From the RFC: https://rust-lang.github.io/rfcs/2325-stable-simd.html

> The standard library will not deviate in naming or type signature of any intrinsic defined by an architecture.

I think this makes sense, just like any other intrinsic: unsafe to use directly, but with safe wrappers.

I believe that there are also some SIMD things that would have to inherently take raw pointers, as they work on pointers that aren't aligned, and/or otherwise not valid for references. In theory you could make only those take raw pointers, but I think the blanket policy of "follow upstream" is more important.

Which also doesn't preclude someone else writing an abstraction on top that provides an API using references.

Absolutely, that's important too, thanks.