X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/7612000cb004ae5b8516e3a34a79ab32050d688e..1e9798d5699ca67718fd3b0d6baa9abcf27e6cd3:/src/reduce.c diff --git a/src/reduce.c b/src/reduce.c index 201864de..164dc72e 100644 --- a/src/reduce.c +++ b/src/reduce.c @@ -1,81 +1,57 @@ /* Grammar reduction for Bison. - Copyright (C) 1988, 1989 Free Software Foundation, Inc. + Copyright (C) 1988, 1989, 2000 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, 675 Mass Ave, Cambridge, MA 02139, 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. */ -/* - * Reduce the grammar: Find and eliminate unreachable terminals, - * nonterminals, and productions. David S. Bakin. - */ +/* Reduce the grammar: Find and eliminate unreachable terminals, + nonterminals, and productions. David S. Bakin. */ -/* - * Don't eliminate unreachable terminals: They may be used by the user's - * parser. - */ +/* Don't eliminate unreachable terminals: They may be used by the + user's parser. */ -#include #include "system.h" +#include "getargs.h" #include "files.h" #include "gram.h" -#include "machine.h" -#include "alloc.h" +#include "xalloc.h" +#include "complain.h" +#include "reduce.h" +#include "reader.h" +#include "getargs.h" - -extern char **tags; /* reader.c */ -extern int verboseflag; /* getargs.c */ -static int statisticsflag; /* XXXXXXX */ - -#ifndef TRUE -#define TRUE (1) -#define FALSE (0) -#endif -typedef int bool; typedef unsigned *BSet; -typedef short *rule; - - -/* - * N is set of all nonterminals which are not useless. P is set of all rules - * which have no useless nonterminals in their RHS. V is the set of all - * accessible symbols. - */ - -static BSet N, P, V, V1; +typedef short *rule; -static int nuseful_productions, nuseless_productions, - nuseful_nonterminals, nuseless_nonterminals; +/* N is set of all nonterminals which are not useless. P is set of + all rules which have no useless nonterminals in their RHS. V is + the set of all accessible symbols. */ -static void useless_nonterminals(); -static void inaccessable_symbols(); -static void reduce_grammar_tables(); -static void print_results(); -static void print_notices(); -void dump_grammar(); +static BSet N, P, V, V1; -extern void fatals (); +static int nuseful_productions; +static int nuseless_productions; +static int nuseful_nonterminals; +static int nuseless_nonterminals; - -bool -bits_equal (L, R, n) -BSet L; -BSet R; -int n; +static bool +bits_equal (BSet L, BSet R, int n) { int i; @@ -86,237 +62,171 @@ int n; } -int -nbits (i) -unsigned i; +static int +nbits (unsigned i) { int count = 0; - while (i != 0) { - i ^= (i & ((unsigned) (- (int) i))); - ++count; - } + while (i != 0) + { + i ^= (i & ((unsigned) (-(int) i))); + ++count; + } return count; } -int -bits_size (S, n) -BSet S; -int n; +static int +bits_size (BSet S, int n) { int i, count = 0; for (i = n - 1; i >= 0; i--) - count += nbits(S[i]); + count += nbits (S[i]); return count; } -void -reduce_grammar () -{ - bool reduced; - - /* Allocate the global sets used to compute the reduced grammar */ - - N = NEW2(WORDSIZE(nvars), unsigned); - P = NEW2(WORDSIZE(nrules + 1), unsigned); - V = NEW2(WORDSIZE(nsyms), unsigned); - V1 = NEW2(WORDSIZE(nsyms), unsigned); - - useless_nonterminals(); - inaccessable_symbols(); - - reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0); - - if (verboseflag) - print_results(); - - if (reduced == FALSE) - goto done_reducing; - - print_notices(); - - if (!BITISSET(N, start_symbol - ntokens)) - fatals(_("Start symbol %s does not derive any sentence"), - tags[start_symbol]); - - reduce_grammar_tables(); - /* if (verboseflag) { - fprintf(foutput, "REDUCED GRAMMAR\n\n"); - dump_grammar(); - } - */ - - /**/ statisticsflag = FALSE; /* someday getopts should handle this */ - if (statisticsflag == TRUE) - fprintf(stderr, - _("reduced %s defines %d terminal%s, %d nonterminal%s\ -, and %d production%s.