src/lalr.c

/* Compute lookahead criteria for Bison.

   Copyright (C) 1984, 1986, 1989, 2000-2010 Free Software Foundation,
   Inc.

   This file is part of Bison, the GNU Compiler Compiler.

   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 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.  */


/* Find which rules need lookahead in each state, and which lookahead
   tokens they accept.  */

#include <config.h>
#include "system.h"

#include <bitset.h>
#include <bitsetv.h>
#include <quotearg.h>

#include "LR0.h"
#include "complain.h"
#include "derives.h"
#include "getargs.h"
#include "gram.h"
#include "lalr.h"
#include "muscle-tab.h"
#include "nullable.h"
#include "reader.h"
#include "relation.h"
#include "symtab.h"

goto_number *goto_map;
goto_number ngotos;
state_number *from_state;
state_number *to_state;
bitsetv goto_follows = NULL;

/* Linked list of goto numbers.  */
typedef struct goto_list
{
  struct goto_list *next;
  goto_number value;
} goto_list;


/* LA is an NLA by NTOKENS matrix of bits.  LA[l, i] is 1 if the rule
   LArule[l] is applicable in the appropriate state when the next
   token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
   it is a conflict.  */

static bitsetv LA = NULL;
size_t nLA;


static goto_number **includes;
static goto_list **lookback;


void
set_goto_map (void)
{
  state_number s;
  goto_number *temp_map;

  goto_map = xcalloc (nvars + 1, sizeof *goto_map);
  temp_map = xnmalloc (nvars + 1, sizeof *temp_map);

  ngotos = 0;
  for (s = 0; s < nstates; ++s)
    {
      transitions *sp = states[s]->transitions;
      int i;
      for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
	{
	  ngotos++;

	  /* Abort if (ngotos + 1) would overflow.  */
	  aver (ngotos != GOTO_NUMBER_MAXIMUM);

	  goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
	}
    }

  {
    goto_number k = 0;
    int i;
    for (i = ntokens; i < nsyms; i++)
      {
	temp_map[i - ntokens] = k;
	k += goto_map[i - ntokens];
      }

    for (i = ntokens; i < nsyms; i++)
      goto_map[i - ntokens] = temp_map[i - ntokens];

    goto_map[nsyms - ntokens] = ngotos;
    temp_map[nsyms - ntokens] = ngotos;
  }

  from_state = xcalloc (ngotos, sizeof *from_state);
  to_state = xcalloc (ngotos, sizeof *to_state);

  for (s = 0; s < nstates; ++s)
    {
      transitions *sp = states[s]->transitions;
      int i;
      for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
	{
	  goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
	  from_state[k] = s;
	  to_state[k] = sp->states[i]->number;
	}
    }

  free (temp_map);
}


goto_number
map_goto (state_number s0, symbol_number sym)
{
  goto_number high;
  goto_number low;
  goto_number middle;
  state_number s;

  low = goto_map[sym - ntokens];
  high = goto_map[sym - ntokens + 1] - 1;

  for (;;)
    {
      aver (low <= high);
      middle = (low + high) / 2;
      s = from_state[middle];
      if (s == s0)
	return middle;
      else if (s < s0)
	low = middle + 1;
      else
	high = middle - 1;
    }
}


static void
initialize_F (void)
{
  goto_number **reads = xnmalloc (ngotos, sizeof *reads);
  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
  goto_number nedges = 0;

  goto_number i;

  goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);

  for (i = 0; i < ngotos; i++)
    {
      state_number stateno = to_state[i];
      transitions *sp = states[stateno]->transitions;

      int j;
      FOR_EACH_SHIFT (sp, j)
	bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));

      for (; j < sp->num; j++)
	{
	  symbol_number sym = TRANSITION_SYMBOL (sp, j);
	  if (nullable[sym - ntokens])
	    edge[nedges++] = map_goto (stateno, sym);
	}

