X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/d0b0fefa03737d162ca8341c979881c70bebb868..fcd32abd3a4b68ef525d7766dbed1c98465e23b9:/src/lalr.c?ds=sidebyside diff --git a/src/lalr.c b/src/lalr.c index 1dfb293d..fbd2800f 100644 --- a/src/lalr.c +++ b/src/lalr.c @@ -1,482 +1,291 @@ -/* Compute look-ahead criteria for bison, - Copyright 1984, 1986, 1989, 2000, 2001 Free Software Foundation, Inc. +/* Compute lookahead criteria for Bison. + + Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005, + 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., 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 tokens they accept. */ +#include #include "system.h" -#include "types.h" + +#include +#include +#include + #include "LR0.h" -#include "gram.h" #include "complain.h" -#include "lalr.h" -#include "nullable.h" #include "derives.h" #include "getargs.h" - -/* All the decorated states, indexed by the state number. */ -state_t **state_table = NULL; - -int tokensetsize; -short *LAruleno; -unsigned *LA; -size_t nLA; - -static int ngotos; -short *goto_map; -short *from_state; -short *to_state; - -/* And for the famous F variable, which name is so descriptive that a - comment is hardly needed. . */ -static unsigned *F = NULL; -#define F(Rule) (F + (Rule) * tokensetsize) - -static short **includes; -static shorts **lookback; - - -/*---------------------------------------------------------------. -| digraph & traverse. | -| | -| The following variables are used as common storage between the | -| two. | -`---------------------------------------------------------------*/ - -static short **R; -static short *INDEX; -static short *VERTICES; -static int top; -static int infinity; - -static void -traverse (int i) -{ - int j; - size_t k; - int height; - size_t size = F (i + 1) - F(i); - - VERTICES[++top] = i; - INDEX[i] = height = top; - - if (R[i]) - for (j = 0; R[i][j] >= 0; ++j) - { - if (INDEX[R[i][j]] == 0) - traverse (R[i][j]); - - if (INDEX[i] > INDEX[R[i][j]]) - INDEX[i] = INDEX[R[i][j]]; - - for (k = 0; k < size; ++k) - F (i)[k] |= F (R[i][j])[k]; - } - - if (INDEX[i] == height) - for (;;) - { - j = VERTICES[top--]; - INDEX[j] = infinity; - - if (i == j) - break; - - for (k = 0; k < size; ++k) - F (j)[k] = F (i)[k]; - } -} - - -static void -digraph (short **relation) +#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 { - int i; - - infinity = ngotos + 2; - INDEX = XCALLOC (short, ngotos + 1); - VERTICES = XCALLOC (short, ngotos + 1); - top = 0; + struct goto_list *next; + goto_number value; +} goto_list; - R = relation; - for (i = 0; i < ngotos; i++) - INDEX[i] = 0; +/* 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. */ - for (i = 0; i < ngotos; i++) - if (INDEX[i] == 0 && R[i]) - traverse (i); +static bitsetv LA = NULL; +size_t nLA; - XFREE (INDEX); - XFREE (VERTICES); -} +static goto_number **includes; +static goto_list **lookback; -static void -initialize_LA (void) -{ - int i; - int j; - short *np; - reductions *rp; - /* Avoid having to special case 0. */ - if (!nLA) - nLA = 1; - LA = XCALLOC (unsigned, nLA * tokensetsize); - LAruleno = XCALLOC (short, nLA); - lookback = XCALLOC (shorts *, nLA); - np = LAruleno; - for (i = 0; i < nstates; i++) - if (!state_table[i]->consistent) - if ((rp = state_table[i]->reductions)) - for (j = 0; j < rp->nreds; j++) - *np++ = rp->rules[j]; -} - - -static void +void set_goto_map (void) { - int state, i; - 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 *sp = state_table[state]->shifts; - for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) + transitions *sp = states[s]->transitions; + int i; + for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i) { - int symbol = state_table[sp->shifts[i]]->accessing_symbol; + ngotos++; - if (ngotos == MAXSHORT) - fatal (_("too many gotos (max %d)"), MAXSHORT); + /* Abort if (ngotos + 1) would overflow. */ + aver (ngotos != GOTO_NUMBER_MAXIMUM); - ngotos++; - goto_map[symbol]++; + 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 (short, ngotos); - to_state = XCALLOC (short, 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 *sp = state_table[state]->shifts; - for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) + transitions *sp = states[s]->transitions; + int i; + for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i) { - int state2 = sp->shifts[i]; - int symbol = state_table[state2]->accessing_symbol; - - int k = temp_map[symbol]++; - from_state[k] = state; - to_state[k] = state2; + 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 (int state, int symbol) +goto_number +map_goto (state_number s0, symbol_number sym) { - int high; - int low; - int middle; - int 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) + if (s == s0) return middle; - else if (s < state) + else if (s < s0) low = middle + 1; else 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 = XCALLOC (unsigned, ngotos * tokensetsize); + goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED); for (i = 0; i < ngotos; i++) { - int stateno = to_state[i]; - shifts *sp = state_table[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++) - { - int symbol = state_table[sp->shifts[j]]->accessing_symbol; - SETBIT (F (i), symbol); - } + FOR_EACH_SHIFT (sp, j) + bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j)); - for (; j < sp->nshifts; j++) + for (; j < sp->num; j++) { - int symbol = state_table[sp->shifts[j]]->accessing_symbol; - if (nullable[symbol]) - edge[nedges++] = map_goto (stateno, symbol); + symbol_number sym = TRANSITION_SYMBOL (sp, j); + if (nullable[sym - ntokens]) + edge[nedges++] = map_goto (stateno, sym); } - if (nedges) + if (nedges == 0) + reads[i] = NULL; + else { - reads[i] = XCALLOC (short, nedges + 1); - shortcpy (reads[i], edge, nedges); - reads[i][nedges] = -1; + reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]); + memcpy (reads[i], edge, nedges * sizeof edge[0]); + reads[i][nedges] = END_NODE; nedges = 0; } } - digraph (reads); + 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 (int stateno, int ruleno, int gotono) +add_lookback_edge (state *s, rule *r, goto_number gotono) { - int i; - shorts *sp; - - for (i = 0; i < state_table[stateno]->nlookaheads; ++i) - if (LAruleno[state_table[stateno]->lookaheadsp + i] == ruleno) - break; - - assert (LAruleno[state_table[stateno]->lookaheadsp + i] == ruleno); - - sp = XCALLOC (shorts, 1); - sp->next = lookback[state_table[stateno]->lookaheadsp + 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_table[stateno]->lookaheadsp + i] = sp; + lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp; } -static void -matrix_print (FILE *out, short **matrix, int n) -{ - int i, j; - - for (i = 0; i < n; ++i) - { - fprintf (out, "%3d: ", i); - if (matrix[i]) - for (j = 0; matrix[i][j] != -1; ++j) - fprintf (out, "%3d ", matrix[i][j]); - fputc ('\n', out); - } - fputc ('\n', out); -} - -/*-------------------------------------------------------------------. -| Return the transpose of R_ARG, of size N. Destroy R_ARG, as it is | -| replaced with the result. | -| | -| R_ARG[I] is NULL or a -1 terminated list of numbers. | -| | -| RESULT[NUM] is NULL or the -1 terminated list of the I such as NUM | -| is in R_ARG[I]. | -`-------------------------------------------------------------------*/ - -static short ** -transpose (short **R_arg, int n) -{ - /* The result. */ - short **new_R = XCALLOC (short *, n); - /* END_R[I] -- next entry of NEW_R[I]. */ - short **end_R = XCALLOC (short *, n); - /* NEDGES[I] -- total size of NEW_R[I]. */ - short *nedges = XCALLOC (short, n); - int i, j; - - if (trace_flag) - { - fputs ("transpose: input\n", stderr); - matrix_print (stderr, R_arg, n); - } - - /* Count. */ - for (i = 0; i < n; i++) - if (R_arg[i]) - for (j = 0; R_arg[i][j] >= 0; ++j) - ++nedges[R_arg[i][j]]; - - /* Allocate. */ - for (i = 0; i < n; i++) - if (nedges[i] > 0) - { - short *sp = XCALLOC (short, nedges[i] + 1); - sp[nedges[i]] = -1; - new_R[i] = sp; - end_R[i] = sp; - } - - /* Store. */ - for (i = 0; i < n; i++) - if (R_arg[i]) - for (j = 0; R_arg[i][j] >= 0; ++j) - { - *end_R[R_arg[i][j]] = i; - ++end_R[R_arg[i][j]]; - } - - free (nedges); - free (end_R); - - /* Free the input: it is replaced with the result. */ - for (i = 0; i < n; i++) - XFREE (R_arg[i]); - free (R_arg); - - if (trace_flag) - { - fputs ("transpose: output\n", stderr); - matrix_print (stderr, new_R, n); - } - - return new_R; -} - static void build_relations (void) { - short *edge = XCALLOC (short, ngotos + 1); - short *states = XCALLOC (short, 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; - int state1 = from_state[i]; - int symbol1 = state_table[to_state[i]]->accessing_symbol; - short *rulep; + symbol_number symbol1 = states[to_state[i]]->accessing_symbol; + rule **rulep; - for (rulep = derives[symbol1]; *rulep > 0; rulep++) + for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++) { - int done; + bool done; int length = 1; - int stateno = state1; - short *rp; - states[0] = state1; + item_number const *rp; + state *s = states[from_state[i]]; + states1[0] = s->number; - for (rp = ritem + rule_table[*rulep].rhs; *rp > 0; rp++) + for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++) { - shifts *sp = state_table[stateno]->shifts; - int j; - for (j = 0; j < sp->nshifts; j++) - { - stateno = sp->shifts[j]; - if (state_table[stateno]->accessing_symbol == *rp) - break; - } - - states[length++] = stateno; + s = transitions_to (s->transitions, + item_number_as_symbol_number (*rp)); + states1[length++] = s->number; } - if (!state_table[stateno]->consistent) - add_lookback_edge (stateno, *rulep, i); + if (!s->consistent) + add_lookback_edge (s, *rulep, i); length--; - done = 0; + done = false; while (!done) { - done = 1; + 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--; - /* JF added rp>=ritem && I hope to god its right! */ - if (rp >= ritem && ISVAR (*rp)) + if (ISVAR (*rp)) { - stateno = states[--length]; - edge[nedges++] = map_goto (stateno, *rp); - if (nullable[*rp]) - done = 0; + /* 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) + if (nedges == 0) + includes[i] = NULL; + else { int j; - includes[i] = XCALLOC (short, nedges + 1); + includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]); for (j = 0; j < nedges; j++) includes[i][j] = edge[j]; - includes[i][nedges] = -1; + includes[i][nedges] = END_NODE; } } - XFREE (edge); - XFREE (states); + free (edge); + free (states1); - includes = transpose (includes, ngotos); + relation_transpose (&includes, ngotos); } @@ -484,86 +293,211 @@ build_relations (void) static void compute_FOLLOWS (void) { - int i; + goto_number i; - digraph (includes); + 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) - { - int size = LA (i + 1) - LA (i); - int j; - for (j = 0; j < size; ++j) - LA (i)[j] |= F (sp->value)[j]; - } + 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); - XFREE (F); + free (lookback); } -/*--------------------------------------. -| Initializing the lookaheads members. | -`--------------------------------------*/ +/*----------------------------------------------------. +| Count the number of lookahead tokens required for S | +| (N_LOOKAHEAD_TOKENS member). | +`----------------------------------------------------*/ -static void -initialize_lookaheads (void) +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) { - int i; + 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 k; - int nlookaheads = 0; - reductions *rp = state_table[i]->reductions; - shifts *sp = state_table[i]->shifts; - - if (rp - && (rp->nreds > 1 || (sp->nshifts && SHIFT_IS_SHIFT (sp, 0)))) - nlookaheads += rp->nreds; - else - state_table[i]->consistent = 1; + int count = + state_lookahead_tokens_count (states[i], + default_reduction_only_for_accept); + if (count) + { + states[i]->reductions->lookahead_tokens = pLA; + pLA += count; + } + } +} - for (k = 0; k < sp->nshifts; k++) - if (SHIFT_IS_ERROR (sp, k)) - { - state_table[i]->consistent = 0; - break; - } - state_table[i]->nlookaheads = nlookaheads; - state_table[i]->lookaheadsp = nLA; - nLA += nlookaheads; +/*---------------------------------------------. +| 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) { - tokensetsize = WORDSIZE (ntokens); - - initialize_lookaheads (); initialize_LA (); 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); +} + + +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); }