Incorrect `f32::NAN as u64/u128` conversion

The code generated for black_box(f32::NAN) as u64/u128 converts it to some junk, but correct result is 0. This happens only with f32::NAN and only when converted to u64/u128. Conversion into i64/i128 works fine, as well as conversions intou8, i8, ... u32,i32.

[antoyo]

This is because gcc gives a negative NAN for 0.0 / 0.0.

Does Rust define that the sign of NAN should be positive?

Possibly relevant: rust-lang/rust#81261

[RalfJung]

rust-lang/rust#55131 also seems very relevant.