X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/30171f79ab0aaad06b88a66653789691c4ed4f2c..78ab8f674f0679b38ca8a6353f562c86b1c95055:/src/reduce.c?ds=sidebyside diff --git a/src/reduce.c b/src/reduce.c index 89ff3c3b..61ad2b2e 100644 --- a/src/reduce.c +++ b/src/reduce.c @@ -1,5 +1,5 @@ /* Grammar reduction for Bison. - Copyright 1988, 1989, 2000, 2001 Free Software Foundation, Inc. + Copyright (C) 1988, 1989, 2000, 2001, 2002 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. @@ -26,72 +26,35 @@ user's parser. */ #include "system.h" +#include "quotearg.h" #include "getargs.h" #include "files.h" +#include "symtab.h" #include "gram.h" #include "complain.h" #include "reduce.h" #include "reader.h" #include "getargs.h" - -typedef unsigned *BSet; -typedef short *rule; - +#include "bitset.h" /* Set of all nonterminals which are not useless. */ -static BSet N; +static bitset N; /* Set of all rules which have no useless nonterminals in their RHS. */ -static BSet P; +static bitset P; /* Set of all accessible symbols. */ -static BSet V; +static bitset V; /* Set of symbols used to define rule precedence (so they are `useless', but no warning should be issued). */ -static BSet V1; +static bitset V1; static int nuseful_productions; -static int nuseless_productions; +int nuseless_productions; static int nuseful_nonterminals; int nuseless_nonterminals; -static bool -bits_equal (BSet L, BSet R, int n) -{ - int i; - - for (i = n - 1; i >= 0; i--) - if (L[i] != R[i]) - return FALSE; - return TRUE; -} - - -static int -nbits (unsigned i) -{ - int count = 0; - - while (i != 0) - { - i ^= (i & ((unsigned) (-(int) i))); - ++count; - } - return count; -} - - -static int -bits_size (BSet S, int n) -{ - int i, count = 0; - - for (i = n - 1; i >= 0; i--) - count += nbits (S[i]); - return count; -} - /*-------------------------------------------------------------------. | 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 | @@ -99,18 +62,17 @@ bits_size (BSet S, int n) `-------------------------------------------------------------------*/ static bool -useful_production (int i, BSet N0) +useful_production (int i, bitset N0) { - rule r; + item_number_t *r; short n; /* A production is useful if all of the nonterminals in its appear in the set of useful nonterminals. */ - for (r = &ritem[rule_table[i].rhs]; *r > 0; r++) - if (ISVAR (n = *r)) - if (!BITISSET (N0, n - ntokens)) - return FALSE; + for (r = rules[i].rhs; *r >= 0; r++) + if (ISVAR (n = *r) && !bitset_test (N0, n - ntokens)) + return FALSE; return TRUE; } @@ -122,13 +84,14 @@ useful_production (int i, BSet N0) static void useless_nonterminals (void) { - BSet Np, Ns; + bitset Np, Ns; int i; /* 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)); + Np = bitset_create (nvars, BITSET_FIXED); + /* The set being computed is a set of nonterminals which can derive the empty string or strings consisting of all terminals. At each @@ -148,26 +111,21 @@ useless_nonterminals (void) while (1) { - for (i = WORDSIZE (nvars) - 1; i >= 0; i--) - Np[i] = N[i]; - for (i = 1; i <= nrules; i++) - { - if (!BITISSET (P, i)) - { - if (useful_production (i, N)) - { - SETBIT (Np, rule_table[i].lhs - ntokens); - SETBIT (P, i); - } - } - } - if (bits_equal (N, Np, WORDSIZE (nvars))) + bitset_copy (Np, N); + for (i = 1; i < nrules + 1; i++) + if (!bitset_test (P, i) + && useful_production (i, N)) + { + bitset_set (Np, rules[i].lhs->number - ntokens); + bitset_set (P, i); + } + if (bitset_equal_p (N, Np)) break; Ns = Np; Np = N; N = Ns; } - XFREE (N); + bitset_free (N); N = Np; } @@ -175,10 +133,10 @@ useless_nonterminals (void) static void inaccessable_symbols (void) { - BSet Vp, Vs, Pp; + bitset Vp, Vs, Pp; int i; short