[llvm] APFloat: Fix signed zero handling in minnum/maxnum (PR #83376)

[via llvm-commits]

================
@@ -1397,6 +1397,8 @@ inline APFloat minnum(const APFloat &A, const APFloat &B) {
     return B;
   if (B.isNaN())
     return A;
+  if (A.isZero() && B.isZero() && (A.isNegative() != B.isNegative()))
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lntue wrote:

Will using:
```
if (A == B) return A.isNegative() ? A : B;
```
be a bit more efficient?

https://github.com/llvm/llvm-project/pull/83376