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 bitset 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 variable */
  46 static int varsetsize;
  47 \f
  48
  49 /*-----------------.
  50 | Debugging code.  |
  51 `-----------------*/
  52
  53 static void
  54 print_closure (const char *title, short *array, size_t size)
  55 {
  56   size_t i;
  57   fprintf (stderr, "Closure: %s\n", title);
  58   for (i = 0; i < size; ++i)
  59     {
  60       short *rp;
  61       fprintf (stderr, "  %2d: .", array[i]);
  62       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  63         fprintf (stderr, " %s", symbols[*rp]->tag);
  64       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  65     }
  66   fputs ("\n\n", stderr);
  67 }
  68
  69
  70 static void
  71 print_firsts (void)
  72 {
  73   int i, j;
  74
  75   fprintf (stderr, "FIRSTS\n");
  76   for (i = ntokens; i < nsyms; i++)
  77     {
  78       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  79       for (j = 0; j < nvars; j++)
  80         if (BITISSET (FIRSTS (i), j))
  81           fprintf (stderr, "\t\t%d (%s)\n",
  82                    j + ntokens, 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   int j;
  93
  94   fprintf (stderr, "FDERIVES\n");
  95
  96   for (i = ntokens; i < nsyms; i++)
  97     {
  98       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
  99       for (j = 0; j <= nrules; j++)
 100         if (bitset_test (FDERIVES (i), j))
 101           {
 102             short *rhsp;
 103             fprintf (stderr, "\t\t%d:", j - 1);
 104             for (rhsp = &ritem[rules[j].rhs]; *rhsp >= 0; ++rhsp)
 105               fprintf (stderr, " %s", symbols[*rhsp]->tag);
 106             fputc ('\n', stderr);
 107           }
 108     }
 109   fprintf (stderr, "\n\n");
 110 }
 111 \f
 112 /*-------------------------------------------------------------------.
 113 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 114 | items can represent the beginning of the input corresponding to    |
 115 | which other items.                                                 |
 116 |                                                                    |
 117 | For example, if some rule expands symbol 5 into the sequence of    |
 118 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 119 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 120 `-------------------------------------------------------------------*/
 121
 122 static void
 123 set_firsts (void)
 124 {
 125   int i, j;
 126
 127   varsetsize = WORDSIZE (nvars);
 128
 129   firsts = XCALLOC (unsigned, nvars * varsetsize);
 130
 131   for (i = ntokens; i < nsyms; i++)
 132     for (j = 0; derives[i][j] >= 0; ++j)
 133       {
 134         int symbol = ritem[rules[derives[i][j]].rhs];
 135         if (ISVAR (symbol))
 136           SETBIT (FIRSTS (i), symbol - ntokens);
 137       }
 138
 139   RTC (firsts, nvars);
 140
 141   if (trace_flag)
 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   int i, j, k;
 159
 160   fderives = XCALLOC (bitset, nvars);
 161   bitset_stats_init ();
 162   for (i = 0 ; i < nvars; ++i)
 163     {
 164       fderives[i] = bitset_create (nrules + 1, BITSET_FIXED);
 165       bitset_zero (fderives[i]);
 166     }
 167
 168   set_firsts ();
 169
 170   for (i = ntokens; i < nsyms; ++i)
 171     for (j = ntokens; j < nsyms; ++j)
 172       if (BITISSET (FIRSTS (i), j - ntokens))
 173         for (k = 0; derives[j][k] > 0; ++k)
 174           bitset_set (FDERIVES (i), derives[j][k]);
 175
 176   if (trace_flag)
 177     print_fderives ();
 178
 179   XFREE (firsts);
 180 }
 181 \f
 182
 183 void
 184 new_closure (int n)
 185 {
 186   itemset = XCALLOC (short, n);
 187
 188   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 189   bitset_zero (ruleset);
 190
 191   set_fderives ();
 192 }
 193
 194
 195
 196 void
 197 closure (short *core, int n)
 198 {
 199   /* Index over CORE. */
 200   int c;
 201
 202   /* An index over RULESET. */
 203   int r;
 204
 205   /* A bit index over RULESET. */
 206   int ruleno;
 207
 208   if (trace_flag)
 209     print_closure ("input", core, n);
 210
 211   if (n == 0)
 212     {
 213       bitset_copy (ruleset, FDERIVES (start_symbol));
 214     }
 215   else
 216     {
 217       bitset_zero (ruleset);
 218
 219       for (c = 0; c < n; ++c)
 220         if (ISVAR (ritem[core[c]]))
 221           bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 222     }
 223
 224   nitemset = 0;
 225   c = 0;
 226   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 227     if (bitset_test (ruleset, ruleno))
 228       {
 229         int itemno = rules[ruleno].rhs;
 230         while (c < n && core[c] < itemno)
 231           {
 232             itemset[nitemset] = core[c];
 233             nitemset++;
 234             c++;
 235           }
 236         itemset[nitemset] = itemno;
 237         nitemset++;
 238       }
 239
 240   while (c < n)
 241     {
 242       itemset[nitemset] = core[c];
 243       nitemset++;
 244       c++;
 245     }
 246
 247   if (trace_flag)
 248     print_closure ("output", itemset, nitemset);
 249 }
 250
 251
 252 void
 253 free_closure (void)
 254 {
 255   int i;
 256   XFREE (itemset);
 257
 258   bitset_free (ruleset);
 259
 260   for (i = 0 ; i < nvars; ++i)
 261     bitset_free (fderives[i]);
 262   free (fderives);
 263 }