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
141
142
143
144
145
146
147
148
|
/*
* arch/xtensa/lib/strnlen_user.S
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file "COPYING" in the main directory of
* this archive for more details.
*
* Returns strnlen, including trailing zero terminator.
* Zero indicates error.
*
* Copyright (C) 2002 Tensilica Inc.
*/
#include <variant/core.h>
/* Load or store instructions that may cause exceptions use the EX macro. */
#define EX(insn,reg1,reg2,offset,handler) \
9: insn reg1, reg2, offset; \
.section __ex_table, "a"; \
.word 9b, handler; \
.previous
/*
* size_t __strnlen_user(const char *s, size_t len)
*/
#ifdef __XTENSA_EB__
# define MASK0 0xff000000
# define MASK1 0x00ff0000
# define MASK2 0x0000ff00
# define MASK3 0x000000ff
#else
# define MASK0 0x000000ff
# define MASK1 0x0000ff00
# define MASK2 0x00ff0000
# define MASK3 0xff000000
#endif
# Register use:
# a2/ src
# a3/ len
# a4/ tmp
# a5/ mask0
# a6/ mask1
# a7/ mask2
# a8/ mask3
# a9/ tmp
# a10/ tmp
.text
.align 4
.global __strnlen_user
.type __strnlen_user,@function
__strnlen_user:
entry sp, 16 # minimal stack frame
# a2/ s, a3/ len
addi a4, a2, -4 # because we overincrement at the end;
# we compensate with load offsets of 4
movi a5, MASK0 # mask for byte 0
movi a6, MASK1 # mask for byte 1
movi a7, MASK2 # mask for byte 2
movi a8, MASK3 # mask for byte 3
bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned
bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned
/*
* String is word-aligned.
*/
.Laligned:
srli a10, a3, 2 # number of loop iterations with 4B per loop
#if XCHAL_HAVE_LOOPS
loopnez a10, .Ldone
#else
beqz a10, .Ldone
slli a10, a10, 2
add a10, a10, a4 # a10 = end of last 4B chunk
#endif /* XCHAL_HAVE_LOOPS */
.Loop:
EX(l32i, a9, a4, 4, lenfixup) # get next word of string
addi a4, a4, 4 # advance string pointer
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
bnone a9, a7, .Lz2 # if byte 2 is zero
bnone a9, a8, .Lz3 # if byte 3 is zero
#if !XCHAL_HAVE_LOOPS
blt a4, a10, .Loop
#endif
.Ldone:
EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks
bbci.l a3, 1, .L100
# check two more bytes (bytes 0, 1 of word)
addi a4, a4, 2 # advance string pointer
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
.L100:
bbci.l a3, 0, .L101
# check one more byte (byte 2 of word)
# Actually, we don't need to check. Zero or nonzero, we'll add one.
# Do not add an extra one for the NULL terminator since we have
# exhausted the original len parameter.
addi a4, a4, 1 # advance string pointer
.L101:
sub a2, a4, a2 # compute length
retw
# NOTE that in several places below, we point to the byte just after
# the zero byte in order to include the NULL terminator in the count.
.Lz3: # byte 3 is zero
addi a4, a4, 3 # point to zero byte
.Lz0: # byte 0 is zero
addi a4, a4, 1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.Lz1: # byte 1 is zero
addi a4, a4, 1+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.Lz2: # byte 2 is zero
addi a4, a4, 2+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.L1mod2: # address is odd
EX(l8ui, a9, a4, 4, lenfixup) # get byte 0
addi a4, a4, 1 # advance string pointer
beqz a9, .Lz3 # if byte 0 is zero
bbci.l a4, 1, .Laligned # if string pointer is now word-aligned
.L2mod4: # address is 2 mod 4
addi a4, a4, 2 # advance ptr for aligned access
EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string
bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero
bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero
# byte 3 is zero
addi a4, a4, 3+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.section .fixup, "ax"
.align 4
lenfixup:
movi a2, 0
retw
|
