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           fprintf (stderr, "\t\t%3d ", r);
 103           rule_rhs_print (&rules[r], stderr);
 104         }
 105     }
 106   fprintf (stderr, "\n\n");
 107 }
 108 \f
 109 /*------------------------------------------------------------------.
 110 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 111 | items can represent the beginning of the input corresponding to   |
 112 | which other items.                                                |
 113 |                                                                   |
 114 | For example, if some rule expands symbol 5 into the sequence of   |
 115 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 116 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 117 | (5)) is set.                                                      |
 118 `------------------------------------------------------------------*/
 119
 120 static void
 121 set_firsts (void)
 122 {
 123   symbol_number_t i, j;
 124
 125   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 126
 127   for (i = ntokens; i < nsyms; i++)
 128     for (j = 0; derives[i][j]; ++j)
 129       {
 130         int symbol = derives[i][j]->rhs[0];
 131         if (ISVAR (symbol))
 132           bitset_set (FIRSTS (i), symbol - ntokens);
 133       }
 134
 135   if (trace_flag & trace_sets)
 136     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 137   bitsetv_reflexive_transitive_closure (firsts);
 138   if (trace_flag & trace_sets)
 139     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 140
 141   if (trace_flag & trace_sets)
 142     print_firsts ();
 143 }
 144
 145 /*-------------------------------------------------------------------.
 146 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 147 | rules can help derive the beginning of the data for each           |
 148 | nonterminal.                                                       |
 149 |                                                                    |
 150 | For example, if symbol 5 can be derived as the sequence of symbols |
 151 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 152 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 153 `-------------------------------------------------------------------*/
 154
 155 static void
 156 set_fderives (void)
 157 {
 158   symbol_number_t i, j;
 159   rule_number_t k;
 160
 161   fderives = bitsetv_create (nvars, nrules, BITSET_FIXED);
 162
 163   set_firsts ();
 164
 165   for (i = ntokens; i < nsyms; ++i)
 166     for (j = ntokens; j < nsyms; ++j)
 167       if (bitset_test (FIRSTS (i), j - ntokens))
 168         for (k = 0; derives[j][k]; ++k)
 169           bitset_set (FDERIVES (i), derives[j][k]->number);
 170
 171   if (trace_flag & trace_sets)
 172     print_fderives ();
 173
 174   bitsetv_free (firsts);
 175 }
 176
 177 \f
 178
 179 void
 180 new_closure (int n)
 181 {
 182   itemset = XCALLOC (item_number_t, n);
 183
 184   ruleset = bitset_create (nrules, BITSET_FIXED);
 185
 186   set_fderives ();
 187 }
 188
 189
 190
 191 void
 192 closure (item_number_t *core, int n)
 193 {
 194   /* Index over CORE. */
 195   int c;
 196
 197   /* A bit index over RULESET. */
 198   rule_number_t ruleno;
 199
 200   bitset_iterator iter;
 201
 202   if (trace_flag & trace_sets)
 203     print_closure ("input", core, n);
 204
 205   bitset_zero (ruleset);
 206
 207   for (c = 0; c < n; ++c)
 208     if (ISVAR (ritem[core[c]]))
 209       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 210
 211   nritemset = 0;
 212   c = 0;
 213   BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
 214     {
 215       item_number_t itemno = rules[ruleno].rhs - ritem;
 216       while (c < n && core[c] < itemno)
 217         {
 218           itemset[nritemset] = core[c];
 219           nritemset++;
 220           c++;
 221         }
 222       itemset[nritemset] = itemno;
 223       nritemset++;
 224     };
 225
 226   while (c < n)
 227     {
 228       itemset[nritemset] = core[c];
 229       nritemset++;
 230       c++;
 231     }
 232
 233   if (trace_flag & trace_sets)
 234     print_closure ("output", itemset, nritemset);
 235 }
 236
 237
 238 void
 239 free_closure (void)
 240 {
 241   XFREE (itemset);
 242   bitset_free (ruleset);
 243   bitsetv_free (fderives);
 244 }