src/state.c

   1 /* Type definitions for the finite state machine for Bison.
   2
   3    Copyright (C) 2001-2007, 2009-2010 Free Software Foundation, Inc.
   4
   5    This file is part of Bison, the GNU Compiler Compiler.
   6
   7    This program is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation, either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <config.h>
  21 #include "system.h"
  22
  23 #include <hash.h>
  24
  25 #include "complain.h"
  26 #include "gram.h"
  27 #include "state.h"
  28 #include "print-xml.h"
  29
  30
  31                         /*-------------------.
  32                         | Shifts and Gotos.  |
  33                         `-------------------*/
  34
  35
  36 /*-----------------------------------------.
  37 | Create a new array of NUM shifts/gotos.  |
  38 `-----------------------------------------*/
  39
  40 static transitions *
  41 transitions_new (int num, state **the_states)
  42 {
  43   size_t states_size = num * sizeof *the_states;
  44   transitions *res = xmalloc (offsetof (transitions, states) + states_size);
  45   res->num = num;
  46   memcpy (res->states, the_states, states_size);
  47   return res;
  48 }
  49
  50
  51 /*-------------------------------------------------------.
  52 | Return the state such that SHIFTS contain a shift/goto |
  53 | to it on SYM.  Abort if none found.                    |
  54 `-------------------------------------------------------*/
  55
  56 state *
  57 transitions_to (transitions *shifts, symbol_number sym)
  58 {
  59   int j;
  60   for (j = 0; ; j++)
  61     {
  62       aver (j < shifts->num);
  63       if (TRANSITION_SYMBOL (shifts, j) == sym)
  64         return shifts->states[j];
  65     }
  66 }
  67
  68
  69                         /*--------------------.
  70                         | Error transitions.  |
  71                         `--------------------*/
  72
  73
  74 /*---------------------------------.
  75 | Create a new array of NUM errs.  |
  76 `---------------------------------*/
  77
  78 errs *
  79 errs_new (int num, symbol **tokens)
  80 {
  81   size_t symbols_size = num * sizeof *tokens;
  82   errs *res = xmalloc (offsetof (errs, symbols) + symbols_size);
  83   res->num = num;
  84   memcpy (res->symbols, tokens, symbols_size);
  85   return res;
  86 }
  87
  88
  89
  90
  91                         /*-------------.
  92                         | Reductions.  |
  93                         `-------------*/
  94
  95
  96 /*---------------------------------------.
  97 | Create a new array of NUM reductions.  |
  98 `---------------------------------------*/
  99
 100 static reductions *
 101 reductions_new (int num, rule **reds)
 102 {
 103   size_t rules_size = num * sizeof *reds;
 104   reductions *res = xmalloc (offsetof (reductions, rules) + rules_size);
 105   res->num = num;
 106   res->lookahead_tokens = NULL;
 107   memcpy (res->rules, reds, rules_size);
 108   return res;
 109 }
 110
 111
 112
 113                         /*---------.
 114                         | States.  |
 115                         `---------*/
 116
 117
 118 state_number nstates = 0;
 119 /* FINAL_STATE is properly set by new_state when it recognizes its
 120    accessing symbol: $end.  */
 121 state *final_state = NULL;
 122
 123
 124 /*------------------------------------------------------------------.
 125 | Create a new state with ACCESSING_SYMBOL, for those items.  Store |
 126 | it in the state hash table.                                       |
 127 `------------------------------------------------------------------*/
 128
 129 state *
 130 state_new (symbol_number accessing_symbol,
 131            size_t nitems, item_number *core)
 132 {
 133   state *res;
 134   size_t items_size = nitems * sizeof *core;
 135
 136   aver (nstates < STATE_NUMBER_MAXIMUM);
 137
 138   res = xmalloc (offsetof (state, items) + items_size);
 139   res->number = nstates++;
 140   res->accessing_symbol = accessing_symbol;
 141   res->transitions = NULL;
 142   res->reductions = NULL;
 143   res->errs = NULL;
 144   res->state_list = NULL;
 145   res->consistent = 0;
 146   res->solved_conflicts = NULL;
 147   res->solved_conflicts_xml = NULL;
 148
 149   res->nitems = nitems;
 150   memcpy (res->items, core, items_size);
 151
 152   state_hash_insert (res);
 153
 154   return res;
 155 }
 156
 157 state *
 158 state_new_isocore (state const *s)
 159 {
 160   state *res;
 161   size_t items_size = s->nitems * sizeof *s->items;
 162
 163   aver (nstates < STATE_NUMBER_MAXIMUM);
 164
 165   res = xmalloc (offsetof (state, items) + items_size);
 166   res->number = nstates++;
 167   res->accessing_symbol = s->accessing_symbol;
 168   res->transitions =
 169     transitions_new (s->transitions->num, s->transitions->states);
 170   res->reductions = reductions_new (s->reductions->num, s->reductions->rules);
 171   res->errs = NULL;
 172   res->state_list = NULL;
 173   res->consistent = s->consistent;
 174   res->solved_conflicts = NULL;
 175   res->solved_conflicts_xml = NULL;
 176
 177   res->nitems = s->nitems;
 178   memcpy (res->items, s->items, items_size);
 179
 180   return res;
 181 }
 182
 183
 184 /*---------.
