[llvm] [ValueTracking] Compute knownbits from known fp classes (PR #86409)

[Matt Arsenault via llvm-commits]

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@@ -1121,6 +1121,40 @@ static void computeKnownBitsFromOperator(const Operator *I,
       break;
     }
 
+    Value *V;
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arsenm wrote:

```suggestion
    const Value *V;
```

https://github.com/llvm/llvm-project/pull/86409