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[VPlan] Remove CanonicalIV when dissolving loop regions (NFC). #142372

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Merged
merged 3 commits into from
Jun 3, 2025
Merged

[VPlan] Remove CanonicalIV when dissolving loop regions (NFC). #142372

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7946c31
[VPlan] Remove CanonicalIV when dissolving loop regions (NFC).
fhahn Jun 2, 2025
cd93b33
Merge remote-tracking branch 'origin/main' into vplan-replace-caniv-w…
fhahn Jun 3, 2025
95b2d84
!fixup fix build failure.
fhahn Jun 3, 2025
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10 changes: 10 additions & 0 deletions llvm/lib/Transforms/Vectorize/VPlan.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -883,6 +883,16 @@ void VPRegionBlock::print(raw_ostream &O, const Twine &Indent,

void VPRegionBlock::dissolveToCFGLoop() {
auto *Header = cast<VPBasicBlock>(getEntry());
if (auto *CanIV = dyn_cast<VPCanonicalIVPHIRecipe>(&Header->front())) {
assert(this == getPlan()->getVectorLoopRegion() &&
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Just an idea, alternatively it could also be replaced in VPlanTransforms::dissolveLoopRegions where you could get it directly from getCanonicalIV()?

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Yep that would also do the trick, but doing it here has the advantage it cannot be missed by potential other users

"Canonical IV must be in the entry of the top-level loop region");
auto *ScalarR = VPBuilder(CanIV).createScalarPhi(
{CanIV->getStartValue(), CanIV->getBackedgeValue()},
CanIV->getDebugLoc(), "index");
CanIV->replaceAllUsesWith(ScalarR);
CanIV->eraseFromParent();
}

VPBlockBase *Preheader = getSinglePredecessor();
auto *ExitingLatch = cast<VPBasicBlock>(getExiting());
VPBlockBase *Middle = getSingleSuccessor();
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10 changes: 3 additions & 7 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Expand Up @@ -2599,14 +2599,10 @@ void VPlanTransforms::convertToConcreteRecipes(VPlan &Plan,
for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
vp_depth_first_deep(Plan.getEntry()))) {
for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
if (isa<VPCanonicalIVPHIRecipe, VPEVLBasedIVPHIRecipe>(&R)) {
auto *PhiR = cast<VPHeaderPHIRecipe>(&R);
StringRef Name =
isa<VPCanonicalIVPHIRecipe>(PhiR) ? "index" : "evl.based.iv";
VPBuilder Builder(PhiR);
auto *ScalarR = Builder.createScalarPhi(
if (auto *PhiR = dyn_cast<VPEVLBasedIVPHIRecipe>(&R)) {
auto *ScalarR = VPBuilder(PhiR).createScalarPhi(
{PhiR->getStartValue(), PhiR->getBackedgeValue()},
PhiR->getDebugLoc(), Name);
PhiR->getDebugLoc(), "evl.based.iv");
PhiR->replaceAllUsesWith(ScalarR);
ToRemove.push_back(PhiR);
continue;
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