| 1 | /* Copyright (C) 1991, 1993, 1995, 1997, 1998, 2003, 2006, 2009 |
| 2 | Free Software Foundation, Inc. |
| 3 | |
| 4 | Contributed by Torbjorn Granlund (tege@sics.se). |
| 5 | |
| 6 | NOTE: The canonical source of this file is maintained with the GNU C Library. |
| 7 | Bugs can be reported to bug-glibc@prep.ai.mit.edu. |
| 8 | |
| 9 | This program is free software: you can redistribute it and/or modify it |
| 10 | under the terms of the GNU General Public License as published by the |
| 11 | Free Software Foundation; either version 3 of the License, or any |
| 12 | later version. |
| 13 | |
| 14 | This program is distributed in the hope that it will be useful, |
| 15 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 17 | GNU General Public License for more details. |
| 18 | |
| 19 | You should have received a copy of the GNU General Public License |
| 20 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 21 | |
| 22 | #ifndef _LIBC |
| 23 | # include <config.h> |
| 24 | #endif |
| 25 | |
| 26 | #include <string.h> |
| 27 | |
| 28 | #undef memcmp |
| 29 | |
| 30 | #ifdef _LIBC |
| 31 | |
| 32 | # include <memcopy.h> |
| 33 | # include <endian.h> |
| 34 | |
| 35 | # if __BYTE_ORDER == __BIG_ENDIAN |
| 36 | # define WORDS_BIGENDIAN |
| 37 | # endif |
| 38 | |
| 39 | #else /* Not in the GNU C library. */ |
| 40 | |
| 41 | # include <sys/types.h> |
| 42 | |
| 43 | /* Type to use for aligned memory operations. |
| 44 | This should normally be the biggest type supported by a single load |
| 45 | and store. Must be an unsigned type. */ |
| 46 | # define op_t unsigned long int |
| 47 | # define OPSIZ (sizeof(op_t)) |
| 48 | |
| 49 | /* Threshold value for when to enter the unrolled loops. */ |
| 50 | # define OP_T_THRES 16 |
| 51 | |
| 52 | /* Type to use for unaligned operations. */ |
| 53 | typedef unsigned char byte; |
| 54 | |
| 55 | # ifndef WORDS_BIGENDIAN |
| 56 | # define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2))) |
| 57 | # else |
| 58 | # define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2))) |
| 59 | # endif |
| 60 | |
| 61 | #endif /* In the GNU C library. */ |
| 62 | |
| 63 | #ifdef WORDS_BIGENDIAN |
| 64 | # define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1) |
| 65 | #else |
| 66 | # define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b)) |
| 67 | #endif |
| 68 | |
| 69 | /* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */ |
| 70 | |
| 71 | /* The strategy of this memcmp is: |
| 72 | |
| 73 | 1. Compare bytes until one of the block pointers is aligned. |
| 74 | |
| 75 | 2. Compare using memcmp_common_alignment or |
| 76 | memcmp_not_common_alignment, regarding the alignment of the other |
| 77 | block after the initial byte operations. The maximum number of |
| 78 | full words (of type op_t) are compared in this way. |
| 79 | |
| 80 | 3. Compare the few remaining bytes. */ |
| 81 | |
| 82 | #ifndef WORDS_BIGENDIAN |
| 83 | /* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine. |
| 84 | A and B are known to be different. |
| 85 | This is needed only on little-endian machines. */ |
| 86 | |
| 87 | # ifdef __GNUC__ |
| 88 | __inline |
| 89 | # endif |
| 90 | static int |
| 91 | memcmp_bytes (long unsigned int a, long unsigned int b) |
| 92 | { |
| 93 | long int srcp1 = (long int) &a; |
| 94 | long int srcp2 = (long int) &b; |
| 95 | op_t a0, b0; |
| 96 | |
| 97 | do |
| 98 | { |
| 99 | a0 = ((byte *) srcp1)[0]; |
| 100 | b0 = ((byte *) srcp2)[0]; |
| 101 | srcp1 += 1; |
| 102 | srcp2 += 1; |
| 103 | } |
| 104 | while (a0 == b0); |
| 105 | return a0 - b0; |
| 106 | } |
| 107 | #endif |
| 108 | |
