[llvm] [ValueTracking] Implement `computeKnownFPClass` for `llvm.vector.reduce.{fmin,fmax,fmaximum,fminimum}` (PR #88408)

[Matt Arsenault via llvm-commits]

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@@ -5007,6 +5007,19 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
         Known.knownNot(fcNegZero);
 
       break;
+    }
+      // reduce min/max will choose an element from one of the vector elements,
+      // so we can infer and class information that is common to all elements.
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arsenm wrote:

Move comment inside the cases?

https://github.com/llvm/llvm-project/pull/88408