X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/ceed8467b7db3615d3c9bfa9f3e5525d54c6a161..e91ff6ce3d2653b41265591dafd4bdb32ae114c2:/src/lalr.c diff --git a/src/lalr.c b/src/lalr.c index 6b78c995..643f8fd9 100644 --- a/src/lalr.c +++ b/src/lalr.c @@ -1,347 +1,228 @@ /* Compute look-ahead criteria for bison, - Copyright (C) 1984, 1986, 1989 Free Software Foundation, Inc. + Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002 + Free Software Foundation, Inc. -This file is part of Bison, the GNU Compiler Compiler. + This file is part of Bison, the GNU Compiler Compiler. -Bison 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. + Bison 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. -Bison 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. + Bison 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. */ + 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. */ -/* Compute how to make the finite state machine deterministic; - find which rules need lookahead in each state, and which lookahead tokens they accept. - -lalr(), the entry point, builds these data structures: - -goto_map, from_state and to_state - record each shift transition which accepts a variable (a nonterminal). -ngotos is the number of such transitions. -from_state[t] is the state number which a transition leads from -and to_state[t] is the state number it leads to. -All the transitions that accept a particular variable are grouped together and -goto_map[i - ntokens] is the index in from_state and to_state of the first of them. - -consistent[s] is nonzero if no lookahead is needed to decide what to do in state s. - -LAruleno is a vector which records the rules that need lookahead in various states. -The elements of LAruleno that apply to state s are those from - lookaheads[s] through lookaheads[s+1]-1. -Each element of LAruleno is a rule number. - -If lr is the length of LAruleno, then a number from 0 to lr-1 -can specify both a rule and a state where the rule might be applied. - -LA is a lr by ntokens matrix of bits. -LA[l, i] is 1 if the rule LAruleno[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. -*/ +/* Compute how to make the finite state machine deterministic; find + which rules need lookahead in each state, and which lookahead + tokens they accept. */ #include "system.h" -#include "types.h" -#include "state.h" -#include "alloc.h" +#include "bitset.h" +#include "bitsetv.h" +#include "quotearg.h" +#include "symtab.h" #include "gram.h" +#include "reader.h" +#include "types.h" +#include "LR0.h" #include "complain.h" +#include "lalr.h" +#include "nullable.h" +#include "derives.h" +#include "getargs.h" -extern short **derives; -extern char *nullable; - - -int tokensetsize; -short *lookaheads; -short *LAruleno; -unsigned *LA; -short *accessing_symbol; -char *consistent; -core **state_table; -shifts **shift_table; -reductions **reduction_table; -short *goto_map; -short *from_state; -short *to_state; - -extern void lalr PARAMS((void)); - -static short **transpose PARAMS((short **, int)); -static void set_state_table PARAMS((void)); -static void set_accessing_symbol PARAMS((void)); -static void set_shift_table PARAMS((void)); -static void set_reduction_table PARAMS((void)); -static void set_maxrhs PARAMS((void)); -static void initialize_LA PARAMS((void)); -static void set_goto_map PARAMS((void)); -static int map_goto PARAMS((int, int)); -static void initialize_F PARAMS((void)); -static void build_relations PARAMS((void)); -static void