From: Ammar Faizi <[email protected]>
To: David Laight <[email protected]>
Cc: "Willy Tarreau" <[email protected]>,
"Thomas Weißschuh" <[email protected]>,
"Nicholas Rosenberg" <[email protected]>,
"Alviro Iskandar Setiawan" <[email protected]>,
"Michael William Jonathan" <[email protected]>,
"GNU/Weeb Mailing List" <[email protected]>,
"Linux Kernel Mailing List" <[email protected]>
Subject: Re: [RFC PATCH v1 0/5] nolibc x86-64 string functions
Date: Fri, 1 Sep 2023 21:41:39 +0700 [thread overview]
Message-ID: <ZPH4I2W+zvhK93U/@biznet-home.integral.gnuweeb.org> (raw)
In-Reply-To: <[email protected]>
On Fri, Sep 01, 2023 at 02:23:28PM +0000, David Laight wrote:
> From: Ammar Faizi
> > Sent: 01 September 2023 14:06
...
> > __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.
What do you mean? They're all 64-bit pointers.
What I know is that the %rdx will be clobbered by "subq %rsi, %rdx"
below and the %rax should be return value. That's why I copy the %rdi
twice. memmove() returns the dst pointer. Did I miss something?
> > " 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.
Alright, I will avoid cld for the forward copy.
> > " 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
next prev parent reply other threads:[~2023-09-01 14:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 13:57 [RFC PATCH v1 0/5] nolibc x86-64 string functions Ammar Faizi
2023-08-30 13:57 ` [RFC PATCH v1 1/5] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()` Ammar Faizi
2023-08-30 13:57 ` [RFC PATCH v1 2/5] tools/nolibc: x86-64: Use `rep stosb` for `memset()` Ammar Faizi
2023-08-30 14:08 ` Alviro Iskandar Setiawan
2023-08-30 14:13 ` Ammar Faizi
2023-08-30 14:24 ` Alviro Iskandar Setiawan
2023-08-30 15:09 ` Ammar Faizi
2023-08-30 15:23 ` Willy Tarreau
2023-08-30 15:44 ` Ammar Faizi
2023-08-30 15:51 ` Willy Tarreau
2023-08-30 16:08 ` Ammar Faizi
2023-08-30 16:11 ` Alviro Iskandar Setiawan
2023-08-30 13:57 ` [RFC PATCH v1 3/5] tools/nolibc: x86-64: Use `rep cmpsb` for `memcmp()` Ammar Faizi
2023-08-30 21:26 ` Willy Tarreau
2023-09-01 3:24 ` Ammar Faizi
2023-09-01 3:35 ` Willy Tarreau
2023-09-01 7:27 ` Ammar Faizi
2023-09-04 8:26 ` David Laight
2023-08-30 13:57 ` [RFC PATCH v1 4/5] tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function Ammar Faizi
2023-08-30 21:27 ` Willy Tarreau
2023-08-30 13:57 ` [RFC PATCH v1 5/5] tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function Ammar Faizi
2023-08-30 21:32 ` [RFC PATCH v1 0/5] nolibc x86-64 string functions Willy Tarreau
2023-09-01 11:34 ` David Laight
2023-09-01 11:46 ` Willy Tarreau
2023-09-01 13:06 ` Ammar Faizi
2023-09-01 14:23 ` David Laight
2023-09-01 14:41 ` Ammar Faizi [this message]
2023-09-01 14:54 ` David Laight
2023-09-01 15:20 ` Ammar Faizi
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