\n"), infile, - ntokens, (ntokens == 1 ? "" : "s"), - nvars, (nvars == 1 ? "" : "s"), - nrules, (nrules == 1 ? "" : "s")); - - done_reducing: - - /* Free the global sets used to compute the reduced grammar */ - - FREE(N); - FREE(V); - FREE(P); - -} - -/* - * Another way to do this would be with a set for each production and then do - * subset tests against N, but even for the C grammar the whole reducing - * process takes only 2 seconds on my 8Mhz AT. - */ +/*-------------------------------------------------------------------. +| Another way to do this would be with a set for each production and | +| then do subset tests against N0, but even for the C grammar the | +| whole reducing process takes only 2 seconds on my 8Mhz AT. | +`-------------------------------------------------------------------*/ static bool -useful_production (i, N) -int i; -BSet N; +useful_production (int i, BSet N0) { - rule r; + rule r; short n; - /* - * A production is useful if all of the nonterminals in its RHS - * appear in the set of useful nonterminals. - */ + /* A production is useful if all of the nonterminals in its appear + in the set of useful nonterminals. */ for (r = &ritem[rrhs[i]]; *r > 0; r++) - if (ISVAR(n = *r)) - if (!BITISSET(N, n - ntokens)) + if (ISVAR (n = *r)) + if (!BITISSET (N0, n - ntokens)) return FALSE; return TRUE; } -/* Remember that rules are 1-origin, symbols are 0-origin. */ +/*---------------------------------------------------------. +| Remember that rules are 1-origin, symbols are 0-origin. | +`---------------------------------------------------------*/ static void -useless_nonterminals () +useless_nonterminals (void) { BSet Np, Ns; - int i, n; - - /* - * N is set as built. Np is set being built this iteration. P is set - * of all productions which have a RHS all in N. - */ - - Np = NEW2(WORDSIZE(nvars), unsigned); - - /* - * The set being computed is a set of nonterminals which can derive - * the empty string or strings consisting of all terminals. At each - * iteration a nonterminal is added to the set if there is a - * production with that nonterminal as its LHS for which all the - * nonterminals in its RHS are already in the set. Iterate until the - * set being computed remains unchanged. Any nonterminals not in the - * set at that point are useless in that they will never be used in - * deriving a sentence of the language. - * - * This iteration doesn't use any special traversal over the - * productions. A set is kept of all productions for which all the - * nonterminals in the RHS are in useful. Only productions not in - * this set are scanned on each iteration. At the end, this set is - * saved to be used when finding useful productions: only productions - * in this set will appear in the final grammar. - */ + int i, n; + + /* N is set as built. Np is set being built this iteration. P is + set of all productions which have a RHS all in N. */ + + Np = XCALLOC (unsigned, WORDSIZE (nvars)); + + /* The set being computed is a set of nonterminals which can derive + the empty string