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
|
/* Optimized strchr implementation for PowerPC.
Copyright (C) 1997-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 <sysdep.h>
/* See strlen.s for comments on how this works. */
/* char * [r3] strchr (const char *s [r3] , int c [r4] ) */
ENTRY (strchr)
#define rTMP1 r0
#define rRTN r3 /* outgoing result */
#define rSTR r8 /* current word pointer */
#define rCHR r4 /* byte we're looking for, spread over the whole word */
#define rWORD r5 /* the current word */
#define rCLZB rCHR /* leading zero byte count */
#define rFEFE r6 /* constant 0xfefefeff (-0x01010101) */
#define r7F7F r7 /* constant 0x7f7f7f7f */
#define rTMP2 r9
#define rIGN r10 /* number of bits we should ignore in the first word */
#define rMASK r11 /* mask with the bits to ignore set to 0 */
#define rTMP3 r12
#define rTMP4 rIGN
#define rTMP5 rMASK
rlwimi rCHR, rCHR, 8, 16, 23
li rMASK, -1
rlwimi rCHR, rCHR, 16, 0, 15
rlwinm rIGN, rRTN, 3, 27, 28
lis rFEFE, -0x101
lis r7F7F, 0x7f7f
clrrwi rSTR, rRTN, 2
addi rFEFE, rFEFE, -0x101
addi r7F7F, r7F7F, 0x7f7f
/* Test the first (partial?) word. */
lwz rWORD, 0(rSTR)
#ifdef __LITTLE_ENDIAN__
slw rMASK, rMASK, rIGN
#else
srw rMASK, rMASK, rIGN
#endif
orc rWORD, rWORD, rMASK
add rTMP1, rFEFE, rWORD
nor rTMP2, r7F7F, rWORD
and. rTMP4, rTMP1, rTMP2
xor rTMP3, rCHR, rWORD
orc rTMP3, rTMP3, rMASK
b L(loopentry)
/* The loop. */
L(loop):
lwzu rWORD, 4(rSTR)
and. rTMP5, rTMP1, rTMP2
/* Test for 0. */
add rTMP1, rFEFE, rWORD /* x - 0x01010101. */
nor rTMP2, r7F7F, rWORD /* ~(x | 0x7f7f7f7f) == ~x & 0x80808080. */
bne L(foundit)
and. rTMP4, rTMP1, rTMP2 /* (x - 0x01010101) & ~x & 0x80808080. */
/* Start test for the bytes we're looking for. */
xor rTMP3, rCHR, rWORD
L(loopentry):
add rTMP1, rFEFE, rTMP3
nor rTMP2, r7F7F, rTMP3
beq L(loop)
/* There is a zero byte in the word, but may also be a matching byte (either
before or after the zero byte). In fact, we may be looking for a
zero byte, in which case we return a match. */
and. rTMP5, rTMP1, rTMP2
li rRTN, 0
beqlr
/* At this point:
rTMP5 bytes are 0x80 for each match of c, 0 otherwise.
rTMP4 bytes are 0x80 for each match of 0, 0 otherwise.
But there may be false matches in the next most significant byte from
a true match due to carries. This means we need to recalculate the
matches using a longer method for big-endian. */
#ifdef __LITTLE_ENDIAN__
addi rTMP1, rTMP5, -1
andc rTMP1, rTMP1, rTMP5
cntlzw rCLZB, rTMP1
addi rTMP2, rTMP4, -1
andc rTMP2, rTMP2, rTMP4
cmplw rTMP1, rTMP2
bgtlr
subfic rCLZB, rCLZB, 32-7
#else
/* I think we could reduce this by two instructions by keeping the "nor"
results from the loop for reuse here. See strlen.S tail. Similarly
one instruction could be pruned from L(foundit). */
and rFEFE, r7F7F, rWORD
or rTMP5, r7F7F, rWORD
and rTMP1, r7F7F, rTMP3
or rTMP4, r7F7F, rTMP3
add rFEFE, rFEFE, r7F7F
add rTMP1, rTMP1, r7F7F
nor rWORD, rTMP5, rFEFE
nor rTMP2, rTMP4, rTMP1
cntlzw rCLZB, rTMP2
cmplw rWORD, rTMP2
bgtlr
#endif
srwi rCLZB, rCLZB, 3
add rRTN, rSTR, rCLZB
blr
L(foundit):
#ifdef __LITTLE_ENDIAN__
addi rTMP1, rTMP5, -1
andc rTMP1, rTMP1, rTMP5
cntlzw rCLZB, rTMP1
subfic rCLZB, rCLZB, 32-7-32
srawi rCLZB, rCLZB, 3
#else
and rTMP1, r7F7F, rTMP3
or rTMP4, r7F7F, rTMP3
add rTMP1, rTMP1, r7F7F
nor rTMP2, rTMP4, rTMP1
cntlzw rCLZB, rTMP2
subi rSTR, rSTR, 4
srwi rCLZB, rCLZB, 3
#endif
add rRTN, rSTR, rCLZB
blr
END (strchr)
weak_alias (strchr, index)
libc_hidden_builtin_def (strchr)
|