      if (nedges == 0)
	reads[i] = NULL;
      else
	{
	  reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]);
	  memcpy (reads[i], edge, nedges * sizeof edge[0]);
	  reads[i][nedges] = END_NODE;
	  nedges = 0;
	}
    }

  relation_digraph (reads, ngotos, &goto_follows);

  for (i = 0; i < ngotos; i++)
    free (reads[i]);

  free (reads);
  free (edge);
}


static void
add_lookback_edge (state *s, rule *r, goto_number gotono)
{
  int ri = state_reduction_find (s, r);
  goto_list *sp = xmalloc (sizeof *sp);
  sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri];
  sp->value = gotono;
  lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
}


static void
build_relations (void)
{
  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
  state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
  goto_number i;

  includes = xnmalloc (ngotos, sizeof *includes);

  for (i = 0; i < ngotos; i++)
    {
      int nedges = 0;
      symbol_number symbol1 = states[to_state[i]]->accessing_symbol;
      rule **rulep;

      for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
	{
	  bool done;
	  int length = 1;
	  item_number const *rp;
	  state *s = states[from_state[i]];
	  states1[0] = s->number;

	  for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++)
	    {
	      s = transitions_to (s->transitions,
				  item_number_as_symbol_number (*rp));
	      states1[length++] = s->number;
	    }

	  if (!s->consistent)
	    add_lookback_edge (s, *rulep, i);

	  length--;
	  done = false;
	  while (!done)
	    {
	      done = true;
	      /* Each rhs ends in a rule number, and there is a
		 sentinel (ritem[-1]=0) before the first rhs, so it is safe to
		 decrement RP here.  */
	      rp--;
	      if (ISVAR (*rp))
		{
		  /* Downcasting from item_number to symbol_number.  */
		  edge[nedges++] = map_goto (states1[--length],
					     item_number_as_symbol_number (*rp));
		  if (nullable[*rp - ntokens])
		    done = false;
		}
	    }
	}

      if (nedges == 0)
	includes[i] = NULL;
      else
	{
	  int j;
	  includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
	  for (j = 0; j < nedges; j++)
	    includes[i][j] = edge[j];
	  includes[i][nedges] = END_NODE;
	}
    }

  free (edge);
  free (states1);

  relation_transpose (&includes, ngotos);
}


static void
compute_FOLLOWS (void)
{
  goto_number i;

  relation_digraph (includes, ngotos, &goto_follows);

  for (i = 0; i < ngotos; i++)
    free (includes[i]);

  free (includes);
}


static void
compute_lookahead_tokens (void)
{
  size_t i;
  goto_list *sp;

  for (i = 0; i < nLA; i++)
    for (sp = lookback[i]; sp; sp = sp->next)
      bitset_or (LA[i], LA[i], goto_follows[sp->value]);

  /* Free LOOKBACK. */
  for (i = 0; i < nLA; i++)
    LIST_FREE (goto_list, lookback[i]);

  free (lookback);
}


/*----------------------------------------------------.
| Count the number of lookahead tokens required for S |
| (N_LOOKAHEAD_TOKENS member).                        |
`----------------------------------------------------*/

static int
state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)
{
  int n_lookahead_tokens = 0;
  reductions *rp = s->reductions;
  transitions *sp = s->transitions;

  /* Transitions are only disabled during conflict resolution, and that
     hasn't happened yet, so there should be no need to check that
     transition 0 hasn't been disabled before checking if it is a shift.
     However, this check was performed at one time, so we leave it as an
     aver.  */
  aver (sp->num == 0 || !TRANSITION_IS_DISABLED (sp, 0));

