1/* Optimized strchr implementation for PowerPC64.
2 Copyright (C) 1997-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20
21/* See strlen.s for comments on how this works. */
22
23/* char * [r3] strchr (const char *s [r3] , int c [r4] ) */
24
25#ifndef STRCHR
26# define STRCHR strchr
27#endif
28
29ENTRY_TOCLESS (STRCHR)
30 CALL_MCOUNT 2
31
32#define rTMP1 r0
33#define rRTN r3 /* outgoing result */
34#define rSTR r8 /* current word pointer */
35#define rCHR r4 /* byte we're looking for, spread over the whole word */
36#define rWORD r5 /* the current word */
37#define rCLZB rCHR /* leading zero byte count */
38#define rFEFE r6 /* constant 0xfefefefefefefeff (-0x0101010101010101) */
39#define r7F7F r7 /* constant 0x7f7f7f7f7f7f7f7f */
40#define rTMP2 r9
41#define rIGN r10 /* number of bits we should ignore in the first word */
42#define rMASK r11 /* mask with the bits to ignore set to 0 */
43#define rTMP3 r12
44#define rTMP4 rIGN
45#define rTMP5 rMASK
46
47 dcbt 0,rRTN
48 insrdi rCHR, rCHR, 8, 48
49 li rMASK, -1
50 insrdi rCHR, rCHR, 16, 32
51 rlwinm rIGN, rRTN, 3, 26, 28
52 insrdi rCHR, rCHR, 32, 0
53 lis rFEFE, -0x101
54 lis r7F7F, 0x7f7f
55 clrrdi rSTR, rRTN, 3
56 addi rFEFE, rFEFE, -0x101
57 addi r7F7F, r7F7F, 0x7f7f
58 sldi rTMP1, rFEFE, 32
59 insrdi r7F7F, r7F7F, 32, 0
60 add rFEFE, rFEFE, rTMP1
61/* Test the first (partial?) word. */
62 ld rWORD, 0(rSTR)
63#ifdef __LITTLE_ENDIAN__
64 sld rMASK, rMASK, rIGN
65#else
66 srd rMASK, rMASK, rIGN
67#endif
68 orc rWORD, rWORD, rMASK
69 add rTMP1, rFEFE, rWORD
70 nor rTMP2, r7F7F, rWORD
71 and. rTMP4, rTMP1, rTMP2
72 xor rTMP3, rCHR, rWORD
73 orc rTMP3, rTMP3, rMASK
74 b L(loopentry)
75
76/* The loop. */
77
78L(loop):
79 ldu rWORD, 8(rSTR)
80 and. rTMP5, rTMP1, rTMP2
81/* Test for 0. */
82 add rTMP1, rFEFE, rWORD /* x - 0x01010101. */
83 nor rTMP2, r7F7F, rWORD /* ~(x | 0x7f7f7f7f) == ~x & 0x80808080. */
84 bne L(foundit)
85 and. rTMP4, rTMP1, rTMP2 /* (x - 0x01010101) & ~x & 0x80808080. */
86/* Start test for the bytes we're looking for. */
87 xor rTMP3, rCHR, rWORD
88L(loopentry):
89 add rTMP1, rFEFE, rTMP3
90 nor rTMP2, r7F7F, rTMP3
91 beq L(loop)
92
93/* There is a zero byte in the word, but may also be a matching byte (either
94 before or after the zero byte). In fact, we may be looking for a
95 zero byte, in which case we return a match. */
96 and. rTMP5, rTMP1, rTMP2
97 li rRTN, 0
98 beqlr
99/* At this point:
100 rTMP5 bytes are 0x80 for each match of c, 0 otherwise.
101 rTMP4 bytes are 0x80 for each match of 0, 0 otherwise.
102 But there may be false matches in the next most significant byte from
103 a true match due to carries. This means we need to recalculate the
104 matches using a longer method for big-endian. */
105#ifdef __LITTLE_ENDIAN__
106 addi rTMP1, rTMP5, -1
107 andc rTMP1, rTMP1, rTMP5
108 cntlzd rCLZB, rTMP1
109 addi rTMP2, rTMP4, -1
110 andc rTMP2, rTMP2, rTMP4
111 cmpld rTMP1, rTMP2
112 bgtlr
113 subfic rCLZB, rCLZB, 64-7
114#else
115/* I think we could reduce this by two instructions by keeping the "nor"
116 results from the loop for reuse here. See strlen.S tail. Similarly
117 one instruction could be pruned from L(foundit). */
118 and rFEFE, r7F7F, rWORD
119 or rTMP5, r7F7F, rWORD
120 and rTMP1, r7F7F, rTMP3
121 or rTMP4, r7F7F, rTMP3
122 add rFEFE, rFEFE, r7F7F
123 add rTMP1, rTMP1, r7F7F
124 nor rWORD, rTMP5, rFEFE
125 nor rTMP2, rTMP4, rTMP1
126 cntlzd rCLZB, rTMP2
127 cmpld rWORD, rTMP2
128 bgtlr
129#endif
130 srdi rCLZB, rCLZB, 3
131 add rRTN, rSTR, rCLZB
132 blr
133
134L(foundit):
135#ifdef __LITTLE_ENDIAN__
136 addi rTMP1, rTMP5, -1
137 andc rTMP1, rTMP1, rTMP5
138 cntlzd rCLZB, rTMP1
139 subfic rCLZB, rCLZB, 64-7-64
140 sradi rCLZB, rCLZB, 3
141#else
142 and rTMP1, r7F7F, rTMP3
143 or rTMP4, r7F7F, rTMP3
144 add rTMP1, rTMP1, r7F7F
145 nor rTMP2, rTMP4, rTMP1
146 cntlzd rCLZB, rTMP2
147 subi rSTR, rSTR, 8
148 srdi rCLZB, rCLZB, 3
149#endif
150 add rRTN, rSTR, rCLZB
151 blr
152END (STRCHR)
153
154weak_alias (strchr, index)
155libc_hidden_builtin_def (strchr)
156

source code of glibc/sysdeps/powerpc/powerpc64/strchr.S