add_lookback_edge PARAMS((int, int, int)); -static void compute_FOLLOWS PARAMS((void)); -static void compute_lookaheads PARAMS((void)); -static void digraph PARAMS((short **)); -static void traverse PARAMS((register int)); - -extern void berror PARAMS((const char *)); +/* All the decorated states, indexed by the state number. */ +state_t **states = NULL; + +rule_t **LArule = NULL; +bitsetv LA = NULL; +size_t nLA; -static int infinity; -static int maxrhs; static int ngotos; -static unsigned *F; +short *goto_map = NULL; +short *from_state = NULL; +short *to_state = NULL; + +/* And for the famous F variable, which name is so descriptive that a + comment is hardly needed. . */ +static bitsetv F = NULL; + 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; - - -void -lalr (void) -{ - tokensetsize = WORDSIZE(ntokens); - - set_state_table(); - set_accessing_symbol(); - set_shift_table(); - set_reduction_table(); - set_maxrhs(); - initialize_LA(); - set_goto_map(); - initialize_F(); - build_relations(); - compute_FOLLOWS(); - compute_lookaheads(); -} - +static int infinity; static void -set_state_table (void) +traverse (int i) { - register core *sp; - - state_table = NEW2(nstates, core *); - - for (sp = first_state; sp; sp = sp->next) - state_table[sp->number] = sp; -} - + int j; + int height; -static void -set_accessing_symbol (void) -{ - register core *sp; + VERTICES[++top] = i; + INDEX[i] = height = top; - accessing_symbol = NEW2(nstates, short); + if (R[i]) + for (j = 0; R[i][j] >= 0; ++j) + { + if (INDEX[R[i][j]] == 0) + traverse (R[i][j]); - for (sp = first_state; sp; sp = sp->next) - accessing_symbol[sp->number] = sp->accessing_symbol; -} + if (INDEX[i] > INDEX[R[i][j]]) + INDEX[i] = INDEX[R[i][j]]; + bitset_or (F[i], F[i], F[R[i][j]]); + } -static void -set_shift_table (void) -{ - register shifts *sp; + if (INDEX[i] == height) + for (;;) + { + j = VERTICES[top--]; + INDEX[j] = infinity; - shift_table = NEW2(nstates, shifts *); + if (i == j) + break; - for (sp = first_shift; sp; sp = sp->next) - shift_table[sp->number] = sp; + bitset_copy (F[j], F[i]); + } } static void -set_reduction_table (void) +digraph (short **relation) { - register reductions *rp; - - reduction_table = NEW2(nstates, reductions *); + int i; - for (rp = first_reduction; rp; rp = rp->next) - reduction_table[rp->number] = rp; -} + infinity = ngotos + 2; + INDEX = XCALLOC (short, ngotos + 1); + VERTICES = XCALLOC (short, ngotos + 1); + top = 0; + R = relation; -static void -set_maxrhs (void) -{ - register short *itemp; - register int length; - register int max; + for (i = 0; i < ngotos; i++) + INDEX[i] = 0; - length = 0; - max = 0; - for (itemp = ritem; *itemp; itemp++) - { - if (*itemp > 0) - { - length++; - } - else - { - if (length > max) max = length; - length = 0; - } - } + for (i = 0; i < ngotos; i++) + if (INDEX[i] == 0 && R[i]) + traverse (i); - maxrhs = max; + XFREE (INDEX); + XFREE (VERTICES); } static void initialize_LA (void) { - register int i; - register int j; - register int count; - register reductions *rp; - register shifts *sp; - register short *np; - - consistent = NEW2(nstates, char); - lookaheads = NEW2(nstates + 1, short); - - count = 0; - for (i = 0; i < nstates; i++) - { - register int k; - - lookaheads[i] = count; - - rp = reduction_table[i]; - sp = shift_table[i]; - if (rp && (rp->nreds > 1 - || (sp && ! ISVAR(accessing_symbol[sp->shifts[0]])))) - count += rp->nreds; - else - consistent[i] = 1; + size_t i; + int j; + rule_t **np; - if (sp) - for (k = 0; k < sp->nshifts; k++) - { - if (accessing_symbol[sp->shifts[k]] == error_token_number) - { - consistent[i] = 0; - break; - } - } - } + /* Avoid having to special case 0. */ + if (!nLA) + nLA = 1; - lookaheads[nstates] = count; + LA = bitsetv_create (nLA, ntokens, BITSET_FIXED); + LArule = XCALLOC (rule_t *, nLA); + lookback = XCALLOC (shorts *, nLA); - if (count == 0) - { - LA = NEW2(1 * tokensetsize, unsigned); - LAruleno = NEW2(1, short); - lookback = NEW2(1, shorts *); - } - else - { - LA = NEW2(count * tokensetsize, unsigned); - LAruleno = NEW2(count, short); - lookback = NEW2(count, shorts *); - } - - np = LAruleno; + np = LArule; for (i = 0; i < nstates; i++) - { - if (!consistent[i]) - { - if ((rp = reduction_table[i])) - for (j = 0; j < rp->nreds; j++) - *np++ = rp->rules[j]; - } - } + if (!states[i]->consistent) + for (j = 0; j < states[i]->reductions->nreds; j++) + *np++ = &rules[states[i]->reductions->rules[j]]; } static void set_goto_map (void) { - register shifts *sp; - register int i; - register int symbol; - register int k; - register short *temp_map; - register int state2; - register int state1; + size_t state; + int i; + short *temp_map; - goto_map = NEW2(nvars + 1, short) - ntokens; - temp_map = NEW2(nvars + 1, short) - ntokens; + goto_map = XCALLOC (short, nvars + 1) - ntokens; + temp_map = XCALLOC (short, nvars + 1) - ntokens; ngotos = 0; - for (sp = first_shift; sp; sp = sp->next) + for (state = 0; state < nstates; ++state) { - for (i = sp->nshifts - 1; i >= 0; i--) + shifts *sp = states[state]->shifts; + for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) { - symbol = accessing_symbol[sp->shifts[i]]; - - if (ISTOKEN(symbol)) break; - - if (ngotos == MAXSHORT) - fatal (_("too many gotos (max %d)"), MAXSHORT); + if (ngotos == SHRT_MAX) + fatal (_("too many gotos (max %d)"), SHRT_MAX); ngotos++; - goto_map[symbol]++; - } + goto_map[SHIFT_SYMBOL (sp, i)]++; + } } - k = 0; - for (i = ntokens; i < nsyms; i++) - { - temp_map[i] = k; - k += goto_map[i]; - } + { + int k = 0; + for (i = ntokens; i < nsyms; i++) + { + temp_map[i] = k; + k += goto_map[i]; + } - for (i = ntokens; i < nsyms; i++) - goto_map[i] = temp_map[i]; + for (i = ntokens; i < nsyms; i++) + goto_map[i] = temp_map[i]; - goto_map[nsyms] = ngotos; - temp_map[nsyms] = ngotos; + goto_map[nsyms] = ngotos; + temp_map[nsyms] = ngotos; + } - from_state = NEW2(ngotos, short); - to_state = NEW2(ngotos, short); + from_state = XCALLOC (short, ngotos); + to_state = XCALLOC (short, ngotos); - for (sp = first_shift; sp; sp = sp->next) + for (state = 0; state < nstates; ++state) { - state1 = sp->number; - for (i = sp->nshifts - 1; i >= 0; i--) + shifts *sp = states[state]->shifts; + for (i = sp->nshifts - 1; i >= 0 && SHIFT_IS_GOTO (sp, i); --i) { - state2 = sp->shifts[i]; - symbol = accessing_symbol[state2]; - - if (ISTOKEN(symbol)) break; - - k = temp_map[symbol]++; - from_state[k] = state1; - to_state[k] = state2; + int k = temp_map[SHIFT_SYMBOL (sp, i)]++; + from_state[k] = state; + to_state[k] = sp->shifts[i]; } } - FREE(temp_map + ntokens); + XFREE (temp_map + ntokens); } -/* Map_goto maps a state/symbol pair into its numeric representation. */ +/*----------------------------------------------------------. +| Map a state/symbol pair into its numeric representation. | +`----------------------------------------------------------*/ static int -map_goto (int state, int symbol) +map_goto (int state, token_number_t symbol) { - register