  /* We need a lookahead either to distinguish different reductions
     (i.e., there are two or more), or to distinguish a reduction from a
     shift.  Otherwise, it is straightforward, and the state is
     `consistent'.  However, do not treat a state with any reductions as
     consistent unless it is the accepting state (because there is never
     a lookahead token that makes sense there, and so no lookahead token
     should be read) if the user has otherwise disabled default
     reductions.  */
  if (rp->num > 1
      || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0))
      || (rp->num == 1 && rp->rules[0]->number != 0
          && default_reduction_only_for_accept))
    n_lookahead_tokens += rp->num;
  else
    s->consistent = 1;

  return n_lookahead_tokens;
}


/*----------------------------------------------------.
| Compute LA, NLA, and the lookahead_tokens members.  |
`----------------------------------------------------*/

void
initialize_LA (void)
{
  state_number i;
  bitsetv pLA;
  bool default_reduction_only_for_accept;
  {
    char *default_reductions =
      muscle_percent_define_get ("lr.default-reductions");
    default_reduction_only_for_accept =
      0 == strcmp (default_reductions, "accepting");
    free (default_reductions);
  }

  /* Compute the total number of reductions requiring a lookahead.  */
  nLA = 0;
  for (i = 0; i < nstates; i++)
    nLA +=
      state_lookahead_tokens_count (states[i],
                                    default_reduction_only_for_accept);
  /* Avoid having to special case 0.  */
  if (!nLA)
    nLA = 1;

  pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);

  /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
     require lookahead tokens.  */
  for (i = 0; i < nstates; i++)
    {
      int count =
        state_lookahead_tokens_count (states[i],
                                      default_reduction_only_for_accept);
      if (count)
	{
	  states[i]->reductions->lookahead_tokens = pLA;
	  pLA += count;
	}
    }
}


/*---------------------------------------------.
| Output the lookahead tokens for each state.  |
`---------------------------------------------*/

static void
lookahead_tokens_print (FILE *out)
{
  state_number i;
  int j, k;
  fprintf (out, "Lookahead tokens: BEGIN\n");
  for (i = 0; i < nstates; ++i)
    {
      reductions *reds = states[i]->reductions;
      bitset_iterator iter;
      int n_lookahead_tokens = 0;

      if (reds->lookahead_tokens)
	for (k = 0; k < reds->num; ++k)
	  if (reds->lookahead_tokens[k])
	    ++n_lookahead_tokens;

      fprintf (out, "State %d: %d lookahead tokens\n",
	       i, n_lookahead_tokens);

      if (reds->lookahead_tokens)
	for (j = 0; j < reds->num; ++j)
	  BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0)
	  {
	    fprintf (out, "   on %d (%s) -> rule %d\n",
		     k, symbols[k]->tag,
		     reds->rules[j]->number);
	  };
    }
  fprintf (out, "Lookahead tokens: END\n");
}

void
lalr (void)
{
  initialize_LA ();
  set_goto_map ();
  initialize_F ();
  lookback = xcalloc (nLA, sizeof *lookback);
  build_relations ();
  compute_FOLLOWS ();
  compute_lookahead_tokens ();

  if (trace_flag & trace_sets)
    lookahead_tokens_print (stderr);
}


void
lalr_update_state_numbers (state_number old_to_new[], state_number nstates_old)
{
  goto_number ngotos_reachable = 0;
  symbol_number nonterminal = 0;
  aver (nsyms == nvars + ntokens);
  {
    goto_number i;
    for (i = 0; i < ngotos; ++i)
      {
        while (i == goto_map[nonterminal])
          goto_map[nonterminal++] = ngotos_reachable;
        /* If old_to_new[from_state[i]] = nstates_old, remove this goto
           entry.  */
        if (old_to_new[from_state[i]] != nstates_old)
          {
            /* from_state[i] is not removed, so it and thus to_state[i] are
               reachable, so to_state[i] != nstates_old.  */
            aver (old_to_new[to_state[i]] != nstates_old);
            from_state[ngotos_reachable] = old_to_new[from_state[i]];
            to_state[ngotos_reachable] = old_to_new[to_state[i]];
            ++ngotos_reachable;
          }
      }
  }
  while (nonterminal <= nvars)
    {
      aver (ngotos == goto_map[nonterminal]);
      goto_map[nonterminal++] = ngotos_reachable;
    }
  ngotos = ngotos_reachable;
}


