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
|
/* $NetBSD: strlen.S,v 1.1 2014/08/10 05:47:35 matt Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Matt Thomas of 3am Software Foundry.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/asm.h>
RCSID("$NetBSD: strlen.S,v 1.1 2014/08/10 05:47:35 matt Exp $")
#ifdef STRNLEN
#define FUNCNAME strnlen
/* LINTSTUB: size_t strnlen(const char *, size_t); */
#else
#define FUNCNAME strlen
/* LINTSTUB: size_t strlen(const char *); */
#endif
#define MASK8_0x01 0x0101010101010101
#define MASK8_0x7f 0x7f7f7f7f7f7f7f7f
ENTRY(FUNCNAME)
mov x4, x0 /* need x0 for return */
add x9, x0, #8 /* start + dword */
#ifdef STRNLEN
add x10, x0, x1 /* don't go past here */
#endif
mov x11, #MASK8_0x01 /* test mask */
ands x3, x4, #7 /* extract alignment */
neg x0, x3 /* alignment fixup */
b.eq .Lstrlen_dword_loop /* already dword aligned */
/*
* Load the dword containing the leading bytes. Make sure bytes
* before the data won't match as NUL.
*/
add x4, x4, x0 /* make dword aligned */
ldr x7, [x4], #8 /* load dword */
lsl x3, x3, #3 /* convert bytes to bits */
#ifdef __AARCH64EB__
lsr x5, x11, x3 /* make mask for BE */
#else
lsl x5, x11, x3 /* make mask for LE */
#endif
eor x5, x5, x11 /* invert mask */
orr x7, x7, x5 /* prevent NULs */
b .Lstrlen_dword_loop_noload
.Lstrlen_dword_loop:
#ifdef STRNLEN
cmp x4, x10
b.ge .Lstrlen_done
#endif
ldr x7, [x4], #8 /* load dword */
.Lstrlen_dword_loop_noload:
/*
* Use the formula (X - 1) & ~(X | 0x7f) to find NUL bytes.
* Any NUL byte found will be replaced by 0x80 otherwise any byte
* will be replaced by 0x00.
*/
sub x6, x7, x11 /* a = X - 1 */
orr x7, x7, #MASK8_0x7f /* b = X | 0x7f */
bic x6, x6, x7 /* a & ~b */
cbz x6, .Lstrlen_dword_loop /* no NULs so get next dword */
/*
* We know there is a NUL in this dword. Use clz to find it.
*/
#ifdef __AARCH64EL__
rev x7, x7 /* convert to BE */
#endif
clz x7, x7 /* find null byte */
add x0, x0, x7, lsr #3 /* add offset to the length */
add x0, x0, x4 /* add end to the length */
sub x0, x0, x9 /* subtract start from the length */
#ifdef STRNLEN
cmp x0, x1 /* did we go too far? */
csel x0, x0, x1, lt /* yes, return max length */
#endif
ret
#ifdef STRNLEN
.Lstrlen_done:
mov x0, x1
ret
#endif
END(FUNCNAME)
|
