src/closure.c

   1 /* Subroutines for bison
   2    Copyright 1984, 1989, 2000, 2001 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 "getargs.h"
  23 #include "symtab.h"
  24 #include "gram.h"
  25 #include "reader.h"
  26 #include "closure.h"
  27 #include "derives.h"
  28 #include "warshall.h"
  29 #include "bitset.h"
  30
  31 /* NITEMSET is the size of the array ITEMSET.  */
  32 short *itemset;
  33 int nitemset;
  34
  35 static unsigned *ruleset;
  36
  37 /* internal data.  See comments before set_fderives and set_firsts.  */
  38 static bitset *fderives;
  39 static unsigned int *firsts;
  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) * varsetsize)
  44
  45 /* number of words required to hold a bit for each rule */
  46 static int rulesetsize;
  47
  48 /* number of words required to hold a bit for each variable */
  49 static int varsetsize;
  50 \f
  51
  52 /*-----------------.
  53 | Debugging code.  |
  54 `-----------------*/
  55
  56 static void
  57 print_closure (const char *title, short *array, size_t size)
  58 {
  59   size_t i;
  60   fprintf (stderr, "Closure: %s\n", title);
  61   for (i = 0; i < size; ++i)
  62     {
  63       short *rp;
  64       fprintf (stderr, "  %2d: .", array[i]);
  65       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  66         fprintf (stderr, " %s", symbols[*rp]->tag);
  67       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  68     }
  69   fputs ("\n\n", stderr);
  70 }
  71
  72
  73 static void
  74 print_firsts (void)
  75 {
  76   int i, j;
  77
  78   fprintf (stderr, "FIRSTS\n");
  79   for (i = ntokens; i < nsyms; i++)
  80     {
  81       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  82       for (j = 0; j < nvars; j++)
  83         if (BITISSET (FIRSTS (i), j))
  84           fprintf (stderr, "\t\t%d (%s)\n",
  85                    j + ntokens, symbols[j + ntokens]->tag);
  86     }
  87   fprintf (stderr, "\n\n");
  88 }
  89
  90
  91 static void
  92 print_fderives (void)
  93 {
  94   int i;
  95   int j;
  96
  97   fprintf (stderr, "FDERIVES\n");
  98
  99   for (i = ntokens; i < nsyms; i++)
 100     {
 101       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 102       for (j = 0; j <= nrules; j++)
 103         if (bitset_test (FDERIVES (i), j))
 104           {
 105             short *rhsp;
 106             fprintf (stderr, "\t\t%d:", j - 1);
 107             for (rhsp = &ritem[rules[j].rhs]; *rhsp >= 0; ++rhsp)
 108               fprintf (stderr, " %s", 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 by NVARS bit matrix 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, 5 - ntokens] in firsts is set.  |
 123 `-------------------------------------------------------------------*/
 124
 125 static void
 126 set_firsts (void)
 127 {
 128   int i, j;
 129
 130   varsetsize = WORDSIZE (nvars);
 131
 132   firsts = XCALLOC (unsigned, nvars * varsetsize);
 133
 134   for (i = ntokens; i < nsyms; i++)
 135     for (j = 0; derives[i][j] >= 0; ++j)
 136       {
 137         int symbol = ritem[rules[derives[i][j]].rhs];
 138         if (ISVAR (symbol))
 139           SETBIT (FIRSTS (i), symbol - ntokens);
 140       }
 141
 142   RTC (firsts, nvars);
 143
 144   if (trace_flag)
 145     print_firsts ();
 146 }
 147
 148 /*-------------------------------------------------------------------.
 149 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 150 | rules can help derive the beginning of the data for each           |
 151 | nonterminal.                                                       |
 152 |                                                                    |
 153 | For example, if symbol 5 can be derived as the sequence of symbols |
 154 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 155 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 156 `-------------------------------------------------------------------*/
 157
 158 static void
 159 set_fderives (void)
 160 {
 161   int i, j, k;
 162
 163   fderives = XCALLOC (bitset, nvars);
 164   bitset_stats_init ();
 165   for (i = 0 ; i < nvars; ++i)
 166     {
 167       fderives[i] = bitset_create (nrules + 1, BITSET_FIXED);
 168       bitset_zero (fderives[i]);
 169     }
 170
 171   set_firsts ();
 172
 173   for (i = ntokens; i < nsyms; ++i)
 174     for (j = ntokens; j < nsyms; ++j)
 175       if (BITISSET (FIRSTS (i), j - ntokens))
 176         for (k = 0; derives[j][k] > 0; ++k)
 177           bitset_set (FDERIVES (i), derives[j][k]);
 178
 179   if (trace_flag)
 180     print_fderives ();
 181
 182   XFREE (firsts);
 183 }
 184 \f
 185
 186 void
 187 new_closure (int n)
 188 {
 189   itemset = XCALLOC (short, n);
 190
 191   rulesetsize = WORDSIZE (nrules + 1);
 192   ruleset = XCALLOC (unsigned, rulesetsize);
 193
 194   set_fderives ();
 195 }
 196
 197
 198
 199 void
 200 closure (short *core, int n)
 201 {
 202   /* Index over CORE. */
 203   int c;
 204
 205   /* An index over RULESET. */
 206   int r;
 207
 208   /* A bit index over RULESET. */
 209   int ruleno;
 210
 211   if (trace_flag)
 212     print_closure ("input", core, n);
 213
 214   if (n == 0)
 215     {
 216       for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 217         if (bitset_test (FDERIVES (start_symbol), ruleno))
 218           SETBIT (ruleset, ruleno);
 219         else
 220           RESETBIT (ruleset, ruleno);
 221     }
 222   else
 223     {
 224       for (r = 0; r < rulesetsize; ++r)
 225         ruleset[r] = 0;
 226
 227       for (c = 0; c < n; ++c)
 228         if (ISVAR (ritem[core[c]]))
 229           for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 230             if (bitset_test (FDERIVES (ritem[core[c]]), ruleno))
 231               SETBIT (ruleset, ruleno);
 232     }
 233
 234   nitemset = 0;
 235   c = 0;
 236   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 237     if (BITISSET (ruleset, ruleno))
 238       {
 239         int itemno = rules[ruleno].rhs;
 240         while (c < n && core[c] < itemno)
 241           {
 242             itemset[nitemset] = core[c];
 243             nitemset++;
 244             c++;
 245           }
 246         itemset[nitemset] = itemno;
 247         nitemset++;
 248       }
 249
 250   while (c < n)
 251     {
 252       itemset[nitemset] = core[c];
 253       nitemset++;
 254       c++;
 255     }
 256
 257   if (trace_flag)
 258     print_closure ("output", itemset, nitemset);
 259 }
 260
 261
 262 void
 263 free_closure (void)
 264 {
 265   int i;
 266   XFREE (itemset);
 267   XFREE (ruleset);
 268
 269   for (i = 0 ; i < nvars; ++i)
 270     bitset_free (fderives[i]);
 271   free (fderives);
 272 }