1 /* Hash tables. 2 Copyright (C) 2000, 2001, 2003, 2004, 2008, 2009 3 Free Software Foundation, Inc. 4 5 This program is free software; you can redistribute it and/or modify it 6 under the terms of the GNU General Public License as published by the 7 Free Software Foundation; either version 3, or (at your option) any 8 later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program; see the file COPYING3. If not see 17 <http://www.gnu.org/licenses/>. 18 19 In other words, you are welcome to use, share and improve this program. 20 You are forbidden to forbid anyone else to use, share and improve 21 what you give them. Help stamp out software-hoarding! */ 22 23 #include "config.h" 24 #include "system.h" 25 #include "symtab.h" 26 27 /* The code below is a specialization of Vladimir Makarov's expandable 28 hash tables (see libiberty/hashtab.c). The abstraction penalty was 29 too high to continue using the generic form. This code knows 30 intrinsically how to calculate a hash value, and how to compare an 31 existing entry with a potential new one. */ 32 33 static unsigned int calc_hash (const unsigned char *, size_t); 34 static void ht_expand (hash_table *); 35 static double approx_sqrt (double); 36 37 /* A deleted entry. */ 38 #define DELETED ((hashnode) -1) 39 40 /* Calculate the hash of the string STR of length LEN. */ 41 42 static unsigned int 43 calc_hash (const unsigned char *str, size_t len) 44 { 45 size_t n = len; 46 unsigned int r = 0; 47 48 while (n--) 49 r = HT_HASHSTEP (r, *str++); 50 51 return HT_HASHFINISH (r, len); 52 } 53 54 /* Initialize an identifier hashtable. */ 55 56 hash_table * 57 ht_create (unsigned int order) 58 { 59 unsigned int nslots = 1 << order; 60 hash_table *table; 61 62 table = XCNEW (hash_table); 63 64 /* Strings need no alignment. */ 65 _obstack_begin (&table->stack, 0, 0, 66 (void *(*) (long)) xmalloc, 67 (void (*) (void *)) free); 68 69 obstack_alignment_mask (&table->stack) = 0; 70 71 table->entries = XCNEWVEC (hashnode, nslots); 72 table->entries_owned = true; 73 table->nslots = nslots; 74 return table; 75 } 76 77 /* Frees all memory associated with a hash table. */ 78 79 void 80 ht_destroy (hash_table *table) 81 { 82 obstack_free (&table->stack, NULL); 83 if (table->entries_owned) 84 free (table->entries); 85 free (table); 86 } 87 88 /* Returns the hash entry for the a STR of length LEN. If that string 89 already exists in the table, returns the existing entry. If the 90 identifier hasn't been seen before, and INSERT is CPP_NO_INSERT, 91 returns NULL. Otherwise insert and returns a new entry. A new 92 string is allocated. */ 93 hashnode 94 ht_lookup (hash_table *table, const unsigned char *str, size_t len, 95 enum ht_lookup_option insert) 96 { 97 return ht_lookup_with_hash (table, str, len, calc_hash (str, len), 98 insert); 99 } 100 101 hashnode 102 ht_lookup_with_hash (hash_table *table, const unsigned char *str, 103 size_t len, unsigned int hash, 104 enum ht_lookup_option insert) 105 { 106 unsigned int hash2; 107 unsigned int index; 108 unsigned int deleted_index = table->nslots; 109 size_t sizemask; 110 hashnode node; 111 112 sizemask = table->nslots - 1; 113 index = hash & sizemask; 114 table->searches++; 115 116 node = table->entries[index]; 117 118 if (node != NULL) 119 { 120 if (node == DELETED) 121 deleted_index = index; 122 else if (node->hash_value == hash 123 && HT_LEN (node) == (unsigned int) len 124 && !memcmp (HT_STR (node), str, len)) 125 return node; 126 127 /* hash2 must be odd, so we're guaranteed to visit every possible 128 location in the table during rehashing. */ 129 hash2 = ((hash * 17) & sizemask) | 1; 130 131 for (;;) 132 { 133 table->collisions++; 134 index = (index + hash2) & sizemask; 135 node = table->entries[index]; 136 if (node == NULL) 137 break; 138 139 if (node == DELETED) 140 { 141 if (deleted_index != table->nslots) 142 deleted_index = index; 143 } 144 else if (node->hash_value == hash 145 && HT_LEN (node) == (unsigned int) len 146 && !memcmp (HT_STR (node), str, len)) 147 return node; 148 } 149 } 150 151 if (insert == HT_NO_INSERT) 152 return NULL; 153 154 /* We prefer to overwrite the first deleted slot we saw. */ 155 if (deleted_index != table->nslots) 156 index = deleted_index; 157 158 node = (*table->alloc_node) (table); 159 table->entries[index] = node; 160 161 HT_LEN (node) = (unsigned int) len; 162 node->hash_value = hash; 163 164 if (table->alloc_subobject) 165 { 166 char *chars = (char *) table->alloc_subobject (len + 1); 167 memcpy (chars, str, len); 168 chars[len] = '\0'; 169 HT_STR (node) = (const unsigned char *) chars; 170 } 171 else 172 HT_STR (node) = (const unsigned char *) obstack_copy0 (&table->stack, 173 str, len); 174 