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[LV]: Ensure fairness when selecting epilogue VF. #155547

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Merged
merged 4 commits into from
Sep 17, 2025
Merged

[LV]: Ensure fairness when selecting epilogue VF. #155547

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c168005
[LV]: Ensure fairness when selecting epilogue VF.
hassnaaHamdi Aug 26, 2025
c892779
rebase
Sep 6, 2025
954acb8
temporarily strip renameing changes from interleaving-reduction test
hassnaaHamdi Sep 9, 2025
1e670a1
update test: interleaving-reduction.ll
hassnaaHamdi Sep 17, 2025
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8 changes: 1 addition & 7 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4310,16 +4310,10 @@ bool LoopVectorizationCostModel::isEpilogueVectorizationProfitable(
if (TTI.getMaxInterleaveFactor(VF) <= 1)
return false;

// TODO: PR #108190 introduced a discrepancy between fixed-width and scalable
// VFs when deciding profitability.
// See related "TODO: extend to support scalable VFs." in
// selectEpilogueVectorizationFactor.
unsigned Multiplier = VF.isFixed() ? IC : 1;
unsigned MinVFThreshold = EpilogueVectorizationMinVF.getNumOccurrences() > 0
? EpilogueVectorizationMinVF
: TTI.getEpilogueVectorizationMinVF();
return estimateElementCount(VF * Multiplier, VScaleForTuning) >=
MinVFThreshold;
return estimateElementCount(VF * IC, VScaleForTuning) >= MinVFThreshold;
}

VectorizationFactor LoopVectorizationPlanner::selectEpilogueVectorizationFactor(
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