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 /* NITEMSET is the size of the array ITEMSET.  */
  30 short *itemset;
  31 int nitemset;
  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 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  40 #define FDERIVES(Var)   (fderives + ((Var) - ntokens) * rulesetsize)
  41 #define   FIRSTS(Var)   (firsts   + ((Var) - ntokens) * varsetsize)
  42
  43 /* number of words required to hold a bit for each rule */
  44 static int rulesetsize;
  45
  46 /* number of words required to hold a bit for each variable */
  47 static int varsetsize;
  48 \f
  49
  50 /*-----------------.
  51 | Debugging code.  |
  52 `-----------------*/
  53
  54 static void
  55 print_closure (const char *title, short *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       short *rp;
  62       fprintf (stderr, "  %2d: .", array[i]);
  63       for (rp = &ritem[array[i]]; *rp > 0; ++rp)
  64         fprintf (stderr, " %s", tags[*rp]);
  65       fprintf (stderr, "  (rule %d)\n", -*rp);
  66     }
  67   fputs ("\n\n", stderr);
  68 }
  69
  70
  71 static void
  72 print_firsts (void)
  73 {
  74   int i, j;
  75
  76   fprintf (stderr, "FIRSTS\n");
  77   for (i = ntokens; i < nsyms; i++)
  78     {
  79       fprintf (stderr, "\t%s firsts\n", tags[i]);
  80       for (j = 0; j < nvars; j++)
  81         if (BITISSET (FIRSTS (i), j))
  82           fprintf (stderr, "\t\t%d (%s)\n", j + ntokens, tags[j + ntokens]);
  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", tags[i]);
  99       for (j = 0; j <= nrules; j++)
 100         if (BITISSET (FDERIVES (i), j))
 101           {
 102             short *rhsp;
 103             fprintf (stderr, "\t\t%d:", j);
 104             for (rhsp = ritem + rule_table[j].rhs; *rhsp > 0; ++rhsp)
 105               fprintf (stderr, " %s", tags[*rhsp]);
 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[rule_table[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 (unsigned, nvars * rulesetsize);
 161
 162   set_firsts ();
 163
 164   for (i = ntokens; i < nsyms; ++i)
 165     for (j = ntokens; j < nsyms; ++j)
 166       if (BITISSET (FIRSTS (i), j - ntokens))
 167         for (k = 0; derives[j][k] > 0; ++k)
 168           SETBIT (FDERIVES (i), derives[j][k]);
 169
 170   if (trace_flag)
 171     print_fderives ();
 172
 173   XFREE (firsts);
 174 }
 175 \f
 176
 177 void
 178 new_closure (int n)
 179 {
 180   itemset = XCALLOC (short, n);
 181
 182   rulesetsize = WORDSIZE (nrules + 1);
 183   ruleset = XCALLOC (unsigned, rulesetsize);
 184
 185   set_fderives ();
 186 }
 187
 188
 189
 190 void
 191 closure (short *core, int n)
 192 {
 193   /* Index over CORE. */
 194   int c;
 195
 196   /* Index over RULESET. */
 197   int r;
 198
 199   /* A bit index over RULESET. */
 200   int ruleno;
 201
 202   if (trace_flag)
 203     print_closure ("input", core, n);
 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   nitemset = 0;
 222   c = 0;
 223   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 224     if (BITISSET (ruleset, ruleno))
 225       {
 226         int itemno = rule_table[ruleno].rhs;
 227         while (c < n && core[c] < itemno)
 228           {
 229             itemset[nitemset] = core[c];
 230             nitemset++;
 231             c++;
 232           }
 233         itemset[nitemset] = itemno;
 234         nitemset++;
 235       }
 236
 237   while (c < n)
 238     {
 239       itemset[nitemset] = core[c];
 240       nitemset++;
 241       c++;
 242     }
 243
 244   if (trace_flag)
 245     print_closure ("output", itemset, nitemset);
 246 }
 247
 248
 249 void
 250 free_closure (void)
 251 {
 252   XFREE (itemset);
 253   XFREE (ruleset);
 254   XFREE (fderives);
 255 }