[llvm] [SelectionDAGBuilder] Remove NoNaNsFPMath uses (PR #169904)

[Matt Arsenault via llvm-commits]

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@@ -8534,7 +8540,7 @@ void SelectionDAGBuilder::visitConstrainedFPIntrinsic(
   case ISD::STRICT_FSETCCS: {
     auto *FPCmp = dyn_cast<ConstrainedFPCmpIntrinsic>(&FPI);
     ISD::CondCode Condition = getFCmpCondCode(FPCmp->getPredicate());
-    if (TM.Options.NoNaNsFPMath)
+    if (DAG.isKnownNeverNaN(Opers[1]) && DAG.isKnownNeverNaN(Opers[2]))
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arsenm wrote:

Transformations like this should stick to checking flags only. Adding new isKnownNeverNaN checks is a step beyond 

https://github.com/llvm/llvm-project/pull/169904