Feature gate: #![feature(stdarch_const_x86)]

This is a tracking issue for unstable const versions of x86(64) intrinsics in stdarch.

Public API

~50% of x86(64) intrinsics in stdarch are amenable to constification. Intel has some weird pecularities in floating point, especially in comparison and conversion, which will be nontrivial to constify. Most integer intrinsics have been constified, with the exception of intrinsics that use saturating operations - LLVM generic saturation support is not great

Steps / History

• Implementation: Make X86 intrinsics const stdarch#1925
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• There are a few very specialized float intrinsics (mostly in AVX512), do we want to constify them?

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