[llvm] [LoopVectorizer][NFC] Update comment regarding VF register pressure. (PR #149478)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Nicholas Guy (NickGuy-Arm)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/149478.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+3-2) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index da3532b2f3385..f142e0796b52a 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -4278,8 +4278,9 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
       if (VF.isScalar())
         continue;
 
-      /// If the VF was proposed due to MaxBandwidth, don't consider the VF if
-      /// it exceeds the number of registers for the target.
+      /// If the register pressure needs to be considered for VF,
+      /// don't consider the VF as valid if it exceeds the number
+      /// of registers for the target.
       if (CM.shouldCalculateRegPressureForVF(VF) &&
           RUs[I].exceedsMaxNumRegs(TTI, ForceTargetNumVectorRegs))
         continue;

``````````

</details>


https://github.com/llvm/llvm-project/pull/149478