src/state.c

   1 /* Type definitions for the finite state machine for Bison.
   2
   3    Copyright (C) 2001-2007, 2009-2015, 2018-2021 Free Software
   4    Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "state.h"
  23
  24 #include "system.h"
  25
  26 #include <hash.h>
  27
  28 #include "closure.h"
  29 #include "complain.h"
  30 #include "getargs.h"
  31 #include "gram.h"
  32 #include "print-xml.h"
  33
  34
  35                         /*-------------------.
  36                         | Shifts and Gotos.  |
  37                         `-------------------*/
  38
  39
  40 /*-----------------------------------------.
  41 | Create a new array of NUM shifts/gotos.  |
  42 `-----------------------------------------*/
  43
  44 static transitions *
  45 transitions_new (int num, state **dst)
  46 {
  47   size_t states_size = num * sizeof *dst;
  48   transitions *res = xmalloc (offsetof (transitions, states) + states_size);
  49   res->num = num;
  50   memcpy (res->states, dst, states_size);
  51   return res;
  52 }
  53
  54
  55 state *
  56 transitions_to (state *s, symbol_number sym)
  57 {
  58   transitions *trans = s->transitions;
  59   for (int i = 0; i < trans->num; ++i)
  60     if (TRANSITION_SYMBOL (trans, i) == sym)
  61       return trans->states[i];
  62   abort ();
  63 }
  64
  65
  66                         /*--------------------.
  67                         | Error transitions.  |
  68                         `--------------------*/
  69
  70
  71 /*---------------------------------.
  72 | Create a new array of NUM errs.  |
  73 `---------------------------------*/
  74
  75 errs *
  76 errs_new (int num, symbol **tokens)
  77 {
  78   size_t symbols_size = num * sizeof *tokens;
  79   errs *res = xmalloc (offsetof (errs, symbols) + symbols_size);
  80   res->num = num;
  81   if (tokens)
  82     memcpy (res->symbols, tokens, symbols_size);
  83   return res;
  84 }
  85
  86
  87
  88
  89                         /*-------------.
  90                         | Reductions.  |
  91                         `-------------*/
  92
  93
  94 /*---------------------------------------.
  95 | Create a new array of NUM reductions.  |
  96 `---------------------------------------*/
  97
  98 static reductions *
  99 reductions_new (int num, rule **reds)
 100 {
 101   size_t rules_size = num * sizeof *reds;
 102   reductions *res = xmalloc (offsetof (reductions, rules) + rules_size);
 103   res->num = num;
 104   res->lookaheads = NULL;
 105   memcpy (res->rules, reds, rules_size);
 106   return res;
 107 }
 108
 109
 110
 111                         /*---------.
 112                         | States.  |
 113                         `---------*/
 114
 115
 116 state_number nstates = 0;
 117 /* FINAL_STATE is properly set by new_state when it recognizes its
 118    accessing symbol: $end.  */
 119 state *final_state = NULL;
 120
 121
 122 /*------------------------------------------------------------------.
 123 | Create a new state with ACCESSING_SYMBOL, for those items.  Store |
 124 | it in the state hash table.                                       |
 125 `------------------------------------------------------------------*/
 126
 127 state *
 128 state_new (symbol_number accessing_symbol,
 129            size_t nitems, item_index *core)
 130 {
 131   aver (nstates < STATE_NUMBER_MAXIMUM);
 132
 133   size_t items_size = nitems * sizeof *core;
 134   state *res = xmalloc (offsetof (state, items) + items_size);
 135   res->number = nstates++;
 136   res->accessing_symbol = accessing_symbol;
 137   res->transitions = NULL;
 138   res->reductions = NULL;
 139   res->errs = NULL;
 140   res->state_list = NULL;
 141   res->consistent = false;
 142   res->solved_conflicts = NULL;
 143   res->solved_conflicts_xml = NULL;
 144
 145   res->nitems = nitems;
 146   memcpy (res->items, core, items_size);
 147
 148   state_hash_insert (res);
 149
 150   return res;
 151 }
 152
 153 state *
 154 state_new_isocore (state const *s)
 155 {
 156   aver (nstates < STATE_NUMBER_MAXIMUM);
 157
 158   size_t items_size = s->nitems * sizeof *s->items;
 159   state *res = xmalloc (offsetof (state, items) + items_size);
 160   res->number = nstates++;
 161   res->accessing_symbol = s->accessing_symbol;
 162   res->transitions =
 163     transitions_new (s->transitions->num, s->transitions->states);
 164   res->reductions = reductions_new (s->reductions->num, s->reductions->rules);
 165   res->errs = NULL;
 166   res->state_list = NULL;
 167   res->consistent = s->consistent;
 168   res->solved_conflicts = NULL;
 169   res->solved_conflicts_xml = NULL;
 170
 171   res->nitems = s->nitems;
 172   memcpy (res->items, s->items, items_size);
 173
 174   return res;
 175 }
 176
 177
 178 /*---------.
