From: Ammar Faizi <[email protected]>
To: Willy Tarreau <[email protected]>
Cc: "Alviro Iskandar Setiawan" <[email protected]>,
"Thomas Weißschuh" <[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 v1 2/5] tools/nolibc: x86-64: Use `rep stosb` for `memset()`
Date: Wed, 30 Aug 2023 22:44:53 +0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On Wed, Aug 30, 2023 at 05:23:22PM +0200, Willy Tarreau wrote:
> Then "xchg %esi, %eax" is just one byte with no memory access ;-)
Perfect!
Now I got this, shorter than "movl %esi, %eax":
```
0000000000001500 <memset>:
1500: 96 xchg %eax,%esi
1501: 48 89 d1 mov %rdx,%rcx
1504: 57 push %rdi
1505: f3 aa rep stos %al,%es:(%rdi)
1507: 58 pop %rax
1508: c3 ret
```
Unfortunately, the xchg trick doesn't yield smaller machine code for
%rdx, %rcx. Lol.
--
Ammar Faizi
next prev parent reply other threads:[~2023-08-30 15:44 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 [this message]
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
2023-09-01 14:54 ` David Laight
2023-09-01 15:20 ` Ammar Faizi
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