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[SCEVPatternMatch] Add signed cst match; use in LV (NFC) (#154568)

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Add a m_scev_SpecificSInt for matching a sign-extended value, and use it
to improve some code in LoopVectorize.
This commit is contained in:
Ramkumar Ramachandra 2025-08-21 16:46:53 +01:00 committed by GitHub
parent 5c36fb3303
commit a96b78cf41
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GPG Key ID: B5690EEEBB952194
2 changed files with 16 additions and 14 deletions
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12
llvm/include/llvm/Analysis/ScalarEvolutionPatternMatch.h
View File

@ -116,6 +116,18 @@ struct is_specific_cst {
/// Match an SCEV constant with a plain unsigned integer.
inline cst_pred_ty<is_specific_cst> m_scev_SpecificInt(uint64_t V) { return V; }
struct is_specific_signed_cst {
int64_t CV;
is_specific_signed_cst(int64_t C) : CV(C) {}
bool isValue(const APInt &C) const { return C.trySExtValue() == CV; }
};
/// Match an SCEV constant with a plain signed integer (sign-extended value will
/// be matched)
inline cst_pred_ty<is_specific_signed_cst> m_scev_SpecificSInt(int64_t V) {
return V;
}
struct bind_cst_ty {
const APInt *&CR;

18
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -5918,21 +5918,11 @@ void LoopVectorizationCostModel::setVectorizedCallDecision(ElementCount VF) {
// TODO: do we need to figure out the cost of an extract to get the
// first lane? Or do we hope that it will be folded away?
ScalarEvolution *SE = PSE.getSE();
const auto *SAR =
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(ScalarParam));
if (!SAR || SAR->getLoop() != TheLoop) {
if (!match(SE->getSCEV(ScalarParam),
m_scev_AffineAddRec(
m_SCEV(), m_scev_SpecificSInt(Param.LinearStepOrPos),
m_SpecificLoop(TheLoop))))
ParamsOk = false;
break;
}
const SCEVConstant *Step =
dyn_cast<SCEVConstant>(SAR->getStepRecurrence(*SE));
if (!Step ||
Step->getAPInt().getSExtValue() != Param.LinearStepOrPos)
ParamsOk = false;
break;
}
case VFParamKind::GlobalPredicate: