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[ValueTracking] clean up lookThroughCast; NFCI 

1. Use auto with dyn_cast.
2. Don't use else after return.
3. Convert chain of 'else if' to switch.
4. Improve variable names.

llvm-svn: 293432
This commit is contained in:
Sanjay Patel 2017-01-29 16:34:57 +00:00
parent 17fe27f1f2
commit 14a4b8185f
1 changed files with 47 additions and 41 deletions
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88
llvm/lib/Analysis/ValueTracking.cpp
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@ -4156,58 +4156,64 @@ static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
Instruction::CastOps *CastOp) {
CastInst *CI = dyn_cast<CastInst>(V1);
Constant *C = dyn_cast<Constant>(V2);
if (!CI)
auto *Cast1 = dyn_cast<CastInst>(V1);
if (!Cast1)
return nullptr;
*CastOp = CI->getOpcode();
if (auto *CI2 = dyn_cast<CastInst>(V2)) {
// If V1 and V2 are both the same cast from the same type, we can look
// through V1.
if (CI2->getOpcode() == CI->getOpcode() &&
CI2->getSrcTy() == CI->getSrcTy())
return CI2->getOperand(0);
return nullptr;
} else if (!C) {
*CastOp = Cast1->getOpcode();
Type *SrcTy = Cast1->getSrcTy();
if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
// If V1 and V2 are both the same cast from the same type, look through V1.
if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
return Cast2->getOperand(0);
return nullptr;
}
auto *C = dyn_cast<Constant>(V2);
if (!C)
return nullptr;
Constant *CastedTo = nullptr;
if (isa<ZExtInst>(CI) && CmpI->isUnsigned())
CastedTo = ConstantExpr::getTrunc(C, CI->getSrcTy());
if (isa<SExtInst>(CI) && CmpI->isSigned())
CastedTo = ConstantExpr::getTrunc(C, CI->getSrcTy(), true);
if (isa<TruncInst>(CI))
CastedTo = ConstantExpr::getIntegerCast(C, CI->getSrcTy(), CmpI->isSigned());
if (isa<FPTruncInst>(CI))
CastedTo = ConstantExpr::getFPExtend(C, CI->getSrcTy(), true);
if (isa<FPExtInst>(CI))
CastedTo = ConstantExpr::getFPTrunc(C, CI->getSrcTy(), true);
if (isa<FPToUIInst>(CI))
CastedTo = ConstantExpr::getUIToFP(C, CI->getSrcTy(), true);
if (isa<FPToSIInst>(CI))
CastedTo = ConstantExpr::getSIToFP(C, CI->getSrcTy(), true);
if (isa<UIToFPInst>(CI))
CastedTo = ConstantExpr::getFPToUI(C, CI->getSrcTy(), true);
if (isa<SIToFPInst>(CI))
CastedTo = ConstantExpr::getFPToSI(C, CI->getSrcTy(), true);
switch (*CastOp) {
case Instruction::ZExt:
if (CmpI->isUnsigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy);
break;
case Instruction::SExt:
if (CmpI->isSigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
break;
case Instruction::Trunc:
CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
break;
case Instruction::FPTrunc:
CastedTo = ConstantExpr::getFPExtend(C, SrcTy, true);
break;
case Instruction::FPExt:
CastedTo = ConstantExpr::getFPTrunc(C, SrcTy, true);
break;
case Instruction::FPToUI:
CastedTo = ConstantExpr::getUIToFP(C, SrcTy, true);
break;
case Instruction::FPToSI:
CastedTo = ConstantExpr::getSIToFP(C, SrcTy, true);
break;
case Instruction::UIToFP:
CastedTo = ConstantExpr::getFPToUI(C, SrcTy, true);
break;
case Instruction::SIToFP:
CastedTo = ConstantExpr::getFPToSI(C, SrcTy, true);
break;
default:
break;
}
if (!CastedTo)
return nullptr;
Constant *CastedBack =
ConstantExpr::getCast(CI->getOpcode(), CastedTo, C->getType(), true);
// Make sure the cast doesn't lose any information.
Constant *CastedBack =
ConstantExpr::getCast(*CastOp, CastedTo, C->getType(), true);
if (CastedBack != C)
return nullptr;