1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
|
/* Set a block of memory to some byte value.
For Intel 80x86, x>=3.
Copyright (C) 1991-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Torbjorn Granlund (tege@sics.se).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <string.h>
#include <memcopy.h>
#ifdef __GNUC__
#undef memset
void *
memset (void *dstpp, int c, size_t len)
{
int d0;
unsigned long int dstp = (unsigned long int) dstpp;
/* This explicit register allocation
improves code very much indeed. */
register op_t x asm("ax");
x = (unsigned char) c;
/* Clear the direction flag, so filling will move forward. */
asm volatile("cld");
/* This threshold value is optimal. */
if (len >= 12)
{
/* Fill X with four copies of the char we want to fill with. */
x |= (x << 8);
x |= (x << 16);
/* Adjust LEN for the bytes handled in the first loop. */
len -= (-dstp) % OPSIZ;
/* There are at least some bytes to set.
No need to test for LEN == 0 in this alignment loop. */
/* Fill bytes until DSTP is aligned on a longword boundary. */
asm volatile("rep\n"
"stosb" /* %0, %2, %3 */ :
"=D" (dstp), "=c" (d0) :
"0" (dstp), "1" ((-dstp) % OPSIZ), "a" (x) :
"memory");
/* Fill longwords. */
asm volatile("rep\n"
"stosl" /* %0, %2, %3 */ :
"=D" (dstp), "=c" (d0) :
"0" (dstp), "1" (len / OPSIZ), "a" (x) :
"memory");
len %= OPSIZ;
}
/* Write the last few bytes. */
asm volatile("rep\n"
"stosb" /* %0, %2, %3 */ :
"=D" (dstp), "=c" (d0) :
"0" (dstp), "1" (len), "a" (x) :
"memory");
return dstpp;
}
libc_hidden_builtin_def (memset)
#else
#include <string/memset.c>
#endif
|
