[llvm] [DAG] Fold freeze(shuffle(x,y,m)) -> shuffle(freeze(x),freeze(y),m) (PR #90952)

[Simon Pilgrim via llvm-commits]

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@@ -15533,8 +15534,16 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
     if (Op.getOpcode() == ISD::UNDEF)
       Op = DAG.getFreeze(Op);
   }
-  // NOTE: this strips poison generating flags.
-  SDValue R = DAG.getNode(N0.getOpcode(), SDLoc(N0), N0->getVTList(), Ops);
+
+  SDValue R;
+  if (auto *SVN = dyn_cast<ShuffleVectorSDNode>(N0)) {
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RKSimon wrote:

ShuffleVectorSDNode embeds the mask in the node itself - its not an operand

https://github.com/llvm/llvm-project/pull/90952