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 "gram.h"
  24 #include "reader.h"
  25 #include "closure.h"
  26 #include "derives.h"
  27 #include "warshall.h"
  28
  29 /* ITEMSETSIZE is the size of the array ITEMSET.  */
  30 short *itemset;
  31 int itemsetsize;
  32
  33 static unsigned *ruleset;
  34
  35 /* internal data.  See comments before set_fderives and set_firsts.  */
  36 static unsigned *fderives;
  37 static unsigned *firsts;
  38
  39 #define FDERIVES(Symbol)   (fderives + (Symbol) * rulesetsize)
  40 #define   FIRSTS(Symbol)   (firsts   + (Symbol) * varsetsize)
  41
  42 /* number of words required to hold a bit for each rule */
  43 static int rulesetsize;
  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 (int n)
  55 {
  56   int i;
  57   fprintf (stderr, "n = %d\n", n);
  58   for (i = 0; i < itemsetsize; ++i)
  59     fprintf (stderr, "   %d\n", itemset[i]);
  60   fprintf (stderr, "\n\n");
  61 }
  62
  63
  64 static void
  65 print_firsts (void)
  66 {
  67   int i, j;
  68
  69   fprintf (stderr, "FIRSTS\n");
  70   for (i = ntokens; i < nsyms; i++)
  71     {
  72       fprintf (stderr, "\t%s firsts\n", tags[i]);
  73       for (j = 0; j < nvars; j++)
  74         if (BITISSET (FIRSTS (i - ntokens), j))
  75           fprintf (stderr, "\t\t%d (%s)\n", j + ntokens, tags[j + ntokens]);
  76     }
  77   fprintf (stderr, "\n\n");
  78 }
  79
  80
  81 static void
  82 print_fderives (void)
  83 {
  84   int i;
  85   int j;
  86
  87   fprintf (stderr, "FDERIVES\n");
  88
  89   for (i = ntokens; i < nsyms; i++)
  90     {
  91       fprintf (stderr, "\t%s derives\n", tags[i]);
  92       for (j = 0; j <= nrules; j++)
  93         if (BITISSET (FDERIVES (i), j))
  94           {
  95             short *rhsp;
  96             fprintf (stderr, "\t\t%d:", j);
  97             for (rhsp = ritem + rule_table[j].rhs; *rhsp > 0; ++rhsp)
  98               fprintf (stderr, " %s", tags[*rhsp]);
  99             fputc ('\n', stderr);
 100           }
 101     }
 102   fprintf (stderr, "\n\n");
 103 }
 104 \f
 105 /*-------------------------------------------------------------------.
 106 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 107 | items can represent the beginning of the input corresponding to    |
 108 | which other items.                                                 |
 109 |                                                                    |
 110 | For example, if some rule expands symbol 5 into the sequence of    |
 111 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 112 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 113 `-------------------------------------------------------------------*/
 114
 115 static void
 116 set_firsts (void)
 117 {
 118   int rowsize;
 119
 120   int i, j;
 121
 122   varsetsize = rowsize = WORDSIZE (nvars);
 123
 124   firsts = XCALLOC (unsigned, nvars * rowsize);
 125
 126   for (i = ntokens; i < nsyms; i++)
 127     for (j = 0; derives[i][j] >= 0; ++j)
 128       {
 129         int symbol = ritem[rule_table[derives[i][j]].rhs];
 130         if (ISVAR (symbol))
 131           SETBIT (FIRSTS (i - ntokens), symbol - ntokens);
 132       }
 133
 134   RTC (firsts, nvars);
 135
 136   if (trace_flag)
 137     print_firsts ();
 138 }
 139
 140 /*-------------------------------------------------------------------.
 141 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 142 | rules can help derive the beginning of the data for each           |
 143 | nonterminal.                                                       |
 144 |                                                                    |
 145 | For example, if symbol 5 can be derived as the sequence of symbols |
 146 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 147 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 148 `-------------------------------------------------------------------*/
 149
 150 static void
 151 set_fderives (void)
 152 {
 153   int i, j, k;
 154
 155   fderives = XCALLOC (unsigned, nvars * rulesetsize) - ntokens * rulesetsize;
 156
 157   set_firsts ();
 158
 159   for (i = ntokens; i < nsyms; ++i)
 160     for (j = ntokens; j < nsyms; ++j)
 161       if (BITISSET (FIRSTS (i - ntokens), j - ntokens))
 162         for (k = 0; derives[j][k] > 0; ++k)
 163           SETBIT (FDERIVES (i), derives[j][k]);
 164
 165   if (trace_flag)
 166     print_fderives ();
 167
 168   XFREE (firsts);
 169 }
 170 \f
 171
 172 void
 173 new_closure (int n)
 174 {
 175   itemset = XCALLOC (short, n);
 176
 177   rulesetsize = WORDSIZE (nrules + 1);
 178   ruleset = XCALLOC (unsigned, rulesetsize);
 179
 180   set_fderives ();
 181 }
 182
 183
 184
 185 void
 186 closure (short *core, int n)
 187 {
 188   /* Index over CORE. */
 189   int c;
 190
 191   /* Index over RULESET. */
 192   int r;
 193
 194   /* A bit index over RULESET. */
 195   int ruleno;
 196
 197   if (trace_flag)
 198     {
 199       fprintf (stderr, "Entering closure (items = {");
 200       for (c = 0; c < n; ++c)
 201         fprintf (stderr, " %d ", core[c]);
 202       fprintf (stderr, "})\n");
 203     }
 204
 205   if (n == 0)
 206     {
 207       for (r = 0; r < rulesetsize; ++r)
 208         ruleset[r] = FDERIVES (start_symbol)[r];
 209     }
 210   else
 211     {
 212       for (r = 0; r < rulesetsize; ++r)
 213         ruleset[r] = 0;
 214
 215       for (c = 0; c < n; ++c)
 216         if (ISVAR (ritem[core[c]]))
 217           for (r = 0; r < rulesetsize; ++r)
 218             ruleset[r] |= FDERIVES (ritem[core[c]])[r];
 219     }
 220
 221   itemsetsize = 0;
 222   c = 0;
 223   for (ruleno = 0; ruleno < rulesetsize * BITS_PER_WORD; ++ruleno)
 224     if (BITISSET (ruleset, ruleno))
 225       {
 226         int itemno = rule_table[ruleno].rhs;
 227         while (c < n && core[c] < itemno)
 228           {
 229             itemset[itemsetsize] = core[c];
 230             itemsetsize++;
 231             c++;
 232           }
 233         itemset[itemsetsize] = itemno;
 234         itemsetsize++;
 235       }
 236
 237   while (c < n)
 238     {
 239       itemset[itemsetsize] = core[c];
 240       itemsetsize++;
 241       c++;
 242     }
 243
 244   if (trace_flag)
 245     print_closure (n);
 246 }
 247
 248
 249 void
 250 free_closure (void)
 251 {
 252   XFREE (itemset);
 253   XFREE (ruleset);
 254   XFREE (fderives + ntokens * rulesetsize);
 255 }