aboutsummaryrefslogtreecommitdiff
path: root/libcpp/symtab.c
blob: 2849929c9199fa07b1c803a62baa5966a62dd1ba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
/* Hash tables.
   Copyright (C) 2000-2016 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3, or (at your option) any
later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.

 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve
 what you give them.   Help stamp out software-hoarding!  */

#include "config.h"
#include "system.h"
#include "symtab.h"

/* The code below is a specialization of Vladimir Makarov's expandable
   hash tables (see libiberty/hashtab.c).  The abstraction penalty was
   too high to continue using the generic form.  This code knows
   intrinsically how to calculate a hash value, and how to compare an
   existing entry with a potential new one.  */

static unsigned int calc_hash (const unsigned char *, size_t);
static void ht_expand (cpp_hash_table *);
static double approx_sqrt (double);

/* A deleted entry.  */
#define DELETED ((hashnode) -1)

/* Calculate the hash of the string STR of length LEN.  */

static unsigned int
calc_hash (const unsigned char *str, size_t len)
{
  size_t n = len;
  unsigned int r = 0;

  while (n--)
    r = HT_HASHSTEP (r, *str++);

  return HT_HASHFINISH (r, len);
}

/* Initialize an identifier hashtable.  */

cpp_hash_table *
ht_create (unsigned int order)
{
  unsigned int nslots = 1 << order;
  cpp_hash_table *table;

  table = XCNEW (cpp_hash_table);

  /* Strings need no alignment.  */
  obstack_specify_allocation (&table->stack, 0, 0, xmalloc, free);

  obstack_alignment_mask (&table->stack) = 0;

  table->entries = XCNEWVEC (hashnode, nslots);
  table->entries_owned = true;
  table->nslots = nslots;
  return table;
}

/* Frees all memory associated with a hash table.  */

void
ht_destroy (cpp_hash_table *table)
{
  obstack_free (&table->stack, NULL);
  if (table->entries_owned)
    free (table->entries);
  free (table);
}

/* Returns the hash entry for the a STR of length LEN.  If that string
   already exists in the table, returns the existing entry.  If the
   identifier hasn't been seen before, and INSERT is CPP_NO_INSERT,
   returns NULL.  Otherwise insert and returns a new entry.  A new
   string is allocated.  */
hashnode
ht_lookup (cpp_hash_table *table, const unsigned char *str, size_t len,
	   enum ht_lookup_option insert)
{
  return ht_lookup_with_hash (table, str, len, calc_hash (str, len),
			      insert);
}

hashnode
ht_lookup_with_hash (cpp_hash_table *table, const unsigned char *str,
		     size_t len, unsigned int hash,
		     enum ht_lookup_option insert)
{
  unsigned int hash2;
  unsigned int index;
  unsigned int deleted_index = table->nslots;
  size_t sizemask;
  hashnode node;

  sizemask = table->nslots - 1;
  index = hash & sizemask;
  table->searches++;

  node = table->entries[index];

  if (node != NULL)
    {
      if (node == DELETED)
	deleted_index = index;
      else if (node->hash_value == hash
	       && HT_LEN (node) == (unsigned int) len
	       && !memcmp (HT_STR (node), str, len))
	return node;

      /* hash2 must be odd, so we're guaranteed to visit every possible
	 location in the table during rehashing.  */
      hash2 = ((hash * 17) & sizemask) | 1;

      for (;;)
	{
	  table->collisions++;
	  index = (index + hash2) & sizemask;
	  node = table->entries[index];
	  if (node == NULL)
	    break;

	  if (node == DELETED)
	    {
	      if (deleted_index != table->nslots)
		deleted_index = index;
	    }
	  else if (node->hash_value == hash
		   && HT_LEN (node) == (unsigned int) len
		   && !memcmp (HT_STR (node), str, len))
	    return node;
	}
    }

  if (insert == HT_NO_INSERT)
    return NULL;

  /* We prefer to overwrite the first deleted slot we saw.  */
  if (deleted_index != table->nslots)
    index = deleted_index;

  node = (*table->alloc_node) (table);
  table->entries[index] = node;

  HT_LEN (node) = (unsigned int) len;
  node->hash_value = hash;

  if (table->alloc_subobject)
    {
      char *chars = (char *) table->alloc_subobject (len + 1);
      memcpy (chars, str, len);
      chars[len] = '\0';
      HT_STR (node) = (const unsigned char *) chars;
    }
  else
    HT_STR (node) = (const unsigned char *) obstack_copy0 (&table->stack,
							   str, len);

  if (++table->nelements * 4 >= table->nslots * 3)
    /* Must expand the string table.  */
    ht_expand (table);

  return node;
}

/* Double the size of a hash table, re-hashing existing entries.  */

static void
ht_expand (cpp_hash_table *table)
{
  hashnode *nentries, *p, *limit;
  unsigned int size, sizemask;

  size = table->nslots * 2;
  nentries = XCNEWVEC (hashnode, size);
  sizemask = size - 1;

  p = table->entries;
  limit = p + table->nslots;
  do
    if (*p && *p != DELETED)
      {
	unsigned int index, hash, hash2;

	hash = (*p)->hash_value;
	index = hash & sizemask;

	if (nentries[index])
	  {
	    hash2 = ((hash * 17) & sizemask) | 1;
	    do
	      {
		index = (index + hash2) & sizemask;
	      }
	    while (nentries[index]);
	  }
	nentries[index] = *p;
      }
  while (++p < limit);

  if (table->entries_owned)
    free (table->entries);
  table->entries_owned = true;
  table->entries = nentries;
  table->nslots = size;
}

