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

[Simon Pilgrim via llvm-commits]

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

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.

>From 328c5c9b36df45241ab7b26d4acacf2a40bc8254 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Thu, 20 Feb 2025 12:23:06 +0000
Subject: [PATCH] [VectorCombine] foldSelectShuffle - remove extra adds of old
 shuffles to worklist

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.
---
 llvm/lib/Transforms/Vectorize/VectorCombine.cpp | 2 --
 1 file changed, 2 deletions(-)

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;
 }