1/* Optimized memchr implementation for PowerPC64/POWER7 using cmpb insn.
2 Copyright (C) 2010-2024 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/* int [r3] memchr (char *s [r3], int byte [r4], int size [r5]) */
22
23#ifndef MEMCHR
24# define MEMCHR __memchr
25#endif
26 .machine power7
27ENTRY_TOCLESS (MEMCHR)
28 CALL_MCOUNT 3
29 dcbt 0,r3
30 clrrdi r8,r3,3
31 insrdi r4,r4,8,48
32
33 /* Calculate the last acceptable address and check for possible
34 addition overflow by using satured math:
35 r7 = r3 + r5
36 r7 |= -(r7 < x) */
37 add r7,r3,r5
38 subfc r6,r3,r7
39 subfe r9,r9,r9
40 extsw r6,r9
41 or r7,r7,r6
42
43 insrdi r4,r4,16,32
44 cmpldi r5,32
45 li r9, -1
46 rlwinm r6,r3,3,26,28 /* Calculate padding. */
47 insrdi r4,r4,32,0
48 addi r7,r7,-1
49#ifdef __LITTLE_ENDIAN__
50 sld r9,r9,r6
51#else
52 srd r9,r9,r6
53#endif
54 ble L(small_range)
55
56 ld r12,0(r8) /* Load doubleword from memory. */
57 cmpb r3,r12,r4 /* Check for BYTEs in DWORD1. */
58 and r3,r3,r9
59 clrldi r5,r7,61 /* Byte count - 1 in last dword. */
60 clrrdi r7,r7,3 /* Address of last doubleword. */
61 cmpldi cr7,r3,0 /* Does r3 indicate we got a hit? */
62 bne cr7,L(done)
63
64 mtcrf 0x01,r8
65 /* Are we now aligned to a quadword boundary? If so, skip to
66 the main loop. Otherwise, go through the alignment code. */
67 bt 28,L(loop_setup)
68
69 /* Handle DWORD2 of pair. */
70 ldu r12,8(r8)
71 cmpb r3,r12,r4
72 cmpldi cr7,r3,0
73 bne cr7,L(done)
74
75L(loop_setup):
76 /* The last dword we want to read in the loop below is the one
77 containing the last byte of the string, ie. the dword at
78 (s + size - 1) & ~7, or r7. The first dword read is at
79 r8 + 8, we read 2 * cnt dwords, so the last dword read will
80 be at r8 + 8 + 16 * cnt - 8. Solving for cnt gives
81 cnt = (r7 - r8) / 16 */
82 sub r6,r7,r8
83 srdi r6,r6,4 /* Number of loop iterations. */
84 mtctr r6 /* Setup the counter. */
85
86 /* Main loop to look for BYTE in the string. Since
87 it's a small loop (8 instructions), align it to 32-bytes. */
88 .align 5
89L(loop):
90 /* Load two doublewords, compare and merge in a
91 single register for speed. This is an attempt
92 to speed up the byte-checking process for bigger strings. */
93 ld r12,8(r8)
94 ldu r11,16(r8)
95 cmpb r3,r12,r4
96 cmpb r9,r11,r4
97 or r6,r9,r3 /* Merge everything in one doubleword. */
98 cmpldi cr7,r6,0
99 bne cr7,L(found)
100 bdnz L(loop)
101
102 /* We may have one more dword to read. */
103 cmpld r8,r7
104 beqlr
105
106 ldu r12,8(r8)
107 cmpb r3,r12,r4
108 cmpldi cr6,r3,0
109 bne cr6,L(done)
110 blr
111
112 .align 4
113L(found):
114 /* OK, one (or both) of the doublewords contains BYTE. Check
115 the first doubleword and decrement the address in case the first
116 doubleword really contains BYTE. */
117 cmpldi cr6,r3,0
118 addi r8,r8,-8
119 bne cr6,L(done)
120
121 /* BYTE must be in the second doubleword. Adjust the address
122 again and move the result of cmpb to r3 so we can calculate the
123 pointer. */
124
125 mr r3,r9
126 addi r8,r8,8
127
128 /* r3 has the output of the cmpb instruction, that is, it contains
129 0xff in the same position as BYTE in the original
130 doubleword from the string. Use that to calculate the pointer.
131 We need to make sure BYTE is *before* the end of the range. */
132L(done):
133#ifdef __LITTLE_ENDIAN__
134 addi r0,r3,-1
135 andc r0,r0,r3
136 popcntd r0,r0 /* Count trailing zeros. */
137#else
138 cntlzd r0,r3 /* Count leading zeros before the match. */
139#endif
140 cmpld r8,r7 /* Are we on the last dword? */
141 srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
142 add r3,r8,r0
143 cmpld cr7,r0,r5 /* If on the last dword, check byte offset. */
144 bnelr
145 blelr cr7
146 li r3,0
147 blr
148
149 .align 4
150L(null):
151 li r3,0
152 blr
153
154/* Deals with size <= 32. */
155 .align 4
156L(small_range):
157 cmpldi r5,0
158 beq L(null)
159 ld r12,0(r8) /* Load word from memory. */
160 cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
161 and r3,r3,r9
162 cmpldi cr7,r3,0
163 clrldi r5,r7,61 /* Byte count - 1 in last dword. */
164 clrrdi r7,r7,3 /* Address of last doubleword. */
165 cmpld r8,r7 /* Are we done already? */
166 bne cr7,L(done)
167 beqlr
168
169 ldu r12,8(r8)
170 cmpb r3,r12,r4
171 cmpldi cr6,r3,0
172 cmpld r8,r7
173 bne cr6,L(done) /* Found something. */
174 beqlr /* Hit end of string (length). */
175
176 ldu r12,8(r8)
177 cmpb r3,r12,r4
178 cmpldi cr6,r3,0
179 cmpld r8,r7
180 bne cr6,L(done)
181 beqlr
182
183 ldu r12,8(r8)
184 cmpb r3,r12,r4
185 cmpldi cr6,r3,0
186 cmpld r8,r7
187 bne cr6,L(done)
188 beqlr
189
190 ldu r12,8(r8)
191 cmpb r3,r12,r4
192 cmpldi cr6,r3,0
193 bne cr6,L(done)
194 blr
195
196END (MEMCHR)
197weak_alias (__memchr, memchr)
198libc_hidden_builtin_def (memchr)
199

source code of glibc/sysdeps/powerpc/powerpc64/power7/memchr.S