 185 | Free S.  |
 186 `---------*/
 187
 188 static void
 189 state_free (state *s)
 190 {
 191   free (s->transitions);
 192   free (s->reductions);
 193   free (s->errs);
 194   free (s);
 195 }
 196
 197
 198 /*---------------------------.
 199 | Set the transitions of S.  |
 200 `---------------------------*/
 201
 202 void
 203 state_transitions_set (state *s, int num, state **trans)
 204 {
 205   aver (!s->transitions);
 206   s->transitions = transitions_new (num, trans);
 207 }
 208
 209
 210 /*--------------------------.
 211 | Set the reductions of S.  |
 212 `--------------------------*/
 213
 214 void
 215 state_reductions_set (state *s, int num, rule **reds)
 216 {
 217   aver (!s->reductions);
 218   s->reductions = reductions_new (num, reds);
 219 }
 220
 221
 222 int
 223 state_reduction_find (state *s, rule *r)
 224 {
 225   int i;
 226   reductions *reds = s->reductions;
 227   for (i = 0; i < reds->num; ++i)
 228     if (reds->rules[i] == r)
 229       return i;
 230   return -1;
 231 }
 232
 233
 234 /*--------------------.
 235 | Set the errs of S.  |
 236 `--------------------*/
 237
 238 void
 239 state_errs_set (state *s, int num, symbol **tokens)
 240 {
 241   aver (!s->errs);
 242   s->errs = errs_new (num, tokens);
 243 }
 244
 245
 246
 247 /*--------------------------------------------------.
 248 | Print on OUT all the lookahead tokens such that S |
 249 | wants to reduce R.                                |
 250 `--------------------------------------------------*/
 251
 252 void
 253 state_rule_lookahead_tokens_print (state *s, rule *r, FILE *out)
 254 {
 255   /* Find the reduction we are handling.  */
 256   reductions *reds = s->reductions;
 257   int red = state_reduction_find (s, r);
 258
 259   /* Print them if there are.  */
 260   if (reds->lookahead_tokens && red != -1)
 261     {
 262       bitset_iterator biter;
 263       int k;
 264       char const *sep = "";
 265       fprintf (out, "  [");
 266       BITSET_FOR_EACH (biter, reds->lookahead_tokens[red], k, 0)
 267         {
 268           fprintf (out, "%s%s", sep, symbols[k]->tag);
 269           sep = ", ";
 270         }
 271       fprintf (out, "]");
 272     }
 273 }
 274
 275 void
 276 state_rule_lookahead_tokens_print_xml (state *s, rule *r,
 277                                        FILE *out, int level)
 278 {
 279   /* Find the reduction we are handling.  */
 280   reductions *reds = s->reductions;
 281   int red = state_reduction_find (s, r);
 282
 283   /* Print them if there are.  */
 284   if (reds->lookahead_tokens && red != -1)
 285     {
 286       bitset_iterator biter;
 287       int k;
 288       xml_puts (out, level, "<lookaheads>");
 289       BITSET_FOR_EACH (biter, reds->lookahead_tokens[red], k, 0)
 290         {
 291           xml_printf (out, level + 1, "<symbol>%s</symbol>",
 292                       xml_escape (symbols[k]->tag));
 293         }
 294       xml_puts (out, level, "</lookaheads>");
 295     }
 296 }
 297
 298
 299 /*---------------------.
