[llvm] [SLP]Fix perfect diamond match with extractelements in scalars (PR #132466)

[Simon Pilgrim via llvm-commits]

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@@ -5339,8 +5338,19 @@ static InstructionCost getScalarizationOverhead(const TargetTransformInfo &TTI,
     }
     return Cost;
   }
-  return TTI.getScalarizationOverhead(Ty, DemandedElts, Insert, Extract,
-                                      CostKind, VL);
+  APInt NewDemandedElts = DemandedElts;
+  InstructionCost Cost = 0;
+  if (!ForPoisonSrc && Insert) {
+    // Handle insert into non-poison vector.
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RKSimon wrote:

OK - add a TODO comment for now please

https://github.com/llvm/llvm-project/pull/132466