[llvm] 8747736 - [SLP] NFC: Simplify CandidateVFs initialization (#144882)

[via llvm-commits]

Author: Sander de Smalen
Date: 2025-06-20T10:00:55+01:00
New Revision: 874773635d31501ab21812c05c44caf281c1acc7

URL: https://github.com/llvm/llvm-project/commit/874773635d31501ab21812c05c44caf281c1acc7
DIFF: https://github.com/llvm/llvm-project/commit/874773635d31501ab21812c05c44caf281c1acc7.diff

LOG: [SLP] NFC: Simplify CandidateVFs initialization (#144882)

Also adds a comment to clarify the meaning of MaxRegVF.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 5eef2497cf90b..1141c1b2babbf 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -21198,7 +21198,11 @@ bool SLPVectorizerPass::vectorizeStores(
         }
       }
 
+      // MaxRegVF represents the number of instructions (scalar, or vector in
+      // case of revec) that can be vectorized to naturally fit in a vector
+      // register.
       unsigned MaxRegVF = MaxVF;
+
       MaxVF = std::min<unsigned>(MaxVF, bit_floor(Operands.size()));
       if (MaxVF < MinVF) {
         LLVM_DEBUG(dbgs() << "SLP: Vectorization infeasible as MaxVF (" << MaxVF
@@ -21207,13 +21211,11 @@ bool SLPVectorizerPass::vectorizeStores(
         continue;
       }
 
-      unsigned Sz = 1 + Log2_32(MaxVF) - Log2_32(MinVF);
-      SmallVector<unsigned> CandidateVFs(Sz + (NonPowerOf2VF > 0 ? 1 : 0));
-      unsigned Size = MinVF;
-      for (unsigned &VF : reverse(CandidateVFs)) {
-        VF = Size > MaxVF ? NonPowerOf2VF : Size;
-        Size *= 2;
-      }
+      SmallVector<unsigned> CandidateVFs;
+      for (unsigned VF = std::max(MaxVF, NonPowerOf2VF); VF >= MinVF;
+           VF = divideCeil(VF, 2))
+        CandidateVFs.push_back(VF);
+
       unsigned End = Operands.size();
       unsigned Repeat = 0;
       constexpr unsigned MaxAttempts = 4;