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[IndVarSimplify] Simplify code using a dictionary 

Possibly very slightly slower, but this code is not performance critical and the readability benefit alone is huge.

llvm-svn: 317012
This commit is contained in:
Philip Reames 2017-10-31 17:06:32 +00:00
parent 39970069b1
commit cd0a5bb96c
1 changed files with 8 additions and 16 deletions
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22
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
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@ -193,27 +193,19 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp,
// cheaply, where cheaply means "we don't need to emit any new
// instructions".
Value *NewLHS = nullptr, *NewRHS = nullptr;
if (S == InvariantLHS || X == InvariantLHS)
NewLHS =
ICmp->getOperand(S == InvariantLHS ? IVOperIdx : (1 - IVOperIdx));
if (S == InvariantRHS || X == InvariantRHS)
NewRHS =
ICmp->getOperand(S == InvariantRHS ? IVOperIdx : (1 - IVOperIdx));
SmallDenseMap<const SCEV*, Value*> CheapExpansions;
CheapExpansions[S] = ICmp->getOperand(IVOperIdx);
CheapExpansions[X] = ICmp->getOperand(1 - IVOperIdx);
// TODO: Support multiple entry loops? (We currently bail out of these in
// the IndVarSimplify pass)
if (auto *BB = L->getLoopPredecessor()) {
Value *Incoming = PN->getIncomingValue(PN->getBasicBlockIndex(BB));
Value *Incoming = PN->getIncomingValueForBlock(BB);
const SCEV *IncomingS = SE->getSCEV(Incoming);
if (!NewLHS && IncomingS == InvariantLHS)
NewLHS = Incoming;
if (!NewRHS && IncomingS == InvariantRHS)
NewRHS = Incoming;
CheapExpansions[IncomingS] = Incoming;
}
Value *NewLHS = CheapExpansions[InvariantLHS];
Value *NewRHS = CheapExpansions[InvariantRHS];
if (!NewLHS || !NewRHS)
// We could not find an existing value to replace either LHS or RHS.