src/closure.c

   1 /* Closures for Bison
   2
   3    Copyright (C) 1984, 1989, 2000, 2001, 2002, 2004 Free Software
   4    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 "system.h"
  24
  25 #include <bitset.h>
  26 #include <bitsetv-print.h>
  27 #include <bitsetv.h>
  28 #include <quotearg.h>
  29
  30 #include "closure.h"
  31 #include "derives.h"
  32 #include "getargs.h"
  33 #include "gram.h"
  34 #include "reader.h"
  35 #include "symtab.h"
  36
  37 /* NITEMSET is the size of the array ITEMSET.  */
  38 item_number *itemset;
  39 size_t nritemset;
  40
  41 static bitset ruleset;
  42
  43 /* internal data.  See comments before set_fderives and set_firsts.  */
  44 static bitsetv fderives = NULL;
  45 static bitsetv firsts = NULL;
  46
  47 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  48 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  49 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  50 \f
  51
  52 /*-----------------.
  53 | Debugging code.  |
  54 `-----------------*/
  55
  56 static void
  57 print_closure (char const *title, item_number *array, size_t size)
  58 {
  59   size_t i;
  60   fprintf (stderr, "Closure: %s\n", title);
  61   for (i = 0; i < size; ++i)
  62     {
  63       item_number *rp;
  64       fprintf (stderr, "  %2d: .", array[i]);
  65       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  66         fprintf (stderr, " %s", symbols[*rp]->tag);
  67       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  68     }
  69   fputs ("\n\n", stderr);
  70 }
  71
  72
  73 static void
  74 print_firsts (void)
  75 {
  76   symbol_number i, j;
  77
  78   fprintf (stderr, "FIRSTS\n");
  79   for (i = ntokens; i < nsyms; i++)
  80     {
  81       bitset_iterator iter;
  82       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  83       BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
  84         {
  85           fprintf (stderr, "\t\t%s\n",
  86                    symbols[j + ntokens]->tag);
  87         }
  88     }
  89   fprintf (stderr, "\n\n");
  90 }
  91
  92
  93 static void
  94 print_fderives (void)
  95 {
  96   int i;
  97   rule_number r;
  98
  99   fprintf (stderr, "FDERIVES\n");
 100   for (i = ntokens; i < nsyms; i++)
 101     {
 102       bitset_iterator iter;
 103       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 104       BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
 105         {
 106           fprintf (stderr, "\t\t%3d ", r);
 107           rule_rhs_print (&rules[r], stderr);
 108         }
 109     }
 110   fprintf (stderr, "\n\n");
 111 }
 112 \f
 113 /*------------------------------------------------------------------.
 114 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 115 | items can represent the beginning of the input corresponding to   |
 116 | which other items.                                                |
 117 |                                                                   |
 118 | For example, if some rule expands symbol 5 into the sequence of   |
 119 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 120 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 121 | (5)) is set.                                                      |
 122 `------------------------------------------------------------------*/
 123
 124 static void
 125 set_firsts (void)
 126 {
 127   symbol_number i, j;
 128
 129   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 130
 131   for (i = ntokens; i < nsyms; i++)
 132     for (j = 0; derives[i - ntokens][j]; ++j)
 133       {
 134         item_number sym = derives[i - ntokens][j]->rhs[0];
 135         if (ISVAR (sym))
 136           bitset_set (FIRSTS (i), sym - ntokens);
 137       }
 138
 139   if (trace_flag & trace_sets)
 140     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 141   bitsetv_reflexive_transitive_closure (firsts);
 142   if (trace_flag & trace_sets)
 143     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 144
 145   if (trace_flag & trace_sets)
 146     print_firsts ();
 147 }
 148
 149 /*-------------------------------------------------------------------.
 150 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 151 | rules can help derive the beginning of the data for each           |
 152 | nonterminal.                                                       |
 153 |                                                                    |
 154 | For example, if symbol 5 can be derived as the sequence of symbols |
 155 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 156 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 157 `-------------------------------------------------------------------*/
 158
 159 static void
 160 set_fderives (void)
 161 {
 162   symbol_number i, j;
 163   rule_number k;
 164
 165   fderives = bitsetv_create (nvars, nrules, BITSET_FIXED);
 166
 167   set_firsts ();
 168
 169   for (i = ntokens; i < nsyms; ++i)
 170     for (j = ntokens; j < nsyms; ++j)
 171       if (bitset_test (FIRSTS (i), j - ntokens))
 172         for (k = 0; derives[j - ntokens][k]; ++k)
 173           bitset_set (FDERIVES (i), derives[j - ntokens][k]->number);
 174
 175   if (trace_flag & trace_sets)
 176     print_fderives ();
 177
 178   bitsetv_free (firsts);
 179 }
 180
 181 \f
 182
 183 void
 184 new_closure (unsigned int n)
 185 {
 186   itemset = xnmalloc (n, sizeof *itemset);
 187
 188   ruleset = bitset_create (nrules, BITSET_FIXED);
 189
 190   set_fderives ();
 191 }
 192
 193
 194
 195 void
 196 closure (item_number *core, size_t n)
 197 {
 198   /* Index over CORE. */
 199   size_t c;
 200
 201   /* A bit index over RULESET. */
 202   rule_number ruleno;
 203
 204   bitset_iterator iter;
 205
 206   if (trace_flag & trace_sets)
 207     print_closure ("input", core, n);
 208
 209   bitset_zero (ruleset);
 210
 211   for (c = 0; c < n; ++c)
 212     if (ISVAR (ritem[core[c]]))
 213       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 214
 215   nritemset = 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[nritemset] = core[c];
 223           nritemset++;
 224           c++;
 225         }
 226       itemset[nritemset] = itemno;
 227       nritemset++;
 228     };
 229
 230   while (c < n)
 231     {
 232       itemset[nritemset] = core[c];
 233       nritemset++;
 234       c++;
 235     }
 236
 237   if (trace_flag & trace_sets)
 238     print_closure ("output", itemset, nritemset);
 239 }
 240
 241
 242 void
 243 free_closure (void)
 244 {
 245   free (itemset);
 246   bitset_free (ruleset);
 247   bitsetv_free (fderives);
 248 }