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       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  78       BITSET_EXECUTE (FIRSTS (i), 0, j,
  79       {
  80         fprintf (stderr, "\t\t%s\n",
  81                  symbols[j + ntokens]->tag);
  82       });
  83     }
  84   fprintf (stderr, "\n\n");
  85 }
  86
  87
  88 static void
  89 print_fderives (void)
  90 {
  91   int i;
  92   rule_number_t r;
  93
  94   fprintf (stderr, "FDERIVES\n");
  95   for (i = ntokens; i < nsyms; i++)
  96     {
  97       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
  98       BITSET_EXECUTE (FDERIVES (i), 0, r,
  99       {
 100         item_number_t *rhsp = NULL;
 101         fprintf (stderr, "\t\t%d:", r - 1);
 102         for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)
 103           fprintf (stderr, " %s", symbols[*rhsp]->tag);
 104         fputc ('\n', stderr);
 105       });
 106     }
 107   fprintf (stderr, "\n\n");
 108 }
 109 \f
 110 /*------------------------------------------------------------------.
 111 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 112 | items can represent the beginning of the input corresponding to   |
 113 | which other items.                                                |
 114 |                                                                   |
 115 | For example, if some rule expands symbol 5 into the sequence of   |
 116 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 117 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 118 | (5)) is set.                                                      |
 119 `------------------------------------------------------------------*/
 120
 121 static void
 122 set_firsts (void)
 123 {
 124   symbol_number_t i, j;
 125
 126   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 127
 128   for (i = ntokens; i < nsyms; i++)
 129     for (j = 0; derives[i][j] >= 0; ++j)
 130       {
 131         int symbol = rules[derives[i][j]].rhs[0];
 132         if (ISVAR (symbol))
 133           bitset_set (FIRSTS (i), symbol - ntokens);
 134       }
 135
 136   if (trace_flag)
 137     bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
 138   bitsetv_reflexive_transitive_closure (firsts);
 139   if (trace_flag)
 140     bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
 141
 142   if (trace_flag)
 143     print_firsts ();
 144 }
 145
 146 /*-------------------------------------------------------------------.
 147 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 148 | rules can help derive the beginning of the data for each           |
 149 | nonterminal.                                                       |
 150 |                                                                    |
 151 | For example, if symbol 5 can be derived as the sequence of symbols |
 152 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 153 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 154 `-------------------------------------------------------------------*/
 155
 156 static void
 157 set_fderives (void)
 158 {
 159   symbol_number_t i, j;
 160   rule_number_t k;
 161
 162   fderives = bitsetv_create (nvars, nrules + 1, BITSET_FIXED);
 163
 164   set_firsts ();
 165
 166   for (i = ntokens; i < nsyms; ++i)
 167     for (j = ntokens; j < nsyms; ++j)
 168       if (bitset_test (FIRSTS (i), j - ntokens))
 169         for (k = 0; derives[j][k] > 0; ++k)
 170           bitset_set (FDERIVES (i), derives[j][k]);
 171
 172   if (trace_flag)
 173     print_fderives ();
 174
 175   bitsetv_free (firsts);
 176 }
 177
 178 \f
 179
 180 void
 181 new_closure (int n)
 182 {
 183   itemset = XCALLOC (item_number_t, n);
 184
 185   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 186
 187   set_fderives ();
 188 }
 189
 190
 191
 192 void
 193 closure (item_number_t *core, int n)
 194 {
 195   /* Index over CORE. */
 196   int c;
 197
 198   /* A bit index over RULESET. */
 199   rule_number_t ruleno;
 200
 201   if (trace_flag)
 202     print_closure ("input", core, n);
 203
 204   bitset_zero (ruleset);
 205
 206   for (c = 0; c < n; ++c)
 207     if (ISVAR (ritem[core[c]]))
 208       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 209
 210   nritemset = 0;
 211   c = 0;
 212   BITSET_EXECUTE (ruleset, 0, ruleno,
 213   {
 214     item_number_t itemno = rules[ruleno].rhs - ritem;
 215     while (c < n && core[c] < itemno)
 216       {
 217         itemset[nritemset] = core[c];
 218         nritemset++;
 219         c++;
 220       }
 221     itemset[nritemset] = itemno;
 222     nritemset++;
 223   });
 224
 225   while (c < n)
 226     {
 227       itemset[nritemset] = core[c];
 228       nritemset++;
 229       c++;
 230     }
 231
 232   if (trace_flag)
 233     print_closure ("output", itemset, nritemset);
 234 }
 235
 236
 237 void
 238 free_closure (void)
 239 {
 240   XFREE (itemset);
 241   bitset_free (ruleset);
 242   bitsetv_free (fderives);
 243 }