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[IndVars] Extract out eliminateIdentitySCEV, NFC 

Summary:
Reflow a comment while at it.

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13459

llvm-svn: 249470
This commit is contained in:
Sanjoy Das 2015-10-06 21:44:39 +00:00
parent c77e92da92
commit 088bb0ea9f
1 changed files with 14 additions and 4 deletions
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18
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
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@ -68,6 +68,8 @@ namespace {
Value *foldIVUser(Instruction *UseInst, Instruction *IVOperand);
bool eliminateIdentitySCEV(Instruction *UseInst, Instruction *IVOperand);
bool eliminateIVUser(Instruction *UseInst, Instruction *IVOperand);
void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
@ -277,9 +279,9 @@ void SimplifyIndvar::eliminateIVRemainder(BinaryOperator *Rem,
DeadInsts.emplace_back(Rem);
}
/// Eliminate an operation that consumes a simple IV and has
/// no observable side-effect given the range of IV values.
/// IVOperand is guaranteed SCEVable, but UseInst may not be.
/// Eliminate an operation that consumes a simple IV and has no observable
/// side-effect given the range of IV values. IVOperand is guaranteed SCEVable,
/// but UseInst may not be.
bool SimplifyIndvar::eliminateIVUser(Instruction *UseInst,
Instruction *IVOperand) {
if (ICmpInst *ICmp = dyn_cast<ICmpInst>(UseInst)) {
@ -294,7 +296,15 @@ bool SimplifyIndvar::eliminateIVUser(Instruction *UseInst,
}
}
// Eliminate any operation that SCEV can prove is an identity function.
if (eliminateIdentitySCEV(UseInst, IVOperand))
return true;
return false;
}
/// Eliminate any operation that SCEV can prove is an identity function.
bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
Instruction *IVOperand) {
if (!SE->isSCEVable(UseInst->getType()) ||
(UseInst->getType() != IVOperand->getType()) ||
(SE->getSCEV(UseInst) != SE->getSCEV(IVOperand)))