X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/574fb2d5682af3cf6917e414b4240879d3e7f008..75ae8299840bbd854fa2474d38402bbb933c6511:/src/lalr.c diff --git a/src/lalr.c b/src/lalr.c index 3267172b..d99f960f 100644 --- a/src/lalr.c +++ b/src/lalr.c @@ -1,242 +1,216 @@ -/* 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 . */ -/* 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 #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 +#include + #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; - -static int ngotos; -short *goto_map = NULL; -state_number_t *from_state = NULL; -state_number_t *to_state = NULL; - -/* And for the famous F variable, which name is so descriptive that a - comment is hardly needed. . */ -static bitsetv F = NULL; +goto_number *goto_map; +goto_number ngotos; +state_number *from_state; +state_number *to_state; +bitsetv goto_follows = NULL; -static short **includes; -static shorts **lookback; +/* 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 void -initialize_LA (void) -{ - state_number_t i; - int j; - rule_t **np; - /* Avoid having to special case 0. */ - if (!nLA) - nLA = 1; +static goto_number **includes; +static goto_list **lookback; - 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->nreds; 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) { - shifts_t *sp = states[state]->shifts; + transitions *sp = states[s]->transitions; int i; - for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) - { - if (ngotos == SHRT_MAX) - fatal (_("too many gotos (max %d)"), SHRT_MAX); - - ngotos++; - goto_map[SHIFT_SYMBOL (sp, 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]++; + } } { - 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) { - shifts_t *sp = states[state]->shifts; + transitions *sp = states[s]->transitions; int i; - for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) - { - int k = temp_map[SHIFT_SYMBOL (sp, i)]++; - from_state[k] = state; - to_state[k] = sp->shifts[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; + } } - 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]; - shifts_t *sp = states[stateno]->shifts; + state_number stateno = to_state[i]; + transitions *sp = states[stateno]->transitions; int j; - for (j = 0; j < sp->nshifts && SHIFT_IS_SHIFT (sp, j); j++) - bitset_set (F[i], SHIFT_SYMBOL (sp, j)); - - for (; j < sp->nshifts; j++) - { - symbol_number_t symbol = SHIFT_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; - } + 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, &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; } @@ -244,66 +218,70 @@ add_lookback_edge (state_t *state, rule_number_t ruleno, int gotono) 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 = shifts_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); } @@ -313,139 +291,210 @@ build_relations (void) 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; - shifts_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->nreds > 1 - || (rp->nreds == 1 && sp->nshifts && SHIFT_IS_SHIFT (sp, 0))) - nlookaheads += rp->nreds; - else - states[i]->consistent = 1; - - for (k = 0; k < sp->nshifts; k++) - if (SHIFT_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); }