Skip to content

[VPlan] Consolidate logic for narrowToSingleScalars (NFCI) #167360

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
artagnon merged 2 commits into from
Dec 3, 2025
Merged

[VPlan] Consolidate logic for narrowToSingleScalars (NFCI) #167360

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ba534e4
[VPlan] Consolidate logic for narrowToSingleScalars (NFCI)
artagnon Jul 31, 2025
4bed81b
[VPlan] Restrict users-check to onlyFirstLaneUsed
artagnon Dec 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
32 changes: 5 additions & 27 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -757,31 +757,6 @@ static void legalizeAndOptimizeInductions(VPlan &Plan) {
if (!PhiR)
continue;

// Try to narrow wide and replicating recipes to uniform recipes, based on
// VPlan analysis.
// TODO: Apply to all recipes in the future, to replace legacy uniformity
// analysis.
auto Users = collectUsersRecursively(PhiR);
for (VPUser *U : reverse(Users)) {
auto *Def = dyn_cast<VPRecipeWithIRFlags>(U);
auto *RepR = dyn_cast<VPReplicateRecipe>(U);
// Skip recipes that shouldn't be narrowed.
if (!Def || !isa<VPReplicateRecipe, VPWidenRecipe>(Def) ||
Def->getNumUsers() == 0 || !Def->getUnderlyingValue() ||
(RepR && (RepR->isSingleScalar() || RepR->isPredicated())))
continue;

// Skip recipes that may have other lanes than their first used.
if (!vputils::isSingleScalar(Def) && !vputils::onlyFirstLaneUsed(Def))
continue;

auto *Clone = new VPReplicateRecipe(Def->getUnderlyingInstr(),
Def->operands(), /*IsUniform*/ true,
/*Mask*/ nullptr, /*Flags*/ *Def);
Clone->insertAfter(Def);
Def->replaceAllUsesWith(Clone);
}

// Replace wide pointer inductions which have only their scalars used by
// PtrAdd(IndStart, ScalarIVSteps (0, Step)).
if (auto *PtrIV = dyn_cast<VPWidenPointerInductionRecipe>(&Phi)) {
Expand Down Expand Up @@ -1546,8 +1521,11 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
continue;
}

// Skip recipes that aren't single scalars.
if (!vputils::isSingleScalar(RepOrWidenR))
// Skip recipes that aren't single scalars and don't just have their first
// lane used.
if (!vputils::isSingleScalar(RepOrWidenR) &&
(!vputils::onlyFirstLaneUsed(RepOrWidenR) ||
RepOrWidenR->getNumUsers() == 0))
continue;

// Skip recipes for which conversion to single-scalar does introduce
Expand Down