[llvm] [ValueTracking] Fix assertion failure when `computeKnownFPClass` returns fcNone (PR #92355)

[Matt Arsenault via llvm-commits]

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@@ -1126,7 +1126,8 @@ static void computeKnownBitsFromOperator(const Operator *I,
       KnownFPClass Result = computeKnownFPClass(V, fcAllFlags, Depth + 1, Q);
       FPClassTest FPClasses = Result.KnownFPClasses;
 
-      if (Result.isKnownNever(fcNormal | fcSubnormal | fcNan)) {
+      if (FPClasses != fcNone &&
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arsenm wrote:

Can we just assume the none case is a 0? 

https://github.com/llvm/llvm-project/pull/92355