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Revert "Revert two GEP-related InstCombine commits"

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This reverts commit r216698 which reverted r216523 and r216598.

We would attempt to perform the transformation even if the match()
failed because, as a side effect, it would set V.  This would trick us
into believing that we correctly found a place to correctly apply the
transform.

An additional test case was added to getelementptr.ll so that we might
not regress in the future.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216890 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-09-01 21:10:02 +00:00
parent 3c7bd3fbef
commit a0b2af46a5
2 changed files with 115 additions and 11 deletions
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53
lib/Transforms/InstCombine/InstructionCombining.cpp
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@ -1508,19 +1508,50 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName());
}
// Canonicalize (gep i8* X, -(ptrtoint Y)) to (sub (ptrtoint X), (ptrtoint Y))
// The GEP pattern is emitted by the SCEV expander for certain kinds of
// pointer arithmetic.
if (DL && GEP.getNumIndices() == 1 &&
match(GEP.getOperand(1), m_Neg(m_PtrToInt(m_Value())))) {
if (DL && GEP.getNumIndices() == 1) {
unsigned AS = GEP.getPointerAddressSpace();
if (GEP.getType() == Builder->getInt8PtrTy(AS) &&
GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
if (GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
DL->getPointerSizeInBits(AS)) {
Operator *Index = cast<Operator>(GEP.getOperand(1));
Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType());
Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1));
return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
Type *PtrTy = GEP.getPointerOperandType();
Type *Ty = PtrTy->getPointerElementType();
uint64_t TyAllocSize = DL->getTypeAllocSize(Ty);
bool Matched = false;
uint64_t C;
Value *V = nullptr;
if (TyAllocSize == 1) {
V = GEP.getOperand(1);
Matched = true;
} else if (match(GEP.getOperand(1),
m_AShr(m_Value(V), m_ConstantInt(C)))) {
if (TyAllocSize == 1ULL << C)
Matched = true;
} else if (match(GEP.getOperand(1),
m_SDiv(m_Value(V), m_ConstantInt(C)))) {
if (TyAllocSize == C)
Matched = true;
}
if (Matched) {
// Canonicalize (gep i8* X, -(ptrtoint Y))
// to (inttoptr (sub (ptrtoint X), (ptrtoint Y)))
// The GEP pattern is emitted by the SCEV expander for certain kinds of
// pointer arithmetic.
if (match(V, m_Neg(m_PtrToInt(m_Value())))) {
Operator *Index = cast<Operator>(V);
Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType());
Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1));
return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
}
// Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X))
// to (bitcast Y)
Value *Y;
if (match(V, m_Sub(m_PtrToInt(m_Value(Y)),
m_PtrToInt(m_Specific(GEP.getOperand(0)))))) {
return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y,
GEP.getType());
}
}
}
}