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
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.file "memset.s"
/*
* memset(sp, c, n)
*
* Set an array of n chars starting at sp to the character c.
* Return sp.
*
* Fast assembler language version of the following C-program for memset
* which represents the `standard' for the C-library.
*
* void *
* memset(void *sp1, int c, size_t n)
* {
* if (n != 0) {
* char *sp = sp1;
* do {
* *sp++ = (char)c;
* } while (--n != 0);
* }
* return (sp1);
* }
*
*
*
* Algorithm used:
* For small stores (6 or fewer bytes), bytes will be stored one at a time.
*
* When setting 15 or more bytes, there will be at least 8 bytes aligned
* on an 8-byte boundary. So, leading bytes will be set, then as many
* 8-byte aligned chunks as possible will be set, followed by any trailing
* bytes.
*
* For between 8 and 14 bytes (inclusive), leading odd bytes will be
* set, followed by 4-byte chunks, followed by trailing bytes.
*
* Inputs:
* o0: pointer to start of area to be set to a given value
* o1: character used to set memory at location in i0
* o2: number of bytes to be set
*
* Outputs:
* o0: pointer to start of area set (same as input value in o0)
*
*/
#include <sys/asm_linkage.h>
ANSI_PRAGMA_WEAK(memset,function)
ENTRY(memset)
mov %o0, %o5 ! need to return this value
cmp %o2, 7
blu,pn %xcc, .wrchar ! small count: just set bytes
and %o1, 0xff, %o1
sll %o1, 8, %o4 ! generate 4 bytes filled with char
or %o1, %o4, %o1
sll %o1, 16, %o4
cmp %o2, 15
blu,pn %xcc, .walign ! not enough to guarantee 8-byte align
or %o1, %o4, %o1
sllx %o1, 32, %o4 ! now fill the other 4 bytes with char
or %o1, %o4, %o1
.dalign: ! Set bytes until 8-byte aligned
btst 7, %o5 ! 8-byte aligned?
bz,a,pn %icc, .wrdbl
andn %o2, 7, %o3 ! o3 has 8-byte multiple
dec %o2
stb %o1, [%o5] ! clear a byte
b .dalign ! go see if aligned yet
inc %o5
.align 32
.wrdbl:
stx %o1, [%o5] ! write aligned 8 bytes
subcc %o3, 8, %o3
bnz,pt %xcc, .wrdbl
inc 8, %o5
b .wrchar ! write the remaining bytes
and %o2, 7, %o2 ! leftover count, if any
.walign: ! Set bytes until 4-byte aligned
btst 3, %o5 ! if bigger, align to 4 bytes
bz,pn %icc, .wrword
andn %o2, 3, %o3 ! create word sized count in %o3
dec %o2 ! decrement count
stb %o1, [%o5] ! clear a byte
b .walign
inc %o5 ! next byte
.wrword:
st %o1, [%o5] ! 4-byte writing loop
subcc %o3, 4, %o3
bnz,pn %xcc, .wrword
inc 4, %o5
and %o2, 3, %o2 ! leftover count, if any
.wrchar:
deccc %o2 ! byte clearing loop
inc %o5
bgeu,a,pt %xcc, .wrchar
stb %o1, [%o5 + -1] ! we've already incremented the address
retl
sub %o0, %g0, %o0
SET_SIZE(memset)
|
