[llvm] [SelectionDAG] Handle more opcodes in canCreateUndefOrPoison (PR #84921)

[Craig Topper via llvm-commits]

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@@ -5091,8 +5101,18 @@ bool SelectionDAG::canCreateUndefOrPoison(SDValue Op, const APInt &DemandedElts,
   case ISD::BITCAST:
   case ISD::BUILD_VECTOR:
   case ISD::BUILD_PAIR:
+  case ISD::SELECT:
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topperc wrote:

Do we need to worry about Fast math flags on SELECT?

https://github.com/llvm/llvm-project/pull/84921