SSE/AVX: How does one convince rustc to recognize after enabling?

[kennystrawnmusic]

After taking to the OSDev wiki and from there figuring out how to set up SSE/AVX in my kernel programmatically, what else needs to be done in order to get crates that take advantage of such registers (like packed_simd_2 for example) to compile? Do I need to create a new custom target to tell Cargo to acknowledge that SSE/AVX are supported, and if so, how do I ensure that SSE and AVX are only used after initialization and not before if I do that? Also, if there's a way to enable artifact dependencies for such a custom target I'd like to know how, because the only alternative is hardcoding paths in my kernel's bootloader helper crate which is not ideal at all.

AVX in particular seems like the only way to effectively support compositing in kernel mode without the need to write a GPU driver from scratch first while still getting decent performance out of it, so that's why I'm trying to actually use SIMD immediately after setting it up. Yet, again, despite getting SIMD properly set up through the use of a combination of the x86_64 crate (SSE) and inline assembly (AVX), crates that take advantage of SIMD still won't compile — why?

[kennystrawnmusic]

Update: turns out there's a function attribute for this