void
lalr_free (void)
{
  state_number s;
  for (s = 0; s < nstates; ++s)
    states[s]->reductions->lookahead_tokens = NULL;
  bitsetv_free (LA);
}
Commit	Line	Data
	1	/* Compute lookahead criteria for Bison.
	2
	3	Copyright (C) 1984, 1986, 1989, 2000-2010 Free Software Foundation,
	4	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 <http://www.gnu.org/licenses/>. */
	20
	21
	22	/* Find which rules need lookahead in each state, and which lookahead
	23	tokens they accept. */
	24
	25	#include <config.h>
	26	#include "system.h"
	27
	28	#include <bitset.h>
	29	#include <bitsetv.h>
	30	#include <quotearg.h>
	31
	32	#include "LR0.h"
	33	#include "complain.h"
	34	#include "derives.h"
	35	#include "getargs.h"
	36	#include "gram.h"
	37	#include "lalr.h"
	38	#include "muscle-tab.h"
	39	#include "nullable.h"
	40	#include "reader.h"
	41	#include "relation.h"
	42	#include "symtab.h"
	43
	44	goto_number *goto_map;
	45	goto_number ngotos;
	46	state_number *from_state;
	47	state_number *to_state;
	48	bitsetv goto_follows = NULL;
	49
	50	/* Linked list of goto numbers. */
	51	typedef struct goto_list
	52	{
	53	struct goto_list *next;
	54	goto_number value;
	55	} goto_list;
	56
	57
	58	/* LA is an NLA by NTOKENS matrix of bits. LA[l, i] is 1 if the rule
	59	LArule[l] is applicable in the appropriate state when the next
	60	token is symbol i. If LA[l, i] and LA[l, j] are both 1 for i != j,
	61	it is a conflict. */
	62
	63	static bitsetv LA = NULL;
	64	size_t nLA;
	65
	66
	67	static goto_number **includes;
	68	static goto_list **lookback;
	69
	70
	71
	72
	73	void
	74	set_goto_map (void)
	75	{
	76	state_number s;
	77	goto_number *temp_map;
	78
	79	goto_map = xcalloc (nvars + 1, sizeof *goto_map);
	80	temp_map = xnmalloc (nvars + 1, sizeof *temp_map);
	81
	82	ngotos = 0;
	83	for (s = 0; s < nstates; ++s)
	84	{
	85	transitions *sp = states[s]->transitions;
	86	int i;
	87	for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
	88	{
	89	ngotos++;
	90
	91	/* Abort if (ngotos + 1) would overflow. */
	92	aver (ngotos != GOTO_NUMBER_MAXIMUM);
	93
	94	goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
	95	}
	96	}
	97
	98	{
	99	goto_number k = 0;
	100	int i;
	101	for (i = ntokens; i < nsyms; i++)
	102	{
	103	temp_map[i - ntokens] = k;
	104	k += goto_map[i - ntokens];
	105	}
	106
	107	for (i = ntokens; i < nsyms; i++)
	108	goto_map[i - ntokens] = temp_map[i - ntokens];
	109
	110	goto_map[nsyms - ntokens] = ngotos;
	111	temp_map[nsyms - ntokens] = ngotos;
	112	}
	113
	114	from_state = xcalloc (ngotos, sizeof *from_state);
	115	to_state = xcalloc (ngotos, sizeof *to_state);
	116
	117	for (s = 0; s < nstates; ++s)
	118	{
	119	transitions *sp = states[s]->transitions;
	120	int i;
	121	for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
	122	{
	123	goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
	124	from_state[k] = s;
	125	to_state[k] = sp->states[i]->number;
	126	}
	127	}
	128
	129	free (temp_map);
	130	}
	131
	132
	133	goto_number
	134	map_goto (state_number s0, symbol_number sym)
	135	{
	136	goto_number high;
	137	goto_number low;
	138	goto_number middle;
	139	state_number s;
	140
	141	low = goto_map[sym - ntokens];
	142	high = goto_map[sym - ntokens + 1] - 1;
