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 size_t 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   unsigned *row;
 128   int symbol;
 129   short *sp;
 130   int rowsize;
 131
 132   int i;
 133
 134   varsetsize = rowsize = WORDSIZE (nvars);
 135
 136   firsts = XCALLOC (unsigned, nvars * rowsize);
 137
 138   row = firsts;
 139   for (i = ntokens; i < nsyms; i++)
 140     {
 141       sp = derives[i];
 142       while (*sp >= 0)
 143         {
 144           symbol = ritem[rule_table[*sp++].rhs];
 145           if (ISVAR (symbol))
 146             {
 147               symbol -= ntokens;
 148               SETBIT (row, symbol);
 149             }
 150         }
 151
 152       row += rowsize;
 153     }
 154
 155   RTC (firsts, nvars);
 156
 157   if (trace_flag)
 158     print_firsts ();
 159 }
 160
 161 /*-------------------------------------------------------------------.
 162 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 163 | rules can help derive the beginning of the data for each           |
 164 | nonterminal.                                                       |
 165 |                                                                    |
 166 | For example, if symbol 5 can be derived as the sequence of symbols |
 167 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 168 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 169 `-------------------------------------------------------------------*/
 170
 171 static void
 172 set_fderives (void)
 173 {
 174   unsigned *rrow;
 175   unsigned *vrow;
 176   int j;
 177   unsigned cword;
 178   short *rp;
 179   int b;
 180
 181   int ruleno;
 182   int i;
 183
 184   fderives = XCALLOC (unsigned, nvars * rulesetsize) - ntokens * rulesetsize;
 185
 186   set_firsts ();
 187
 188   rrow = FDERIVES (ntokens);
 189
 190   for (i = ntokens; i < nsyms; i++)
 191     {
 192       vrow = FIRSTS (i - ntokens);
 193       cword = *vrow++;
 194       b = 0;
 195       for (j = ntokens; j < nsyms; j++)
 196         {
 197           if (cword & (1 << b))
 198             {
 199               rp = derives[j];
 200               while ((ruleno = *rp++) > 0)
 201                 SETBIT (rrow, ruleno);
 202             }
 203
 204           b++;
 205           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 206             {
 207               cword = *vrow++;
 208               b = 0;
 209             }
 210         }
 211
 212       rrow += rulesetsize;
 213     }
 214
 215   if (trace_flag)
 216     print_fderives ();
 217
 218   XFREE (firsts);
 219 }
 220 \f
 221
 222 void
 223 new_closure (int n)
 224 {
 225   itemset = XCALLOC (short, n);
 226
 227   rulesetsize = WORDSIZE (nrules + 1);
 228   ruleset = XCALLOC (unsigned, rulesetsize);
 229
 230   set_fderives ();
 231 }
 232
 233
 234
 235 void
 236 closure (short *core, int n)
 237 {
 238   int ruleno;
 239   short *csp;
 240
 241   int itemno;
 242   int i;
 243
 244   if (trace_flag)
 245     {
 246       fprintf (stderr, "Entering closure (items = {");
 247       for (i = 0; i < n; ++i)
 248         fprintf (stderr, " %d ", core[i]);
 249       fprintf (stderr, "}, nitems = %d)\n", n);
 250     }
 251
 252   if (n == 0)
 253     {
 254       for (i = 0; i < rulesetsize; ++i)
 255         ruleset[i] = FDERIVES (start_symbol)[i];
 256     }
 257   else
 258     {
 259       for (i = 0; i < rulesetsize; ++i)
 260         ruleset[i] = 0;
 261
 262       for (i = 0; i < n; ++i)
 263         {
 264           int symbol = ritem[core[i]];
 265           if (ISVAR (symbol))
 266             {
 267               int j;
 268               for (j = 0; j < rulesetsize; ++j)
 269                 ruleset[j] |= FDERIVES (symbol)[j];
 270             }
 271         }
 272     }
 273
 274   ruleno = 0;
 275   itemsetsize = 0;
 276   csp = core;
 277   for (i = 0; i < rulesetsize; ++i)
 278     {
 279       int word = ruleset[i];
 280       if (word == 0)
 281         {
 282           ruleno += BITS_PER_WORD;
 283         }
 284       else
 285         {
 286           int b;
 287
 288           for (b = 0; b < BITS_PER_WORD; b++)
 289             {
 290               if (word & (1 << b))
 291                 {
 292                   itemno = rule_table[ruleno].rhs;
 293                   while (csp < (core + n) && *csp < itemno)
 294                     itemset[itemsetsize++] = *csp++;
 295                   itemset[itemsetsize++] = itemno;
 296                 }
 297
 298               ruleno++;
 299             }
 300         }
 301     }
 302
 303   while (csp < (core + n))
 304     itemset[itemsetsize++] = *csp++;
 305
 306   if (trace_flag)
 307     print_closure (n);
 308 }
 309
 310
 311 void
 312 free_closure (void)
 313 {
 314   XFREE (itemset);
 315   XFREE (ruleset);
 316   XFREE (fderives + ntokens * rulesetsize);
 317 }