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
  30 /* NITEMSET is the size of the array ITEMSET.  */
  31 short *itemset;
  32 int nitemset;
  33
  34 static unsigned *ruleset;
  35
  36 /* internal data.  See comments before set_fderives and set_firsts.  */
  37 static unsigned *fderives;
  38 static unsigned *firsts;
  39
  40 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  41 #define FDERIVES(Var)   (fderives + ((Var) - ntokens) * rulesetsize)
  42 #define   FIRSTS(Var)   (firsts   + ((Var) - ntokens) * varsetsize)
  43
  44 /* number of words required to hold a bit for each rule */
  45 static int rulesetsize;
  46
  47 /* number of words required to hold a bit for each variable */
  48 static int varsetsize;
  49 \f
  50
  51 /*-----------------.
  52 | Debugging code.  |
  53 `-----------------*/
  54
  55 static void
  56 print_closure (const char *title, short *array, size_t size)
  57 {
  58   size_t i;
  59   fprintf (stderr, "Closure: %s\n", title);
  60   for (i = 0; i < size; ++i)
  61     {
  62       short *rp;
  63       fprintf (stderr, "  %2d: .", array[i]);
  64       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  65         fprintf (stderr, " %s", symbols[*rp]->tag);
  66       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  67     }
  68   fputs ("\n\n", stderr);
  69 }
  70
  71
  72 static void
  73 print_firsts (void)
  74 {
  75   int i, j;
  76
  77   fprintf (stderr, "FIRSTS\n");
  78   for (i = ntokens; i < nsyms; i++)
  79     {
  80       fprintf (stderr, "\t%s firsts\n", symbols[i]->tag);
  81       for (j = 0; j < nvars; j++)
  82         if (BITISSET (FIRSTS (i), j))
  83           fprintf (stderr, "\t\t%d (%s)\n",
  84                    j + ntokens, symbols[j + ntokens]->tag);
  85     }
  86   fprintf (stderr, "\n\n");
  87 }
  88
  89
  90 static void
  91 print_fderives (void)
  92 {
  93   int i;
  94   int j;
  95
  96   fprintf (stderr, "FDERIVES\n");
  97
  98   for (i = ntokens; i < nsyms; i++)
  99     {
 100       fprintf (stderr, "\t%s derives\n", symbols[i]->tag);
 101       for (j = 0; j <= nrules; j++)
 102         if (BITISSET (FDERIVES (i), j))
 103           {
 104             short *rhsp;
 105             fprintf (stderr, "\t\t%d:", j - 1);
 106             for (rhsp = &ritem[rules[j].rhs]; *rhsp >= 0; ++rhsp)
 107               fprintf (stderr, " %s", symbols[*rhsp]->tag);
 108             fputc ('\n', stderr);
 109           }
 110     }
 111   fprintf (stderr, "\n\n");
 112 }
 113 \f
 114 /*-------------------------------------------------------------------.
 115 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 116 | items can represent the beginning of the input corresponding to    |
 117 | which other items.                                                 |
 118 |                                                                    |
 119 | For example, if some rule expands symbol 5 into the sequence of    |
 120 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 121 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 122 `-------------------------------------------------------------------*/
 123
 124 static void
 125 set_firsts (void)
 126 {
 127   int i, j;
 128
 129   varsetsize = WORDSIZE (nvars);
 130
 131   firsts = XCALLOC (unsigned, nvars * varsetsize);
 132
 133   for (i = ntokens; i < nsyms; i++)
 134     for (j = 0; derives[i][j] >= 0; ++j)
 135       {
 136         int symbol = ritem[rules[derives[i][j]].rhs];
 137         if (ISVAR (symbol))
 138           SETBIT (FIRSTS (i), symbol - ntokens);
 139       }
 140
 141   RTC (firsts, nvars);
 142
 143   if (trace_flag)
 144     print_firsts ();
 145 }
 146
 147 /*-------------------------------------------------------------------.
 148 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 149 | rules can help derive the beginning of the data for each           |
 150 | nonterminal.                                                       |
 151 |                                                                    |
 152 | For example, if symbol 5 can be derived as the sequence of symbols |
 153 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 154 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 155 `-------------------------------------------------------------------*/
 156
 157 static void
 158 set_fderives (void)
 159 {
 160   int i, j, k;
 161
 162   fderives = XCALLOC (unsigned, nvars * rulesetsize);
 163
 164   set_firsts ();
 165
 166   for (i = ntokens; i < nsyms; ++i)
 167     for (j = ntokens; j < nsyms; ++j)
 168       if (BITISSET (FIRSTS (i), j - ntokens))
 169         for (k = 0; derives[j][k] > 0; ++k)
 170           SETBIT (FDERIVES (i), derives[j][k]);
 171
 172   if (trace_flag)
 173     print_fderives ();
 174
 175   XFREE (firsts);
 176 }
 177 \f
 178
 179 void
 180 new_closure (int n)
 181 {
 182   itemset = XCALLOC (short, n);
 183
 184   rulesetsize = WORDSIZE (nrules + 1);
 185   ruleset = XCALLOC (unsigned, rulesetsize);
 186
 187   set_fderives ();
 188 }
 189
 190
 191
 192 void
 193 closure (short *core, int n)
 194 {
 195   /* Index over CORE. */
 196   int c;
 197
 198   /* An index over RULESET. */
 199   int r;
 200
 201   /* A bit index over RULESET. */
 202   int ruleno;
 203
 204   if (trace_flag)
 205     print_closure ("input", core, n);
 206
 207   if (n == 0)
 208     {
 209       for (r = 0; r < rulesetsize; ++r)
 210         ruleset[r] = FDERIVES (start_symbol)[r];
 211     }
 212   else
 213     {
 214       for (r = 0; r < rulesetsize; ++r)
 215         ruleset[r] = 0;
 216
 217       for (c = 0; c < n; ++c)
 218         if (ISVAR (ritem[core[c]]))
 219           for (r = 0; r < rulesetsize; ++r)
 220             ruleset[r] |= FDERIVES (ritem[core[c]])[r];
 221     }
 222
 223   nitemset = 0;
 224   c = 0;
 225   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 226     if (BITISSET (ruleset, ruleno))
 227       {
 228         int itemno = rules[ruleno].rhs;
 229         while (c < n && core[c] < itemno)
 230           {
 231             itemset[nitemset] = core[c];
 232             nitemset++;
 233             c++;
 234           }
 235         itemset[nitemset] = itemno;
 236         nitemset++;
 237       }
 238
 239   while (c < n)
 240     {
 241       itemset[nitemset] = core[c];
 242       nitemset++;
 243       c++;
 244     }
 245
 246   if (trace_flag)
 247     print_closure ("output", itemset, nitemset);
 248 }
 249
 250
 251 void
 252 free_closure (void)
 253 {
 254   XFREE (itemset);
 255   XFREE (ruleset);
 256   XFREE (fderives);
 257 }