[llvm] [LV] Clarify code in isPredicatedInst (NFC) (PR #134251)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon created https://github.com/llvm/llvm-project/pull/134251

None

>From 9824bc1edf0a3d02a10e4c02e47773fedb4a0aff Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Thu, 3 Apr 2025 14:49:08 +0100
Subject: [PATCH] [LV] Clarify code in isPredicatedInst (NFC)

---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

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