[Pannoniae]

sadly inline assembly is still at the ergonomics of "one compiler doesn't support it in x64 mode" and "you can choose between the readable syntax (which is a black box to the compiler) and the unreadable syntax (which can specify I/O/clobber regs)"

[msla]

OK, is there a horrible speed penalty for writing your SIMD in pure assembly functions and then calling those functions? If you're writing assembly anyway, just drop the "inline" part.

[Pannoniae]

Sure, if you're willing to write a large enough chunk that you can eat the cost of not inlining it. If you just write a small leaf function or two, it will probably be a wash or perform worse.