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",
  63                  quotearg_style (escape_quoting_style, symbols[*rp]->tag));
  64       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  65     }
  66   fputs ("\n\n", stderr);
  67 }
  68
  69
  70 static void
  71 print_firsts (void)
  72 {
  73   int i, j;
  74
  75   fprintf (stderr, "FIRSTS\n");
  76   for (i = ntokens; i < nsyms; i++)
  77     {
  78       fprintf (stderr, "\t%s firsts\n",
  79                quotearg_style (escape_quoting_style, symbols[i]->tag));
  80       for (j = 0; j < nvars; j++)
  81         if (bitset_test (FIRSTS (i), j))
  82           fprintf (stderr, "\t\t%s\n",
  83                    quotearg_style (escape_quoting_style,
  84                                    symbols[j + ntokens]->tag));
  85     }
  86   fprintf (stderr, "\n\n");
  87 }
  88
  89
  90 static void
  91 print_fderives (void)
  92 {
  93   int i, j;
  94
  95   fprintf (stderr, "FDERIVES\n");
  96   for (i = ntokens; i < nsyms; i++)
  97     {
  98       fprintf (stderr, "\t%s derives\n",
  99                quotearg_style (escape_quoting_style, symbols[i]->tag));
 100       for (j = 0; j < nrules + 1; j++)
 101         if (bitset_test (FDERIVES (i), j))
 102           {
 103             item_number_t *rhsp;
 104             fprintf (stderr, "\t\t%d:", j - 1);
 105             for (rhsp = rules[j].rhs; *rhsp >= 0; ++rhsp)
 106               fprintf (stderr, " %s",
 107                        quotearg_style (escape_quoting_style,
 108                                        symbols[*rhsp]->tag));
 109             fputc ('\n', stderr);
 110           }
 111     }
 112   fprintf (stderr, "\n\n");
 113 }
 114 \f
 115 /*------------------------------------------------------------------.
 116 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 117 | items can represent the beginning of the input corresponding to   |
 118 | which other items.                                                |
 119 |                                                                   |
 120 | For example, if some rule expands symbol 5 into the sequence of   |
 121 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 122 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 123 | (5)) is set.                                                      |
 124 `------------------------------------------------------------------*/
 125
 126 static void
 127 set_firsts (void)
 128 {
 129   int i, j;
 130
 131   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 132
 133   for (i = ntokens; i < nsyms; i++)
 134     for (j = 0; derives[i][j] >= 0; ++j)
 135       {
 136         int symbol = rules[derives[i][j]].rhs[0];
 137         if (ISVAR (symbol))
 138           bitset_set (FIRSTS (i), symbol - ntokens);
 139       }
 140
 141   if (trace_flag)
 142     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 143   bitsetv_reflexive_transitive_closure (firsts);
 144   if (trace_flag)
 145     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 146
 147   if (trace_flag)
 148     print_firsts ();
 149 }
 150
 151 /*-------------------------------------------------------------------.
 152 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 153 | rules can help derive the beginning of the data for each           |
 154 | nonterminal.                                                       |
 155 |                                                                    |
 156 | For example, if symbol 5 can be derived as the sequence of symbols |
 157 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 158 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 159 `-------------------------------------------------------------------*/
 160
 161 static void
 162 set_fderives (void)
 163 {
 164   int i, j, k;
 165
 166   fderives = bitsetv_create (nvars, nrules + 1, 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][k] > 0; ++k)
 174           bitset_set (FDERIVES (i), derives[j][k]);
 175
 176   if (trace_flag)
 177     print_fderives ();
 178
 179   bitsetv_free (firsts);
 180 }
 181
 182 \f
 183
 184 void
 185 new_closure (int n)
 186 {
 187   itemset = XCALLOC (item_number_t, n);
 188
 189   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 190
 191   set_fderives ();
 192 }
 193
 194
 195
 196 void
 197 closure (item_number_t *core, int n)
 198 {
 199   /* Index over CORE. */
 200   int c;
 201
 202   /* A bit index over RULESET. */
 203   int ruleno;
 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   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 217     if (bitset_test (ruleset, ruleno))
 218       {
 219         item_number_t 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)
 238     print_closure ("output", itemset, nritemset);
 239 }
 240
 241
 242 void
 243 free_closure (void)
 244 {
 245   XFREE (itemset);
 246   bitset_free (ruleset);
 247   bitsetv_free (fderives);
 248 }