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[VPlan] Introduce vputils::getSingleScalarClone #161667

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[VPlan] Introduce vputils::getSingleScalarClone #161667

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c08940d
[VPlan] Introduce vputils::getSingleScalarClone
artagnon Oct 2, 2025
7d71949
[VPlan] Address review
artagnon Oct 21, 2025
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26 changes: 5 additions & 21 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -189,19 +189,7 @@ static bool sinkScalarOperands(VPlan &Plan) {
if (NeedsDuplicating) {
if (ScalarVFOnly)
continue;
VPSingleDefRecipe *Clone;
if (auto *SinkCandidateRepR =
dyn_cast<VPReplicateRecipe>(SinkCandidate)) {
// TODO: Handle converting to uniform recipes as separate transform,
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Do we want to keep the TODO?

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Perhaps not? I think we wanted to address it sometime in the past, but I don't think it's the case any longer?

// then cloning should be sufficient here.
Instruction *I = SinkCandidate->getUnderlyingInstr();
Clone = new VPReplicateRecipe(I, SinkCandidate->operands(), true,
nullptr /*Mask*/, *SinkCandidateRepR);
// TODO: add ".cloned" suffix to name of Clone's VPValue.
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Worth adding the TODO to getSingleScalarClone?

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Worth noting that the constructor doesn't accept a Name field, so I'm not sure if we're going to resolve this: kept it for now.

} else {
Clone = SinkCandidate->clone();
}

VPSingleDefRecipe *Clone = vputils::getSingleScalarClone(SinkCandidate);
Clone->insertBefore(SinkCandidate);
SinkCandidate->replaceUsesWithIf(Clone, [SinkTo](VPUser &U, unsigned) {
return cast<VPRecipeBase>(&U)->getParent() != SinkTo;
Expand Down Expand Up @@ -667,8 +655,7 @@ static void legalizeAndOptimizeInductions(VPlan &Plan) {
if (!vputils::isSingleScalar(Def) && !vputils::onlyFirstLaneUsed(Def))
continue;

auto *Clone = new VPReplicateRecipe(Def->getUnderlyingInstr(),
Def->operands(), /*IsUniform*/ true);
VPSingleDefRecipe *Clone = vputils::getSingleScalarClone(Def);
Clone->insertAfter(Def);
Def->replaceAllUsesWith(Clone);
}
Expand Down Expand Up @@ -1335,9 +1322,8 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
auto *RepOrWidenR = cast<VPSingleDefRecipe>(&R);
if (RepR && isa<StoreInst>(RepR->getUnderlyingInstr()) &&
vputils::isSingleScalar(RepR->getOperand(1))) {
auto *Clone = new VPReplicateRecipe(
RepOrWidenR->getUnderlyingInstr(), RepOrWidenR->operands(),
true /*IsSingleScalar*/, nullptr /*Mask*/, *RepR /*Metadata*/);
auto *Clone =
cast<VPReplicateRecipe>(vputils::getSingleScalarClone(RepOrWidenR));
Clone->insertBefore(RepOrWidenR);
unsigned ExtractOpc =
vputils::isUniformAcrossVFsAndUFs(RepR->getOperand(1))
Expand All @@ -1362,9 +1348,7 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
}))
continue;

auto *Clone = new VPReplicateRecipe(RepOrWidenR->getUnderlyingInstr(),
RepOrWidenR->operands(),
true /*IsSingleScalar*/);
VPSingleDefRecipe *Clone = vputils::getSingleScalarClone(RepOrWidenR);
Clone->insertBefore(RepOrWidenR);
RepOrWidenR->replaceAllUsesWith(Clone);
}
Expand Down
22 changes: 22 additions & 0 deletions llvm/lib/Transforms/Vectorize/VPlanUtils.cpp
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Expand Up @@ -253,3 +253,25 @@ vputils::getRecipesForUncountableExit(VPlan &Plan,

return UncountableCondition;
}

VPSingleDefRecipe *vputils::getSingleScalarClone(VPSingleDefRecipe *R) {
// TODO: add ".cloned" suffix to name of Clone's VPValue.
return TypeSwitch<VPSingleDefRecipe *, VPSingleDefRecipe *>(R)
.Case<VPInstruction, VPWidenRecipe, VPWidenSelectRecipe,
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What about all the other VPSingleDefRecipe types, i.e. VPWidenPHIRecipe, VPBlendRecipe, VPExpressionRecipe, VPWidenCanonicalIVRecipe, etc? I'm a bit nervous that we might be missing some cases here. Have you tried running the LLVM test suite to catch any missing cases?

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Should be fine for the moment, as all the uses in the use-sites are covered: when we add more recipes to handle in the use-sites, we should update this (follow-ups planned).

VPWidenCallRecipe, VPReplicateRecipe>([](auto *I) {
return new VPReplicateRecipe(I->getUnderlyingInstr(), I->operands(),
/*IsSingleScalar*/ true,
/*Mask*/ nullptr,
/*Metadata*/ *I);
})
.Case<VPWidenGEPRecipe>([](auto *I) {
// WidenGEP does not have metadata.
return new VPReplicateRecipe(I->getUnderlyingInstr(), I->operands(),
/*IsSingleScalar*/ true, /*Mask*/ nullptr);
})
.Case<VPScalarIVStepsRecipe>([](auto *I) { return I->clone(); })
.Default([](auto *I) {
llvm_unreachable("Don't know how to convert to single-scalar");
return nullptr;
});
}
4 changes: 4 additions & 0 deletions llvm/lib/Transforms/Vectorize/VPlanUtils.h
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Expand Up @@ -122,6 +122,10 @@ std::optional<VPValue *>
getRecipesForUncountableExit(VPlan &Plan,
SmallVectorImpl<VPRecipeBase *> &Recipes,
SmallVectorImpl<VPRecipeBase *> &GEPs);

/// Returns a single-scalar version of \p R, creating a fresh single-scalar
/// VPReplicateRecipe or just cloning the recipe.
VPSingleDefRecipe *getSingleScalarClone(VPSingleDefRecipe *R);
} // namespace vputils

//===----------------------------------------------------------------------===//
Expand Down