or strings consisting of all terminals. At each + iteration a nonterminal is added to the set if there is a + production with that nonterminal as its LHS for which all the + nonterminals in its RHS are already in the set. Iterate until + the set being computed remains unchanged. Any nonterminals not + in the set at that point are useless in that they will never be + used in deriving a sentence of the language. + + This iteration doesn't use any special traversal over the + productions. A set is kept of all productions for which all the + nonterminals in the RHS are in useful. Only productions not in + this set are scanned on each iteration. At the end, this set is + saved to be used when finding useful productions: only + productions in this set will appear in the final grammar. */ n = 0; while (1) { - for (i = WORDSIZE(nvars) - 1; i >= 0; i--) + for (i = WORDSIZE (nvars) - 1; i >= 0; i--) Np[i] = N[i]; for (i = 1; i <= nrules; i++) { - if (!BITISSET(P, i)) + if (!BITISSET (P, i)) { - if (useful_production(i, N)) + if (useful_production (i, N)) { - SETBIT(Np, rlhs[i] - ntokens); - SETBIT(P, i); + SETBIT (Np, rlhs[i] - ntokens); + SETBIT (P, i); } } } - if (bits_equal(N, Np, WORDSIZE(nvars))) + if (bits_equal (N, Np, WORDSIZE (nvars))) break; Ns = Np; Np = N; N = Ns; } - FREE(N); + XFREE (N); N = Np; } - + + static void -inaccessable_symbols () +inaccessable_symbols (void) { - BSet Vp, Vs, Pp; - int i, n; + BSet Vp, Vs, Pp; + int i, n; short t; - rule r; - - /* - * Find out which productions are reachable and which symbols are - * used. Starting with an empty set of productions and a set of - * symbols which only has the start symbol in it, iterate over all - * productions until the set of productions remains unchanged for an - * iteration. For each production which has a LHS in the set of - * reachable symbols, add the production to the set of reachable - * productions, and add all of the nonterminals in the RHS of the - * production to the set of reachable symbols. - * - * Consider only the (partially) reduced grammar which has only - * nonterminals in N and productions in P. - * - * The result is the set P of productions in the reduced grammar, and - * the set V of symbols in the reduced grammar. - * - * Although this algorithm also computes the set of terminals which are - * reachable, no terminal will be deleted from the grammar. Some - * terminals might not be in the grammar but might be generated by - * semantic routines, and so the user might want them available with - * specified numbers. (Is this true?) However, the nonreachable - * terminals are printed (if running in verbose mode) so that the user - * can know. - */ - - Vp = NEW2(WORDSIZE(nsyms), unsigned); - Pp = NEW2(WORDSIZE(nrules + 1), unsigned); + rule r; + + /* Find out which productions are reachable and which symbols are + used. Starting with an empty set of productions and a set of + symbols which only has the start symbol in it, iterate over all + productions until the set of productions remains unchanged for an + iteration. For each production which has a LHS in the set of + reachable symbols, add the production to the set of reachable + productions, and add all of the nonterminals in the RHS of the + production to the set of reachable symbols. + + Consider only the (partially) reduced grammar which has only + nonterminals in N and productions in P. + + The result is the set P of productions in the reduced grammar, + and the set V