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review.blissroms.org / platform_bionic / bd192b470b69e00e9313680b70c5572a609e535d / . / libc / arch-arm / bionic / memcmp16.S
blob: f398588a444fd3ff4a76cedc92fbccff9a15ab7c [file] [log] [blame]
The Android Open Source Project1dc9e472009-03-03 19:28:35 -0800[diff] [blame]1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <machine/cpu-features.h>
30
31 .text
32
33 .global __memcmp16
34 .type __memcmp16, %function
35 .align 4
36
37/*
38 * Optimized memcmp16() for ARM9.
39 * This would not be optimal on XScale or ARM11, where more prefetching
40 * and use of PLD will be needed.
41 * The 2 major optimzations here are
42 * (1) The main loop compares 16 bytes at a time
43 * (2) The loads are scheduled in a way they won't stall
44 */
45
46__memcmp16:
Ben Chengbd192b42009-09-15 13:41:14 -0700[diff] [blame^]47 .fnstart
The Android Open Source Project1dc9e472009-03-03 19:28:35 -0800[diff] [blame]48 PLD (r0, #0)
49 PLD (r1, #0)
50
51 /* take of the case where length is nul or the buffers are the same */
52 cmp r0, r1
53 cmpne r2, #0
54 moveq r0, #0
55 bxeq lr
56
57 /* since r0 hold the result, move the first source
58 * pointer somewhere else
59 */
60
61 mov r3, r0
62
63 /* make sure we have at least 12 words, this simplify things below
64 * and avoid some overhead for small blocks
65 */
66
67 cmp r2, #12
68 bpl 0f
69
70 /* small blocks (less then 12 words) */
71 PLD (r0, #32)
72 PLD (r1, #32)
73
741: ldrh r0, [r3], #2
75 ldrh ip, [r1], #2
76 subs r0, r0, ip
77 bxne lr
78 subs r2, r2, #1
79 bne 1b
80 bx lr
81
82
Ben Chengbd192b42009-09-15 13:41:14 -0700[diff] [blame^]83 .save {r4, lr}
The Android Open Source Project1dc9e472009-03-03 19:28:35 -0800[diff] [blame]84 /* save registers */
850: stmfd sp!, {r4, lr}
86
87 /* align first pointer to word boundary */
88 tst r3, #2
89 beq 0f
90
91 ldrh r0, [r3], #2
92 ldrh ip, [r1], #2
93 sub r2, r2, #1
94 subs r0, r0, ip
95 /* restore registers and return */
96 ldmnefd sp!, {r4, lr}
97 bxne lr
Ben Chengbd192b42009-09-15 13:41:14 -0700[diff] [blame^]98 .fnend
The Android Open Source Project1dc9e472009-03-03 19:28:35 -0800[diff] [blame]99
100
101
1020: /* here the first pointer is aligned, and we have at least 3 words
103 * to process.
104 */
105
106 /* see if the pointers are congruent */
107 eor r0, r3, r1
108 ands r0, r0, #2
109 bne 5f
110
111 /* congruent case, 16 half-words per iteration
112 * We need to make sure there are at least 16+2 words left
113 * because we effectively read ahead one long word, and we could
114 * read past the buffer (and segfault) if we're not careful.
115 */
116
117 ldr ip, [r1]
118 subs r2, r2, #(16 + 2)
119 bmi 1f
120
1210:
122 PLD (r3, #64)
123 PLD (r1, #64)
124 ldr r0, [r3], #4
125 ldr lr, [r1, #4]!
126 eors r0, r0, ip
127 ldreq r0, [r3], #4
128 ldreq ip, [r1, #4]!
129 eoreqs r0, r0, lr
130 ldreq r0, [r3], #4
131 ldreq lr, [r1, #4]!
132 eoreqs r0, r0, ip
133 ldreq r0, [r3], #4
134 ldreq ip, [r1, #4]!
135 eoreqs r0, r0, lr
136 ldreq r0, [r3], #4
137 ldreq lr, [r1, #4]!
138 eoreqs r0, r0, ip
139 ldreq r0, [r3], #4
140 ldreq ip, [r1, #4]!
141 eoreqs r0, r0, lr
142 ldreq r0, [r3], #4
143 ldreq lr, [r1, #4]!
144 eoreqs r0, r0, ip
145 ldreq r0, [r3], #4
146 ldreq ip, [r1, #4]!
147 eoreqs r0, r0, lr
148 bne 2f
149 subs r2, r2, #16
150 bhs 0b
151
152 /* do we have at least 2 words left? */
1531: adds r2, r2, #(16 - 2 + 2)
154 bmi 4f
155
156 /* finish off 2 words at a time */
1573: ldr r0, [r3], #4
158 ldr ip, [r1], #4
159 eors r0, r0, ip
160 bne 2f
161 subs r2, r2, #2
162 bhs 3b
163
164 /* are we done? */
1654: adds r2, r2, #2
166 bne 8f
167 /* restore registers and return */
168 mov r0, #0
169 ldmfd sp!, {r4, lr}
170 bx lr
171
1722: /* the last 2 words are different, restart them */
173 ldrh r0, [r3, #-4]
174 ldrh ip, [r1, #-4]
175 subs r0, r0, ip
176 ldreqh r0, [r3, #-2]
177 ldreqh ip, [r1, #-2]
178 subeqs r0, r0, ip
179 /* restore registers and return */
180 ldmfd sp!, {r4, lr}
181 bx lr
182
183 /* process the last few words */
1848: ldrh r0, [r3], #2
185 ldrh ip, [r1], #2
186 subs r0, r0, ip
187 bne 9f
188 subs r2, r2, #1
189 bne 8b
190
1919: /* restore registers and return */
192 ldmfd sp!, {r4, lr}
193 bx lr
194
195
1965: /*************** non-congruent case ***************/
197
198 /* align the unaligned pointer */
199 bic r1, r1, #3
200 ldr lr, [r1], #4
201 sub r2, r2, #8
202
2036:
204 PLD (r3, #64)
205 PLD (r1, #64)
206 mov ip, lr, lsr #16
207 ldr lr, [r1], #4
208 ldr r0, [r3], #4
209 orr ip, ip, lr, lsl #16
210 eors r0, r0, ip
211 moveq ip, lr, lsr #16
212 ldreq lr, [r1], #4
213 ldreq r0, [r3], #4
214 orreq ip, ip, lr, lsl #16
215 eoreqs r0, r0, ip
216 moveq ip, lr, lsr #16
217 ldreq lr, [r1], #4
218 ldreq r0, [r3], #4
219 orreq ip, ip, lr, lsl #16
220 eoreqs r0, r0, ip
221 moveq ip, lr, lsr #16
222 ldreq lr, [r1], #4
223 ldreq r0, [r3], #4
224 orreq ip, ip, lr, lsl #16
225 eoreqs r0, r0, ip
226 bne 7f
227 subs r2, r2, #8
228 bhs 6b
229 sub r1, r1, #2
230 /* are we done? */
231 adds r2, r2, #8
232 moveq r0, #0
233 beq 9b
234 /* finish off the remaining bytes */
235 b 8b
236
2377: /* fix up the 2 pointers and fallthrough... */
238 sub r1, r1, #2
239 b 2b