[llvm] [LV] Clarify code in isPredicatedInst (NFC) (PR #134251)
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Thu Apr 3 06:53:45 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-vectorizers
Author: Ramkumar Ramachandra (artagnon)
<details>
<summary>Changes</summary>
---
Full diff: https://github.com/llvm/llvm-project/pull/134251.diff
1 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+5-3)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 55cc801e91452..727098bd19a56 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3244,11 +3244,9 @@ bool LoopVectorizationCostModel::isScalarWithPredication(
// TODO: Fold into LoopVectorizationLegality::isMaskRequired.
bool LoopVectorizationCostModel::isPredicatedInst(Instruction *I) const {
- // If predication is not needed, avoid it.
// TODO: We can use the loop-preheader as context point here and get
// context sensitive reasoning for isSafeToSpeculativelyExecute.
- if (!blockNeedsPredicationForAnyReason(I->getParent()) ||
- isSafeToSpeculativelyExecute(I) ||
+ if (isSafeToSpeculativelyExecute(I) ||
(isa<LoadInst, StoreInst, CallInst>(I) && !Legal->isMaskRequired(I)) ||
isa<BranchInst, SwitchInst, PHINode, AllocaInst>(I))
return false;
@@ -3258,6 +3256,10 @@ bool LoopVectorizationCostModel::isPredicatedInst(Instruction *I) const {
if (Legal->blockNeedsPredication(I->getParent()))
return true;
+ // If we're not folding the tail by masking, predication is unnecessary.
+ if (!foldTailByMasking())
+ return false;
+
// All that remain are instructions with side-effects originally executed in
// the loop unconditionally, but now execute under a tail-fold mask (only)
// having at least one active lane (the first). If the side-effects of the
``````````
</details>
https://github.com/llvm/llvm-project/pull/134251
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