src/closure.c

   1 /* Closures for Bison
   2
   3    Copyright (C) 1984, 1989, 2000, 2001, 2002, 2004, 2005, 2007 Free
   4    Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    Bison is free software; you can redistribute it and/or modify it
   9    under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2, or (at your option)
  11    any later version.
  12
  13    Bison is distributed in the hope that it will be useful, but
  14    WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16    General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with Bison; see the file COPYING.  If not, write to the Free
  20    Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  21    02110-1301, USA.  */
  22
  23 #include <config.h>
  24 #include "system.h"
  25
  26 #include <bitset.h>
  27 #include <bitsetv-print.h>
  28 #include <bitsetv.h>
  29 #include <quotearg.h>
  30
  31 #include "closure.h"
  32 #include "derives.h"
  33 #include "getargs.h"
  34 #include "gram.h"
  35 #include "reader.h"
  36 #include "symtab.h"
  37
  38 /* NITEMSET is the size of the array ITEMSET.  */
  39 item_number *itemset;
  40 size_t nitemset;
  41
  42 static bitset ruleset;
  43
  44 /* internal data.  See comments before set_fderives and set_firsts.  */
  45 static bitsetv fderives = NULL;
  46 static bitsetv firsts = NULL;
  47
  48 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  49 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  50 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  51 \f
  52
  53 /*-----------------.
  54 | Debugging code.  |
  55 `-----------------*/
  56
  57 static void
  58 print_closure (char const *title, item_number *array, size_t size)
  59 {
  60   size_t i;
  61   fprintf (stderr, "Closure: %s\n", title);
  62   for (i = 0; i < size; ++i)
  63     {
  64       item_number *rp;
  65       fprintf (stderr, "  %2d: .", array[i]);
  66       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  67         fprintf (stderr, " %s", symbols[*rp]->tag);
  68       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  69     }
  70   fputs ("\n\n", stderr);
  71 }
  72
  73
  74 static void
  75 print_firsts (void)
  76 {
  77   symbol_number i, j;
  78
  79   fprintf (stderr, "FIRSTS\n");
  80   for (i = ntokens; i < nsyms; i++)
  81     {
  82       bitset_iterator iter;
  83       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  84       BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
  85         {
  86           fprintf (stderr, "\t\t%s\n",
  87                    symbols[j + ntokens]->tag);
  88         }
  89     }
  90   fprintf (stderr, "\n\n");
  91 }
  92
  93
  94 static void
  95 print_fderives (void)
  96 {
  97   int i;
  98   rule_number r;
  99
 100   fprintf (stderr, "FDERIVES\n");
 101   for (i = ntokens; i < nsyms; i++)
 102     {
 103       bitset_iterator iter;
 104       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 105       BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
 106         {
 107           fprintf (stderr, "\t\t%3d ", r);
 108           rule_rhs_print (&rules[r], stderr);
 109         }
 110     }
 111   fprintf (stderr, "\n\n");
 112 }
 113 \f
 114 /*------------------------------------------------------------------.
 115 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 116 | items can represent the beginning of the input corresponding to   |
 117 | which other items.                                                |
 118 |                                                                   |
 119 | For example, if some rule expands symbol 5 into the sequence of   |
 120 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 121 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 122 | (5)) is set.                                                      |
 123 `------------------------------------------------------------------*/
 124
 125 static void
 126 set_firsts (void)
 127 {
 128   symbol_number i, j;
 129
 130   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 131
 132   for (i = ntokens; i < nsyms; i++)
 133     for (j = 0; derives[i - ntokens][j]; ++j)
 134       {
 135         item_number sym = derives[i - ntokens][j]->rhs[0];
 136         if (ISVAR (sym))
 137           bitset_set (FIRSTS (i), sym - ntokens);
 138       }
 139
 140   if (trace_flag & trace_sets)
 141     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 142   bitsetv_reflexive_transitive_closure (firsts);
 143   if (trace_flag & trace_sets)
 144     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 145
 146   if (trace_flag & trace_sets)
 147     print_firsts ();
 148 }
 149
 150 /*-------------------------------------------------------------------.
 151 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 152 | rules can help derive the beginning of the data for each           |
 153 | nonterminal.                                                       |
 154 |                                                                    |
 155 | For example, if symbol 5 can be derived as the sequence of symbols |
 156 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 157 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 158 `-------------------------------------------------------------------*/
 159
 160 static void
 161 set_fderives (void)
 162 {
 163   symbol_number i, j;
 164   rule_number k;
 165
 166   fderives = bitsetv_create (nvars, nrules, BITSET_FIXED);
 167
 168   set_firsts ();
 169
 170   for (i = ntokens; i < nsyms; ++i)
 171     for (j = ntokens; j < nsyms; ++j)
 172       if (bitset_test (FIRSTS (i), j - ntokens))
 173         for (k = 0; derives[j - ntokens][k]; ++k)
 174           bitset_set (FDERIVES (i), derives[j - ntokens][k]->number);
 175
 176   if (trace_flag & trace_sets)
 177     print_fderives ();
 178
 179   bitsetv_free (firsts);
 180 }
 181
 182 \f
 183
 184 void
 185 new_closure (unsigned int n)
 186 {
 187   itemset = xnmalloc (n, sizeof *itemset);
 188
 189   ruleset = bitset_create (nrules, BITSET_FIXED);
 190
 191   set_fderives ();
 192 }
 193
 194
 195
 196 void
 197 closure (item_number *core, size_t n)
 198 {
 199   /* Index over CORE. */
 200   size_t c;
 201
 202   /* A bit index over RULESET. */
 203   rule_number ruleno;
 204
 205   bitset_iterator iter;
 206
 207   if (trace_flag & trace_sets)
 208     print_closure ("input", core, n);
 209
 210   bitset_zero (ruleset);
 211
 212   for (c = 0; c < n; ++c)
 213     if (ISVAR (ritem[core[c]]))
 214       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 215
 216   /* core is sorted on item number from ritem, which is sorted on rule number.
 217      Compute itemset with the same sort.  */
 218   nitemset = 0;
 219   c = 0;
 220   BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
 221     {
 222       item_number itemno = rules[ruleno].rhs - ritem;
 223       while (c < n && core[c] < itemno)
 224         {
 225           itemset[nitemset] = core[c];
 226           nitemset++;
 227           c++;
 228         }
 229       itemset[nitemset] = itemno;
 230       nitemset++;
 231     };
 232
 233   while (c < n)
 234     {
 235       itemset[nitemset] = core[c];
 236       nitemset++;
 237       c++;
 238     }
 239
 240   if (trace_flag & trace_sets)
 241     print_closure ("output", itemset, nitemset);
 242 }
 243
 244
 245 void
 246 free_closure (void)
 247 {
 248   free (itemset);
 249   bitset_free (ruleset);
 250   bitsetv_free (fderives);
 251 }