-/* Compute look-ahead criteria for bison,
- Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002
- Free Software Foundation, Inc.
+/* Compute lookahead criteria for Bison.
+
+ Copyright (C) 1984, 1986, 1989, 2000-2013 Free Software Foundation,
+ Inc.
This file is part of Bison, the GNU Compiler Compiler.
- Bison is free software; you can redistribute it and/or modify
+ 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 2, or (at your option)
- any later version.
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
- Bison is distributed in the hope that it will be useful,
+ 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 Bison; see the file COPYING. If not, write to
- the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
-/* Compute how to make the finite state machine deterministic; find
- which rules need lookahead in each state, and which lookahead
+/* 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 "relation.h"
-#include "quotearg.h"
-#include "symtab.h"
-#include "gram.h"
-#include "reader.h"
-#include "types.h"
+
+#include <bitset.h>
+#include <bitsetv.h>
+
#include "LR0.h"
#include "complain.h"
-#include "lalr.h"
-#include "nullable.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"
-rule_t **LArule = NULL;
-bitsetv LA = NULL;
-size_t nLA;
+goto_number *goto_map;
+goto_number ngotos;
+state_number *from_state;
+state_number *to_state;
+bitsetv goto_follows = NULL;
-static int ngotos;
-short *goto_map = NULL;
-state_number_t *from_state = NULL;
-state_number_t *to_state = NULL;
+/* Linked list of goto numbers. */
+typedef struct goto_list
+{
+ struct goto_list *next;
+ goto_number value;
+} goto_list;
-/* And for the famous F variable, which name is so descriptive that a
- comment is hardly needed. <grin>. */
-static bitsetv F = NULL;
-static short **includes;
-static shorts **lookback;
+/* 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;
-static void
-initialize_LA (void)
-{
- state_number_t i;
- int j;
- rule_t **np;
-
- /* Avoid having to special case 0. */
- if (!nLA)
- nLA = 1;
- LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
- LArule = XCALLOC (rule_t *, nLA);
- lookback = XCALLOC (shorts *, nLA);
-
- np = LArule;
- for (i = 0; i < nstates; i++)
- if (!states[i]->consistent)
- for (j = 0; j < states[i]->reductions->num; j++)
- *np++ = &rules[states[i]->reductions->rules[j]];
-}
-static void
+void
set_goto_map (void)
{
- state_number_t state;
- short *temp_map;
+ state_number s;
+ goto_number *temp_map;
- goto_map = XCALLOC (short, nvars + 1) - ntokens;
- temp_map = XCALLOC (short, nvars + 1) - ntokens;
+ goto_map = xcalloc (nvars + 1, sizeof *goto_map);
+ temp_map = xnmalloc (nvars + 1, sizeof *temp_map);
ngotos = 0;
- for (state = 0; state < nstates; ++state)
+ for (s = 0; s < nstates; ++s)
{
- transitions_t *sp = states[state]->shifts;
+ transitions *sp = states[s]->transitions;
int i;
for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
- {
- if (ngotos == SHRT_MAX)
- fatal (_("too many gotos (max %d)"), SHRT_MAX);
+ {
+ ngotos++;
- ngotos++;
- goto_map[TRANSITION_SYMBOL (sp, i)]++;
- }
+ /* Abort if (ngotos + 1) would overflow. */
+ aver (ngotos != GOTO_NUMBER_MAXIMUM);
+
+ goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+ }
}
{
- int k = 0;
+ goto_number k = 0;
int i;
for (i = ntokens; i < nsyms; i++)
{
- temp_map[i] = k;
- k += goto_map[i];
+ temp_map[i - ntokens] = k;
+ k += goto_map[i - ntokens];
}
for (i = ntokens; i < nsyms; i++)
- goto_map[i] = temp_map[i];
+ goto_map[i - ntokens] = temp_map[i - ntokens];
- goto_map[nsyms] = ngotos;
- temp_map[nsyms] = ngotos;
+ goto_map[nsyms - ntokens] = ngotos;
+ temp_map[nsyms - ntokens] = ngotos;
}
- from_state = XCALLOC (state_number_t, ngotos);
- to_state = XCALLOC (state_number_t, ngotos);
+ from_state = xcalloc (ngotos, sizeof *from_state);
+ to_state = xcalloc (ngotos, sizeof *to_state);
- for (state = 0; state < nstates; ++state)
+ for (s = 0; s < nstates; ++s)
{
- transitions_t *sp = states[state]->shifts;
+ transitions *sp = states[s]->transitions;
int i;
for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
- {
- int k = temp_map[TRANSITION_SYMBOL (sp, i)]++;
- from_state[k] = state;
- to_state[k] = sp->states[i];
- }
+ {
+ goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+ from_state[k] = s;
+ to_state[k] = sp->states[i]->number;
+ }
}
- XFREE (temp_map + ntokens);
+ free (temp_map);
}
-
-/*----------------------------------------------------------.
