[llvm] [SLP] Exit early if MaxVF < MinVF (NFCI). (PR #83283)

[Florian Hahn via llvm-commits]

https://github.com/fhahn created https://github.com/llvm/llvm-project/pull/83283

Exit early if MaxVF < MinVF. In that case, the loop body below will never get entered. Note that this adjusts the condition from MaxVF <= MinVF. If MaxVF == MinVF, vectorization may still be feasible (and the loop below gets entered).

>From 3eacfa64a35f0aed09180c00cbb5272c4a4c9ca0 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Wed, 28 Feb 2024 16:03:14 +0000
Subject: [PATCH] [SLP] Exit early if MaxVF < MinVF (NFCI).

Exit early if MaxVF < MinVF. In that case, the loop body below will
never get entered. Note that this adjusts the condition from MaxVF <=
MinVF. If MaxVF == MinVF, vectorization may still be feasible (and the
loop below gets entered).
---
 llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 2b7d518c1c1a78..e381cd2c5794b1 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -13912,10 +13912,11 @@ bool SLPVectorizerPass::vectorizeStores(ArrayRef<StoreInst *> Stores,
       unsigned MinVF = TTI->getStoreMinimumVF(
           R.getMinVF(DL->getTypeSizeInBits(ValueTy)), StoreTy, ValueTy);
 
-      if (MaxVF <= MinVF) {
+      if (MaxVF < MinVF) {
         LLVM_DEBUG(dbgs() << "SLP: Vectorization infeasible as MaxVF (" << MaxVF
                           << ") <= "
                           << "MinVF (" << MinVF << ")\n");
+        return;
       }
 
       // FIXME: Is division-by-2 the correct step? Should we assert that the