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Rewrite ScalarEvolution::hasOperand to use an explicit worklist instead

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of recursion, to avoid excessive stack usage on deep expressions.

llvm-svn: 156554
This commit is contained in:
Dan Gohman 2012-05-10 17:21:30 +00:00
parent ea7b37e3ae
commit bfbda3087c
1 changed files with 50 additions and 35 deletions
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85
lib/Analysis/ScalarEvolution.cpp
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@ -6860,43 +6860,58 @@ bool ScalarEvolution::properlyDominates(const SCEV *S, const BasicBlock *BB) {
}
bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
switch (S->getSCEVType()) {
case scConstant:
return false;
case scTruncate:
case scZeroExtend:
case scSignExtend: {
const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
const SCEV *CastOp = Cast->getOperand();
return Op == CastOp || hasOperand(CastOp, Op);
}
case scAddRecExpr:
case scAddExpr:
case scMulExpr:
case scUMaxExpr:
case scSMaxExpr: {
const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
I != E; ++I) {
const SCEV *NAryOp = *I;
if (NAryOp == Op || hasOperand(NAryOp, Op))
SmallVector<const SCEV *, 8> Worklist;
Worklist.push_back(S);
do {
S = Worklist.pop_back_val();
switch (S->getSCEVType()) {
case scConstant:
break;
case scTruncate:
case scZeroExtend:
case scSignExtend: {
const SCEVCastExpr *Cast = cast<SCEVCastExpr>(S);
const SCEV *CastOp = Cast->getOperand();
if (Op == CastOp)
return true;
Worklist.push_back(CastOp);
break;
}
return false;
}
case scUDivExpr: {
const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
return LHS == Op || hasOperand(LHS, Op) ||
RHS == Op || hasOperand(RHS, Op);
}
case scUnknown:
return false;
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
default:
llvm_unreachable("Unknown SCEV kind!");
}
case scAddRecExpr:
case scAddExpr:
case scMulExpr:
case scUMaxExpr:
case scSMaxExpr: {
const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(S);
for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
I != E; ++I) {
const SCEV *NAryOp = *I;
if (NAryOp == Op)
return true;
Worklist.push_back(NAryOp);
}
break;
}
case scUDivExpr: {
const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
const SCEV *LHS = UDiv->getLHS(), *RHS = UDiv->getRHS();
if (LHS == Op || RHS == Op)
return true;
Worklist.push_back(LHS);
Worklist.push_back(RHS);
break;
}
case scUnknown:
break;
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
default:
llvm_unreachable("Unknown SCEV kind!");
}
} while (!Worklist.empty());
return false;
}
void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {