[llvm] [DAGCombiner] Add combine for vector interleave of splats (PR #151110)

[David Sherwood via llvm-commits]

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@@ -25397,6 +25429,9 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
     return DAG.getBuildVector(VT, SDLoc(N), Opnds);
   }
 
+  if (SDValue V = combineConcatVectorInterleave(N, DAG))
+    return V;
+
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david-arm wrote:

OK, I've tried the suggestion of doing the combine on the VECTOR_INTERLEAVE only, but it also required adding a separate combine for concat_vector(splat, splat, ...).

https://github.com/llvm/llvm-project/pull/151110