	143
	144	for (;;)
	145	{
	146	aver (low <= high);
	147	middle = (low + high) / 2;
	148	s = from_state[middle];
	149	if (s == s0)
	150	return middle;
	151	else if (s < s0)
	152	low = middle + 1;
	153	else
	154	high = middle - 1;
	155	}
	156	}
	157
	158
	159	static void
	160	initialize_F (void)
	161	{
	162	goto_number *reads = xnmalloc (ngotos, sizeof reads);
	163	goto_number edge = xnmalloc (ngotos + 1, sizeof edge);
	164	goto_number nedges = 0;
	165
	166	goto_number i;
	167
	168	goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
	169
	170	for (i = 0; i < ngotos; i++)
	171	{
	172	state_number stateno = to_state[i];
	173	transitions *sp = states[stateno]->transitions;
	174
	175	int j;
	176	FOR_EACH_SHIFT (sp, j)
	177	bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));
	178
	179	for (; j < sp->num; j++)
	180	{
	181	symbol_number sym = TRANSITION_SYMBOL (sp, j);
	182	if (nullable[sym - ntokens])
	183	edge[nedges++] = map_goto (stateno, sym);
	184	}
	185
	186	if (nedges == 0)
	187	reads[i] = NULL;
	188	else
	189	{
	190	reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]);
	191	memcpy (reads[i], edge, nedges * sizeof edge[0]);
	192	reads[i][nedges] = END_NODE;
	193	nedges = 0;
	194	}
	195	}
	196
	197	relation_digraph (reads, ngotos, &goto_follows);
	198
	199	for (i = 0; i < ngotos; i++)
	200	free (reads[i]);
	201
	202	free (reads);
	203	free (edge);
	204	}
	205
	206
	207	static void
	208	add_lookback_edge (state s, rule r, goto_number gotono)
	209	{
	210	int ri = state_reduction_find (s, r);
	211	goto_list sp = xmalloc (sizeof sp);
	212	sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri];
	213	sp->value = gotono;
	214	lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
	215	}
	216
	217
	218
	219	static void
	220	build_relations (void)
	221	{
	222	goto_number edge = xnmalloc (ngotos + 1, sizeof edge);
	223	state_number states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof states1);
	224	goto_number i;
	225
	226	includes = xnmalloc (ngotos, sizeof *includes);
	227
	228	for (i = 0; i < ngotos; i++)
	229	{
	230	int nedges = 0;
	231	symbol_number symbol1 = states[to_state[i]]->accessing_symbol;
	232	rule **rulep;
	233
	234	for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
	235	{
	236	bool done;
	237	int length = 1;
	238	item_number const *rp;
	239	state *s = states[from_state[i]];
	240	states1[0] = s->number;
	241
	242	for (rp = (rulep)->rhs; ! item_number_is_rule_number (rp); rp++)
	243	{
	244	s = transitions_to (s->transitions,
	245	item_number_as_symbol_number (*rp));
	246	states1[length++] = s->number;
	247	}
	248
	249	if (!s->consistent)
	250	add_lookback_edge (s, *rulep, i);
	251
	252	length--;
	253	done = false;
	254	while (!done)
	255	{
	256	done = true;
	257	/* Each rhs ends in a rule number, and there is a
	258	sentinel (ritem[-1]=0) before the first rhs, so it is safe to
	259	decrement RP here. */
	260	rp--;
	261	if (ISVAR (*rp))
	262	{
	263	/* Downcasting from item_number to symbol_number. */
	264	edge[nedges++] = map_goto (states1[--length],
	265	item_number_as_symbol_number (*rp));
	266	if (nullable[*rp - ntokens])
	267	done = false;
	268	}
	269	}
	270	}
	271
	272	if (nedges == 0)
	273	includes[i] = NULL;
