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Message-Id: <20230830135726.1939997-1-ammarfaizi2@gnuweeb.org>
Date: Wed, 30 Aug 2023 20:57:21 +0700
From: Ammar Faizi <ammarfaizi2@...weeb.org>
To: Willy Tarreau <w@....eu>,
Thomas Weißschuh <linux@...ssschuh.net>
Cc: Ammar Faizi <ammarfaizi2@...weeb.org>,
Nicholas Rosenberg <inori@...x.org>,
Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>,
Michael William Jonathan <moe@...weeb.org>,
GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH v1 0/5] nolibc x86-64 string functions
Hi Willy,
This is an RFC patchset for nolibc x86-64 string functions. There are 5
patches in this series.
## Patch 1-3: Use `rep movsb`, `rep stosb`, and `rep cmpsb` for:
- memcpy() and memmove()
- memset()
- memcmp()
respectively. They can simplify the generated ASM code.
Patch 4 and 5 are not related, just a small cleanup.
## Patch 4: Remove the `_nolibc_memcpy_down()` function
This nolibc internal function is not used. Delete it. It was probably
supposed to handle memmove(), but today the memmove() has its own
implementation.
## Patch 5: Remove the `_nolibc_memcpy_up()` function
This function is only called by memcpy(), there is no real reason to
have this wrapper. Delete this function and move the code to memcpy()
directly.
Before this series:
```
0000000000001479 <memmove>:
1479: f3 0f 1e fa endbr64
147d: 48 39 f7 cmp %rsi,%rdi
1480: 48 c7 c1 ff ff ff ff mov $0xffffffffffffffff,%rcx
1487: 48 89 f8 mov %rdi,%rax
148a: 48 0f 43 ca cmovae %rdx,%rcx
148e: 48 19 ff sbb %rdi,%rdi
1491: 83 e7 02 and $0x2,%edi
1494: 48 ff cf dec %rdi
1497: 48 85 d2 test %rdx,%rdx
149a: 74 10 je 14ac <memmove+0x33>
149c: 48 01 f9 add %rdi,%rcx
149f: 48 ff ca dec %rdx
14a2: 44 8a 04 0e mov (%rsi,%rcx,1),%r8b
14a6: 44 88 04 08 mov %r8b,(%rax,%rcx,1)
14aa: eb eb jmp 1497 <memmove+0x1e>
14ac: c3 ret
00000000000014ad <memcpy>:
14ad: f3 0f 1e fa endbr64
14b1: 48 89 f8 mov %rdi,%rax
14b4: 31 c9 xor %ecx,%ecx
14b6: 48 39 ca cmp %rcx,%rdx
14b9: 74 0d je 14c8 <memcpy+0x1b>
14bb: 40 8a 3c 0e mov (%rsi,%rcx,1),%dil
14bf: 40 88 3c 08 mov %dil,(%rax,%rcx,1)
14c3: 48 ff c1 inc %rcx
14c6: eb ee jmp 14b6 <memcpy+0x9>
14c8: c3 ret
00000000000014c9 <memset>:
14c9: f3 0f 1e fa endbr64
14cd: 48 89 f8 mov %rdi,%rax
14d0: 31 c9 xor %ecx,%ecx
14d2: 48 39 ca cmp %rcx,%rdx
14d5: 74 09 je 14e0 <memset+0x17>
14d7: 40 88 34 08 mov %sil,(%rax,%rcx,1)
14db: 48 ff c1 inc %rcx
14de: eb f2 jmp 14d2 <memset+0x9>
14e0: c3 ret
```
After this series:
```
000000000000140a <memmove>:
140a: 48 89 f8 mov %rdi,%rax
140d: 48 89 d1 mov %rdx,%rcx
1410: 48 8d 7c 0f ff lea -0x1(%rdi,%rcx,1),%rdi
1415: 48 8d 74 0e ff lea -0x1(%rsi,%rcx,1),%rsi
141a: fd std
141b: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi)
141d: fc cld
141e: c3 ret
000000000000141f <memcpy>:
141f: 48 89 f8 mov %rdi,%rax
1422: 48 89 d1 mov %rdx,%rcx
1425: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi)
1427: c3 ret
0000000000001428 <memset>:
1428: 48 89 f0 mov %rsi,%rax
142b: 48 89 d1 mov %rdx,%rcx
142e: 48 89 fa mov %rdi,%rdx
1431: f3 aa rep stos %al,%es:(%rdi)
1433: 48 89 d0 mov %rdx,%rax
1436: c3 ret
```
Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
---
Ammar Faizi (5):
tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()`
tools/nolibc: x86-64: Use `rep stosb` for `memset()`
tools/nolibc: x86-64: Use `rep cmpsb` for `memcmp()`
tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function
tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function
tools/include/nolibc/arch-x86_64.h | 60 ++++++++++++++++++++++++++++++
tools/include/nolibc/string.h | 38 ++++++++-----------
2 files changed, 75 insertions(+), 23 deletions(-)
base-commit: 3c9b7c4a228bf8cca2f92abb65575cdd54065302
--
Ammar Faizi
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