t; - rule r; + item_number_t *r; /* Find out which productions are reachable and which symbols are used. Starting with an empty set of productions and a set of @@ -203,31 +161,30 @@ inaccessable_symbols (void) 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)); + Vp = bitset_create (nsyms, BITSET_FIXED); + Pp = bitset_create (nrules + 1, BITSET_FIXED); /* If the start symbol isn't useful, then nothing will be useful. */ - if (BITISSET (N, start_symbol - ntokens)) + if (bitset_test (N, start_symbol - ntokens)) { - SETBIT (V, start_symbol); + bitset_set (V, start_symbol); while (1) { - for (i = WORDSIZE (nsyms) - 1; i >= 0; i--) - Vp[i] = V[i]; - for (i = 1; i <= nrules; i++) + bitset_copy (Vp, V); + for (i = 1; i < nrules + 1; i++) { - if (!BITISSET (Pp, i) - && BITISSET (P, i) - && BITISSET (V, rule_table[i].lhs)) + if (!bitset_test (Pp, i) + && bitset_test (P, i) + && bitset_test (V, rules[i].lhs->number)) { - for (r = &ritem[rule_table[i].rhs]; *r >= 0; r++) - if (ISTOKEN (t = *r) || BITISSET (N, t - ntokens)) - SETBIT (Vp, t); - SETBIT (Pp, i); + for (r = rules[i].rhs; *r >= 0; r++) + if (ISTOKEN (t = *r) || bitset_test (N, t - ntokens)) + bitset_set (Vp, t); + bitset_set (Pp, i); } } - if (bits_equal (V, Vp, WORDSIZE (nsyms))) + if (bitset_equal_p (V, Vp)) break; Vs = Vp; Vp = V; @@ -235,94 +192,82 @@ inaccessable_symbols (void) } } - XFREE (V); + bitset_free (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 */ + bitset_set (V, eoftoken->number); /* end-of-input token */ + bitset_set (V, errtoken->number); /* error token */ + bitset_set (V, undeftoken->number); /* some undefined token */ - XFREE (P); + bitset_free (P); P = Pp; - nuseful_productions = bits_size (P, WORDSIZE (nrules + 1)); + nuseful_productions = bitset_count (P); nuseless_productions = nrules - nuseful_productions; nuseful_nonterminals = 0; for (i = ntokens; i < nsyms; i++) - if (BITISSET (V, i)) + if (bitset_test (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 (rule_table[i].precsym != 0) - SETBIT (V1, rule_table[i].precsym); + for (i = 1; i < nrules + 1; i++) + if (rules[i].precsym != 0) + bitset_set (V1, rules[i].precsym->number); } + +/*-------------------------------------------------------------------. +| Put the useless productions at the end of RULES, and adjust NRULES | +| accordingly. | +`-------------------------------------------------------------------*/ + static void reduce_grammar_tables (void) { - /* This is turned off because we would need to change the numbers in - the case statements in the actions file. - - We don't disable it via CPP so that it is still checked with the - rest of the code, to avoid its becoming completely obsolete. + /* Flag useless productions. */ + { + int pn; + for (pn = 1; pn < nrules + 1; pn++) + rules[pn].useful = bitset_test (P, pn); + } - FIXME: I think the comment above demonstrates this code must be - turned off for *semantic* parser, not in the general case. Try - to understand this better --akim. */ + /* Map the nonterminals to their new index: useful first, useless + afterwards. Kept for later report. */ + { + int useful = 1; + int useless = nrules + 1 - nuseless_productions; + rule_t *rules_sorted = XMALLOC (rule_t, nrules + 1) - 1; + int i; + for (i = 1; i < nrules + 1; ++i) + rules_sorted[rules[i].useful ? useful++ : useless++] = rules[i]; + free (rules + 1); + rules = rules_sorted; - if (0) - /* remove useless productions */ - if (nuseless_productions > 0) + /* Renumber the rules markers in RITEMS. */ + for (i = 1; i < nrules + 1; ++i) { - short np, pn, ni, pi; - - np = 0; - ni = 0; - for (pn = 1; pn <= nrules; pn++) - if (BITISSET (P, pn)) - { - np++; - if (pn != np) - { - rule_table[np].lhs = rule_table[pn].lhs; - rule_table[np].line = rule_table[pn].line; - rule_table[np].prec = rule_table[pn].prec; - rule_table[np].assoc = rule_table[pn].assoc; - rule_table[np].rhs = rule_table[pn].rhs; - if (rule_table[np].rhs != ni) - { - pi = rule_table[np].rhs; - rule_table[np].rhs = ni; - while (ritem[pi] >= 0) - ritem[ni++] = ritem[pi++]; - ritem[ni++] = -np; - } - } - else - { - while (ritem[ni++] >= 0); - } - } - - ritem[ni] = 0; - nrules -= nuseless_productions; - nitems = ni; - - /* Is it worth it to reduce the amount of memory for the - grammar? Probably not. */ + item_number_t *rhsp = rules[i].rhs; + for (/* Nothing. */; *rhsp >= 0; ++rhsp) + /* Nothing. */; + *rhsp = -i; + rules[i].number = i; } + nrules -= nuseless_productions; + } - /* Disable useless productions. */ - if (nuseless_productions > 0) - { - int pn; - for (pn = 1; pn <= nrules; pn++) - rule_table[pn].useful = BITISSET (P, pn); - } + /* Adjust NRITEMS and NITEMS. */ + { + int r; + int length; + for (r = nrules + 1; r < nrules + 1 + nuseless_productions; ++r) + { + length = rule_rhs_length (&rules[r]); + nritems -= length + 1; + } + } } @@ -333,59 +278,37 @@ reduce_grammar_tables (void) static void nonterminals_reduce (void) { - int i, n; - rule r; + token_number_t i, n; /* Map the nonterminals to their new index: useful first, useless afterwards. Kept for later report. */ - short *nontermmap = XCALLOC (short, nvars) - ntokens; + token_number_t *nontermmap = XCALLOC (token_number_t, nvars) - ntokens; n = ntokens; for (i = ntokens; i < nsyms; i++) - if (BITISSET (V, i)) + if (bitset_test (V, i)) nontermmap[i] = n++; for (i = ntokens; i < nsyms; i++) - if (!BITISSET (V, i)) + if (!bitset_test (V, i)) nontermmap[i] = n++; /* Shuffle elements of tables indexed by symbol number. */ { - short *sassoc_sorted = XMALLOC (short, nvars) - ntokens; - short *sprec_sorted = XMALLOC (short, nvars) - ntokens; - char **tags_sorted = XMALLOC (char *, nvars) - ntokens; + symbol_t **symbols_sorted = XMALLOC (symbol_t *, nvars) - ntokens; for (i = ntokens; i < nsyms; i++) - { - n = nontermmap[i]; - sassoc_sorted[n] = sassoc[i]; - sprec_sorted[n] = sprec[i]; - tags_sorted[n] = tags[i]; - } + symbols[i]->number = nontermmap[i]; for (i = ntokens; i < nsyms; i++) - { - sassoc[i] = sassoc_sorted[i]; - sprec[i] = sprec_sorted[i]; - tags[i] = tags_sorted[i]; - } - free (sassoc_sorted + ntokens); - free (sprec_sorted + ntokens); - free (tags_sorted + ntokens); + symbols_sorted[nontermmap[i]] = symbols[i]; + for (i = ntokens; i < nsyms; i++) + symbols[i] = symbols_sorted[i]; + free (symbols_sorted + ntokens); } - /* Replace all symbol numbers in valid data structures. */ - - for (i = 1; i <= nrules; i++) - { - rule_table[i].lhs = nontermmap[rule_table[i].lhs]; - if (ISVAR (rule_table[i].precsym)) - /* Can this happen? */ - rule_table[i].precsym = nontermmap[rule_table[i].precsym]; - } - - for (r = ritem; *r; r++) - if (ISVAR (*r)) - *r = nontermmap[*r]; + for (i = 0; i < nritems; ++i) + if (ISVAR (ritem[i])) + ritem[i] = token_number_as_item_number (nontermmap[ritem[i]]); start_symbol = nontermmap[start_symbol]; @@ -408,7 +331,8 @@ reduce_output (FILE *out) int i; fprintf (out, "%s\n\n", _("Useless nonterminals:")); for (i = 0; i < nuseless_nonterminals; ++i) - fprintf (out, " %s\n", tags[nsyms + i]); + fprintf (out, " %s\n", quotearg_style (escape_quoting_style, + symbols[nsyms + i]->tag)); fputs ("\n\n", out); } @@ -416,12 +340,13 @@ reduce_output (FILE *out) bool b = FALSE; int i; for (i = 0; i < ntokens; i++) - if (!BITISSET (V, i) && !BITISSET (V1, i)) + if (!bitset_test (V, i) && !bitset_test (V1, i)) { if (!b) fprintf (out, "%s\n\n", _("Terminals which are not used:")); b = TRUE; - fprintf (out, " %s\n", tags[i]); + fprintf (out, " %s\n", quotearg_style (escape_quoting_style, + symbols[i]->tag)); } if (b) fputs ("\n\n", out); @@ -431,64 +356,22 @@ reduce_output (FILE *out) { int i; fprintf (out, "%s\n\n", _("Useless rules:")); - for (i = 1; i <= nrules; i++) - if (!rule_table[i].useful) - { - rule r; - fprintf (out, "#%-4d ", i - 1); - fprintf (out, "%s:", tags[rule_table[i].lhs]); - for (r = &ritem[rule_table[i].rhs]; *r >= 0; r++) - fprintf (out, " %s", tags[*r]); - fputs (";\n", out); - } + for (i = nrules + 1; i < nuseless_productions + nrules + 1; i++) + { + item_number_t *r; + fprintf (out, "#%-4d ", rules[i].user_number - 1); + fprintf (out, "%s:", quotearg_style (escape_quoting_style, + rules[i].lhs->tag)); + for (r = rules[i].rhs; *r >= 0; r++) + fprintf (out, " %s", quotearg_style (escape_quoting_style, + symbols[*r]->tag)); + fputs (";\n", out); + } fputs ("\n\n", out); } } -static void -dump_grammar (FILE *out) -{ - int i; - rule r; - - fprintf (out, "REDUCED GRAMMAR\n\n"); - fprintf (out, - "ntokens = %d, nvars = %d, nsyms = %d, nrules = %d, nitems = %d\n\n", - ntokens, nvars, nsyms, nrules, nitems); - fprintf (out, "Variables\n---------\n\n"); - fprintf (out, "Value Sprec Sassoc Tag\n"); - for (i = ntokens; i < nsyms; i++) - fprintf (out, "%5d %5d %5d %s\n", i, sprec[i], sassoc[i], tags[i]); - fprintf (out, "\n\n"); - fprintf (out, "Rules\n-----\n\n"); - fprintf (out, "Num (Prec, Assoc, Useful, Ritem Range) Lhs -> Rhs (Ritem range) [Num]\n"); - for (i = 1; i <= nrules; i++) - { - int rhs_count = 0; - /* Find the last RHS index in ritems. */ - for (r = &ritem[rule_table[i].rhs]; *r > 0; ++r) - ++rhs_count; - fprintf (out, "%3d (%2d, %2d, %2d, %2d-%2d) %2d ->", - i, - rule_table[i].prec, rule_table[i].assoc, rule_table[i].useful, - rule_table[i].rhs, rule_table[i].rhs + rhs_count - 1, - rule_table[i].lhs); - /* Dumped the RHS. */ - for (r = &ritem[rule_table[i].rhs]; *r > 0; r++) - fprintf (out, "%3d", *r); - fprintf (out, " [%d]\n", -(*r)); - } - fprintf (out, "\n\n"); - fprintf (out, "Rules interpreted\n-----------------\n\n"); - for (i = 1; i <= nrules; i++) - { - fprintf (out, "%-5d %s :", i, tags[rule_table[i].lhs]); - for (r = &ritem[rule_table[i].rhs]; *r > 0; r++) - fprintf (out, " %s", tags[*r]); - fputc ('\n', out); - } - fprintf (out, "\n\n"); -} + @@ -532,32 +415,35 @@ reduce_grammar (void) /* 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)); + N = bitset_create (nvars, BITSET_FIXED); + P = bitset_create (nrules + 1, BITSET_FIXED); + V = bitset_create (nsyms, BITSET_FIXED); + V1 = bitset_create (nsyms, BITSET_FIXED); useless_nonterminals (); inaccessable_symbols (); reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0); - if (!reduced) return; reduce_print (); - if (!BITISSET (N, start_symbol - ntokens)) + if (!bitset_test (N, start_symbol - ntokens)) fatal (_("Start symbol %s does not derive any sentence"), - tags[start_symbol]); + quotearg_style (escape_quoting_style, symbols[start_symbol]->tag)); - reduce_grammar_tables (); + /* First reduce the nonterminals, as they renumber themselves in the + whole grammar. If you change the order, nonterms would be + renumbered only in the reduced grammar. */ if (nuseless_nonterminals > 0) nonterminals_reduce (); + if (nuseless_productions > 0) + reduce_grammar_tables (); if (trace_flag) { - dump_grammar (stderr); + grammar_dump (stderr, "Reduced Grammar"); fprintf (stderr, "reduced %s defines %d terminals, %d nonterminals\ , and %d productions.\n", @@ -573,8 +459,8 @@ reduce_grammar (void) void reduce_free (void) { - XFREE (N); - XFREE (V); - XFREE (V1); - XFREE (P); + bitset_free (N); + bitset_free (V); + bitset_free (V1); + bitset_free (P); }