/* For all nodes in TABLE, callback CB with parameters TABLE->PFILE,
   the node, and V.  */
void
ht_forall (cpp_hash_table *table, ht_cb cb, const void *v)
{
  hashnode *p, *limit;

  p = table->entries;
  limit = p + table->nslots;
  do
    if (*p && *p != DELETED)
      {
	if ((*cb) (table->pfile, *p, v) == 0)
	  break;
      }
  while (++p < limit);
}

/* Like ht_forall, but a nonzero return from the callback means that
   the entry should be removed from the table.  */
void
ht_purge (cpp_hash_table *table, ht_cb cb, const void *v)
{
  hashnode *p, *limit;

  p = table->entries;
  limit = p + table->nslots;
  do
    if (*p && *p != DELETED)
      {
	if ((*cb) (table->pfile, *p, v))
	  *p = DELETED;
      }
  while (++p < limit);
}

/* Restore the hash table.  */
void
ht_load (cpp_hash_table *ht, hashnode *entries,
	 unsigned int nslots, unsigned int nelements,
	 bool own)
{
  if (ht->entries_owned)
    free (ht->entries);
  ht->entries = entries;
  ht->nslots = nslots;
  ht->nelements = nelements;
  ht->entries_owned = own;
}

/* Dump allocation statistics to stderr.  */

void
ht_dump_statistics (cpp_hash_table *table)
{
  size_t nelts, nids, overhead, headers;
  size_t total_bytes, longest, deleted = 0;
  double sum_of_squares, exp_len, exp_len2, exp2_len;
  hashnode *p, *limit;

#define SCALE(x) ((unsigned long) ((x) < 1024*10 \
		  ? (x) \
		  : ((x) < 1024*1024*10 \
		     ? (x) / 1024 \
		     : (x) / (1024*1024))))
#define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))

  total_bytes = longest = sum_of_squares = nids = 0;
  p = table->entries;
  limit = p + table->nslots;
  do
    if (*p == DELETED)
      ++deleted;
    else if (*p)
      {
	size_t n = HT_LEN (*p);

	total_bytes += n;
	sum_of_squares += (double) n * n;
	if (n > longest)
	  longest = n;
	nids++;
      }
  while (++p < limit);

  nelts = table->nelements;
  overhead = obstack_memory_used (&table->stack) - total_bytes;
  headers = table->nslots * sizeof (hashnode);

  fprintf (stderr, "\nString pool\nentries\t\t%lu\n",
	   (unsigned long) nelts);
  fprintf (stderr, "identifiers\t%lu (%.2f%%)\n",
	   (unsigned long) nids, nids * 100.0 / nelts);
  fprintf (stderr, "slots\t\t%lu\n",
	   (unsigned long) table->nslots);
  fprintf (stderr, "deleted\t\t%lu\n",
	   (unsigned long) deleted);
  fprintf (stderr, "bytes\t\t%lu%c (%lu%c overhead)\n",
	   SCALE (total_bytes), LABEL (total_bytes),
	   SCALE (overhead), LABEL (overhead));
  fprintf (stderr, "table size\t%lu%c\n",
	   SCALE (headers), LABEL (headers));

  exp_len = (double)total_bytes / (double)nelts;
  exp2_len = exp_len * exp_len;
  exp_len2 = (double) sum_of_squares / (double) nelts;

  fprintf (stderr, "coll/search\t%.4f\n",
	   (double) table->collisions / (double) table->searches);
  fprintf (stderr, "ins/search\t%.4f\n",
	   (double) nelts / (double) table->searches);
  fprintf (stderr, "avg. entry\t%.2f bytes (+/- %.2f)\n",
	   exp_len, approx_sqrt (exp_len2 - exp2_len));
  fprintf (stderr, "longest entry\t%lu\n",
	   (unsigned long) longest);
#undef SCALE
#undef LABEL
}

/* Return the approximate positive square root of a number N.  This is for
   statistical reports, not code generation.  */
static double
approx_sqrt (double x)
{
  double s, d;

  if (x < 0)
    abort ();
  if (x == 0)
    return 0;

  s = x;
  do
    {
      d = (s * s - x) / (2 * s);
      s -= d;
    }
  while (d > .0001);
  return s;
}