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[LV] Use SCEV::getElementCount in selectEpilogueVectorizationFactor. #150018

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Merged
fhahn merged 3 commits into from
Jul 28, 2025
Merged

[LV] Use SCEV::getElementCount in selectEpilogueVectorizationFactor. #150018

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53b49fa
[LV] Use SCEV::getElementCount in selectEpilogueVectorizationFactor.
fhahn Jul 22, 2025
20b735e
!fixup add vscale-based tests.
fhahn Jul 23, 2025
3415ce5
!fixup update tests after rebase
fhahn Jul 28, 2025
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22 changes: 10 additions & 12 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4500,19 +4500,17 @@ VectorizationFactor LoopVectorizationPlanner::selectEpilogueVectorizationFactor(
Type *TCType = Legal->getWidestInductionType();
const SCEV *RemainingIterations = nullptr;
unsigned MaxTripCount = 0;
if (MainLoopVF.isFixed()) {
// TODO: extend to support scalable VFs.
const SCEV *TC = vputils::getSCEVExprForVPValue(
getPlanFor(MainLoopVF).getTripCount(), SE);
assert(!isa<SCEVCouldNotCompute>(TC) &&
"Trip count SCEV must be computable");
RemainingIterations = SE.getURemExpr(
TC, SE.getConstant(TCType, MainLoopVF.getFixedValue() * IC));

// No iterations left to process in the epilogue.
if (RemainingIterations->isZero())
return Result;
const SCEV *TC =
vputils::getSCEVExprForVPValue(getPlanFor(MainLoopVF).getTripCount(), SE);
assert(!isa<SCEVCouldNotCompute>(TC) && "Trip count SCEV must be computable");
RemainingIterations =
SE.getURemExpr(TC, SE.getElementCount(TCType, MainLoopVF * IC));

// No iterations left to process in the epilogue.
if (RemainingIterations->isZero())
return Result;

if (MainLoopVF.isFixed()) {
MaxTripCount = MainLoopVF.getFixedValue() * IC - 1;
if (SE.isKnownPredicate(CmpInst::ICMP_ULT, RemainingIterations,
SE.getConstant(TCType, MaxTripCount))) {
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