The SIMD RFC nicely split the feature into three parts: types, operations, and feature detection. IIUC, the type types part is already implemented but using them results in “error: SIMD types are experimental and possibly buggy (see issue #27731)”.
In my crypto work, I already have SIMD-optimized implementations of basically every mainstream crypto primitive on every mainstream platform, written in external assembly language files (.s/.asm files). However, I don’t have a convenient and safe way of using all of them from Rust because Rust doesn’t provide a way of declaring struct members that are aligned to the platform’s SIMD requirements, and some of the functions require SIMD alignment.
It seems like it would be a while before all of the SIMD groundwork feature can be stabilized. However, it seems like
#repr(simd) is in good enough shape to stabilize, especially after https://github.com/rust-lang/rust/issues/26403 is resolved.
Would anybody object to an RFC that split out
#[repr(simd)] from the rest for stabilization?