[Bug middle-end/70140] Inefficient expansion of __builtin_mempcpy

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70140

--- Comment #7 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #6)
> Created attachment 41772 [details]
> Patch candidate
> 
> I'm going to prepare some test-cases for that. Does it look good?

Yes, it now inlines small constant sizes. However large and variable sized
copies have the wrong return value:

void *f1(void *p, void *q) { return __builtin_mempcpy(p, q, 256); }

f1:
        mov     x2, 256
        b       memcpy