[llvm-branch-commits] [llvm] DAG: Avoid breaking legal vector_shuffle with multiple uses (PR #123712)

[Matt Arsenault via llvm-branch-commits]

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@@ -23172,6 +23172,11 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
     }
 
     if (SVInVec.getOpcode() == ISD::BUILD_VECTOR) {
+      // TODO: Check if shuffle mask is legal?
+      if (LegalOperations && TLI.isOperationLegal(ISD::VECTOR_SHUFFLE, VecVT) &&
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arsenm wrote:

I started to, but the usage in the combiner seems inconsistent. Implementing it accurately results in regressions independently of this 

https://github.com/llvm/llvm-project/pull/123712