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