-| Map a state/symbol pair into its numeric representation. |
-`----------------------------------------------------------*/
-
-static int
-map_goto (state_number_t state, symbol_number_t symbol)
+goto_number
+map_goto (state_number s0, symbol_number sym)
{
- int high;
- int low;
- int middle;
- state_number_t s;
+ goto_number high;
+ goto_number low;
+ goto_number middle;
+ state_number s;
- low = goto_map[symbol];
- high = goto_map[symbol + 1] - 1;
+ low = goto_map[sym - ntokens];
+ high = goto_map[sym - ntokens + 1] - 1;
- while (low <= high)
+ for (;;)
{
+ aver (low <= high);
middle = (low + high) / 2;
s = from_state[middle];
- if (s == state)
- return middle;
- else if (s < state)
- low = middle + 1;
+ if (s == s0)
+ return middle;
+ else if (s < s0)
+ low = middle + 1;
else
- high = middle - 1;
+ high = middle - 1;
}
-
- assert (0);
- /* NOTREACHED */
- return 0;
}
static void
initialize_F (void)
{
- short **reads = XCALLOC (short *, ngotos);
- short *edge = XCALLOC (short, ngotos + 1);
- int nedges = 0;
+ goto_number **reads = xnmalloc (ngotos, sizeof *reads);
+ goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+ goto_number nedges = 0;
- int i;
+ goto_number i;
- F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+ goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
for (i = 0; i < ngotos; i++)
{
- state_number_t stateno = to_state[i];
- transitions_t *sp = states[stateno]->shifts;
+ state_number stateno = to_state[i];
+ transitions *sp = states[stateno]->transitions;
int j;
- for (j = 0; j < sp->num && TRANSITION_IS_SHIFT (sp, j); j++)
- bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
+ FOR_EACH_SHIFT (sp, j)
+ bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));
for (; j < sp->num; j++)
- {
- symbol_number_t symbol = TRANSITION_SYMBOL (sp, j);
- if (nullable[symbol])
- edge[nedges++] = map_goto (stateno, symbol);
- }
-
- if (nedges)
- {
- reads[i] = XCALLOC (short, nedges + 1);
- memcpy (reads[i], edge, nedges * sizeof (edge[0]));
- reads[i][nedges] = -1;
- nedges = 0;
- }
+ {
+ 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, &F);
+ relation_digraph (reads, ngotos, &goto_follows);
for (i = 0; i < ngotos; i++)
- XFREE (reads[i]);
+ free (reads[i]);
- XFREE (reads);
- XFREE (edge);
+ free (reads);
+ free (edge);
}
static void
-add_lookback_edge (state_t *state, rule_number_t ruleno, int gotono)
+add_lookback_edge (state *s, rule *r, goto_number gotono)
{
- int i;
- shorts *sp;
-
- for (i = 0; i < state->nlookaheads; ++i)
- if (state->lookaheads_rule[i]->number == ruleno)
- break;
-
- assert (state->lookaheads_rule[i]->number == ruleno);
-
- sp = XCALLOC (shorts, 1);
- sp->next = lookback[(state->lookaheads - LA) + i];
+ 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[(state->lookaheads - LA) + i] = sp;
+ lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
}
static void
build_relations (void)
{
- short *edge = XCALLOC (short, ngotos + 1);
- state_number_t *states1 = XCALLOC (state_number_t, ritem_longest_rhs () + 1);
- int i;
+ goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+ state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
+ goto_number i;
- includes = XCALLOC (short *, ngotos);
+ includes = xnmalloc (ngotos, sizeof *includes);
for (i = 0; i < ngotos; i++)
{
int nedges = 0;
- symbol_number_t symbol1 = states[to_state[i]]->accessing_symbol;
- rule_number_t *rulep;
-
- for (rulep = derives[symbol1]; *rulep > 0; rulep++)
- {
- int done;
- int length = 1;
- item_number_t *rp;
- state_t *state = states[from_state[i]];
- states1[0] = state->number;
-
- for (rp = rules[*rulep].rhs; *rp >= 0; rp++)
- {
- state = transitions_to (state->shifts,
- item_number_as_symbol_number (*rp));
- states1[length++] = state->number;
- }
-
- if (!state->consistent)
- add_lookback_edge (state, *rulep, i);
-
- length--;
- done = 0;
- while (!done)
- {
- done = 1;
- rp--;
- /* JF added rp>=ritem && I hope to god its right! */
- if (rp >= ritem && ISVAR (*rp))
- {
- /* Downcasting from item_number_t to symbol_number_t. */
- edge[nedges++] = map_goto (states1[--length],
- item_number_as_symbol_number (*rp));
- if (nullable[*rp])
- done = 0;
- }
- }
- }
-
- if (nedges)
- {
- int j;
- includes[i] = XCALLOC (short, nedges + 1);
- for (j = 0; j < nedges; j++)
- includes[i][j] = edge[j];
- includes[i][nedges] = -1;
- }
+ 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;
+ }
}
- XFREE (edge);
- XFREE (states1);
+ free (edge);
+ free (states1);
relation_transpose (&includes, ngotos);
}
static void
compute_FOLLOWS (void)
{
- int i;
+ goto_number i;
- relation_digraph (includes, ngotos, &F);
+ relation_digraph (includes, ngotos, &goto_follows);
for (i = 0; i < ngotos; i++)
- XFREE (includes[i]);
+ free (includes[i]);
- XFREE (includes);
+ free (includes);
}
static void
-compute_lookaheads (void)
+compute_lookahead_tokens (void)
{
size_t i;
- shorts *sp;
+ goto_list *sp;
for (i = 0; i < nLA; i++)
for (sp = lookback[i]; sp; sp = sp->next)
- bitset_or (LA[i], LA[i], F[sp->value]);
+ bitset_or (LA[i], LA[i], goto_follows[sp->value]);
/* Free LOOKBACK. */
for (i = 0; i < nLA; i++)
- LIST_FREE (shorts, lookback[i]);
+ LIST_FREE (goto_list, lookback[i]);
- XFREE (lookback);
- bitsetv_free (F);
+ free (lookback);
}
-/*-------------------------------------------------------------.