	274	else
	275	{
	276	int j;
	277	includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
	278	for (j = 0; j < nedges; j++)
	279	includes[i][j] = edge[j];
	280	includes[i][nedges] = END_NODE;
	281	}
	282	}
	283
	284	free (edge);
	285	free (states1);
	286
	287	relation_transpose (&includes, ngotos);
	288	}
	289
	290
	291
	292	static void
	293	compute_FOLLOWS (void)
	294	{
	295	goto_number i;
	296
	297	relation_digraph (includes, ngotos, &goto_follows);
	298
	299	for (i = 0; i < ngotos; i++)
	300	free (includes[i]);
	301
	302	free (includes);
	303	}
	304
	305
	306	static void
	307	compute_lookahead_tokens (void)
	308	{
	309	size_t i;
	310	goto_list *sp;
	311
	312	for (i = 0; i < nLA; i++)
	313	for (sp = lookback[i]; sp; sp = sp->next)
	314	bitset_or (LA[i], LA[i], goto_follows[sp->value]);
	315
	316	/* Free LOOKBACK. */
	317	for (i = 0; i < nLA; i++)
	318	LIST_FREE (goto_list, lookback[i]);
	319
	320	free (lookback);
	321	}
	322
	323
	324	/*----------------------------------------------------.
	325	\| Count the number of lookahead tokens required for S \|
	326	\| (N_LOOKAHEAD_TOKENS member). \|
	327	`----------------------------------------------------*/
	328
	329	static int
	330	state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)
	331	{
	332	int n_lookahead_tokens = 0;
	333	reductions *rp = s->reductions;
	334	transitions *sp = s->transitions;
	335
	336	/* Transitions are only disabled during conflict resolution, and that
	337	hasn't happened yet, so there should be no need to check that
	338	transition 0 hasn't been disabled before checking if it is a shift.
	339	However, this check was performed at one time, so we leave it as an
	340	aver. */
	341	aver (sp->num == 0 \|\| !TRANSITION_IS_DISABLED (sp, 0));
	342
	343	/* We need a lookahead either to distinguish different reductions
	344	(i.e., there are two or more), or to distinguish a reduction from a
	345	shift. Otherwise, it is straightforward, and the state is
	346	`consistent'. However, do not treat a state with any reductions as
	347	consistent unless it is the accepting state (because there is never
	348	a lookahead token that makes sense there, and so no lookahead token
	349	should be read) if the user has otherwise disabled default
	350	reductions. */
	351	if (rp->num > 1
	352	\|\| (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0))
	353	\|\| (rp->num == 1 && rp->rules[0]->number != 0
	354	&& default_reduction_only_for_accept))
	355	n_lookahead_tokens += rp->num;
	356	else
	357	s->consistent = 1;
	358
	359	return n_lookahead_tokens;
	360	}
	361
	362
	363	/*----------------------------------------------------.
	364	\| Compute LA, NLA, and the lookahead_tokens members. \|
	365	`----------------------------------------------------*/
	366
	367	void
	368	initialize_LA (void)
	369	{
	370	state_number i;
	371	bitsetv pLA;
	372	bool default_reduction_only_for_accept;
	373	{
	374	char *default_reductions =
	375	muscle_percent_define_get ("lr.default-reductions");
	376	default_reduction_only_for_accept =
	377	0 == strcmp (default_reductions, "accepting");
	378	free (default_reductions);
	379	}
	380
	381	/* Compute the total number of reductions requiring a lookahead. */
	382	nLA = 0;
