1 /* Copyright (C) 1991,1993,1995,1997,1998,2003,2004
2 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Torbjorn Granlund (tege@sics.se).
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
27 #if __BYTE_ORDER == __BIG_ENDIAN
28 # define WORDS_BIGENDIAN
31 #ifdef WORDS_BIGENDIAN
32 # define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1)
34 # define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b))
37 /* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */
39 /* The strategy of this memcmp is:
41 1. Compare bytes until one of the block pointers is aligned.
43 2. Compare using memcmp_common_alignment or
44 memcmp_not_common_alignment, regarding the alignment of the other
45 block after the initial byte operations. The maximum number of
46 full words (of type op_t) are compared in this way.
48 3. Compare the few remaining bytes. */
50 #ifndef WORDS_BIGENDIAN
51 /* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
52 A and B are known to be different.
53 This is needed only on little-endian machines. */
55 static int memcmp_bytes __P((op_t, op_t));
64 long int srcp1 = (long int) &a;
65 long int srcp2 = (long int) &b;
70 a0 = ((byte *) srcp1)[0];
71 b0 = ((byte *) srcp2)[0];
80 static int memcmp_common_alignment __P((long, long, size_t));
82 /* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t'
83 objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for
84 memory operations on `op_t's. */
86 memcmp_common_alignment (srcp1, srcp2, len)
96 default: /* Avoid warning about uninitialized local variables. */
98 a0 = ((op_t *) srcp1)[0];
99 b0 = ((op_t *) srcp2)[0];
105 a1 = ((op_t *) srcp1)[0];
106 b1 = ((op_t *) srcp2)[0];
112 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
114 a0 = ((op_t *) srcp1)[0];
115 b0 = ((op_t *) srcp2)[0];
118 a1 = ((op_t *) srcp1)[0];
119 b1 = ((op_t *) srcp2)[0];
123 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
130 a0 = ((op_t *) srcp1)[0];
131 b0 = ((op_t *) srcp2)[0];
133 return CMP_LT_OR_GT (a1, b1);
136 a1 = ((op_t *) srcp1)[1];
137 b1 = ((op_t *) srcp2)[1];
139 return CMP_LT_OR_GT (a0, b0);
142 a0 = ((op_t *) srcp1)[2];
143 b0 = ((op_t *) srcp2)[2];
145 return CMP_LT_OR_GT (a1, b1);
148 a1 = ((op_t *) srcp1)[3];
149 b1 = ((op_t *) srcp2)[3];
151 return CMP_LT_OR_GT (a0, b0);
159 /* This is the right position for do0. Please don't move
163 return CMP_LT_OR_GT (a1, b1);
167 static int memcmp_not_common_alignment __P((long, long, size_t));
169 /* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN
170 `op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory
171 operations on `op_t', but SRCP1 *should be unaligned*. */
173 memcmp_not_common_alignment (srcp1, srcp2, len)
183 /* Calculate how to shift a word read at the memory operation
184 aligned srcp1 to make it aligned for comparison. */
186 shl = 8 * (srcp1 % OPSIZ);
187 shr = 8 * OPSIZ - shl;
189 /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t'
190 it points in the middle of. */
195 default: /* Avoid warning about uninitialized local variables. */
197 a1 = ((op_t *) srcp1)[0];
198 a2 = ((op_t *) srcp1)[1];
199 b2 = ((op_t *) srcp2)[0];
205 a0 = ((op_t *) srcp1)[0];
206 a1 = ((op_t *) srcp1)[1];
207 b1 = ((op_t *) srcp2)[0];
212 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
214 a3 = ((op_t *) srcp1)[0];
215 a0 = ((op_t *) srcp1)[1];
216 b0 = ((op_t *) srcp2)[0];
220 a2 = ((op_t *) srcp1)[0];
221 a3 = ((op_t *) srcp1)[1];
222 b3 = ((op_t *) srcp2)[0];
226 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
233 a0 = ((op_t *) srcp1)[0];
234 b0 = ((op_t *) srcp2)[0];
235 x = MERGE(a2, shl, a3, shr);
237 return CMP_LT_OR_GT (x, b3);
240 a1 = ((op_t *) srcp1)[1];
241 b1 = ((op_t *) srcp2)[1];
242 x = MERGE(a3, shl, a0, shr);
244 return CMP_LT_OR_GT (x, b0);
247 a2 = ((op_t *) srcp1)[2];
248 b2 = ((op_t *) srcp2)[2];
249 x = MERGE(a0, shl, a1, shr);
251 return CMP_LT_OR_GT (x, b1);
254 a3 = ((op_t *) srcp1)[3];
255 b3 = ((op_t *) srcp2)[3];
256 x = MERGE(a1, shl, a2, shr);
258 return CMP_LT_OR_GT (x, b2);
266 /* This is the right position for do0. Please don't move
269 x = MERGE(a2, shl, a3, shr);
271 return CMP_LT_OR_GT (x, b3);
276 memcmp (const __ptr_t s1, const __ptr_t s2, size_t len)
280 long int srcp1 = (long int) s1;
281 long int srcp2 = (long int) s2;
284 if (len >= OP_T_THRES)
286 /* There are at least some bytes to compare. No need to test
287 for LEN == 0 in this alignment loop. */
288 while (srcp2 % OPSIZ != 0)
290 a0 = ((byte *) srcp1)[0];
291 b0 = ((byte *) srcp2)[0];
300 /* SRCP2 is now aligned for memory operations on `op_t'.
301 SRCP1 alignment determines if we can do a simple,
302 aligned compare or need to shuffle bits. */
304 if (srcp1 % OPSIZ == 0)
305 res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ);
307 res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ);
311 /* Number of bytes remaining in the interval [0..OPSIZ-1]. */
312 srcp1 += len & -OPSIZ;
313 srcp2 += len & -OPSIZ;
317 /* There are just a few bytes to compare. Use byte memory operations. */
320 a0 = ((byte *) srcp1)[0];
321 b0 = ((byte *) srcp2)[0];
332 libc_hidden_proto(memcmp)
333 libc_hidden_def(memcmp)
334 strong_alias(memcmp,bcmp)