[llvm] DAG: Fix vector bin op scalarize defining a partially undef vector (PR #122459)

[Simon Pilgrim via llvm-commits]

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@@ -27525,23 +27525,25 @@ static SDValue scalarizeBinOpOfSplats(SDNode *N, SelectionDAG &DAG,
   if ((Opcode == ISD::MULHS || Opcode == ISD::MULHU) && !TLI.isTypeLegal(EltVT))
     return SDValue();
 
-  SDValue IndexC = DAG.getVectorIdxConstant(Index0, DL);
-  SDValue X = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, EltVT, Src0, IndexC);
-  SDValue Y = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, EltVT, Src1, IndexC);
-  SDValue ScalarBO = DAG.getNode(Opcode, DL, EltVT, X, Y, N->getFlags());
-
   // If all lanes but 1 are undefined, no need to splat the scalar result.
   // TODO: Keep track of undefs and use that info in the general case.
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RKSimon wrote:

We don't check for all-but-one undef lanes though anymore?

https://github.com/llvm/llvm-project/pull/122459