[llvm] [KnownFPClass] Add support for non-intrinsic math libcalls (PR #216234)

[Matt Arsenault via llvm-commits]

================
@@ -5767,6 +5767,49 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
         Known.knownNot(fcSubnormal);
       break;
     }
+    case Intrinsic::not_intrinsic: {
+      // Recognize the libcall directly for functions with no intrinsic
+      // equivalent. TLI validates the declaration's prototype and rejects calls
+      // marked 'nobuiltin'. Do not recognize locally-defined functions.
+      if (!Q.TLI)
+        break;
+      const Function *F = II->getCalledFunction();
+      if (!F || F->hasLocalLinkage())
----------------
arsenm wrote:

Make sure the !F case is tested, by using a mis-typed call site.

The linkage check seems off, but you probably can't do better right now. I would also expect the linkage check to be handled by TLI but I'd need to check if it actually does 

https://github.com/llvm/llvm-project/pull/216234