pub use std::simd::Float;

[workingjubilee]

Closes #91422.

While consulting with @simulacrum on how to make available the float functions that currently require runtime support for Simd<f32, N> and Simd<f64, N>, we realized breaking coherence with the classic approach of lang items was, since {core,std}::simd::Simd is a ty::Adt, likely to be quite a bit nasty. The project group has a long-term plan for how to get around this kind of issue and move the associated functions into libcore, but that will likely take time as well. Since all routes forward are temporally costly, we probably will skip the lang item approach entirely and go the "proper" route, but in the interests of having something this year for people to play around with, this extension trait was whipped up.

For now, while it involves a lot of fairly internal details most users shouldn't have to care about, I went ahead and fully documented the situation for any passerby to read on the trait, as the situation is quite unusual and puzzling to begin with.

For further (and purely optional) reading, see:

• extern "platform-intrinsics" float functions often call libm portable-simd#76
• Create a Vector Math library to allow SimdF32::sin and similar to work in core portable-simd#109
• Tracking issue for f32 and f64 methods in libcore #50145
• Move sqrt from std to core #63455

[rust-highfive]

r? @joshtriplett

(rust-highfive has picked a reviewer for you, use r? to override)

[workingjubilee]

Superceded by #93146.