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 "bitset.h"
  23 #include "bitsetv.h"
  24 #include "getargs.h"
  25 #include "symtab.h"
  26 #include "gram.h"
  27 #include "reader.h"
  28 #include "closure.h"
  29 #include "derives.h"
  30
  31 /* NITEMSET is the size of the array ITEMSET.  */
  32 short *itemset;
  33 int nitemset;
  34
  35 static bitset ruleset;
  36
  37 /* internal data.  See comments before set_fderives and set_firsts.  */
  38 static bitsetv fderives = NULL;
  39 static bitsetv firsts = NULL;
  40
  41 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  42 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  43 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  44 \f
  45
  46 /*-----------------.
  47 | Debugging code.  |
  48 `-----------------*/
  49
  50 static void
  51 print_closure (const char *title, short *array, size_t size)
  52 {
  53   size_t i;
  54   fprintf (stderr, "Closure: %s\n", title);
  55   for (i = 0; i < size; ++i)
  56     {
  57       short *rp;
  58       fprintf (stderr, "  %2d: .", array[i]);
  59       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  60         fprintf (stderr, " %s", symbols[*rp]->tag);
  61       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  62     }
  63   fputs ("\n\n", stderr);
  64 }
  65
  66
  67 static void
  68 print_firsts (void)
  69 {
  70   int i, j;
  71
  72   fprintf (stderr, "FIRSTS\n");
  73   for (i = ntokens; i < nsyms; i++)
  74     {
  75       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  76       for (j = 0; j < nvars; j++)
  77         if (bitset_test (FIRSTS (i), j))
  78           fprintf (stderr, "\t\t%d (%s)\n",
  79                    j + ntokens, symbols[j + ntokens]->tag);
  80     }
  81   fprintf (stderr, "\n\n");
  82 }
  83
  84
  85 static void
  86 print_fderives (void)
  87 {
  88   int i, j;
  89
  90   fprintf (stderr, "FDERIVES\n");
  91   for (i = ntokens; i < nsyms; i++)
  92     {
  93       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
  94       for (j = 0; j < nrules + 1; j++)
  95         if (bitset_test (FDERIVES (i), j))
  96           {
  97             short *rhsp;
  98             fprintf (stderr, "\t\t%d:", j - 1);
  99             for (rhsp = rules[j].rhs; *rhsp >= 0; ++rhsp)
 100               fprintf (stderr, " %s", symbols[*rhsp]->tag);
 101             fputc ('\n', stderr);
 102           }
 103     }
 104   fprintf (stderr, "\n\n");
 105 }
 106
 107 /*--------------------------------------------------------.
 108 | Display the MATRIX array of SIZE bitsets of size SIZE.  |
 109 `--------------------------------------------------------*/
 110
 111 static void
 112 bitmatrix_print (const char *title, bitsetv matrix)
 113 {
 114   size_t i, j;
 115   size_t size = bitset_size (matrix[0]);
 116
 117   /* Title. */
 118   fprintf (stderr, "%s BEGIN\n", title);
 119
 120   /* Column numbers. */
 121   fputs ("   ", stderr);
 122   for (i = 0; i < size; ++i)
 123     putc (i / 10 ? '0' + i / 10 : ' ', stderr);
 124   putc ('\n', stderr);
 125   fputs ("   ", stderr);
 126   for (i = 0; i < size; ++i)
 127     fprintf (stderr, "%d", i % 10);
 128   putc ('\n', stderr);
 129
 130   /* Bar. */
 131   fputs ("  .", stderr);
 132   for (i = 0; i < size; ++i)
 133     putc ('-', stderr);
 134   fputs (".\n", stderr);
 135
 136   /* Contents. */
 137   for (i = 0; i < size; ++i)
 138     {
 139       fprintf (stderr, "%2d|", i);
 140       for (j = 0; j < size; ++j)
 141         fputs (bitset_test (matrix[i], j) ? "1" : " ", stderr);
 142       fputs ("|\n", stderr);
 143     }
 144
 145   /* Bar. */
 146   fputs ("  `", stderr);
 147   for (i = 0; i < size; ++i)
 148     putc ('-', stderr);
 149   fputs ("'\n", stderr);
 150
 151   /* End title. */
 152   fprintf (stderr, "%s END\n\n", title);
 153 }
 154 \f
 155 /*------------------------------------------------------------------.
