[PATCH] msvcrt: Import memmove from musl

[Piotr Caban]

On 8/26/20 5:19 PM, Gabriel Ivăncescu wrote:
> Also, sorry I forgot to mention a small thing, is there a reason you're 
> using movdq(a|u) instead of movaps/movups (which are also SSE1 not 
> SSE2)? They have smaller encoding and should very slightly help with the 
> instruction cache, and no CPU cares about floating vs int states when 
> doing only moves. (even if it did, most operations on SSE tend to be for 
> floats anyway, assuming some broken CPU has some false dependency on 
> them, but I doubt it)
I was considering adding a "fast path" that uses movntdq for large 
moves. It generally speeds things up if whole dest buffer doesn't fit 
into cache. The movntdq has no SSE1 equivalent and I didn't want to mix 
SSE1 and SSE2 instructions (I was also planning to guard this code with 
sse2_enabled variable so it will not run on non-SSE2 capable hardware 
(see _set_SSE2_enable function)).

I'm still not sure how the final implementation will look like. Maybe it 
will make sense to use movaps instead.

Thanks,
Piotr