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[VPlan] Strip dead code in replaceSymbolicStrides (NFC) #164296

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[VPlan] Strip dead code in replaceSymbolicStrides (NFC) #164296

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[VPlan] Strip dead code in replaceSymbolicStrides (NFC)
artagnon Oct 20, 2025
db33919
[VPlan] Restore comment
artagnon Oct 21, 2025
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9 changes: 2 additions & 7 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2911,11 +2911,6 @@ void VPlanTransforms::replaceSymbolicStrides(
const DenseMap<Value *, const SCEV *> &StridesMap) {
// Replace VPValues for known constant strides guaranteed by predicate scalar
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This still holds I think, it make ssure we only replace users that are guaranteed to be dominated by the runtime checks we insert.

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The comment is the explanation for the check below, which I think should be kept to ensure we only replace strides we know will be guarded by runtime checks

// evolution.
auto CanUseVersionedStride = [&Plan](VPUser &U, unsigned) {
auto *R = cast<VPRecipeBase>(&U);
return R->getRegion() ||
R->getParent() == Plan.getVectorLoopRegion()->getSinglePredecessor();
};
ValueToSCEVMapTy RewriteMap;
for (const SCEV *Stride : StridesMap.values()) {
using namespace SCEVPatternMatch;
Expand All @@ -2928,7 +2923,7 @@ void VPlanTransforms::replaceSymbolicStrides(
auto *CI =
Plan.getOrAddLiveIn(ConstantInt::get(Stride->getType(), *StrideConst));
if (VPValue *StrideVPV = Plan.getLiveIn(StrideV))
StrideVPV->replaceUsesWithIf(CI, CanUseVersionedStride);
StrideVPV->replaceAllUsesWith(CI);

// The versioned value may not be used in the loop directly but through a
// sext/zext. Add new live-ins in those cases.
Expand All @@ -2942,7 +2937,7 @@ void VPlanTransforms::replaceSymbolicStrides(
APInt C =
isa<SExtInst>(U) ? StrideConst->sext(BW) : StrideConst->zext(BW);
VPValue *CI = Plan.getOrAddLiveIn(ConstantInt::get(U->getType(), C));
StrideVPV->replaceUsesWithIf(CI, CanUseVersionedStride);
StrideVPV->replaceAllUsesWith(CI);
}
RewriteMap[StrideV] = PSE.getSCEV(StrideV);
}
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