src/closure.c

   1 /* Subroutines for bison
   2    Copyright (C) 1984, 1989, 2000 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
  22 #include "system.h"
  23 #include "alloc.h"
  24 #include "gram.h"
  25 #include "closure.h"
  26
  27 extern short **derives;
  28
  29 extern void RTC PARAMS ((unsigned *, int));
  30
  31 short *itemset;
  32 short *itemsetend;
  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 /* number of words required to hold a bit for each rule */
  40 static int rulesetsize;
  41
  42 /* number of words required to hold a bit for each variable */
  43 static int varsetsize;
  44 \f
  45 #if DEBUG
  46
  47 /*-----------------.
  48 | Debugging code.  |
  49 `-----------------*/
  50
  51 static void
  52 print_closure (int n)
  53 {
  54   short *isp;
  55
  56   printf ("\n\nn = %d\n\n", n);
  57   for (isp = itemset; isp < itemsetend; isp++)
  58     printf ("   %d\n", *isp);
  59 }
  60
  61
  62 static void
  63 print_firsts (void)
  64 {
  65   int i;
  66   int j;
  67   unsigned *rowp;
  68
  69   printf ("\n\n\nFIRSTS\n\n");
  70
  71   for (i = ntokens; i < nsyms; i++)
  72     {
  73       printf ("\n\n%s firsts\n\n", tags[i]);
  74
  75       rowp = firsts + ((i - ntokens) * varsetsize);
  76
  77       for (j = 0; j < nvars; j++)
  78         if (BITISSET (rowp, j))
  79           printf ("   %s\n", tags[j + ntokens]);
  80     }
  81 }
  82
  83
  84 static void
  85 print_fderives (void)
  86 {
  87   int i;
  88   int j;
  89   unsigned *rp;
  90
  91   printf ("\n\n\nFDERIVES\n");
  92
  93   for (i = ntokens; i < nsyms; i++)
  94     {
  95       printf ("\n\n%s derives\n\n", tags[i]);
  96       rp = fderives + i * rulesetsize;
  97
  98       for (j = 0; j <= nrules; j++)
  99         if (BITISSET (rp, j))
 100           printf ("   %d\n", j);
 101     }
 102
 103   fflush (stdout);
 104 }
 105 #endif
 106 \f
 107 /*-------------------------------------------------------------------.
 108 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 109 | items can represent the beginning of the input corresponding to    |
 110 | which other items.                                                 |
 111 |                                                                    |
 112 | For example, if some rule expands symbol 5 into the sequence of    |
 113 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 114 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 115 `-------------------------------------------------------------------*/
 116
 117 static void
 118 set_firsts (void)
 119 {
 120   unsigned *row;
 121   int symbol;
 122   short *sp;
 123   int rowsize;
 124
 125   int i;
 126
 127   varsetsize = rowsize = WORDSIZE (nvars);
 128
 129   firsts = NEW2 (nvars * rowsize, unsigned);
 130
 131   row = firsts;
 132   for (i = ntokens; i < nsyms; i++)
 133     {
 134       sp = derives[i];
 135       while (*sp >= 0)
 136         {
 137           symbol = ritem[rrhs[*sp++]];
 138           if (ISVAR (symbol))
 139             {
 140               symbol -= ntokens;
 141               SETBIT (row, symbol);
 142             }
 143         }
 144
 145       row += rowsize;
 146     }
 147
 148   RTC (firsts, nvars);
 149
 150 #ifdef  DEBUG
 151   print_firsts ();
 152 #endif
 153 }
 154
 155 /*-------------------------------------------------------------------.
