1 /* 2 * Copyright (c) 2011 The Android Open Source Project 3 * Copyright (c) 2008 ARM Ltd 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the company may not be used to endorse or promote 15 * products derived from this software without specific prior written 16 * permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED 19 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 20 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 23 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 24 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 25 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 26 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include <machine/cpu-features.h> 31 #include <private/bionic_asm.h> 32 33 .text 34 35 #ifdef __ARMEB__ 36 #define SHFT2LSB lsl 37 #define SHFT2LSBEQ lsleq 38 #define SHFT2MSB lsr 39 #define SHFT2MSBEQ lsreq 40 #define MSB 0x000000ff 41 #define LSB 0xff000000 42 #else 43 #define SHFT2LSB lsr 44 #define SHFT2LSBEQ lsreq 45 #define SHFT2MSB lsl 46 #define SHFT2MSBEQ lsleq 47 #define MSB 0xff000000 48 #define LSB 0x000000ff 49 #endif 50 51 #define magic1(REG) REG 52 #define magic2(REG) REG, lsl #7 53 54 ENTRY(strcmp) 55 pld [r0, #0] 56 pld [r1, #0] 57 eor r2, r0, r1 58 tst r2, #3 59 60 /* Strings not at same byte offset from a word boundary. */ 61 bne .Lstrcmp_unaligned 62 ands r2, r0, #3 63 bic r0, r0, #3 64 bic r1, r1, #3 65 ldr ip, [r0], #4 66 it eq 67 ldreq r3, [r1], #4 68 beq 1f 69 70 /* Although s1 and s2 have identical initial alignment, they are 71 * not currently word aligned. Rather than comparing bytes, 72 * make sure that any bytes fetched from before the addressed 73 * bytes are forced to 0xff. Then they will always compare 74 * equal. 75 */ 76 eor r2, r2, #3 77 lsl r2, r2, #3 78 mvn r3, #MSB 79 SHFT2LSB r2, r3, r2 80 ldr r3, [r1], #4 81 orr ip, ip, r2 82 orr r3, r3, r2 83 1: 84 /* Load the 'magic' constant 0x01010101. */ 85 str r4, [sp, #-4]! 86 mov r4, #1 87 orr r4, r4, r4, lsl #8 88 orr r4, r4, r4, lsl #16 89 .p2align 2 90 4: 91 pld [r0, #8] 92 pld [r1, #8] 93 sub r2, ip, magic1(r4) 94 cmp ip, r3 95 itttt eq 96 97 /* check for any zero bytes in first word */ 98 biceq r2, r2, ip 99 tsteq r2, magic2(r4) 100 ldreq ip, [r0], #4 101 ldreq r3, [r1], #4 102 beq 4b 103 2: 104 /* There's a zero or a different byte in the word */ 105 SHFT2MSB r0, ip, #24 106 SHFT2LSB ip, ip, #8 107 cmp r0, #1 108 it cs 109 cmpcs r0, r3, SHFT2MSB #24 110 it eq 111 SHFT2LSBEQ r3, r3, #8 112 beq 2b 113 /* On a big-endian machine, r0 contains the desired byte in bits 114 * 0-7; on a little-endian machine they are in bits 24-31. In 115 * both cases the other bits in r0 are all zero. For r3 the 116 * interesting byte is at the other end of the word, but the 117 * other bits are not necessarily zero. We need a signed result 118 * representing the differnece in the unsigned bytes, so for the 119 * little-endian case we can't just shift the interesting bits up. 120 */ 121 #ifdef __ARMEB__ 122 sub r0, r0, r3, lsr #24 123 #else 124 and r3, r3, #255 125 /* No RSB instruction in Thumb2 */ 126 #ifdef __thumb2__ 127 lsr r0, r0, #24 128 sub r0, r0, r3 129 #else 130 rsb r0, r3, r0, lsr #24 131 #endif 132 #endif 133 ldr r4, [sp], #4 134 bx lr 135 136 .Lstrcmp_unaligned: 137 wp1 .req r0 138 wp2 .req r1 139 b1 .req r2 140 w1 .req r4 141 w2 .req r5 142 t1 .req ip 143 @ r3 is scratch 144 145 /* First of all, compare bytes until wp1(sp1) is word-aligned. */ 146 1: 147 tst wp1, #3 148 beq 2f 149 ldrb r2, [wp1], #1 150 ldrb r3, [wp2], #1 151 cmp r2, #1 152 it cs 153 cmpcs r2, r3 154 beq 1b 155 sub r0, r2, r3 156 bx lr 157 158 2: 159 str r5, [sp, #-4]! 