 179 | Free S.  |
 180 `---------*/
 181
 182 static void
 183 state_free (state *s)
 184 {
 185   free (s->transitions);
 186   free (s->reductions);
 187   free (s->errs);
 188   free (s);
 189 }
 190
 191
 192 void
 193 state_transitions_print (const state *s, FILE *out)
 194 {
 195   const transitions *trans = s->transitions;
 196   fprintf (out, "transitions of %d (%d):\n",
 197            s->number, trans->num);
 198   for (int i = 0; i < trans->num; ++i)
 199     fprintf (out, "  %d: (%d, %s, %d)\n",
 200              i,
 201              s->number,
 202              symbols[s->transitions->states[i]->accessing_symbol]->tag,
 203              s->transitions->states[i]->number);
 204 }
 205
 206
 207 /*---------------------------.
 208 | Set the transitions of S.  |
 209 `---------------------------*/
 210
 211 void
 212 state_transitions_set (state *s, int num, state **dst)
 213 {
 214   aver (!s->transitions);
 215   s->transitions = transitions_new (num, dst);
 216   if (trace_flag & trace_automaton)
 217     state_transitions_print (s, stderr);
 218 }
 219
 220
 221 /*--------------------------.
 222 | Set the reductions of S.  |
 223 `--------------------------*/
 224
 225 void
 226 state_reductions_set (state *s, int num, rule **reds)
 227 {
 228   aver (!s->reductions);
 229   s->reductions = reductions_new (num, reds);
 230 }
 231
 232
 233 int
 234 state_reduction_find (state const *s, rule const *r)
 235 {
 236   reductions *reds = s->reductions;
 237   for (int i = 0; i < reds->num; ++i)
 238     if (reds->rules[i] == r)
 239       return i;
 240   abort ();
 241 }
 242
 243
 244 /*--------------------.
 245 | Set the errs of S.  |
 246 `--------------------*/
 247
 248 void
 249 state_errs_set (state *s, int num, symbol **tokens)
 250 {
 251   aver (!s->errs);
 252   s->errs = errs_new (num, tokens);
 253 }
 254
 255
 256
 257 /*--------------------------------------------------.
 258 | Print on OUT all the lookahead tokens such that S |
 259 | wants to reduce R.                                |
 260 `--------------------------------------------------*/
 261
 262 void
 263 state_rule_lookaheads_print (state const *s, rule const *r, FILE *out)
 264 {
 265   /* Find the reduction we are handling.  */
 266   reductions *reds = s->reductions;
 267   int red = state_reduction_find (s, r);
 268
 269   /* Print them if there are.  */
 270   if (reds->lookaheads && red != -1)
 271     {
 272       bitset_iterator biter;
 273       int k;
 274       char const *sep = "";
 275       fprintf (out, "  [");
 276       BITSET_FOR_EACH (biter, reds->lookaheads[red], k, 0)
 277         {
 278           fprintf (out, "%s%s", sep, symbols[k]->tag);
 279           sep = ", ";
 280         }
 281       fprintf (out, "]");
 282     }
 283 }
 284
 285 void
 286 state_rule_lookaheads_print_xml (state const *s, rule const *r,
 287                                        FILE *out, int level)
 288 {
 289   /* Find the reduction we are handling.  */
 290   reductions *reds = s->reductions;
 291   int red = state_reduction_find (s, r);
 292
 293   /* Print them if there are.  */
 294   if (reds->lookaheads && red != -1)
 295     {
 296       bitset_iterator biter;
 297       int k;
 298       xml_puts (out, level, "<lookaheads>");
 299       BITSET_FOR_EACH (biter, reds->lookaheads[red], k, 0)
 300         {
 301           xml_printf (out, level + 1, "<symbol>%s</symbol>",
 302                       xml_escape (symbols[k]->tag));
 303         }
 304       xml_puts (out, level, "</lookaheads>");
 305     }
 306 }
 307
 308
 309 /*---------------------.
