[llvm] [VectorCombine] foldSelectShuffle - remove extra adds of old shuffles to worklist (PR #127999)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-vectorizers

Author: Simon Pilgrim (RKSimon)

<details>
<summary>Changes</summary>

We already push the old shuffles to the worklist as part of the replaceValue calls, so we shouldn't need to add them to the deferred list as well - my guess is this was to ensure that the instructions got erased first to help cleanup unused instructions, but eraseInstruction should handle this now.

---
Full diff: https://github.com/llvm/llvm-project/pull/127999.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/VectorCombine.cpp (-2) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 746742e14d080..cdb8853f7503c 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -3036,8 +3036,6 @@ bool VectorCombine::foldSelectShuffle(Instruction &I, bool FromReduction) {
   Worklist.pushValue(NSV0B);
   Worklist.pushValue(NSV1A);
   Worklist.pushValue(NSV1B);
-  for (auto *S : Shuffles)
-    Worklist.add(S);
   return true;
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/127999