of symbols in the reduced grammar. + + Although this algorithm also computes the set of terminals which + are reachable, no terminal will be deleted from the grammar. Some + terminals might not be in the grammar but might be generated by + semantic routines, and so the user might want them available with + specified numbers. (Is this true?) However, the nonreachable + terminals are printed (if running in verbose mode) so that the + user can know. */ + + Vp = XCALLOC (unsigned, WORDSIZE (nsyms)); + Pp = XCALLOC (unsigned, WORDSIZE (nrules + 1)); /* If the start symbol isn't useful, then nothing will be useful. */ - if (!BITISSET(N, start_symbol - ntokens)) + if (!BITISSET (N, start_symbol - ntokens)) goto end_iteration; - SETBIT(V, start_symbol); + SETBIT (V, start_symbol); n = 0; while (1) { - for (i = WORDSIZE(nsyms) - 1; i >= 0; i--) + for (i = WORDSIZE (nsyms) - 1; i >= 0; i--) Vp[i] = V[i]; for (i = 1; i <= nrules; i++) { - if (!BITISSET(Pp, i) && BITISSET(P, i) && - BITISSET(V, rlhs[i])) + if (!BITISSET (Pp, i) && BITISSET (P, i) && BITISSET (V, rlhs[i])) { for (r = &ritem[rrhs[i]]; *r >= 0; r++) { - if (ISTOKEN(t = *r) - || BITISSET(N, t - ntokens)) + if (ISTOKEN (t = *r) || BITISSET (N, t - ntokens)) { - SETBIT(Vp, t); + SETBIT (Vp, t); } } - SETBIT(Pp, i); + SETBIT (Pp, i); } } - if (bits_equal(V, Vp, WORDSIZE(nsyms))) + if (bits_equal (V, Vp, WORDSIZE (nsyms))) { break; } @@ -324,36 +234,36 @@ inaccessable_symbols () Vp = V; V = Vs; } - end_iteration: +end_iteration: - FREE(V); + XFREE (V); V = Vp; /* Tokens 0, 1, and 2 are internal to Bison. Consider them useful. */ - SETBIT(V, 0); /* end-of-input token */ - SETBIT(V, 1); /* error token */ - SETBIT(V, 2); /* some undefined token */ + SETBIT (V, 0); /* end-of-input token */ + SETBIT (V, 1); /* error token */ + SETBIT (V, 2); /* some undefined token */ - FREE(P); + XFREE (P); P = Pp; - nuseful_productions = bits_size(P, WORDSIZE(nrules + 1)); + nuseful_productions = bits_size (P, WORDSIZE (nrules + 1)); nuseless_productions = nrules - nuseful_productions; nuseful_nonterminals = 0; for (i = ntokens; i < nsyms; i++) - if (BITISSET(V, i)) + if (BITISSET (V, i)) nuseful_nonterminals++; nuseless_nonterminals = nvars - nuseful_nonterminals; /* A token that was used in %prec should not be warned about. */ for (i = 1; i < nrules; i++) if (rprecsym[i] != 0) - SETBIT(V1, rprecsym[i]); + SETBIT (V1, rprecsym[i]); } - + static void -reduce_grammar_tables () +reduce_grammar_tables (void) { /* This is turned off because we would need to change the numbers in the case statements in the actions file. */ @@ -367,7 +277,7 @@ reduce_grammar_tables () ni = 0; for (pn = 1; pn <= nrules; pn++) { - if (BITISSET(P, pn)) + if (BITISSET (P, pn)) { np++; if (pn != np) @@ -385,7 +295,9 @@ reduce_grammar_tables () ritem[ni++] = ritem[pi++]; ritem[ni++] = -np; } - } else { + } + else + { while (ritem[ni++] >= 0); } } @@ -394,10 +306,8 @@ reduce_grammar_tables () nrules -= nuseless_productions; nitems = ni; - /* - * Is it worth it to reduce the amount of memory for the - * grammar? Probably not. - */ + /* Is it worth it to reduce the amount of memory for the + grammar? Probably not. */ } #endif /* 0 */ @@ -410,7 +320,7 @@ reduce_grammar_tables () for (pn = 1; pn <= nrules; pn++) { - if (!BITISSET(P, pn)) + if (!BITISSET (P, pn)) { rlhs[pn] = -1; } @@ -421,24 +331,22 @@ reduce_grammar_tables () if (nuseless_nonterminals > 0) { - int i, n; + int i, n; /* short j; JF unused */ short *nontermmap; - rule r; + rule r; - /* - * create a map of nonterminal number to new nonterminal - * number. -1 in the map means it was useless and is being - * eliminated. - */ + /* Create a map of nonterminal number to new nonterminal + number. -1 in the map means it was useless and is being + eliminated. */ - nontermmap = NEW2(nvars, short) - ntokens; + nontermmap = XCALLOC (short, nvars) - ntokens; for (i = ntokens; i < nsyms; i++) nontermmap[i] = -1; n = ntokens; for (i = ntokens; i < nsyms; i++) - if (BITISSET(V, i)) + if (BITISSET (V, i)) nontermmap[i] = n++; /* Shuffle elements of tables indexed by symbol number. */ @@ -451,8 +359,10 @@ reduce_grammar_tables () sassoc[n] = sassoc[i]; sprec[n] = sprec[i]; tags[n] = tags[i]; - } else { - free(tags[i]); + } + else + { + free (tags[i]); } } @@ -469,7 +379,7 @@ reduce_grammar_tables () } for (r = ritem; *r; r++) - if (ISVAR(*r)) + if (ISVAR (*r)) *r = nontermmap[*r]; start_symbol = nontermmap[start_symbol]; @@ -477,122 +387,183 @@ reduce_grammar_tables () nsyms -= nuseless_nonterminals; nvars -= nuseless_nonterminals; - free(&nontermmap[ntokens]); + free (&nontermmap[ntokens]); } } - + static void -print_results () +print_results (void) { - int i; + int i; /* short j; JF unused */ - rule r; - bool b; + rule r; + bool b; if (nuseless_nonterminals > 0) { - fprintf(foutput, _("Useless nonterminals:\n\n")); + fputs (_("Useless nonterminals:"), foutput); + fputs ("\n\n", foutput); for (i = ntokens; i < nsyms; i++) - if (!BITISSET(V, i)) - fprintf(foutput, " %s\n", tags[i]); + if (!BITISSET (V, i)) + fprintf (foutput, " %s\n", tags[i]); } b = FALSE; for (i = 0; i < ntokens; i++) { - if (!BITISSET(V, i) && !BITISSET(V1, i)) + if (!BITISSET (V, i) && !BITISSET (V1, i)) { if (!b) { - fprintf(foutput, _("\n\nTerminals which are not used:\n\n")); + fputs ("\n\n", foutput); + fprintf (foutput, _("Terminals which are not used:")); + fputs ("\n\n", foutput); b = TRUE; } - fprintf(foutput, " %s\n", tags[i]); + fprintf (foutput, " %s\n", tags[i]); } } if (nuseless_productions > 0) { - fprintf(foutput, _("\n\nUseless rules:\n\n")); + fputs ("\n\n", foutput); + fprintf (foutput, _("Useless rules:")); + fputs ("\n\n", foutput); for (i = 1; i <= nrules; i++) { - if (!BITISSET(P, i)) + if (!BITISSET (P, i)) { - fprintf(foutput, "#%-4d ", i); - fprintf(foutput, "%s :\t", tags[rlhs[i]]); + fprintf (foutput, "#%-4d ", i); + fprintf (foutput, "%s :\t", tags[rlhs[i]]); for (r = &ritem[rrhs[i]]; *r >= 0; r++) { - fprintf(foutput, " %s", tags[*r]); + fprintf (foutput, " %s", tags[*r]); } - fprintf(foutput, ";\n"); + fprintf (foutput, ";\n"); } } } if (nuseless_nonterminals > 0 || nuseless_productions > 0 || b) - fprintf(foutput, "\n\n"); + fputs ("\n\n", foutput); } -void -dump_grammar () +#if 0 /* XXX currently unused. */ +static void +dump_grammar (void) { int i; rule r; - fprintf(foutput, - "ntokens = %d, nvars = %d, nsyms = %d, nrules = %d, nitems = %d\n\n", - ntokens, nvars, nsyms, nrules, nitems); - fprintf(foutput, _("Variables\n---------\n\n")); - fprintf(foutput, _("Value Sprec Sassoc Tag\n")); + fprintf (foutput, + "ntokens = %d, nvars = %d, nsyms = %d, nrules = %d, nitems = %d\n\n", + ntokens, nvars, nsyms, nrules, nitems); + fprintf (foutput, _("Variables\n---------\n\n")); + fprintf (foutput, _("Value Sprec Sassoc Tag\n")); for (i = ntokens; i < nsyms; i++) - fprintf(foutput, "%5d %5d %5d %s\n", - i, sprec[i], sassoc[i], tags[i]); - fprintf(foutput, "\n\n"); - fprintf(foutput, _("Rules\n-----\n\n")); + fprintf (foutput, "%5d %5d %5d %s\n", i, sprec[i], sassoc[i], tags[i]); + fprintf (foutput, "\n\n"); + fprintf (foutput, _("Rules\n-----\n\n")); for (i = 1; i <= nrules; i++) { - fprintf(foutput, "%-5d(%5d%5d)%5d : (@%-5d)", - i, rprec[i], rassoc[i], rlhs[i], rrhs[i]); + fprintf (foutput, "%-5d(%5d%5d)%5d : (@%-5d)", + i, rprec[i], rassoc[i], rlhs[i], rrhs[i]); for (r = &ritem[rrhs[i]]; *r > 0; r++) - fprintf(foutput, "%5d", *r); - fprintf(foutput, " [%d]\n", -(*r)); + fprintf (foutput, "%5d", *r); + fprintf (foutput, " [%d]\n", -(*r)); } - fprintf(foutput, "\n\n"); - fprintf(foutput, _("Rules interpreted\n-----------------\n\n")); + fprintf (foutput, "\n\n"); + fprintf (foutput, _("Rules interpreted\n-----------------\n\n")); for (i = 1; i <= nrules; i++) { - fprintf(foutput, "%-5d %s :", i, tags[rlhs[i]]); + fprintf (foutput, "%-5d %s :", i, tags[rlhs[i]]); for (r = &ritem[rrhs[i]]; *r > 0; r++) - fprintf(foutput, " %s", tags[*r]); - fprintf(foutput, "\n"); + fprintf (foutput, " %s", tags[*r]); + fprintf (foutput, "\n"); } - fprintf(foutput, "\n\n"); + fprintf (foutput, "\n\n"); } +#endif + static void -print_notices () +print_notices (void) { - extern int fixed_outfiles; + if (yacc_flag && nuseless_productions) + fprintf (stderr, _("%d rules never reduced\n"), nuseless_productions); - if (fixed_outfiles && nuseless_productions) - fprintf(stderr, _("%d rules never reduced\n"), nuseless_productions); - - fprintf(stderr, _("%s contains "), infile); + fprintf (stderr, _("%s contains "), infile); if (nuseless_nonterminals > 0) { - fprintf(stderr, _("%d useless nonterminal%s"), - nuseless_nonterminals, - (nuseless_nonterminals == 1 ? "" : "s")); + fprintf (stderr, _("%d useless nonterminal%s"), + nuseless_nonterminals, + (nuseless_nonterminals == 1 ? "" : "s")); } if (nuseless_nonterminals > 0 && nuseless_productions > 0) - fprintf(stderr, _(" and ")); + fprintf (stderr, _(" and ")); if (nuseless_productions > 0) { - fprintf(stderr, _("%d useless rule%s"), - nuseless_productions, - (nuseless_productions == 1 ? "" : "s")); + fprintf (stderr, _("%d useless rule%s"), + nuseless_productions, (nuseless_productions == 1 ? "" : "s")); } - fprintf(stderr, "\n"); - fflush(stderr); + fprintf (stderr, "\n"); + fflush (stderr); +} + +void +reduce_grammar (void) +{ + bool reduced; + + /* Allocate the global sets used to compute the reduced grammar */ + + N = XCALLOC (unsigned, WORDSIZE (nvars)); + P = XCALLOC (unsigned, WORDSIZE (nrules + 1)); + V = XCALLOC (unsigned, WORDSIZE (nsyms)); + V1 = XCALLOC (unsigned, WORDSIZE (nsyms)); + + useless_nonterminals (); + inaccessable_symbols (); + + reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0); + + if (verbose_flag) + print_results (); + + if (reduced == FALSE) + goto done_reducing; + + print_notices (); + + if (!BITISSET (N, start_symbol - ntokens)) + fatal (_("Start symbol %s does not derive any sentence"), + tags[start_symbol]); + + reduce_grammar_tables (); +#if 0 + if (verbose_flag) + { + fprintf (foutput, "REDUCED GRAMMAR\n\n"); + dump_grammar (); + } +#endif + + if (statistics_flag) + fprintf (stderr, _("reduced %s defines %d terminal%s, %d nonterminal%s\ +, and %d production%s.\n"), + infile, + ntokens, + (ntokens == 1 ? "" : "s"), + nvars, + (nvars == 1 ? "" : "s"), + nrules, + (nrules == 1 ? "" : "s")); + +done_reducing: + /* Free the global sets used to compute the reduced grammar */ + + XFREE (N); + XFREE (V); + XFREE (P); }