From: Ammar Faizi
> Sent: 01 September 2023 14:06
...
> > You're completely right indeed, reminds me about the copy_up/copy_down
> > that were not used anymore :-)
>
> I'm an idiot, will fix that. Another attempt as suggested below:
>
> __asm__ (
> ".section .text.nolibc_memmove\n"
> ".weak memmove\n"
> "memmove:\n"
> " movq %rdx, %rcx\n"
> " movq %rdi, %rdx\n"
> " movq %rdi, %rax\n"
You seem to have confused yourself about whether you are using %eax or %edx.
> " subq %rsi, %rdx\n"
> " cmpq %rcx, %rdx\n"
> " jnb .Lforward_copy\n"
I think I'd fall through to the forwards copy
and not worry about replicating the 'reps movsb' and 'ret'.
IIRC 'cld' can be slow as well.
> " leaq -1(%rdi, %rcx, 1), %rdi\n"
> " leaq -1(%rsi, %rcx, 1), %rsi\n"
> " std\n"
> ".Lforward_copy:\n"
> " rep movsb\n"
> " cld\n"
> " ret\n"
> );
>
> --
> Ammar Faizi
David
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