[llvm] APFloat: Add minimumnum and maximumnum (PR #96304)

[YunQiang Su via llvm-commits]

================
@@ -1496,6 +1509,19 @@ inline APFloat maximum(const APFloat &A, const APFloat &B) {
   return A < B ? B : A;
 }
 
+/// Implements IEEE 754-2019 maximumNumber semantics. Returns the larger
+/// of 2 arguments, not propagating NaNs and treating -0 as less than +0.
+LLVM_READONLY
+inline APFloat maximumnum(const APFloat &A, const APFloat &B) {
+  if (A.isNaN())
+    return B.isNaN() ? B.makeQuiet() : B;
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wzssyqa wrote:

No. in `lib/Support/APFloat.cpp`,
```
void IEEEFloat::makeQuiet() {
  assert(isNaN());
  if (semantics->nonFiniteBehavior != fltNonfiniteBehavior::NanOnly)
    APInt::tcSetBit(significandParts(), semantics->precision - 2);
} 
```

It means that, only NaN is supported by `makeQuiet `.

https://github.com/llvm/llvm-project/pull/96304