	383	for (i = 0; i < nstates; i++)
	384	nLA +=
	385	state_lookahead_tokens_count (states[i],
	386	default_reduction_only_for_accept);
	387	/* Avoid having to special case 0. */
	388	if (!nLA)
	389	nLA = 1;
	390
	391	pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
	392
	393	/* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
	394	require lookahead tokens. */
	395	for (i = 0; i < nstates; i++)
	396	{
	397	int count =
	398	state_lookahead_tokens_count (states[i],
	399	default_reduction_only_for_accept);
	400	if (count)
	401	{
	402	states[i]->reductions->lookahead_tokens = pLA;
	403	pLA += count;
	404	}
	405	}
	406	}
	407
	408
	409	/*---------------------------------------------.
	410	\| Output the lookahead tokens for each state. \|
	411	`---------------------------------------------*/
	412
	413	static void
	414	lookahead_tokens_print (FILE *out)
	415	{
	416	state_number i;
	417	int j, k;
	418	fprintf (out, "Lookahead tokens: BEGIN\n");
	419	for (i = 0; i < nstates; ++i)
	420	{
	421	reductions *reds = states[i]->reductions;
	422	bitset_iterator iter;
	423	int n_lookahead_tokens = 0;
	424
	425	if (reds->lookahead_tokens)
	426	for (k = 0; k < reds->num; ++k)
	427	if (reds->lookahead_tokens[k])
	428	++n_lookahead_tokens;
	429
	430	fprintf (out, "State %d: %d lookahead tokens\n",
	431	i, n_lookahead_tokens);
	432
	433	if (reds->lookahead_tokens)
	434	for (j = 0; j < reds->num; ++j)
	435	BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0)
	436	{
	437	fprintf (out, " on %d (%s) -> rule %d\n",
	438	k, symbols[k]->tag,
	439	reds->rules[j]->number);
	440	};
	441	}
	442	fprintf (out, "Lookahead tokens: END\n");
	443	}
	444
	445	void
	446	lalr (void)
	447	{
	448	initialize_LA ();
	449	set_goto_map ();
	450	initialize_F ();
	451	lookback = xcalloc (nLA, sizeof *lookback);
	452	build_relations ();
	453	compute_FOLLOWS ();
	454	compute_lookahead_tokens ();
	455
	456	if (trace_flag & trace_sets)
	457	lookahead_tokens_print (stderr);
	458	}
	459
	460
	461	void
	462	lalr_update_state_numbers (state_number old_to_new[], state_number nstates_old)
	463	{
	464	goto_number ngotos_reachable = 0;
	465	symbol_number nonterminal = 0;
	466	aver (nsyms == nvars + ntokens);
	467	{
	468	goto_number i;
	469	for (i = 0; i < ngotos; ++i)
	470	{
	471	while (i == goto_map[nonterminal])
	472	goto_map[nonterminal++] = ngotos_reachable;
	473	/* If old_to_new[from_state[i]] = nstates_old, remove this goto
	474	entry. */
	475	if (old_to_new[from_state[i]] != nstates_old)
	476	{
	477	/* from_state[i] is not removed, so it and thus to_state[i] are
	478	reachable, so to_state[i] != nstates_old. */
	479	aver (old_to_new[to_state[i]] != nstates_old);
	480	from_state[ngotos_reachable] = old_to_new[from_state[i]];
	481	to_state[ngotos_reachable] = old_to_new[to_state[i]];
	482	++ngotos_reachable;
	483	}
	484	}
	485	}
	486	while (nonterminal <= nvars)
	487	{
	488	aver (ngotos == goto_map[nonterminal]);
	489	goto_map[nonterminal++] = ngotos_reachable;
	490	}
	491	ngotos = ngotos_reachable;
	492	}
	493
	494
	495	void
	496	lalr_free (void)
	497	{
	498	state_number s;
	499	for (s = 0; s < nstates; ++s)
	500	states[s]->reductions->lookahead_tokens = NULL;
	501	bitsetv_free (LA);
	502	}