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;
  68   int j;
  69   unsigned *rowp;
  70
  71   fprintf (stderr, "FIRSTS\n");
  72
  73   for (i = ntokens; i < nsyms; i++)
  74     {
  75       fprintf (stderr, "\t%s firsts\n", tags[i]);
  76
  77       rowp = FIRSTS (i - ntokens);
  78
  79       for (j = 0; j < nvars; j++)
  80         if (BITISSET (rowp, j))
  81           fprintf (stderr, "\t\t%d (%s)\n", j + ntokens, tags[j + ntokens]);
  82     }
  83   fprintf (stderr, "\n\n");
  84 }
  85
  86
  87 static void
  88 print_fderives (void)
  89 {
  90   int i;
  91   int j;
  92   unsigned *rp;
  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       rp = FDERIVES (i);
 100
 101       for (j = 0; j <= nrules; j++)
 102         if (BITISSET (rp, j))
 103           {
 104             short *rhsp;
 105             fprintf (stderr, "\t\t%d:", j);
 106             for (rhsp = ritem + rule_table[j].rhs; *rhsp > 0; ++rhsp)
 107               fprintf (stderr, " %s", tags[*rhsp]);
 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 rowsize;
 128
 129   int i, j;
 130
 131   varsetsize = rowsize = WORDSIZE (nvars);
 132
 133   firsts = XCALLOC (unsigned, nvars * rowsize);
 134
 135   for (i = ntokens; i < nsyms; i++)
 136     for (j = 0; derives[i][j] >= 0; ++j)
 137       {
 138         int symbol = ritem[rule_table[derives[i][j]].rhs];
 139         if (ISVAR (symbol))
 140           {
 141             symbol -= ntokens;
 142             SETBIT (FIRSTS (i - ntokens), symbol);
 143           }
 144       }
 145
 146   RTC (firsts, nvars);
 147
 148   if (trace_flag)
 149     print_firsts ();
 150 }
 151
 152 /*-------------------------------------------------------------------.
 153 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 154 | rules can help derive the beginning of the data for each           |
 155 | nonterminal.                                                       |
 156 |                                                                    |
 157 | For example, if symbol 5 can be derived as the sequence of symbols |
 158 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 159 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 160 `-------------------------------------------------------------------*/
 161
 162 static void
 163 set_fderives (void)
 164 {
 165   unsigned *rrow;
 166   unsigned *vrow;
 167   int j;
 168   unsigned cword;
 169   short *rp;
 170   int b;
 171
 172   int ruleno;
 173   int i;
 174
 175   fderives = XCALLOC (unsigned, nvars * rulesetsize) - ntokens * rulesetsize;
 176
 177   set_firsts ();
 178
 179   rrow = FDERIVES (ntokens);
 180
 181   for (i = ntokens; i < nsyms; i++)
 182     {
 183       vrow = FIRSTS (i - ntokens);
 184       cword = *vrow++;
 185       b = 0;
 186       for (j = ntokens; j < nsyms; j++)
 187         {
 188           if (cword & (1 << b))
 189             {
 190               rp = derives[j];
 191               while ((ruleno = *rp++) > 0)
 192                 SETBIT (rrow, ruleno);
 193             }
 194
 195           b++;
 196           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 197             {
 198               cword = *vrow++;
 199               b = 0;
 200             }
 201         }
 202
 203       rrow += rulesetsize;
 204     }
 205
 206   if (trace_flag)
 207     print_fderives ();
 208
 209   XFREE (firsts);
 210 }
 211 \f
 212
 213 void
 214 new_closure (int n)
 215 {
 216   itemset = XCALLOC (short, n);
 217
 218   rulesetsize = WORDSIZE (nrules + 1);
 219   ruleset = XCALLOC (unsigned, rulesetsize);
 220
 221   set_fderives ();
 222 }
 223
 224
 225
 226 void
 227 closure (short *core, int n)
 228 {
 229   /* Index over CORE. */
 230   int c;
 231
 232   /* Index over RULESET. */
 233   int r;
 234
 235   /* A bit index over RULESET. */
 236   int ruleno;
 237
 238   if (trace_flag)
 239     {
 240       fprintf (stderr, "Entering closure (items = {");
 241       for (c = 0; c < n; ++c)
 242         fprintf (stderr, " %d ", core[c]);
 243       fprintf (stderr, "})\n");
 244     }
 245
 246   if (n == 0)
 247     {
 248       for (r = 0; r < rulesetsize; ++r)
 249         ruleset[r] = FDERIVES (start_symbol)[r];
 250     }
 251   else
 252     {
 253       for (r = 0; r < rulesetsize; ++r)
 254         ruleset[r] = 0;
 255
 256       for (c = 0; c < n; ++c)
 257         if (ISVAR (ritem[core[c]]))
 258           for (r = 0; r < rulesetsize; ++r)
 259             ruleset[r] |= FDERIVES (ritem[core[c]])[r];
 260     }
 261
 262   itemsetsize = 0;
 263   c = 0;
 264   for (ruleno = 0; ruleno < rulesetsize * BITS_PER_WORD; ++ruleno)
 265     if (BITISSET (ruleset, ruleno))
 266       {
 267         int itemno = rule_table[ruleno].rhs;
 268         while (c < n && core[c] < itemno)
 269           {
 270             itemset[itemsetsize] = core[c];
 271             itemsetsize++;
 272             c++;
 273           }
 274         itemset[itemsetsize] = itemno;
 275         itemsetsize++;
 276       }
 277
 278   while (c < n)
 279     {
 280       itemset[itemsetsize] = core[c];
 281       itemsetsize++;
 282       c++;
 283     }
 284
 285   if (trace_flag)
 286     print_closure (n);
 287 }
 288
 289
 290 void
 291 free_closure (void)
 292 {
 293   XFREE (itemset);
 294   XFREE (ruleset);
 295   XFREE (fderives + ntokens * rulesetsize);
 296 }