| 109 | /* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t' |
| 110 | objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for |
| 111 | memory operations on `op_t's. */ |
| 112 | #ifdef __GNUC__ |
| 113 | __inline |
| 114 | #endif |
| 115 | static int |
| 116 | memcmp_common_alignment (long int srcp1, long int srcp2, size_t len) |
| 117 | { |
| 118 | op_t a0, a1; |
| 119 | op_t b0, b1; |
| 120 | |
| 121 | switch (len % 4) |
| 122 | { |
| 123 | default: /* Avoid warning about uninitialized local variables. */ |
| 124 | case 2: |
| 125 | a0 = ((op_t *) srcp1)[0]; |
| 126 | b0 = ((op_t *) srcp2)[0]; |
| 127 | srcp1 -= 2 * OPSIZ; |
| 128 | srcp2 -= 2 * OPSIZ; |
| 129 | len += 2; |
| 130 | goto do1; |
| 131 | case 3: |
| 132 | a1 = ((op_t *) srcp1)[0]; |
| 133 | b1 = ((op_t *) srcp2)[0]; |
| 134 | srcp1 -= OPSIZ; |
| 135 | srcp2 -= OPSIZ; |
| 136 | len += 1; |
| 137 | goto do2; |
| 138 | case 0: |
| 139 | if (OP_T_THRES <= 3 * OPSIZ && len == 0) |
| 140 | return 0; |
| 141 | a0 = ((op_t *) srcp1)[0]; |
| 142 | b0 = ((op_t *) srcp2)[0]; |
| 143 | goto do3; |
| 144 | case 1: |
| 145 | a1 = ((op_t *) srcp1)[0]; |
| 146 | b1 = ((op_t *) srcp2)[0]; |
| 147 | srcp1 += OPSIZ; |
| 148 | srcp2 += OPSIZ; |
| 149 | len -= 1; |
| 150 | if (OP_T_THRES <= 3 * OPSIZ && len == 0) |
| 151 | goto do0; |
| 152 | /* Fall through. */ |
| 153 | } |
| 154 | |
| 155 | do |
| 156 | { |
| 157 | a0 = ((op_t *) srcp1)[0]; |
| 158 | b0 = ((op_t *) srcp2)[0]; |
| 159 | if (a1 != b1) |
| 160 | return CMP_LT_OR_GT (a1, b1); |
| 161 | |
| 162 | do3: |
| 163 | a1 = ((op_t *) srcp1)[1]; |
| 164 | b1 = ((op_t *) srcp2)[1]; |
| 165 | if (a0 != b0) |
| 166 | return CMP_LT_OR_GT (a0, b0); |
| 167 | |
| 168 | do2: |
| 169 | a0 = ((op_t *) srcp1)[2]; |
| 170 | b0 = ((op_t *) srcp2)[2]; |
| 171 | if (a1 != b1) |
| 172 | return CMP_LT_OR_GT (a1, b1); |
| 173 | |
| 174 | do1: |
| 175 | a1 = ((op_t *) srcp1)[3]; |
| 176 | b1 = ((op_t *) srcp2)[3]; |
| 177 | if (a0 != b0) |
| 178 | return CMP_LT_OR_GT (a0, b0); |
| 179 | |
| 180 | srcp1 += 4 * OPSIZ; |
| 181 | srcp2 += 4 * OPSIZ; |
| 182 | len -= 4; |
| 183 | } |
| 184 | while (len != 0); |
| 185 | |
| 186 | /* This is the right position for do0. Please don't move |
| 187 | it into the loop. */ |
| 188 | do0: |
| 189 | if (a1 != b1) |
| 190 | return CMP_LT_OR_GT (a1, b1); |
| 191 | return 0; |
| 192 | } |
| 193 | |
| 194 | /* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN |
| 195 | `op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory |
| 196 | operations on `op_t', but SRCP1 *should be unaligned*. */ |
| 197 | #ifdef __GNUC__ |
| 198 | __inline |
| 199 | #endif |
| 200 | static int |
| 201 | memcmp_not_common_alignment (long int srcp1, long int srcp2, size_t len) |
| 202 | { |
| 203 | op_t a0, a1, a2, a3; |
| 204 | op_t b0, b1, b2, b3; |
| 205 | op_t x; |
| 206 | int shl, shr; |
| 207 | |
| 208 | /* Calculate how to shift a word read at the memory operation |
| 209 | aligned srcp1 to make it aligned for comparison. */ |
| 210 | |
| 211 | shl = 8 * (srcp1 % OPSIZ); |
| 212 | shr = 8 * OPSIZ - shl; |
| 213 | |
| 214 | /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t' |
| 215 | it points in the middle of. */ |
| 216 | srcp1 &= -OPSIZ; |
| 217 | |
| 218 | switch (len % 4) |
| 219 | { |
| 220 | default: /* Avoid warning about uninitialized local variables. */ |
| 221 | case 2: |
| 222 | a1 = ((op_t *) srcp1)[0]; |
| 223 | a2 = ((op_t *) srcp1)[1]; |
| 224 | b2 = ((op_t *) srcp2)[0]; |
| 225 | srcp1 -= 1 * OPSIZ; |
| 226 | srcp2 -= 2 * OPSIZ; |
| 227 | len += 2; |
| 228 | goto do1; |
| 229 | case 3: |
| 230 | a0 = ((op_t *) srcp1)[0]; |
| 231 | a1 = ((op_t *) srcp1)[1]; |
