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[/] [openrisc/] [trunk/] [gnu-src/] [gdb-7.1/] [gdb/] [gnulib/] [memcmp.c] - Blame information for rev 493

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1 227 jeremybenn
/* Copyright (C) 1991, 1993, 1995, 1997, 1998, 2003, 2006, 2009, 2010
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,
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   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
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# 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;
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55
# ifndef WORDS_BIGENDIAN
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#  define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
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# else
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#  define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
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# 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))
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#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
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      block after the initial byte operations.  The maximum number of
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      full words (of type op_t) are compared in this way.
79
 
80
   3. Compare the few remaining bytes.  */
81
 
82
#ifndef WORDS_BIGENDIAN
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/* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
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   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

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