src/closure.c

   1 /* Closures for Bison
   2
   3    Copyright (C) 1984, 1989, 2000-2002, 2004-2005, 2007, 2009-2012 Free
   4    Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include <bitset.h>
  25 #include <bitsetv-print.h>
  26 #include <bitsetv.h>
  27
  28 #include "closure.h"
  29 #include "derives.h"
  30 #include "getargs.h"
  31 #include "gram.h"
  32 #include "reader.h"
  33 #include "symtab.h"
  34
  35 /* NITEMSET is the size of the array ITEMSET.  */
  36 item_number *itemset;
  37 size_t nitemset;
  38
  39 static bitset ruleset;
  40
  41 /* internal data.  See comments before set_fderives and set_firsts.  */
  42 static bitsetv fderives = NULL;
  43 static bitsetv firsts = NULL;
  44
  45 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  46 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  47 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  48 \f
  49
  50 /*-----------------.
  51 | Debugging code.  |
  52 `-----------------*/
  53
  54 static void
  55 print_closure (char const *title, item_number *array, size_t size)
  56 {
  57   size_t i;
  58   fprintf (stderr, "Closure: %s\n", title);
  59   for (i = 0; i < size; ++i)
  60     {
  61       item_number *rp;
  62       fprintf (stderr, "  %2d: .", array[i]);
  63       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  64         fprintf (stderr, " %s", symbols[*rp]->tag);
  65       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  66     }
  67   fputs ("\n\n", stderr);
  68 }
  69
  70
  71 static void
  72 print_firsts (void)
  73 {
  74   symbol_number i, j;
  75
  76   fprintf (stderr, "FIRSTS\n");
  77   for (i = ntokens; i < nsyms; i++)
  78     {
  79       bitset_iterator iter;
  80       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  81       BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
  82         {
  83           fprintf (stderr, "\t\t%s\n",
  84                    symbols[j + ntokens]->tag);
  85         }
  86     }
  87   fprintf (stderr, "\n\n");
  88 }
  89
  90
  91 static void
  92 print_fderives (void)
  93 {
  94   int i;
  95   rule_number r;
  96
  97   fprintf (stderr, "FDERIVES\n");
  98   for (i = ntokens; i < nsyms; i++)
  99     {
 100       bitset_iterator iter;
 101       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 102       BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
 103         {
 104           fprintf (stderr, "\t\t%3d ", r);
 105           rule_rhs_print (&rules[r], stderr);
 106         }
 107     }
 108   fprintf (stderr, "\n\n");
 109 }
 110 \f
 111 /*------------------------------------------------------------------.
 112 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 113 | items can represent the beginning of the input corresponding to   |
 114 | which other items.                                                |
 115 |                                                                   |
 116 | For example, if some rule expands symbol 5 into the sequence of   |
 117 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 118 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 119 | (5)) is set.                                                      |
 120 `------------------------------------------------------------------*/
 121
 122 static void
 123 set_firsts (void)
 124 {
 125   symbol_number i, j;
 126
 127   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 128
 129   for (i = ntokens; i < nsyms; i++)
 130     for (j = 0; derives[i - ntokens][j]; ++j)
 131       {
 132         item_number sym = derives[i - ntokens][j]->rhs[0];
 133         if (ISVAR (sym))
 134           bitset_set (FIRSTS (i), sym - ntokens);
 135       }
 136
 137   if (trace_flag & trace_sets)
 138     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 139   bitsetv_reflexive_transitive_closure (firsts);
 140   if (trace_flag & trace_sets)
 141     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 142
 143   if (trace_flag & trace_sets)
 144     print_firsts ();
 145 }
 146
 147 /*-------------------------------------------------------------------.
 148 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 149 | rules can help derive the beginning of the data for each           |
 150 | nonterminal.                                                       |
 151 |                                                                    |
 152 | For example, if symbol 5 can be derived as the sequence of symbols |
 153 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 154 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 155 `-------------------------------------------------------------------*/
 156
 157 static void
 158 set_fderives (void)
 159 {
 160   symbol_number i, j;
 161   rule_number k;
 162
 163   fderives = bitsetv_create (nvars, nrules, BITSET_FIXED);
 164
 165   set_firsts ();
 166
 167   for (i = ntokens; i < nsyms; ++i)
 168     for (j = ntokens; j < nsyms; ++j)
 169       if (bitset_test (FIRSTS (i), j - ntokens))
 170         for (k = 0; derives[j - ntokens][k]; ++k)
 171           bitset_set (FDERIVES (i), derives[j - ntokens][k]->number);
 172
 173   if (trace_flag & trace_sets)
 174     print_fderives ();
 175
 176   bitsetv_free (firsts);
 177 }
 178
 179 \f
 180
 181 void
 182 new_closure (unsigned int n)
 183 {
 184   itemset = xnmalloc (n, sizeof *itemset);
 185
 186   ruleset = bitset_create (nrules, BITSET_FIXED);
 187
 188   set_fderives ();
 189 }
 190
 191
 192
 193 void
 194 closure (item_number *core, size_t n)
 195 {
 196   /* Index over CORE. */
 197   size_t c;
 198
 199   /* A bit index over RULESET. */
 200   rule_number ruleno;
 201
 202   bitset_iterator iter;
 203
 204   if (trace_flag & trace_sets)
 205     print_closure ("input", core, n);
 206
 207   bitset_zero (ruleset);
 208
 209   for (c = 0; c < n; ++c)
 210     if (ISVAR (ritem[core[c]]))
 211       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 212
 213   /* core is sorted on item index in ritem, which is sorted on rule number.
 214      Compute itemset with the same sort.  */
 215   nitemset = 0;
 216   c = 0;
 217   BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
 218     {
 219       item_number itemno = rules[ruleno].rhs - ritem;
 220       while (c < n && core[c] < itemno)
 221         {
 222           itemset[nitemset] = core[c];
 223           nitemset++;
 224           c++;
 225         }
 226       itemset[nitemset] = itemno;
 227       nitemset++;
 228     };
 229
 230   while (c < n)
 231     {
 232       itemset[nitemset] = core[c];
 233       nitemset++;
 234       c++;
 235     }
 236
 237   if (trace_flag & trace_sets)
 238     print_closure ("output", itemset, nitemset);
 239 }
 240
 241
 242 void
 243 free_closure (void)
 244 {
 245   free (itemset);
 246   bitset_free (ruleset);
 247   bitsetv_free (fderives);
 248 }