 156 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 157 | rules can help derive the beginning of the data for each           |
 158 | nonterminal.                                                       |
 159 |                                                                    |
 160 | For example, if symbol 5 can be derived as the sequence of symbols |
 161 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 162 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 163 `-------------------------------------------------------------------*/
 164
 165 static void
 166 set_fderives (void)
 167 {
 168   unsigned *rrow;
 169   unsigned *vrow;
 170   int j;
 171   unsigned cword;
 172   short *rp;
 173   int b;
 174
 175   int ruleno;
 176   int i;
 177
 178   fderives = NEW2 (nvars * rulesetsize, unsigned) - ntokens * rulesetsize;
 179
 180   set_firsts ();
 181
 182   rrow = fderives + ntokens * rulesetsize;
 183
 184   for (i = ntokens; i < nsyms; i++)
 185     {
 186       vrow = firsts + ((i - ntokens) * varsetsize);
 187       cword = *vrow++;
 188       b = 0;
 189       for (j = ntokens; j < nsyms; j++)
 190         {
 191           if (cword & (1 << b))
 192             {
 193               rp = derives[j];
 194               while ((ruleno = *rp++) > 0)
 195                 {
 196                   SETBIT (rrow, ruleno);
 197                 }
 198             }
 199
 200           b++;
 201           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 202             {
 203               cword = *vrow++;
 204               b = 0;
 205             }
 206         }
 207
 208       rrow += rulesetsize;
 209     }
 210
 211 #ifdef  DEBUG
 212   print_fderives ();
 213 #endif
 214
 215   FREE (firsts);
 216 }
 217 \f
 218
 219 void
 220 new_closure (int n)
 221 {
 222   itemset = NEW2 (n, short);
 223
 224   rulesetsize = WORDSIZE (nrules + 1);
 225   ruleset = NEW2 (rulesetsize, unsigned);
 226
 227   set_fderives ();
 228 }
 229
 230
 231
 232 void
 233 closure (short *core, int n)
 234 {
 235   int ruleno;
 236   unsigned word;
 237   short *csp;
 238   unsigned *dsp;
 239   unsigned *rsp;
 240
 241   short *csend;
 242   unsigned *rsend;
 243   int symbol;
 244   int itemno;
 245
 246   rsp = ruleset;
 247   rsend = ruleset + rulesetsize;
 248   csend = core + n;
 249
 250   if (n == 0)
 251     {
 252       dsp = fderives + start_symbol * rulesetsize;
 253       while (rsp < rsend)
 254         *rsp++ = *dsp++;
 255     }
 256   else
 257     {
 258       while (rsp < rsend)
 259         *rsp++ = 0;
 260
 261       csp = core;
 262       while (csp < csend)
 263         {
 264           symbol = ritem[*csp++];
 265           if (ISVAR (symbol))
 266             {
 267               dsp = fderives + symbol * rulesetsize;
 268               rsp = ruleset;
 269               while (rsp < rsend)
 270                 *rsp++ |= *dsp++;
 271             }
 272         }
 273     }
 274
 275   ruleno = 0;
 276   itemsetend = itemset;
 277   csp = core;
 278   rsp = ruleset;
 279   while (rsp < rsend)
 280     {
 281       word = *rsp++;
 282       if (word == 0)
 283         {
 284           ruleno += BITS_PER_WORD;
 285         }
 286       else
 287         {
 288           int b;
 289
 290           for (b = 0; b < BITS_PER_WORD; b++)
 291             {
 292               if (word & (1 << b))
 293                 {
 294                   itemno = rrhs[ruleno];
 295                   while (csp < csend && *csp < itemno)
 296                     *itemsetend++ = *csp++;
 297                   *itemsetend++ = itemno;
 298                 }
 299
 300               ruleno++;
 301             }
 302         }
 303     }
 304
 305   while (csp < csend)
 306     *itemsetend++ = *csp++;
 307
 308 #if DEBUG
 309   print_closure (n);
 310 #endif
 311 }
 312
 313
 314 void
 315 free_closure (void)
 316 {
 317   FREE (itemset);
 318   FREE (ruleset);
 319   FREE (fderives + ntokens * rulesetsize);
 320 }