[llvm] [DAG] isSplatValue - only accept binop splats if they share all the same demanded undef elements (PR #135597)

[Nikita Popov via llvm-commits]

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@@ -3002,9 +3002,12 @@ bool SelectionDAG::isSplatValue(SDValue V, const APInt &DemandedElts,
     APInt UndefLHS, UndefRHS;
     SDValue LHS = V.getOperand(0);
     SDValue RHS = V.getOperand(1);
+    // Ensure common demanded undef elts for both operands, otherwise we might
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nikic wrote:

```suggestion
    // Only propagate common undef elts for both operands, otherwise we might
```
maybe?

https://github.com/llvm/llvm-project/pull/135597