Messages in this thread | | | Date | Sat, 2 Sep 2023 08:22:37 +0200 | From | Willy Tarreau <> | Subject | Re: [RFC PATCH v2 1/4] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()` |
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On Sat, Sep 02, 2023 at 01:11:06PM +0700, Ammar Faizi wrote: > On Sat, Sep 02, 2023 at 01:07:50PM +0700, Alviro Iskandar Setiawan wrote: > > Btw, sir, this can be simplified more by merging the forward copy > > path, only using two "rep movsb" for both memmove() and memcpy() > > should be enough? > > ``` > > __asm__ ( > > ".section .text.nolibc_memmove_memcpy\n" > > ".weak memmove\n" > > ".weak memcpy\n" > > "memmove:\n" > > "movq %rdx, %rcx\n" > > "movq %rdi, %rdx\n" > > "movq %rdi, %rax\n" > > "subq %rsi, %rdx\n" > > "cmpq %rcx, %rdx\n" > > "jnb __nolibc_forward_copy\n" > > "leaq -1(%rdi, %rcx, 1), %rdi\n" > > "leaq -1(%rsi, %rcx, 1), %rsi\n" > > "std\n" > > "rep movsb\n" > > "cld\n" > > "retq\n" > > > > "memcpy:\n" > > "movq %rdi, %rax\n" > > "movq %rdx, %rcx\n" > > "__nolibc_forward_copy:\n" > > "rep movsb\n" > > "retq\n" > > ); > > ``` > > Looks good. I'll apply that change.
Note that in this case we simply don't need a special version of memcpy(), memmove() is always OK for this, so you can simplify this further by starting with:
memcpy: memmove: ...
Willy
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