From: Willy Tarreau <[email protected]>
To: Ammar Faizi <[email protected]>
Cc: "Alviro Iskandar Setiawan" <[email protected]>,
"Thomas Weißschuh" <[email protected]>,
"David Laight" <[email protected]>,
"Nicholas Rosenberg" <[email protected]>,
"Michael William Jonathan" <[email protected]>,
"GNU/Weeb Mailing List" <[email protected]>,
"Linux Kernel Mailing List" <[email protected]>
Subject: Re: [RFC PATCH v2 1/4] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()`
Date: Sat, 2 Sep 2023 08:22:37 +0200 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <ZPLR+mO/6/[email protected]>
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
next prev parent reply other threads:[~2023-09-02 6:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-02 5:50 [RFC PATCH v2 0/4] nolibc x86-64 string functions Ammar Faizi
2023-09-02 5:50 ` [RFC PATCH v2 1/4] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()` Ammar Faizi
2023-09-02 6:07 ` Alviro Iskandar Setiawan
2023-09-02 6:11 ` Ammar Faizi
2023-09-02 6:22 ` Willy Tarreau [this message]
2023-09-02 6:37 ` Ammar Faizi
2023-09-02 12:29 ` Alviro Iskandar Setiawan
2023-09-02 12:36 ` Ammar Faizi
2023-09-03 20:35 ` David Laight
2023-09-02 5:50 ` [RFC PATCH v2 2/4] tools/nolibc: x86-64: Use `rep stosb` for `memset()` Ammar Faizi
2023-09-02 5:50 ` [RFC PATCH v2 3/4] tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function Ammar Faizi
2023-09-02 5:50 ` [RFC PATCH v2 4/4] tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function Ammar Faizi
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