[llvm] [X86] SimplifyDemandedVectorEltsForTargetNode - reduce width of X86 conversions nodes when upper elements are not demanded. (PR #102882)

[Simon Pilgrim via llvm-commits]

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@@ -42518,6 +42518,25 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       SDValue Insert =
           insertSubVector(UndefVec, ExtOp, 0, TLO.DAG, DL, ExtSizeInBits);
       return TLO.CombineTo(Op, Insert);
+    }
+      // Conversions.
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RKSimon wrote:

Absolutely, I was thinking of adding them when I have test cases - but I can try to add them all now if you prefer?

https://github.com/llvm/llvm-project/pull/102882