
// If casting the result of a getelementptr instruction with no offset, turn
// this into a cast of the original pointer!
if (GEP->hasAllZeroIndices()) {
// Changing the cast operand is usually not a good idea but it is safe
// here because the pointer operand is being replaced with another
// pointer operand so the opcode doesn't need to change.
AddToWorkList(GEP);
CI.setOperand(0, GEP->getOperand(0));
return &CI;
}
// If the GEP has a single use, and the base pointer is a bitcast, and the
// GEP computes a constant offset, see if we can convert these three
// instructions into fewer. This typically happens with unions and other
// non-type-safe code.
if (GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0))) {
if (GEP->hasAllConstantIndices()) {
// We are guaranteed to get a constant from EmitGEPOffset.
ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP, CI, *this));
int64_t Offset = OffsetV->getSExtValue();
// Get the base pointer input of the bitcast, and the type it points to.
Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
const Type *GEPIdxTy =
cast<PointerType>(OrigBase->getType())->getElementType();
if (GEPIdxTy->isSized()) {
SmallVector<Value*, 8> NewIndices;
// Start with the index over the outer type.
const Type *IntPtrTy = TD->getIntPtrType();
int64_t TySize = TD->getTypeSize(GEPIdxTy);
int64_t FirstIdx = Offset/TySize;
Offset %= TySize;
// Handle silly modulus not returning values values [0..TySize).
if (Offset < 0) {
assert(FirstIdx == 0);
FirstIdx = -1;
Offset += TySize;
assert(Offset >= 0);
}
NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
// Index into the types. If we fail, set OrigBase to null.
while (Offset) {
if (const StructType *STy = dyn_cast<StructType>(GEPIdxTy)) {
const StructLayout *SL = TD->getStructLayout(STy);
unsigned Elt = SL->getElementContainingOffset(Offset);
NewIndices.push_back(ConstantInt::get(Type::Int32Ty, Elt));
Offset -= SL->getElementOffset(Elt);
GEPIdxTy = STy->getElementType(Elt);
} else if (isa<ArrayType>(GEPIdxTy) || isa<VectorType>(GEPIdxTy)) {
const SequentialType *STy = cast<SequentialType>(GEPIdxTy);
uint64_t EltSize = TD->getTypeSize(STy->getElementType());
NewIndices.push_back(ConstantInt::get(IntPtrTy, Offset/EltSize));
Offset %= EltSize;
GEPIdxTy = STy->getElementType();
} else {
// Otherwise, we can't index into this, bail out.
Offset = 0;
OrigBase = 0;
}
}
if (OrigBase) {
// If we were able to index down into an element, create the GEP
// and bitcast the result. This eliminates one bitcast, potentially
// two.
Instruction *NGEP = new GetElementPtrInst(OrigBase, &NewIndices[0],
NewIndices.size(), "");
InsertNewInstBefore(NGEP, CI);
NGEP->takeName(GEP);
cerr << "\nZAP: " << *GEP->getOperand(0);
cerr << "ZAP: " << *GEP;
cerr << "ZAP: " << CI << "\n";
cerr << "NEW: " << *NGEP << "\n";
if (isa<BitCastInst>(CI))
return new BitCastInst(NGEP, CI.getType());
assert(isa<PtrToIntInst>(CI));
return new PtrToIntInst(NGEP, CI.getType());
}
}
}
}
}
return commonCastTransforms(CI);
@ -7306,10 +7397,7 @@ static unsigned GetKnownAlignment(Value *V, TargetData *TD) {
if (isa<PointerType>(CI->getOperand(0)->getType()))
return GetKnownAlignment(CI->getOperand(0), TD);
return 0;
} else if (isa<GetElementPtrInst>(V) ||
(isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode()==Instruction::GetElementPtr)) {
User *GEPI = cast<User>(V);
} else if (User *GEPI = dyn_castGetElementPtr(V)) {
unsigned BaseAlignment = GetKnownAlignment(GEPI->getOperand(0), TD);
if (BaseAlignment == 0) return 0;
@ -8107,7 +8195,7 @@ static Value *InsertCastToIntPtrTy(Value *V, const Type *DTy,
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
// Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// Is it 'getelementptr %P, i32 0' or 'getelementptr %P'
// If so, eliminate the noop.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, PtrOp);
@ -8122,22 +8210,11 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, PtrOp);
// Keep track of whether all indices are zero constants integers.
bool AllZeroIndices = true;
// Eliminate unneeded casts for indices.
bool MadeChange = false;
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI) {
// Track whether this GEP has all zero indices, if so, it doesn't move the
// input pointer, it just changes its type.
if (AllZeroIndices) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(i)))
AllZeroIndices = CI->isZero();
else
AllZeroIndices = false;
}
if (isa<SequentialType>(*GTI)) {
if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
if (CI->getOpcode() == Instruction::ZExt ||
@ -8173,7 +8250,7 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// If this GEP instruction doesn't move the pointer, and if the input operand
// is a bitcast of another pointer, just replace the GEP with a bitcast of the
// real input to the dest type.
if (AllZeroIndices && isa<BitCastInst>(GEP.getOperand(0)))
if (GEP.hasAllZeroIndices() && isa<BitCastInst>(GEP.getOperand(0)))
return new BitCastInst(cast<BitCastInst>(GEP.getOperand(0))->getOperand(0),
GEP.getType());
@ -8573,8 +8650,7 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
}
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op))
if (isa<ConstantPointerNull>(GEPI->getOperand(0)) ||
isa<UndefValue>(GEPI->getOperand(0))) {
if (isa<ConstantPointerNull>(GEPI->getOperand(0))) {
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the