 300 | A state hash table.  |
 301 `---------------------*/
 302
 303 /* Initial capacity of states hash table.  */
 304 #define HT_INITIAL_CAPACITY 257
 305
 306 static struct hash_table *state_table = NULL;
 307
 308 /* Two states are equal if they have the same core items.  */
 309 static inline bool
 310 state_compare (state const *s1, state const *s2)
 311 {
 312   size_t i;
 313
 314   if (s1->nitems != s2->nitems)
 315     return false;
 316
 317   for (i = 0; i < s1->nitems; ++i)
 318     if (s1->items[i] != s2->items[i])
 319       return false;
 320
 321   return true;
 322 }
 323
 324 static bool
 325 state_comparator (void const *s1, void const *s2)
 326 {
 327   return state_compare (s1, s2);
 328 }
 329
 330 static inline size_t
 331 state_hash (state const *s, size_t tablesize)
 332 {
 333   /* Add up the state's item numbers to get a hash key.  */
 334   size_t key = 0;
 335   size_t i;
 336   for (i = 0; i < s->nitems; ++i)
 337     key += s->items[i];
 338   return key % tablesize;
 339 }
 340
 341 static size_t
 342 state_hasher (void const *s, size_t tablesize)
 343 {
 344   return state_hash (s, tablesize);
 345 }
 346
 347
 348 /*-------------------------------.
 349 | Create the states hash table.  |
 350 `-------------------------------*/
 351
 352 void
 353 state_hash_new (void)
 354 {
 355   state_table = hash_initialize (HT_INITIAL_CAPACITY,
 356                                  NULL,
 357                                  state_hasher,
 358                                  state_comparator,
 359                                  NULL);
 360 }
 361
 362
 363 /*---------------------------------------------.
 364 | Free the states hash table, not the states.  |
 365 `---------------------------------------------*/
 366
 367 void
 368 state_hash_free (void)
 369 {
 370   hash_free (state_table);
 371 }
 372
 373
 374 /*-----------------------------------.
 375 | Insert S in the state hash table.  |
 376 `-----------------------------------*/
 377
 378 void
 379 state_hash_insert (state *s)
 380 {
 381   if (!hash_insert (state_table, s))
 382     xalloc_die ();
 383 }
 384
 385
 386 /*------------------------------------------------------------------.
 387 | Find the state associated to the CORE, and return it.  If it does |
 388 | not exist yet, return NULL.                                       |
 389 `------------------------------------------------------------------*/
 390
 391 state *
 392 state_hash_lookup (size_t nitems, item_number *core)
 393 {
 394   size_t items_size = nitems * sizeof *core;
 395   state *probe = xmalloc (offsetof (state, items) + items_size);
 396   state *entry;
 397
 398   probe->nitems = nitems;
 399   memcpy (probe->items, core, items_size);
 400   entry = hash_lookup (state_table, probe);
 401   free (probe);
 402   return entry;
 403 }
 404
 405
 406 /*--------------------------------------------------------.
 407 | Record S and all states reachable from S in REACHABLE.  |
 408 `--------------------------------------------------------*/
 409
 410 static void
 411 state_record_reachable_states (state *s, bitset reachable)
 412 {
 413   if (bitset_test (reachable, s->number))
 414     return;
 415   bitset_set (reachable, s->number);
 416   {
 417     int i;
 418     for (i = 0; i < s->transitions->num; ++i)
 419       if (!TRANSITION_IS_DISABLED (s->transitions, i))
 420         state_record_reachable_states (s->transitions->states[i], reachable);
 421   }
 422 }
 423
 424 void
 425 state_remove_unreachable_states (state_number old_to_new[])
 426 {
 427   state_number nstates_reachable = 0;
 428   bitset reachable = bitset_create (nstates, BITSET_FIXED);
 429   state_record_reachable_states (states[0], reachable);
 430   {
 431     state_number i;
 432     for (i = 0; i < nstates; ++i)
 433       {
 434         if (bitset_test (reachable, states[i]->number))
 435           {
 436             states[nstates_reachable] = states[i];
 437             states[nstates_reachable]->number = nstates_reachable;
 438             old_to_new[i] = nstates_reachable++;
 439           }
 440         else
 441           {
 442             state_free (states[i]);
 443             old_to_new[i] = nstates;
 444           }
 445       }
 446   }
 447   nstates = nstates_reachable;
 448   bitset_free (reachable);
 449 }
 450
 451 /* All the decorated states, indexed by the state number.  */
 452 state **states = NULL;
 453
 454
 455 /*----------------------.
 456 | Free all the states.  |
 457 `----------------------*/
 458
 459 void
 460 states_free (void)
 461 {
 462   state_number i;
 463   for (i = 0; i < nstates; ++i)
 464     state_free (states[i]);
 465   free (states);
 466 }