 156 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 157 | items can represent the beginning of the input corresponding to   |
 158 | which other items.                                                |
 159 |                                                                   |
 160 | For example, if some rule expands symbol 5 into the sequence of   |
 161 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 162 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 163 | (5)) is set.                                                      |
 164 `------------------------------------------------------------------*/
 165
 166 static void
 167 set_firsts (void)
 168 {
 169   int i, j;
 170
 171   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 172
 173   for (i = ntokens; i < nsyms; i++)
 174     for (j = 0; derives[i][j] >= 0; ++j)
 175       {
 176         int symbol = rules[derives[i][j]].rhs[0];
 177         if (ISVAR (symbol))
 178           bitset_set (FIRSTS (i), symbol - ntokens);
 179       }
 180
 181   if (trace_flag)
 182     bitmatrix_print ("RTC: Input", firsts);
 183   bitsetv_reflexive_transitive_closure (firsts);
 184   if (trace_flag)
 185     bitmatrix_print ("RTC: Output", firsts);
 186
 187   if (trace_flag)
 188     print_firsts ();
 189 }
 190
 191 /*-------------------------------------------------------------------.
 192 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 193 | rules can help derive the beginning of the data for each           |
 194 | nonterminal.                                                       |
 195 |                                                                    |
 196 | For example, if symbol 5 can be derived as the sequence of symbols |
 197 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 198 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 199 `-------------------------------------------------------------------*/
 200
 201 static void
 202 set_fderives (void)
 203 {
 204   int i, j, k;
 205
 206   fderives = bitsetv_create (nvars, nrules + 1, BITSET_FIXED);
 207
 208   set_firsts ();
 209
 210   for (i = ntokens; i < nsyms; ++i)
 211     for (j = ntokens; j < nsyms; ++j)
 212       if (bitset_test (FIRSTS (i), j - ntokens))
 213         for (k = 0; derives[j][k] > 0; ++k)
 214           bitset_set (FDERIVES (i), derives[j][k]);
 215
 216   if (trace_flag)
 217     print_fderives ();
 218
 219   bitsetv_free (firsts);
 220 }
 221 \f
 222
 223 void
 224 new_closure (int n)
 225 {
 226   itemset = XCALLOC (short, n);
 227
 228   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 229
 230   set_fderives ();
 231 }
 232
 233
 234
 235 void
 236 closure (short *core, int n)
 237 {
 238   /* Index over CORE. */
 239   int c;
 240
 241   /* A bit index over RULESET. */
 242   int ruleno;
 243
 244   if (trace_flag)
 245     print_closure ("input", core, n);
 246
 247   if (n == 0)
 248     {
 249       bitset_copy (ruleset, FDERIVES (start_symbol));
 250     }
 251   else
 252     {
 253       bitset_zero (ruleset);
 254
 255       for (c = 0; c < n; ++c)
 256         if (ISVAR (ritem[core[c]]))
 257           bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 258     }
 259
 260   nitemset = 0;
 261   c = 0;
 262   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 263     if (bitset_test (ruleset, ruleno))
 264       {
 265         int itemno = rules[ruleno].rhs - ritem;
 266         while (c < n && core[c] < itemno)
 267           {
 268             itemset[nitemset] = core[c];
 269             nitemset++;
 270             c++;
 271           }
 272         itemset[nitemset] = itemno;
 273         nitemset++;
 274       }
 275
 276   while (c < n)
 277     {
 278       itemset[nitemset] = core[c];
 279       nitemset++;
 280       c++;
 281     }
 282
 283   if (trace_flag)
 284     print_closure ("output", itemset, nitemset);
 285 }
 286
 287
 288 void
 289 free_closure (void)
 290 {
 291   XFREE (itemset);
 292   bitset_free (ruleset);
 293   bitsetv_free (fderives);
 294 }