1/* Highly optimized version for i586.
2 Copyright (C) 1997-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20#include "asm-syntax.h"
21
22#define PARMS 4+8 /* space for 2 saved regs */
23#define RTN PARMS
24#define DEST RTN
25#define SRC DEST+4
26#define LEN SRC+4
27
28 .text
29#if defined PIC && IS_IN (libc)
30ENTRY (__memcpy_chk)
31 movl 12(%esp), %eax
32 cmpl %eax, 16(%esp)
33 jb HIDDEN_JUMPTARGET (__chk_fail)
34END (__memcpy_chk)
35libc_hidden_builtin_def (__memcpy_chk)
36#endif
37ENTRY (memcpy)
38
39 pushl %edi
40 cfi_adjust_cfa_offset (4)
41 pushl %esi
42 cfi_adjust_cfa_offset (4)
43
44 movl DEST(%esp), %edi
45 cfi_rel_offset (edi, 4)
46 movl SRC(%esp), %esi
47 cfi_rel_offset (esi, 0)
48 movl LEN(%esp), %ecx
49 movl %edi, %eax
50
51 /* We need this in any case. */
52 cld
53
54 /* Cutoff for the big loop is a size of 32 bytes since otherwise
55 the loop will never be entered. */
56 cmpl $32, %ecx
57 jbe L(1)
58
59 negl %eax
60 andl $3, %eax
61 subl %eax, %ecx
62 xchgl %eax, %ecx
63
64 rep; movsb
65
66 movl %eax, %ecx
67 subl $32, %ecx
68 js L(2)
69
70 /* Read ahead to make sure we write in the cache since the stupid
71 i586 designers haven't implemented read-on-write-miss. */
72 movl (%edi), %eax
73L(3): movl 28(%edi), %edx
74
75 /* Now correct the loop counter. Please note that in the following
76 code the flags are not changed anymore. */
77 subl $32, %ecx
78
79 movl (%esi), %eax
80 movl 4(%esi), %edx
81 movl %eax, (%edi)
82 movl %edx, 4(%edi)
83 movl 8(%esi), %eax
84 movl 12(%esi), %edx
85 movl %eax, 8(%edi)
86 movl %edx, 12(%edi)
87 movl 16(%esi), %eax
88 movl 20(%esi), %edx
89 movl %eax, 16(%edi)
90 movl %edx, 20(%edi)
91 movl 24(%esi), %eax
92 movl 28(%esi), %edx
93 movl %eax, 24(%edi)
94 movl %edx, 28(%edi)
95
96 leal 32(%esi), %esi
97 leal 32(%edi), %edi
98
99 jns L(3)
100
101 /* Correct extra loop counter modification. */
102L(2): addl $32, %ecx
103#ifndef USE_AS_MEMPCPY
104 movl DEST(%esp), %eax
105#endif
106
107L(1): rep; movsb
108
109#ifdef USE_AS_MEMPCPY
110 movl %edi, %eax
111#endif
112
113 popl %esi
114 cfi_adjust_cfa_offset (-4)
115 cfi_restore (esi)
116 popl %edi
117 cfi_adjust_cfa_offset (-4)
118 cfi_restore (edi)
119
120 ret
121END (memcpy)
122#ifndef USE_AS_MEMPCPY
123libc_hidden_builtin_def (memcpy)
124#endif
125

source code of glibc/sysdeps/i386/i586/memcpy.S