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[ValueTracking] Make the code in lookThroughCast 

No functionality change is intended.

llvm-svn: 268108
This commit is contained in:
David Majnemer 2016-04-29 21:22:04 +00:00
parent 1ffa28a3f1
commit 826e9831a7
1 changed files with 12 additions and 19 deletions
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31
llvm/lib/Analysis/ValueTracking.cpp
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@ -3714,30 +3714,23 @@ static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
return nullptr;
}
if (isa<ZExtInst>(CI) && CmpI->isUnsigned())
return ConstantExpr::getTrunc(C, CI->getSrcTy());
if (isa<TruncInst>(CI))
return ConstantExpr::getIntegerCast(C, CI->getSrcTy(), CmpI->isSigned());
if (isa<FPTruncInst>(CI))
return ConstantExpr::getFPExtend(C, CI->getSrcTy(), true);
if (isa<FPExtInst>(CI))
return ConstantExpr::getFPTrunc(C, CI->getSrcTy(), true);
// Sophisticated constants can have values which we cannot easily reason
// about. Skip them for the fp<->int case.
if (isa<ConstantExpr>(C))
return nullptr;
Constant *CastedTo = nullptr;
// This is only valid if the truncated value can be sign-extended
// back to the original value.
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);