| 232 | b1 = ((op_t *) srcp2)[0]; |
| 233 | srcp2 -= 1 * OPSIZ; |
| 234 | len += 1; |
| 235 | goto do2; |
| 236 | case 0: |
| 237 | if (OP_T_THRES <= 3 * OPSIZ && len == 0) |
| 238 | return 0; |
| 239 | a3 = ((op_t *) srcp1)[0]; |
| 240 | a0 = ((op_t *) srcp1)[1]; |
| 241 | b0 = ((op_t *) srcp2)[0]; |
| 242 | srcp1 += 1 * OPSIZ; |
| 243 | goto do3; |
| 244 | case 1: |
| 245 | a2 = ((op_t *) srcp1)[0]; |
| 246 | a3 = ((op_t *) srcp1)[1]; |
| 247 | b3 = ((op_t *) srcp2)[0]; |
| 248 | srcp1 += 2 * OPSIZ; |
| 249 | srcp2 += 1 * OPSIZ; |
| 250 | len -= 1; |
| 251 | if (OP_T_THRES <= 3 * OPSIZ && len == 0) |
| 252 | goto do0; |
| 253 | /* Fall through. */ |
| 254 | } |
| 255 | |
| 256 | do |
| 257 | { |
| 258 | a0 = ((op_t *) srcp1)[0]; |
| 259 | b0 = ((op_t *) srcp2)[0]; |
| 260 | x = MERGE(a2, shl, a3, shr); |
| 261 | if (x != b3) |
| 262 | return CMP_LT_OR_GT (x, b3); |
| 263 | |
| 264 | do3: |
| 265 | a1 = ((op_t *) srcp1)[1]; |
| 266 | b1 = ((op_t *) srcp2)[1]; |
| 267 | x = MERGE(a3, shl, a0, shr); |
| 268 | if (x != b0) |
| 269 | return CMP_LT_OR_GT (x, b0); |
| 270 | |
| 271 | do2: |
| 272 | a2 = ((op_t *) srcp1)[2]; |
| 273 | b2 = ((op_t *) srcp2)[2]; |
| 274 | x = MERGE(a0, shl, a1, shr); |
| 275 | if (x != b1) |
| 276 | return CMP_LT_OR_GT (x, b1); |
| 277 | |
| 278 | do1: |
| 279 | a3 = ((op_t *) srcp1)[3]; |
| 280 | b3 = ((op_t *) srcp2)[3]; |
| 281 | x = MERGE(a1, shl, a2, shr); |
| 282 | if (x != b2) |
| 283 | return CMP_LT_OR_GT (x, b2); |
| 284 | |
| 285 | srcp1 += 4 * OPSIZ; |
| 286 | srcp2 += 4 * OPSIZ; |
| 287 | len -= 4; |
| 288 | } |
| 289 | while (len != 0); |
| 290 | |
| 291 | /* This is the right position for do0. Please don't move |
| 292 | it into the loop. */ |
| 293 | do0: |
| 294 | x = MERGE(a2, shl, a3, shr); |
| 295 | if (x != b3) |
| 296 | return CMP_LT_OR_GT (x, b3); |
| 297 | return 0; |
| 298 | } |
| 299 | |
| 300 | int |
| 301 | rpl_memcmp (const void *s1, const void *s2, size_t len) |
| 302 | { |
| 303 | op_t a0; |
| 304 | op_t b0; |
| 305 | long int srcp1 = (long int) s1; |
| 306 | long int srcp2 = (long int) s2; |
| 307 | op_t res; |
| 308 | |
| 309 | if (len >= OP_T_THRES) |
| 310 | { |
| 311 | /* There are at least some bytes to compare. No need to test |
| 312 | for LEN == 0 in this alignment loop. */ |
| 313 | while (srcp2 % OPSIZ != 0) |
| 314 | { |
| 315 | a0 = ((byte *) srcp1)[0]; |
| 316 | b0 = ((byte *) srcp2)[0]; |
| 317 | srcp1 += 1; |
| 318 | srcp2 += 1; |
| 319 | res = a0 - b0; |
| 320 | if (res != 0) |
| 321 | return res; |
| 322 | len -= 1; |
| 323 | } |
| 324 | |
| 325 | /* SRCP2 is now aligned for memory operations on `op_t'. |
| 326 | SRCP1 alignment determines if we can do a simple, |
| 327 | aligned compare or need to shuffle bits. */ |
| 328 | |
| 329 | if (srcp1 % OPSIZ == 0) |
| 330 | res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ); |
| 331 | else |
| 332 | res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ); |
| 333 | if (res != 0) |
| 334 | return res; |
| 335 | |
| 336 | /* Number of bytes remaining in the interval [0..OPSIZ-1]. */ |
| 337 | srcp1 += len & -OPSIZ; |
| 338 | srcp2 += len & -OPSIZ; |
| 339 | len %= OPSIZ; |
| 340 | } |
| 341 | |
| 342 | /* There are just a few bytes to compare. Use byte memory operations. */ |
| 343 | while (len != 0) |
| 344 | { |
| 345 | a0 = ((byte *) srcp1)[0]; |
| 346 | b0 = ((byte *) srcp2)[0]; |
| 347 | srcp1 += 1; |
| 348 | srcp2 += 1; |
| 349 | res = a0 - b0; |
| 350 | if (res != 0) |
| 351 | return res; |
| 352 | len -= 1; |
| 353 | } |
| 354 | |
| 355 | return 0; |
| 356 | } |
| 357 | |
| 358 | #ifdef weak_alias |
| 359 | # undef bcmp |
| 360 | weak_alias (memcmp, bcmp) |
| 361 | #endif |