-| Count the number of lookaheads required for each state |
-| (NLOOKAHEADS member). Compute the total number of LA, NLA. |
-`-------------------------------------------------------------*/
+/*----------------------------------------------------.
+| Count the number of lookahead tokens required for S |
+| (N_LOOKAHEAD_TOKENS member). |
+`----------------------------------------------------*/
-static void
-states_lookaheads_count (void)
+static int
+state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)
{
- state_number_t i;
- nLA = 0;
-
- /* Count */
- for (i = 0; i < nstates; i++)
- {
- int k;
- int nlookaheads = 0;
- reductions_t *rp = states[i]->reductions;
- transitions_t *sp = states[i]->shifts;
-
- /* 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'. */
- if (rp->num > 1
- || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0)))
- nlookaheads += rp->num;
- else
- states[i]->consistent = 1;
-
- for (k = 0; k < sp->num; k++)
- if (TRANSITION_IS_ERROR (sp, k))
- {
- states[i]->consistent = 0;
- break;
- }
-
- states[i]->nlookaheads = nlookaheads;
- nLA += nlookaheads;
- }
+ 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;
}
-/*--------------------------------------.
-| Initializing the lookaheads members. |
-`--------------------------------------*/
+/*----------------------------------------------------.
+| Compute LA, NLA, and the lookahead_tokens members. |
+`----------------------------------------------------*/
-static void
-states_lookaheads_initialize (void)
+void
+initialize_LA (void)
{
- state_number_t i;
- bitsetv pLA = LA;
- rule_t **pLArule = LArule;
+ state_number i;
+ bitsetv pLA;
+ bool default_reduction_only_for_accept;
+ {
+ char *default_reductions =
+ muscle_percent_define_get ("lr.default-reduction");
+ default_reduction_only_for_accept = STREQ (default_reductions, "accepting");
+ free (default_reductions);
+ }
- /* Initialize the members LOOKAHEADS and LOOKAHEADS_RULE for each
- state. */
+ /* 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++)
{
- states[i]->lookaheads = pLA;
- states[i]->lookaheads_rule = pLArule;
- pLA += states[i]->nlookaheads;
- pLArule += states[i]->nlookaheads;
+ 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 lookaheads for each state. |
-`---------------------------------------*/
+/*---------------------------------------------.
+| Output the lookahead tokens for each state. |
+`---------------------------------------------*/
static void
-lookaheads_print (FILE *out)
+lookahead_tokens_print (FILE *out)
{
- state_number_t i;
+ state_number i;
int j, k;
- fprintf (out, "Lookaheads: BEGIN\n");
+ fprintf (out, "Lookahead tokens: BEGIN\n");
for (i = 0; i < nstates; ++i)
{
- fprintf (out, "State %d: %d lookaheads\n",
- i, states[i]->nlookaheads);
-
- for (j = 0; j < states[i]->nlookaheads; ++j)
- BITSET_EXECUTE (states[i]->lookaheads[j], 0, k,
- {
- fprintf (out, " on %d (%s) -> rule %d\n",
- k, symbol_tag_get (symbols[k]),
- states[i]->lookaheads_rule[j]->number - 1);
- });
+ 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, "Lookaheads: END\n");
+ fprintf (out, "Lookahead tokens: END\n");
}
void
lalr (void)
{
- states_lookaheads_count ();
initialize_LA ();
- states_lookaheads_initialize ();
set_goto_map ();
initialize_F ();
+ lookback = xcalloc (nLA, sizeof *lookback);
build_relations ();
compute_FOLLOWS ();
- compute_lookaheads ();
+ compute_lookahead_tokens ();
+
+ if (trace_flag & trace_sets)
+ lookahead_tokens_print (stderr);
+}
- if (trace_flag)
- lookaheads_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);
}
projects / bison.git / blobdiff