src/closure.c

   1 /* Closures for Bison
   2
   3    Copyright (C) 1984, 1989, 2000-2002, 2004-2005, 2007, 2009-2012 Free
   4    Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include <bitset.h>
  25 #include <bitsetv-print.h>
  26 #include <bitsetv.h>
  27
  28 #include "closure.h"
  29 #include "derives.h"
  30 #include "getargs.h"
  31 #include "gram.h"
  32 #include "reader.h"
  33 #include "symtab.h"
  34
  35 /* NITEMSET is the size of the array ITEMSET.  */
  36 item_number *itemset;
  37 size_t nitemset;
  38
  39 static bitset ruleset;
  40
  41 /* internal data.  See comments before set_fderives and set_firsts.  */
  42 static bitsetv fderives = NULL;
  43 static bitsetv firsts = NULL;
  44
  45 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  46 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  47 #define FIRSTS(Var)   firsts[(Var) - ntokens]
  48 \f
  49
  50 /*-----------------.
  51 | Debugging code.  |
  52 `-----------------*/
  53
  54 static void
  55 print_closure (char const *title, item_number *array, size_t size)
  56 {
  57   size_t i;
  58   fprintf (stderr, "Closure: %s\n", title);
  59   for (i = 0; i < size; ++i)
  60     {
  61       item_number *rp;
  62       fprintf (stderr, "  %2d: .", array[i]);
  63       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  64         fprintf (stderr, " %s", symbols[*rp]->tag);
  65       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  66     }
  67   fputs ("\n\n", stderr);
  68 }
  69
  70
  71 static void
  72 print_firsts (void)
  73 {
  74   symbol_number i, j;
  75
  76   fprintf (stderr, "FIRSTS\n");
  77   for (i = ntokens; i < nsyms; i++)
  78     {
  79       bitset_iterator iter;
  80       fprintf (stderr, "  %s firsts\n", symbols[i]->tag);
  81       BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
  82         fprintf (stderr, "    %s\n", symbols[j + ntokens]->tag);
  83     }
  84   fprintf (stderr, "\n\n");
  85 }
  86
  87
  88 static void
  89 print_fderives (void)
  90 {
  91   int i;
  92   rule_number r;
  93
  94   fprintf (stderr, "FDERIVES\n");
  95   for (i = ntokens; i < nsyms; i++)
  96     {
  97       bitset_iterator iter;
  98       fprintf (stderr, "  %s derives\n", symbols[i]->tag);
  99       BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
 100         {
 101           fprintf (stderr, "    %3d ", r);
 102           rule_rhs_print (&rules[r], stderr);
 103           fprintf (stderr, "\n");
 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 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 - ntokens][j]; ++j)
 129       {
 130         item_number sym = derives[i - ntokens][j]->rhs[0];
 131         if (ISVAR (sym))
 132           bitset_set (FIRSTS (i), sym - 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 i, j;
 159   rule_number 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 - ntokens][k]; ++k)
 169           bitset_set (FDERIVES (i), derives[j - ntokens][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 (unsigned int n)
 181 {
 182   itemset = xnmalloc (n, sizeof *itemset);
 183
 184   ruleset = bitset_create (nrules, BITSET_FIXED);
 185
 186   set_fderives ();
 187 }
 188
 189
 190
 191 void
 192 closure (item_number *core, size_t n)
 193 {
 194   /* Index over CORE. */
 195   size_t c;
 196
 197   /* A bit index over RULESET. */
 198   rule_number 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   /* core is sorted on item index in ritem, which is sorted on rule number.
 212      Compute itemset with the same sort.  */
 213   nitemset = 0;
 214   c = 0;
 215   BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
 216     {
 217       item_number itemno = rules[ruleno].rhs - ritem;
 218       while (c < n && core[c] < itemno)
 219         {
 220           itemset[nitemset] = core[c];
 221           nitemset++;
 222           c++;
 223         }
 224       itemset[nitemset] = itemno;
 225       nitemset++;
 226     };
 227
 228   while (c < n)
 229     {
 230       itemset[nitemset] = core[c];
 231       nitemset++;
 232       c++;
 233     }
 234
 235   if (trace_flag & trace_sets)
 236     print_closure ("output", itemset, nitemset);
 237 }
 238
 239
 240 void
 241 free_closure (void)
 242 {
 243   free (itemset);
 244   bitset_free (ruleset);
 245   bitsetv_free (fderives);
 246 }