src/closure.c

   1 /* Subroutines for bison
   2    Copyright (C) 1984, 1989, 2000, 2001, 2002 Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19    02111-1307, USA.  */
  20
  21 #include "system.h"
  22 #include "quotearg.h"
  23 #include "bitset.h"
  24 #include "bitsetv.h"
  25 #include "bitsetv-print.h"
  26 #include "getargs.h"
  27 #include "symtab.h"
  28 #include "gram.h"
  29 #include "reader.h"
  30 #include "closure.h"
  31 #include "derives.h"
  32
  33 /* NITEMSET is the size of the array ITEMSET.  */
  34 item_number_t *itemset;
  35 int nritemset;
  36
  37 static bitset ruleset;
  38
  39 /* internal data.  See comments before set_fderives and set_firsts.  */
  40 static bitsetv fderives = NULL;
  41 static bitsetv firsts = NULL;
  42
  43 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  44 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  45 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  46 \f
  47
  48 /*-----------------.
  49 | Debugging code.  |
  50 `-----------------*/
  51
  52 static void
  53 print_closure (const char *title, item_number_t *array, size_t size)
  54 {
  55   size_t i;
  56   fprintf (stderr, "Closure: %s\n", title);
  57   for (i = 0; i < size; ++i)
  58     {
  59       item_number_t *rp;
  60       fprintf (stderr, "  %2d: .", array[i]);
  61       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  62         fprintf (stderr, " %s", symbols[*rp]->tag);
  63       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  64     }
  65   fputs ("\n\n", stderr);
  66 }
  67
  68
  69 static void
  70 print_firsts (void)
  71 {
  72   symbol_number_t i, j;
  73
  74   fprintf (stderr, "FIRSTS\n");
  75   for (i = ntokens; i < nsyms; i++)
  76     {
  77       bitset_iterator iter;
  78       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  79       BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
  80         {
  81           fprintf (stderr, "\t\t%s\n",
  82                    symbols[j + ntokens]->tag);
  83         }
  84     }
  85   fprintf (stderr, "\n\n");
  86 }
  87
  88
  89 static void
  90 print_fderives (void)
  91 {
  92   int i;
  93   rule_number_t r;
  94
  95   fprintf (stderr, "FDERIVES\n");
  96   for (i = ntokens; i < nsyms; i++)
  97     {
  98       bitset_iterator iter;
  99       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 100       BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
 101         {
 102           item_number_t *rhsp = NULL;
 103           fprintf (stderr, "\t\t%d:", r - 1);
 104           for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)
 105             fprintf (stderr, " %s", symbols[*rhsp]->tag);
 106           fputc ('\n', stderr);
 107         }
 108     }
 109   fprintf (stderr, "\n\n");
 110 }
 111 \f
 112 /*------------------------------------------------------------------.
 113 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 114 | items can represent the beginning of the input corresponding to   |
 115 | which other items.                                                |
 116 |                                                                   |
 117 | For example, if some rule expands symbol 5 into the sequence of   |
 118 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 119 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 120 | (5)) is set.                                                      |
 121 `------------------------------------------------------------------*/
 122
 123 static void
 124 set_firsts (void)
 125 {
 126   symbol_number_t i, j;
 127
 128   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 129
 130   for (i = ntokens; i < nsyms; i++)
 131     for (j = 0; derives[i][j] >= 0; ++j)
 132       {
 133         int symbol = rules[derives[i][j]].rhs[0];
 134         if (ISVAR (symbol))
 135           bitset_set (FIRSTS (i), symbol - ntokens);
 136       }
 137
 138   if (trace_flag)
 139     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 140   bitsetv_reflexive_transitive_closure (firsts);
 141   if (trace_flag)
 142     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 143
 144   if (trace_flag)
 145     print_firsts ();
 146 }
 147
 148 /*-------------------------------------------------------------------.
 149 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 150 | rules can help derive the beginning of the data for each           |
 151 | nonterminal.                                                       |
 152 |                                                                    |
 153 | For example, if symbol 5 can be derived as the sequence of symbols |
 154 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 155 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 156 `-------------------------------------------------------------------*/
 157
 158 static void
 159 set_fderives (void)
 160 {
 161   symbol_number_t i, j;
 162   rule_number_t k;
 163
 164   fderives = bitsetv_create (nvars, nrules + 1, BITSET_FIXED);
 165
 166   set_firsts ();
 167
 168   for (i = ntokens; i < nsyms; ++i)
 169     for (j = ntokens; j < nsyms; ++j)
 170       if (bitset_test (FIRSTS (i), j - ntokens))
 171         for (k = 0; derives[j][k] > 0; ++k)
 172           bitset_set (FDERIVES (i), derives[j][k]);
 173
 174   if (trace_flag)
 175     print_fderives ();
 176
 177   bitsetv_free (firsts);
 178 }
 179
 180 \f
 181
 182 void
 183 new_closure (int n)
 184 {
 185   itemset = XCALLOC (item_number_t, n);
 186
 187   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 188
 189   set_fderives ();
 190 }
 191
 192
 193
 194 void
 195 closure (item_number_t *core, int n)
 196 {
 197   /* Index over CORE. */
 198   int c;
 199
 200   /* A bit index over RULESET. */
 201   rule_number_t ruleno;
 202
 203   bitset_iterator iter;
 204
 205   if (trace_flag)
 206     print_closure ("input", core, n);
 207
 208   bitset_zero (ruleset);
 209
 210   for (c = 0; c < n; ++c)
 211     if (ISVAR (ritem[core[c]]))
 212       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 213
 214   nritemset = 0;
 215   c = 0;
 216   BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
 217     {
 218       item_number_t itemno = rules[ruleno].rhs - ritem;
 219       while (c < n && core[c] < itemno)
 220         {
 221           itemset[nritemset] = core[c];
 222           nritemset++;
 223           c++;
 224         }
 225       itemset[nritemset] = itemno;
 226       nritemset++;
 227     };
 228
 229   while (c < n)
 230     {
 231       itemset[nritemset] = core[c];
 232       nritemset++;
 233       c++;
 234     }
 235
 236   if (trace_flag)
 237     print_closure ("output", itemset, nritemset);
 238 }
 239
 240
 241 void
 242 free_closure (void)
 243 {
 244   XFREE (itemset);
 245   bitset_free (ruleset);
 246   bitsetv_free (fderives);
 247 }