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[InstCombine] improve readability for icmp with cast folds; NFC

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1. Update function name and stale code comments.
2. Use variable names that are less ambiguous.
3. Move operand checks into the function as early exits.

llvm-svn: 369390
This commit is contained in:
Sanjay Patel 2019-08-20 14:56:44 +00:00
parent 54215e5d31
commit 5950893514
2 changed files with 42 additions and 47 deletions
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87
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -4026,74 +4026,78 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
return nullptr;
}
/// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
/// far.
Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
Value *LHSCIOp = LHSCI->getOperand(0);
Type *SrcTy = LHSCIOp->getType();
Type *DestTy = LHSCI->getType();
/// Handle icmp (cast x), (cast or constant).
Instruction *InstCombiner::foldICmpWithCastOp(ICmpInst &ICmp) {
auto *CastOp0 = dyn_cast<CastInst>(ICmp.getOperand(0));
if (!CastOp0)
return nullptr;
if (!isa<Constant>(ICmp.getOperand(1)) && !isa<CastInst>(ICmp.getOperand(1)))
return nullptr;
Value *Op0Src = CastOp0->getOperand(0);
Type *SrcTy = CastOp0->getSrcTy();
Type *DestTy = CastOp0->getDestTy();
// Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
// integer type is the same size as the pointer type.
const auto& CompatibleSizes = [&](Type* SrcTy, Type* DestTy) -> bool {
auto CompatibleSizes = [&](Type *SrcTy, Type *DestTy) {
if (isa<VectorType>(SrcTy)) {
SrcTy = cast<VectorType>(SrcTy)->getElementType();
DestTy = cast<VectorType>(DestTy)->getElementType();
}
return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
};
if (LHSCI->getOpcode() == Instruction::PtrToInt &&
if (CastOp0->getOpcode() == Instruction::PtrToInt &&
CompatibleSizes(SrcTy, DestTy)) {
Value *RHSOp = nullptr;
if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
Value *RHSCIOp = RHSC->getOperand(0);
if (RHSCIOp->getType()->getPointerAddressSpace() ==
LHSCIOp->getType()->getPointerAddressSpace()) {
RHSOp = RHSC->getOperand(0);
Value *NewOp1 = nullptr;
if (auto *PtrToIntOp1 = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
Value *PtrSrc = PtrToIntOp1->getOperand(0);
if (PtrSrc->getType()->getPointerAddressSpace() ==
Op0Src->getType()->getPointerAddressSpace()) {
NewOp1 = PtrToIntOp1->getOperand(0);
// If the pointer types don't match, insert a bitcast.
if (LHSCIOp->getType() != RHSOp->getType())
RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
if (Op0Src->getType() != NewOp1->getType())
NewOp1 = Builder.CreateBitCast(NewOp1, Op0Src->getType());
}
} else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
NewOp1 = ConstantExpr::getIntToPtr(RHSC, SrcTy);
}
if (RHSOp)
return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
if (NewOp1)
return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
}
// The code below only handles extension cast instructions, so far.
// Enforce this.
if (LHSCI->getOpcode() != Instruction::ZExt &&
LHSCI->getOpcode() != Instruction::SExt)
if (CastOp0->getOpcode() != Instruction::ZExt &&
CastOp0->getOpcode() != Instruction::SExt)
return nullptr;
bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
bool isSignedExt = CastOp0->getOpcode() == Instruction::SExt;
bool isSignedCmp = ICmp.isSigned();
if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
// Not an extension from the same type?
Value *RHSCIOp = CI->getOperand(0);
if (RHSCIOp->getType() != LHSCIOp->getType())
Value *Op1Src = CastOp1->getOperand(0);
if (Op1Src->getType() != Op0Src->getType())
return nullptr;
// If the signedness of the two casts doesn't agree (i.e. one is a sext
// and the other is a zext), then we can't handle this.
if (CI->getOpcode() != LHSCI->getOpcode())
if (CastOp1->getOpcode() != CastOp0->getOpcode())
return nullptr;
// Deal with equality cases early.
if (ICmp.isEquality())
return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
return new ICmpInst(ICmp.getPredicate(), Op0Src, Op1Src);
// A signed comparison of sign extended values simplifies into a
// signed comparison.
if (isSignedCmp && isSignedExt)
return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
return new ICmpInst(ICmp.getPredicate(), Op0Src, Op1Src);
// The other three cases all fold into an unsigned comparison.
return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
return new ICmpInst(ICmp.getUnsignedPredicate(), Op0Src, Op1Src);
}
// If we aren't dealing with a constant on the RHS, exit early.
@ -4104,21 +4108,21 @@ Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
// Compute the constant that would happen if we truncated to SrcTy then
// re-extended to DestTy.
Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
Constant *Res2 = ConstantExpr::getCast(CastOp0->getOpcode(), Res1, DestTy);
// If the re-extended constant didn't change...
if (Res2 == C) {
// Deal with equality cases early.
if (ICmp.isEquality())
return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
return new ICmpInst(ICmp.getPredicate(), Op0Src, Res1);
// A signed comparison of sign extended values simplifies into a
// signed comparison.
if (isSignedExt && isSignedCmp)
return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
return new ICmpInst(ICmp.getPredicate(), Op0Src, Res1);
// The other three cases all fold into an unsigned comparison.
return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
return new ICmpInst(ICmp.getUnsignedPredicate(), Op0Src, Res1);
}
// The re-extended constant changed, partly changed (in the case of a vector),
@ -4137,7 +4141,7 @@ Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
// We're performing an unsigned comp with a sign extended value.
// This is true if the input is >= 0. [aka >s -1]
Constant *NegOne = Constant::getAllOnesValue(SrcTy);
Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
Value *Result = Builder.CreateICmpSGT(Op0Src, NegOne, ICmp.getName());
// Finally, return the value computed.
if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
@ -5212,17 +5216,8 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (Instruction *Res = foldICmpBitCast(I, Builder))
return Res;
if (isa<CastInst>(Op0)) {
// Handle the special case of: icmp (cast bool to X), <cst>
// This comes up when you have code like
// int X = A < B;
// if (X) ...
// For generality, we handle any zero-extension of any operand comparison
// with a constant or another cast from the same type.
if (isa<Constant>(Op1) || isa<CastInst>(Op1))
if (Instruction *R = foldICmpWithCastAndCast(I))
return R;
}
if (Instruction *R = foldICmpWithCastOp(I))
return R;
if (Instruction *Res = foldICmpBinOp(I))
return Res;

2
lib/Transforms/InstCombine/InstCombineInternal.h
View File

@ -861,7 +861,7 @@ private:
Constant *RHSC);
Instruction *foldICmpAddOpConst(Value *X, const APInt &C,
ICmpInst::Predicate Pred);
Instruction *foldICmpWithCastAndCast(ICmpInst &ICI);
Instruction *foldICmpWithCastOp(ICmpInst &ICI);
Instruction *foldICmpUsingKnownBits(ICmpInst &Cmp);
Instruction *foldICmpWithDominatingICmp(ICmpInst &Cmp);