[llvm] [Verifier] Verify attribute `denormal-fp-math[-f32]` (PR #112310)

[Matt Arsenault via llvm-commits]

================
@@ -2401,6 +2401,25 @@ void Verifier::verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
     if (!Info)
       CheckFailed("invalid name for a VFABI variant: " + S, V);
   }
+
+  auto IsValidDenormalMode = [](StringRef S) {
+    DenormalMode Denormals = parseDenormalFPAttribute(S);
+    return Denormals.Input != DenormalMode::Invalid &&
+           Denormals.Output != DenormalMode::Invalid;
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arsenm wrote:

```suggestion
    return Denormals.isValid();
```

https://github.com/llvm/llvm-project/pull/112310