-/* Compute look-ahead criteria for Bison.
+/* Compute lookahead criteria for Bison.
Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005,
- 2006 Free Software Foundation, Inc.
+ 2006, 2007, 2008, 2009 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., 51 Franklin Street, Fifth Floor,
- Boston, MA 02110-1301, 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 look-ahead in each state, and which look-ahead
+ which rules need lookahead in each state, and which lookahead
tokens they accept. */
#include <config.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;
-static goto_number ngotos;
+goto_number ngotos;
state_number *from_state;
state_number *to_state;
+bitsetv goto_follows = NULL;
/* Linked list of goto numbers. */
typedef struct goto_list
} goto_list;
-/* LA is a LR by NTOKENS matrix of bits. LA[l, i] is 1 if the rule
+/* 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. */
size_t nLA;
-/* And for the famous F variable, which name is so descriptive that a
- comment is hardly needed. <grin>. */
-static bitsetv F = NULL;
-
static goto_number **includes;
static goto_list **lookback;
-static void
+void
set_goto_map (void)
{
state_number s;
ngotos++;
/* Abort if (ngotos + 1) would overflow. */
- if (ngotos == GOTO_NUMBER_MAXIMUM)
- abort ();
+ aver (ngotos != GOTO_NUMBER_MAXIMUM);
goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
}
}
-
-/*----------------------------------------------------------.
-| Map a state/symbol pair into its numeric representation. |
-`----------------------------------------------------------*/
-
-static goto_number
+goto_number
map_goto (state_number s0, symbol_number sym)
{
goto_number high;
for (;;)
{
- if (high < low)
- abort ();
+ aver (low <= high);
middle = (low + high) / 2;
s = from_state[middle];
if (s == s0)
goto_number i;
- F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+ goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
for (i = 0; i < ngotos; i++)
{
int j;
FOR_EACH_SHIFT (sp, j)
- bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
+ bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));
for (; j < sp->num; j++)
{
}
}
- relation_digraph (reads, ngotos, &F);
+ relation_digraph (reads, ngotos, &goto_follows);
for (i = 0; i < ngotos; i++)
free (reads[i]);
{
int ri = state_reduction_find (s, r);
goto_list *sp = xmalloc (sizeof *sp);
- sp->next = lookback[(s->reductions->look_ahead_tokens - LA) + ri];
+ sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri];
sp->value = gotono;
- lookback[(s->reductions->look_ahead_tokens - LA) + ri] = sp;
+ lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;
}
while (!done)
{
done = true;
- /* Each rhs ends in an item number, and there is a
- sentinel before the first rhs, so it is safe to
+ /* 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))
{
goto_number i;
- relation_digraph (includes, ngotos, &F);
+ relation_digraph (includes, ngotos, &goto_follows);
for (i = 0; i < ngotos; i++)
free (includes[i]);
static void
-compute_look_ahead_tokens (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], F[sp->value]);
+ 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);
- bitsetv_free (F);
}
-/*-----------------------------------------------------.
-| Count the number of look-ahead tokens required for S |
-| (N_LOOK_AHEAD_TOKENS member). |
-`-----------------------------------------------------*/
+/*----------------------------------------------------.
+| Count the number of lookahead tokens required for S |
+| (N_LOOKAHEAD_TOKENS member). |
+`----------------------------------------------------*/
static int
-state_look_ahead_tokens_count (state *s)
+state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)
{
- int k;
- int n_look_ahead_tokens = 0;
+ int n_lookahead_tokens = 0;
reductions *rp = s->reductions;
transitions *sp = s->transitions;
- /* We need a look-ahead 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'. */
+ /* 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, treat only the accepting state as
+ consistent (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_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0)))
- n_look_ahead_tokens += rp->num;
+ || (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;
- for (k = 0; k < sp->num; k++)
- if (!TRANSITION_IS_DISABLED (sp, k) && TRANSITION_IS_ERROR (sp, k))
- {
- s->consistent = 0;
- break;
- }
-
- return n_look_ahead_tokens;
+ return n_lookahead_tokens;
}
-/*-----------------------------------------------------.
-| Compute LA, NLA, and the look_ahead_tokens members. |
-`-----------------------------------------------------*/
+/*----------------------------------------------------.
+| Compute LA, NLA, and the lookahead_tokens members. |
+`----------------------------------------------------*/
-static void
+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 look-ahead. */
+ /* Compute the total number of reductions requiring a lookahead. */
nLA = 0;
for (i = 0; i < nstates; i++)
- nLA += state_look_ahead_tokens_count (states[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);
- lookback = xcalloc (nLA, sizeof *lookback);
- /* Initialize the members LOOK_AHEAD_TOKENS for each state whose reductions
- require look-ahead tokens. */
+ /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
+ require lookahead tokens. */
for (i = 0; i < nstates; i++)
{
- int count = state_look_ahead_tokens_count (states[i]);
+ int count =
+ state_lookahead_tokens_count (states[i],
+ default_reduction_only_for_accept);
if (count)
{
- states[i]->reductions->look_ahead_tokens = pLA;
+ states[i]->reductions->lookahead_tokens = pLA;
pLA += count;
}
}
}
-/*----------------------------------------------.
-| Output the look-ahead tokens for each state. |
-`----------------------------------------------*/
+/*---------------------------------------------.
+| Output the lookahead tokens for each state. |
+`---------------------------------------------*/
static void
-look_ahead_tokens_print (FILE *out)
+lookahead_tokens_print (FILE *out)
{
state_number i;
int j, k;
- fprintf (out, "Look-ahead tokens: BEGIN\n");
+ fprintf (out, "Lookahead tokens: BEGIN\n");
for (i = 0; i < nstates; ++i)
{
reductions *reds = states[i]->reductions;
bitset_iterator iter;
- int n_look_ahead_tokens = 0;
+ int n_lookahead_tokens = 0;
- if (reds->look_ahead_tokens)
+ if (reds->lookahead_tokens)
for (k = 0; k < reds->num; ++k)
- if (reds->look_ahead_tokens[k])
- ++n_look_ahead_tokens;
+ if (reds->lookahead_tokens[k])
+ ++n_lookahead_tokens;
- fprintf (out, "State %d: %d look-ahead tokens\n",
- i, n_look_ahead_tokens);
+ fprintf (out, "State %d: %d lookahead tokens\n",
+ i, n_lookahead_tokens);
- if (reds->look_ahead_tokens)
+ if (reds->lookahead_tokens)
for (j = 0; j < reds->num; ++j)
- BITSET_FOR_EACH (iter, reds->look_ahead_tokens[j], k, 0)
+ 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, "Look-ahead tokens: END\n");
+ fprintf (out, "Lookahead tokens: END\n");
}
void
initialize_LA ();
set_goto_map ();
initialize_F ();
+ lookback = xcalloc (nLA, sizeof *lookback);
build_relations ();
compute_FOLLOWS ();
- compute_look_ahead_tokens ();
+ compute_lookahead_tokens ();
if (trace_flag & trace_sets)
- look_ahead_tokens_print (stderr);
+ 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;
}
{
state_number s;
for (s = 0; s < nstates; ++s)
- states[s]->reductions->look_ahead_tokens = NULL;
+ states[s]->reductions->lookahead_tokens = NULL;
bitsetv_free (LA);
}
projects / bison.git / blobdiff