175 if (++table->nelements * 4 >= table->nslots * 3) 176 /* Must expand the string table. */ 177 ht_expand (table); 178 179 return node; 180 } 181 182 /* Double the size of a hash table, re-hashing existing entries. */ 183 184 static void 185 ht_expand (hash_table *table) 186 { 187 hashnode *nentries, *p, *limit; 188 unsigned int size, sizemask; 189 190 size = table->nslots * 2; 191 nentries = XCNEWVEC (hashnode, size); 192 sizemask = size - 1; 193 194 p = table->entries; 195 limit = p + table->nslots; 196 do 197 if (*p && *p != DELETED) 198 { 199 unsigned int index, hash, hash2; 200 201 hash = (*p)->hash_value; 202 index = hash & sizemask; 203 204 if (nentries[index]) 205 { 206 hash2 = ((hash * 17) & sizemask) | 1; 207 do 208 { 209 index = (index + hash2) & sizemask; 210 } 211 while (nentries[index]); 212 } 213 nentries[index] = *p; 214 } 215 while (++p < limit); 216 217 if (table->entries_owned) 218 free (table->entries); 219 table->entries_owned = true; 220 table->entries = nentries; 221 table->nslots = size; 222 } 223 224 /* For all nodes in TABLE, callback CB with parameters TABLE->PFILE, 225 the node, and V. */ 226 void 227 ht_forall (hash_table *table, ht_cb cb, const void *v) 228 { 229 hashnode *p, *limit; 230 231 p = table->entries; 232 limit = p + table->nslots; 233 do 234 if (*p && *p != DELETED) 235 { 236 if ((*cb) (table->pfile, *p, v) == 0) 237 break; 238 } 239 while (++p < limit); 240 } 241 242 /* Like ht_forall, but a nonzero return from the callback means that 243 the entry should be removed from the table. */ 244 void 245 ht_purge (hash_table *table, ht_cb cb, const void *v) 246 { 247 hashnode *p, *limit; 248 249 p = table->entries; 250 limit = p + table->nslots; 251 do 252 if (*p && *p != DELETED) 253 { 254 if ((*cb) (table->pfile, *p, v)) 255 *p = DELETED; 256 } 257 while (++p < limit); 258 } 259 260 /* Restore the hash table. */ 261 void 262 ht_load (hash_table *ht, hashnode *entries, 263 unsigned int nslots, unsigned int nelements, 264 bool own) 265 { 266 if (ht->entries_owned) 267 free (ht->entries); 268 ht->entries = entries; 269 ht->nslots = nslots; 270 ht->nelements = nelements; 271 ht->entries_owned = own; 272 } 273 274 /* Dump allocation statistics to stderr. */ 275 276 void 277 ht_dump_statistics (hash_table *table) 278 { 279 size_t nelts, nids, overhead, headers; 280 size_t total_bytes, longest, deleted = 0; 281 double sum_of_squares, exp_len, exp_len2, exp2_len; 282 hashnode *p, *limit; 283 284 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \ 285 ? (x) \ 286 : ((x) < 1024*1024*10 \ 287 ? (x) / 1024 \ 288 : (x) / (1024*1024)))) 289 #define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M')) 290 291 total_bytes = longest = sum_of_squares = nids = 0; 292 p = table->entries; 293 limit = p + table->nslots; 294 do 295 if (*p == DELETED) 296 ++deleted; 297 else if (*p) 298 { 299 size_t n = HT_LEN (*p); 300 301 total_bytes += n; 302 sum_of_squares += (double) n * n; 303 if (n > longest) 304 longest = n; 305 nids++; 306 } 307 while (++p < limit); 308 309 nelts = table->nelements; 310 overhead = obstack_memory_used (&table->stack) - total_bytes; 311 headers = table->nslots * sizeof (hashnode); 312 313 fprintf (stderr, "\nString pool\nentries\t\t%lu\n", 314 (unsigned long) nelts); 315 fprintf (stderr, "identifiers\t%lu (%.2f%%)\n", 316 (unsigned long) nids, nids * 100.0 / nelts); 317 fprintf (stderr, "slots\t\t%lu\n", 318 (unsigned long) table->nslots); 319 fprintf (stderr, "deleted\t\t%lu\n", 320 (unsigned long) deleted); 321 fprintf (stderr, "bytes\t\t%lu%c (%lu%c overhead)\n", 322 SCALE (total_bytes), LABEL (total_bytes), 323 SCALE (overhead), LABEL (overhead)); 324 fprintf (stderr, "table size\t%lu%c\n", 325 SCALE (headers), LABEL (headers)); 326 327 exp_len = (double)total_bytes / (double)nelts; 328 exp2_len = exp_len * exp_len; 329 exp_len2 = (double) sum_of_squares / (double) nelts; 330 331 fprintf (stderr, "coll/search\t%.4f\n", 332 (double) table->collisions / (double) table->searches); 333 fprintf (stderr, "ins/search\t%.4f\n", 334 (double) nelts / (double) table->searches); 335 fprintf (stderr, "avg. entry\t%.2f bytes (+/- %.2f)\n", 336 exp_len, approx_sqrt (exp_len2 - exp2_len)); 337 fprintf (stderr, "longest entry\t%lu\n", 338 (unsigned long) longest); 339 #undef SCALE 340 #undef LABEL 341 } 342 343 /* Return the approximate positive square root of a number N. This is for 344 statistical reports, not code generation. */ 345 static double 346 approx_sqrt (double x) 347 { 348 double s, d; 349 350 if (x < 0) 351 abort (); 352 if (x == 0) 353 return 0; 354 355 s = x; 356 do 357 { 358 d = (s * s - x) / (2 * s); 359 s -= d; 360 } 361 while (d > .0001); 362 return s; 363 } 364