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, see
18 <http://www.gnu.org/licenses/>. */
26 #if __BYTE_ORDER == __BIG_ENDIAN
27 # define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1)
29 # define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b))
32 /* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */
34 /* The strategy of this memcmp is:
36 1. Compare bytes until one of the block pointers is aligned.
38 2. Compare using memcmp_common_alignment or
39 memcmp_not_common_alignment, regarding the alignment of the other
40 block after the initial byte operations. The maximum number of
41 full words (of type op_t) are compared in this way.
43 3. Compare the few remaining bytes. */
45 #if __BYTE_ORDER != __BIG_ENDIAN
46 /* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
47 A and B are known to be different.
48 This is needed only on little-endian machines. */
51 memcmp_bytes (op_t a, op_t b)
53 long int srcp1 = (long int) &a;
54 long int srcp2 = (long int) &b;
59 a0 = ((byte *) srcp1)[0];
60 b0 = ((byte *) srcp2)[0];
69 /* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t'
70 objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for
71 memory operations on `op_t's. */
73 memcmp_common_alignment (long int srcp1, long int srcp2, size_t len)
80 default: /* Avoid warning about uninitialized local variables. */
82 a0 = ((op_t *) srcp1)[0];
83 b0 = ((op_t *) srcp2)[0];
89 a1 = ((op_t *) srcp1)[0];
90 b1 = ((op_t *) srcp2)[0];
96 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
98 a0 = ((op_t *) srcp1)[0];
99 b0 = ((op_t *) srcp2)[0];
102 a1 = ((op_t *) srcp1)[0];
103 b1 = ((op_t *) srcp2)[0];
107 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
114 a0 = ((op_t *) srcp1)[0];
115 b0 = ((op_t *) srcp2)[0];
117 return CMP_LT_OR_GT (a1, b1);
120 a1 = ((op_t *) srcp1)[1];
121 b1 = ((op_t *) srcp2)[1];
123 return CMP_LT_OR_GT (a0, b0);
126 a0 = ((op_t *) srcp1)[2];
127 b0 = ((op_t *) srcp2)[2];
129 return CMP_LT_OR_GT (a1, b1);
132 a1 = ((op_t *) srcp1)[3];
133 b1 = ((op_t *) srcp2)[3];
135 return CMP_LT_OR_GT (a0, b0);
143 /* This is the right position for do0. Please don't move
147 return CMP_LT_OR_GT (a1, b1);
151 /* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN
152 `op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory
153 operations on `op_t', but SRCP1 *should be unaligned*. */
155 memcmp_not_common_alignment (long int srcp1, long int srcp2, size_t len)
162 /* Calculate how to shift a word read at the memory operation
163 aligned srcp1 to make it aligned for comparison. */
165 shl = 8 * (srcp1 % OPSIZ);
166 shr = 8 * OPSIZ - shl;
168 /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t'
169 it points in the middle of. */
174 default: /* Avoid warning about uninitialized local variables. */
176 a1 = ((op_t *) srcp1)[0];
177 a2 = ((op_t *) srcp1)[1];
178 b2 = ((op_t *) srcp2)[0];
184 a0 = ((op_t *) srcp1)[0];
185 a1 = ((op_t *) srcp1)[1];
186 b1 = ((op_t *) srcp2)[0];
191 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
193 a3 = ((op_t *) srcp1)[0];
194 a0 = ((op_t *) srcp1)[1];
195 b0 = ((op_t *) srcp2)[0];
199 a2 = ((op_t *) srcp1)[0];
200 a3 = ((op_t *) srcp1)[1];
201 b3 = ((op_t *) srcp2)[0];
205 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
212 a0 = ((op_t *) srcp1)[0];
213 b0 = ((op_t *) srcp2)[0];
214 x = MERGE(a2, shl, a3, shr);
216 return CMP_LT_OR_GT (x, b3);
219 a1 = ((op_t *) srcp1)[1];
220 b1 = ((op_t *) srcp2)[1];
221 x = MERGE(a3, shl, a0, shr);
223 return CMP_LT_OR_GT (x, b0);
226 a2 = ((op_t *) srcp1)[2];
227 b2 = ((op_t *) srcp2)[2];
228 x = MERGE(a0, shl, a1, shr);
230 return CMP_LT_OR_GT (x, b1);
233 a3 = ((op_t *) srcp1)[3];
234 b3 = ((op_t *) srcp2)[3];
235 x = MERGE(a1, shl, a2, shr);
237 return CMP_LT_OR_GT (x, b2);
245 /* This is the right position for do0. Please don't move
248 x = MERGE(a2, shl, a3, shr);
250 return CMP_LT_OR_GT (x, b3);
255 memcmp (const __ptr_t s1, const __ptr_t s2, size_t len)
259 long int srcp1 = (long int) s1;
260 long int srcp2 = (long int) s2;
263 if (len >= OP_T_THRES)
265 /* There are at least some bytes to compare. No need to test
266 for LEN == 0 in this alignment loop. */
267 while (srcp2 % OPSIZ != 0)
269 a0 = ((byte *) srcp1)[0];
270 b0 = ((byte *) srcp2)[0];
279 /* SRCP2 is now aligned for memory operations on `op_t'.
280 SRCP1 alignment determines if we can do a simple,
281 aligned compare or need to shuffle bits. */
283 if (srcp1 % OPSIZ == 0)
284 res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ);
286 res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ);
290 /* Number of bytes remaining in the interval [0..OPSIZ-1]. */
291 srcp1 += len & -OPSIZ;
292 srcp2 += len & -OPSIZ;
296 /* There are just a few bytes to compare. Use byte memory operations. */
299 a0 = ((byte *) srcp1)[0];
300 b0 = ((byte *) srcp2)[0];
311 libc_hidden_weak(memcmp)
312 #ifdef __UCLIBC_SUSV3_LEGACY__
313 strong_alias(memcmp,bcmp)