1/* Optimized memrchr 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] memrchr (char *s [r3], int byte [r4], int size [r5]) */
22
23#ifndef MEMRCHR
24# define MEMRCHR __memrchr
25#endif
26 .machine power7
27ENTRY_TOCLESS (MEMRCHR)
28 CALL_MCOUNT 3
29 add r7,r3,r5 /* Calculate the last acceptable address. */
30 neg r0,r7
31 addi r7,r7,-1
32 mr r10,r3
33 clrrdi r6,r7,7
34 li r9,3<<5
35 dcbt r9,r6,8 /* Stream hint, decreasing addresses. */
36
37 /* Replicate BYTE to doubleword. */
38 insrdi r4,r4,8,48
39 insrdi r4,r4,16,32
40 insrdi r4,r4,32,0
41 li r6,-8
42 li r9,-1
43 rlwinm r0,r0,3,26,28 /* Calculate padding. */
44 clrrdi r8,r7,3
45 srd r9,r9,r0
46 cmpldi r5,32
47 clrrdi r0,r10,3
48 ble L(small_range)
49
50#ifdef __LITTLE_ENDIAN__
51 ldx r12,0,r8
52#else
53 ldbrx r12,0,r8 /* Load reversed doubleword from memory. */
54#endif
55 cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
56 and r3,r3,r9
57 cmpldi cr7,r3,0 /* If r3 == 0, no BYTEs have been found. */
58 bne cr7,L(done)
59
60 mtcrf 0x01,r8
61 /* Are we now aligned to a quadword boundary? If so, skip to
62 the main loop. Otherwise, go through the alignment code. */
63 bf 28,L(loop_setup)
64
65 /* Handle DWORD2 of pair. */
66#ifdef __LITTLE_ENDIAN__
67 ldx r12,r8,r6
68#else
69 ldbrx r12,r8,r6
70#endif
71 addi r8,r8,-8
72 cmpb r3,r12,r4
73 cmpldi cr7,r3,0
74 bne cr7,L(done)
75
76L(loop_setup):
77 /* The last dword we want to read in the loop below is the one
78 containing the first byte of the string, ie. the dword at
79 s & ~7, or r0. The first dword read is at r8 - 8, we
80 read 2 * cnt dwords, so the last dword read will be at
81 r8 - 8 - 16 * cnt + 8. Solving for cnt gives
82 cnt = (r8 - r0) / 16 */
83 sub r5,r8,r0
84 addi r8,r8,-8
85 srdi r9,r5,4 /* Number of loop iterations. */
86 mtctr r9 /* Setup the counter. */
87
88 /* Main loop to look for BYTE backwards in the string.
89 FIXME: Investigate whether 32 byte align helps with this
90 9 instruction loop. */
91 .align 5
92L(loop):
93 /* Load two doublewords, compare and merge in a
94 single register for speed. This is an attempt
95 to speed up the byte-checking process for bigger strings. */
96
97#ifdef __LITTLE_ENDIAN__
98 ldx r12,0,r8
99 ldx r11,r8,r6
100#else
101 ldbrx r12,0,r8
102 ldbrx r11,r8,r6
103#endif
104 cmpb r3,r12,r4
105 cmpb r9,r11,r4
106 or r5,r9,r3 /* Merge everything in one doubleword. */
107 cmpldi cr7,r5,0
108 bne cr7,L(found)
109 addi r8,r8,-16
110 bdnz L(loop)
111
112 /* We may have one more word to read. */
113 cmpld r8,r0
114 bnelr
115
116#ifdef __LITTLE_ENDIAN__
117 ldx r12,0,r8
118#else
119 ldbrx r12,0,r8
120#endif
121 cmpb r3,r12,r4
122 cmpldi cr7,r3,0
123 bne cr7,L(done)
124 blr
125
126 .align 4
127L(found):
128 /* OK, one (or both) of the dwords contains BYTE. Check
129 the first dword. */
130 cmpldi cr6,r3,0
131 bne cr6,L(done)
132
133 /* BYTE must be in the second word. Adjust the address
134 again and move the result of cmpb to r3 so we can calculate the
135 pointer. */
136
137 mr r3,r9
138 addi r8,r8,-8
139
140 /* r3 has the output of the cmpb instruction, that is, it contains
141 0xff in the same position as BYTE in the original
142 word from the string. Use that to calculate the pointer.
143 We need to make sure BYTE is *before* the end of the
144 range. */
145L(done):
146 cntlzd r9,r3 /* Count leading zeros before the match. */
147 cmpld r8,r0 /* Are we on the last word? */
148 srdi r6,r9,3 /* Convert leading zeros to bytes. */
149 addi r0,r6,-7
150 sub r3,r8,r0
151 cmpld cr7,r3,r10
152 bnelr
153 bgelr cr7
154 li r3,0
155 blr
156
157 .align 4
158L(null):
159 li r3,0
160 blr
161
162/* Deals with size <= 32. */
163 .align 4
164L(small_range):
165 cmpldi r5,0
166 beq L(null)
167
168#ifdef __LITTLE_ENDIAN__
169 ldx r12,0,r8
170#else
171 ldbrx r12,0,r8 /* Load reversed doubleword from memory. */
172#endif
173 cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
174 and r3,r3,r9
175 cmpldi cr7,r3,0
176 bne cr7,L(done)
177
178 /* Are we done already? */
179 cmpld r8,r0
180 addi r8,r8,-8
181 beqlr
182
183 .align 5
184L(loop_small):
185#ifdef __LITTLE_ENDIAN__
186 ldx r12,0,r8
187#else
188 ldbrx r12,0,r8
189#endif
190 cmpb r3,r12,r4
191 cmpld r8,r0
192 cmpldi cr7,r3,0
193 bne cr7,L(done)
194 addi r8,r8,-8
195 bne L(loop_small)
196 blr
197
198END (MEMRCHR)
199libc_hidden_def (__memrchr)
200weak_alias (__memrchr, memrchr)
201libc_hidden_builtin_def (memrchr)
202

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