int high; - register int low; - register int middle; - register int s; + int high; + int low; + int middle; + int s; low = goto_map[symbol]; high = goto_map[symbol + 1] - 1; @@ -358,8 +239,8 @@ map_goto (int state, int symbol) high = middle - 1; } - berror("map_goto"); -/* NOTREACHED */ + assert (0); + /* NOTREACHED */ return 0; } @@ -367,396 +248,340 @@ map_goto (int state, int symbol) static void initialize_F (void) { - register int i; - register int j; - register int k; - register shifts *sp; - register short *edge; - register unsigned *rowp; - register short *rp; - register short **reads; - register int nedges; - register int stateno; - register int symbol; - register int nwords; - - nwords = ngotos * tokensetsize; - F = NEW2(nwords, unsigned); - - reads = NEW2(ngotos, short *); - edge = NEW2(ngotos + 1, short); - nedges = 0; - - rowp = F; - for (i = 0; i < ngotos; i++) - { - stateno = to_state[i]; - sp = shift_table[stateno]; + short **reads = XCALLOC (short *, ngotos); + short *edge = XCALLOC (short, ngotos + 1); + int nedges = 0; - if (sp) - { - k = sp->nshifts; + int i; - for (j = 0; j < k; j++) - { - symbol = accessing_symbol[sp->shifts[j]]; - if (ISVAR(symbol)) - break; - SETBIT(rowp, symbol); - } - - for (; j < k; j++) - { - symbol = accessing_symbol[sp->shifts[j]]; - if (nullable[symbol]) - edge[nedges++] = map_goto(stateno, symbol); - } - - if (nedges) - { - reads[i] = rp = NEW2(nedges + 1, short); - - for (j = 0; j < nedges; j++) - rp[j] = edge[j]; - - rp[nedges] = -1; - nedges = 0; - } - } - - rowp += tokensetsize; - } - - digraph(reads); + F = bitsetv_create (ngotos, ntokens, BITSET_FIXED); for (i = 0; i < ngotos; i++) { - if (reads[i]) - FREE(reads[i]); - } - - FREE(reads); - FREE(edge); -} + int stateno = to_state[i]; + shifts *sp = states[stateno]->shifts; + int j; + for (j = 0; j < sp->nshifts && SHIFT_IS_SHIFT (sp, j); j++) + bitset_set (F[i], SHIFT_SYMBOL (sp, j)); -static void -build_relations (void) -{ - register int i; - register int j; - register int k; - register short *rulep; - register short *rp; - register shifts *sp; - register int length; - register int nedges; - register int done; - register int state1; - register int stateno; - register int symbol1; - register int symbol2; - register short *shortp; - register short *edge; - register short *states; - register short **new_includes; - - includes = NEW2(ngotos, short *); - edge = NEW2(ngotos + 1, short); - states = NEW2(maxrhs + 1, short); - - for (i = 0; i < ngotos; i++) - { - nedges = 0; - state1 = from_state[i]; - symbol1 = accessing_symbol[to_state[i]]; - - for (rulep = derives[symbol1]; *rulep > 0; rulep++) + for (; j < sp->nshifts; j++) { - length = 1; - states[0] = state1; - stateno = state1; - - for (rp = ritem + rrhs[*rulep]; *rp > 0; rp++) - { - symbol2 = *rp; - sp = shift_table[stateno]; - k = sp->nshifts; - - for (j = 0; j < k; j++) - { - stateno = sp->shifts[j]; - if (accessing_symbol[stateno] == symbol2) break; - } - - states[length++] = stateno; - } - - if (!consistent[stateno]) - add_lookback_edge(stateno, *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)) - { - stateno = states[--length]; - edge[nedges++] = map_goto(stateno, *rp); - if (nullable[*rp]) done = 0; - } - } + token_number_t symbol = SHIFT_SYMBOL (sp, j); + if (nullable[symbol]) + edge[nedges++] = map_goto (stateno, symbol); } if (nedges) { - includes[i] = shortp = NEW2(nedges + 1, short); - for (j = 0; j < nedges; j++) - shortp[j] = edge[j]; - shortp[nedges] = -1; + reads[i] = XCALLOC (short, nedges + 1); + memcpy (reads[i], edge, nedges * sizeof (edge[0])); + reads[i][nedges] = -1; + nedges = 0; } } - new_includes = transpose(includes, ngotos); + digraph (reads); for (i = 0; i < ngotos; i++) - if (includes[i]) - FREE(includes[i]); + XFREE (reads[i]); - FREE(includes); - - includes = new_includes; - - FREE(edge); - FREE(states); + XFREE (reads); + XFREE (edge); } static void -add_lookback_edge (int stateno, int ruleno, int gotono) +add_lookback_edge (state_t *state, int ruleno, int gotono) { - register int i; - register int k; - register int found; - register shorts *sp; - - i = lookaheads[stateno]; - k = lookaheads[stateno + 1]; - found = 0; - while (!found && i < k) - { - if (LAruleno[i] == ruleno) - found = 1; - else - i++; - } + int i; + shorts *sp; - if (found == 0) - berror("add_lookback_edge"); + for (i = 0; i < state->nlookaheads; ++i) + if (LArule[state->lookaheadsp + i]->number == ruleno) + break; - sp = NEW(shorts); - sp->next = lookback[i]; + assert (LArule[state->lookaheadsp + i]->number == ruleno); + + sp = XCALLOC (shorts, 1); + sp->next = lookback[state->lookaheadsp + i]; sp->value = gotono; - lookback[i] = sp; + lookback[state->lookaheadsp + i] = 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) { - register short **new_R; - register short **temp_R; - register short *nedges; - register short *sp; - register int i; - register int k; - - nedges = NEW2(n, short); - - for (i = 0; i < n; i++) + /* 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) { - sp = R_arg[i]; - if (sp) - { - while (*sp >= 0) - nedges[*sp++]++; - } + fputs ("transpose: input\n", stderr); + matrix_print (stderr, R_arg, n); } - new_R = NEW2(n, short *); - temp_R = NEW2(n, short *); + /* 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++) - { - k = nedges[i]; - if (k > 0) + 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) { - sp = NEW2(k + 1, short); - new_R[i] = sp; - temp_R[i] = sp; - sp[k] = -1; + *end_R[R_arg[i][j]] = i; + ++end_R[R_arg[i][j]]; } - } - FREE(nedges); + 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) { - sp = R_arg[i]; - if (sp) - { - while (*sp >= 0) - *temp_R[*sp++]++ = i; - } + fputs ("transpose: output\n", stderr); + matrix_print (stderr, new_R, n); } - FREE(temp_R); - return new_R; } static void -compute_FOLLOWS (void) +build_relations (void) { - register int i; + short *edge = XCALLOC (short, ngotos + 1); + short *states1 = XCALLOC (short, ritem_longest_rhs () + 1); + int i; - digraph(includes); + includes = XCALLOC (short *, ngotos); for (i = 0; i < ngotos; i++) { - if (includes[i]) FREE(includes[i]); - } + int nedges = 0; + token_number_t symbol1 = states[to_state[i]]->accessing_symbol; + short *rulep; - FREE(includes); -} + 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++) + { + shifts *sp = state->shifts; + int j; + for (j = 0; j < sp->nshifts; j++) + { + state = states[sp->shifts[j]]; + if (state->accessing_symbol + == item_number_as_token_number (*rp)) + break; + } -static void -compute_lookaheads (void) -{ - register int i; - register int n; - register unsigned *fp1; - register unsigned *fp2; - register unsigned *fp3; - register shorts *sp; - register unsigned *rowp; -/* register short *rulep; JF unused */ -/* register int count; JF unused */ - register shorts *sptmp;/* JF */ - - rowp = LA; - n = lookaheads[nstates]; - for (i = 0; i < n; i++) - { - fp3 = rowp + tokensetsize; - for (sp = lookback[i]; sp; sp = sp->next) - { - fp1 = rowp; - fp2 = F + tokensetsize * sp->value; - while (fp1 < fp3) - *fp1++ |= *fp2++; + 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 token_number_t. */ + edge[nedges++] = map_goto (states1[--length], + item_number_as_token_number (*rp)); + if (nullable[*rp]) + done = 0; + } + } } - rowp = fp3; + 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; + } } - for (i = 0; i < n; i++) - {/* JF removed ref to freed storage */ - for (sp = lookback[i]; sp; sp = sptmp) { - sptmp=sp->next; - FREE(sp); - } - } + XFREE (edge); + XFREE (states1); - FREE(lookback); - FREE(F); + includes = transpose (includes, ngotos); } + static void -digraph (short **relation) +compute_FOLLOWS (void) { - register int i; - - infinity = ngotos + 2; - INDEX = NEW2(ngotos + 1, short); - VERTICES = NEW2(ngotos + 1, short); - top = 0; + int i; - R = relation; + digraph (includes); for (i = 0; i < ngotos; i++) - INDEX[i] = 0; + XFREE (includes[i]); - for (i = 0; i < ngotos; i++) - { - if (INDEX[i] == 0 && R[i]) - traverse(i); - } - - FREE(INDEX); - FREE(VERTICES); + XFREE (includes); } static void -traverse (register int i) +compute_lookaheads (void) { - register unsigned *fp1; - register unsigned *fp2; - register unsigned *fp3; - register int j; - register short *rp; + size_t i; + shorts *sp; - int height; - unsigned *base; + for (i = 0; i < nLA; i++) + for (sp = lookback[i]; sp; sp = sp->next) + bitset_or (LA[i], LA[i], F[sp->value]); - VERTICES[++top] = i; - INDEX[i] = height = top; - - base = F + i * tokensetsize; - fp3 = base + tokensetsize; - - rp = R[i]; - if (rp) - { - while ((j = *rp++) >= 0) - { - if (INDEX[j] == 0) - traverse(j); + /* Free LOOKBACK. */ + for (i = 0; i < nLA; i++) + LIST_FREE (shorts, lookback[i]); - if (INDEX[i] > INDEX[j]) - INDEX[i] = INDEX[j]; + XFREE (lookback); + bitsetv_free (F); +} - fp1 = base; - fp2 = F + j * tokensetsize; - while (fp1 < fp3) - *fp1++ |= *fp2++; - } - } +/*--------------------------------------. +| Initializing the lookaheads members. | +`--------------------------------------*/ - if (INDEX[i] == height) +static void +initialize_lookaheads (void) +{ + size_t i; + nLA = 0; + for (i = 0; i < nstates; i++) { - for (;;) - { - j = VERTICES[top--]; - INDEX[j] = infinity; + int k; + int nlookaheads = 0; + reductions *rp = states[i]->reductions; + shifts *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; - if (i == j) + for (k = 0; k < sp->nshifts; k++) + if (SHIFT_IS_ERROR (sp, k)) + { + states[i]->consistent = 0; break; + } - fp1 = base; - fp2 = F + j * tokensetsize; + states[i]->nlookaheads = nlookaheads; + states[i]->lookaheadsp = nLA; + nLA += nlookaheads; + } +} - while (fp1 < fp3) - *fp2++ = *fp1++; - } + +/*---------------------------------------. +| Output the lookaheads for each state. | +`---------------------------------------*/ + +static void +lookaheads_print (FILE *out) +{ + size_t i; + int j, k; + fprintf (out, "Lookaheads: 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) + for (k = 0; k < ntokens; ++k) + if (bitset_test (LA[states[i]->lookaheadsp + j], k)) + fprintf (out, " on %d (%s) -> rule %d\n", + k, quotearg_style (escape_quoting_style, symbols[k]->tag), + LArule[states[i]->lookaheadsp + j]->number - 1); } + fprintf (out, "Lookaheads: END\n"); +} + +void +lalr (void) +{ + initialize_lookaheads (); + initialize_LA (); + set_goto_map (); + initialize_F (); + build_relations (); + compute_FOLLOWS (); + compute_lookaheads (); + + if (trace_flag) + lookaheads_print (stderr); }