 310 | A state hash table.  |
 311 `---------------------*/
 312
 313 /* Initial capacity of states hash table.  */
 314 #define HT_INITIAL_CAPACITY 257
 315
 316 static struct hash_table *state_table = NULL;
 317
 318 /* Two states are equal if they have the same core items.  */
 319 static inline bool
 320 state_compare (state const *s1, state const *s2)
 321 {
 322   if (s1->nitems != s2->nitems)
 323     return false;
 324
 325   for (size_t i = 0; i < s1->nitems; ++i)
 326     if (s1->items[i] != s2->items[i])
 327       return false;
 328
 329   return true;
 330 }
 331
 332 static bool
 333 state_comparator (void const *s1, void const *s2)
 334 {
 335   return state_compare (s1, s2);
 336 }
 337
 338 static inline size_t
 339 state_hash (state const *s, size_t tablesize)
 340 {
 341   /* Add up the state's item numbers to get a hash key.  */
 342   size_t key = 0;
 343   for (size_t i = 0; i < s->nitems; ++i)
 344     key += s->items[i];
 345   return key % tablesize;
 346 }
 347
 348 static size_t
 349 state_hasher (void const *s, size_t tablesize)
 350 {
 351   return state_hash (s, tablesize);
 352 }
 353
 354
 355 /*-------------------------------.
 356 | Create the states hash table.  |
 357 `-------------------------------*/
 358
 359 void
 360 state_hash_new (void)
 361 {
 362   state_table = hash_xinitialize (HT_INITIAL_CAPACITY,
 363                                   NULL,
 364                                   state_hasher,
 365                                   state_comparator,
 366                                   NULL);
 367 }
 368
 369
 370 /*---------------------------------------------.
 371 | Free the states hash table, not the states.  |
 372 `---------------------------------------------*/
 373
 374 void
 375 state_hash_free (void)
 376 {
 377   hash_free (state_table);
 378 }
 379
 380
 381 /*-----------------------------------.
 382 | Insert S in the state hash table.  |
 383 `-----------------------------------*/
 384
 385 void
 386 state_hash_insert (state *s)
 387 {
 388   hash_xinsert (state_table, s);
 389 }
 390
 391
 392 /*------------------------------------------------------------------.
 393 | Find the state associated to the CORE, and return it.  If it does |
 394 | not exist yet, return NULL.                                       |
 395 `------------------------------------------------------------------*/
 396
 397 state *
 398 state_hash_lookup (size_t nitems, const item_index *core)
 399 {
 400   size_t items_size = nitems * sizeof *core;
 401   state *probe = xmalloc (offsetof (state, items) + items_size);
 402   probe->nitems = nitems;
 403   memcpy (probe->items, core, items_size);
 404   state *entry = hash_lookup (state_table, probe);
 405   free (probe);
 406   return entry;
 407 }
 408
 409
 410 /*--------------------------------------------------------.
 411 | Record S and all states reachable from S in REACHABLE.  |
 412 `--------------------------------------------------------*/
 413
 414 static void
 415 state_record_reachable_states (state *s, bitset reachable)
 416 {
 417   if (bitset_test (reachable, s->number))
 418     return;
 419   bitset_set (reachable, s->number);
 420   for (int i = 0; i < s->transitions->num; ++i)
 421     if (!TRANSITION_IS_DISABLED (s->transitions, i))
 422       state_record_reachable_states (s->transitions->states[i], reachable);
 423 }
 424
 425 void
 426 state_remove_unreachable_states (state_number old_to_new[])
 427 {
 428   state_number nstates_reachable = 0;
 429   bitset reachable = bitset_create (nstates, BITSET_FIXED);
 430   state_record_reachable_states (states[0], reachable);
 431   for (state_number i = 0; i < nstates; ++i)
 432     {
 433       if (bitset_test (reachable, states[i]->number))
 434         {
 435           states[nstates_reachable] = states[i];
 436           states[nstates_reachable]->number = nstates_reachable;
 437           old_to_new[i] = nstates_reachable++;
 438         }
 439       else
 440         {
 441           state_free (states[i]);
 442           old_to_new[i] = nstates;
 443         }
 444     }
 445   nstates = nstates_reachable;
 446   bitset_free (reachable);
 447 }
 448
 449 /* All the decorated states, indexed by the state number.  */
 450 state **states = NULL;
 451
 452
 453 /*----------------------.
 454 | Free all the states.  |
 455 `----------------------*/
 456
 457 void
 458 states_free (void)
 459 {
 460   closure_free ();
 461   for (state_number i = 0; i < nstates; ++i)
 462     state_free (states[i]);
 463   free (states);
 464 }