160 str r4, [sp, #-4]! 161 mov b1, #1 162 orr b1, b1, b1, lsl #8 163 orr b1, b1, b1, lsl #16 164 165 and t1, wp2, #3 166 bic wp2, wp2, #3 167 ldr w1, [wp1], #4 168 ldr w2, [wp2], #4 169 cmp t1, #2 170 beq 2f 171 bhi 3f 172 173 /* Critical inner Loop: Block with 3 bytes initial overlap */ 174 .p2align 2 175 1: 176 bic t1, w1, #MSB 177 cmp t1, w2, SHFT2LSB #8 178 sub r3, w1, b1 179 bic r3, r3, w1 180 bne 4f 181 ands r3, r3, b1, lsl #7 182 it eq 183 ldreq w2, [wp2], #4 184 bne 5f 185 eor t1, t1, w1 186 cmp t1, w2, SHFT2MSB #24 187 bne 6f 188 ldr w1, [wp1], #4 189 b 1b 190 4: 191 SHFT2LSB w2, w2, #8 192 b 8f 193 194 5: 195 #ifdef __ARMEB__ 196 /* The syndrome value may contain false ones if the string ends 197 * with the bytes 0x01 0x00 198 */ 199 tst w1, #0xff000000 200 itt ne 201 tstne w1, #0x00ff0000 202 tstne w1, #0x0000ff00 203 beq 7f 204 #else 205 bics r3, r3, #0xff000000 206 bne 7f 207 #endif 208 ldrb w2, [wp2] 209 SHFT2LSB t1, w1, #24 210 #ifdef __ARMEB__ 211 lsl w2, w2, #24 212 #endif 213 b 8f 214 215 6: 216 SHFT2LSB t1, w1, #24 217 and w2, w2, #LSB 218 b 8f 219 220 /* Critical inner Loop: Block with 2 bytes initial overlap */ 221 .p2align 2 222 2: 223 SHFT2MSB t1, w1, #16 224 sub r3, w1, b1 225 SHFT2LSB t1, t1, #16 226 bic r3, r3, w1 227 cmp t1, w2, SHFT2LSB #16 228 bne 4f 229 ands r3, r3, b1, lsl #7 230 it eq 231 ldreq w2, [wp2], #4 232 bne 5f 233 eor t1, t1, w1 234 cmp t1, w2, SHFT2MSB #16 235 bne 6f 236 ldr w1, [wp1], #4 237 b 2b 238 239 5: 240 #ifdef __ARMEB__ 241 /* The syndrome value may contain false ones if the string ends 242 * with the bytes 0x01 0x00 243 */ 244 tst w1, #0xff000000 245 it ne 246 tstne w1, #0x00ff0000 247 beq 7f 248 #else 249 lsls r3, r3, #16 250 bne 7f 251 #endif 252 ldrh w2, [wp2] 253 SHFT2LSB t1, w1, #16 254 #ifdef __ARMEB__ 255 lsl w2, w2, #16 256 #endif 257 b 8f 258 259 6: 260 SHFT2MSB w2, w2, #16 261 SHFT2LSB t1, w1, #16 262 4: 263 SHFT2LSB w2, w2, #16 264 b 8f 265 266 /* Critical inner Loop: Block with 1 byte initial overlap */ 267 .p2align 2 268 3: 269 and t1, w1, #LSB 270 cmp t1, w2, SHFT2LSB #24 271 sub r3, w1, b1 272 bic r3, r3, w1 273 bne 4f 274 ands r3, r3, b1, lsl #7 275 it eq 276 ldreq w2, [wp2], #4 277 bne 5f 278 eor t1, t1, w1 279 cmp t1, w2, SHFT2MSB #8 280 bne 6f 281 ldr w1, [wp1], #4 282 b 3b 283 4: 284 SHFT2LSB w2, w2, #24 285 b 8f 286 5: 287 /* The syndrome value may contain false ones if the string ends 288 * with the bytes 0x01 0x00 289 */ 290 tst w1, #LSB 291 beq 7f 292 ldr w2, [wp2], #4 293 6: 294 SHFT2LSB t1, w1, #8 295 bic w2, w2, #MSB 296 b 8f 297 7: 298 mov r0, #0 299 ldr r4, [sp], #4 300 ldr r5, [sp], #4 301 bx lr 302 303 8: 304 and r2, t1, #LSB 305 and r0, w2, #LSB 306 cmp r0, #1 307 it cs 308 cmpcs r0, r2 309 itt eq 310 SHFT2LSBEQ t1, t1, #8 311 SHFT2LSBEQ w2, w2, #8 312 beq 8b 313 sub r0, r2, r0 314 ldr r4, [sp], #4 315 ldr r5, [sp], #4 316 bx lr 317 END(strcmp) 318
