From: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
To: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Cc: "Willy Tarreau" <w@1wt.eu>,
"Thomas Weißschuh" <linux@weissschuh.net>,
"Nicholas Rosenberg" <inori@vnlx.org>,
"Michael William Jonathan" <moe@gnuweeb.org>,
"GNU/Weeb Mailing List" <gwml@vger.gnuweeb.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v1 2/5] tools/nolibc: x86-64: Use `rep stosb` for `memset()`
Date: Wed, 30 Aug 2023 21:24:45 +0700 [thread overview]
Message-ID: <CAOG64qNGdPjXHTvrpYxjizOYvMRaB9_2t2raw6DJ3kK852KUHg@mail.gmail.com> (raw)
In-Reply-To: <20230830135726.1939997-3-ammarfaizi2@gnuweeb.org>
On Wed, Aug 30, 2023 at 8:57 PM Ammar Faizi wrote:
> 00000000000010b1 <memset>:
> 10b1: 48 89 f0 mov %rsi,%rax
> 10b4: 48 89 d1 mov %rdx,%rcx
> 10b7: 48 89 fa mov %rdi,%rdx
> 10ba: f3 aa rep stos %al,%es:(%rdi)
> 10bc: 48 89 d0 mov %rdx,%rax
> 10bf: c3 ret
Just a small idea to shrink this more, "mov %rdi, %rdx" and "mov %rdx,
%rax" can be replaced with "push %rdi" and "pop %rax" (they are just a
byte). So we can save 4 bytes more.
0000000000001500 <memset>:
1500: 48 89 f0 mov %rsi,%rax
1503: 48 89 d1 mov %rdx,%rcx
1506: 57 push %rdi
1507: f3 aa rep stos %al,%es:(%rdi)
1509: 58 pop %rax
150a: c3 ret
But I know you don't like it because it costs extra memory access.
-- Viro
next prev parent reply other threads:[~2023-08-30 14:24 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 [this message]
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
2023-09-01 14:54 ` David Laight
2023-09-01 15:20 ` Ammar Faizi
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