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 #include "system.h"
  22 #include "alloc.h"
  23 #include "gram.h"
  24 #include "closure.h"
  25 #include "derives.h"
  26
  27 short *itemset;
  28 short *itemsetend;
  29 static unsigned *ruleset;
  30
  31 /* internal data.  See comments before set_fderives and set_firsts.  */
  32 static unsigned *fderives;
  33 static unsigned *firsts;
  34
  35 /* number of words required to hold a bit for each rule */
  36 static int rulesetsize;
  37
  38 /* number of words required to hold a bit for each variable */
  39 static int varsetsize;
  40 \f
  41 #if DEBUG
  42
  43 /*-----------------.
  44 | Debugging code.  |
  45 `-----------------*/
  46
  47 static void
  48 print_closure (int n)
  49 {
  50   short *isp;
  51
  52   printf ("\n\nn = %d\n\n", n);
  53   for (isp = itemset; isp < itemsetend; isp++)
  54     printf ("   %d\n", *isp);
  55 }
  56
  57
  58 static void
  59 print_firsts (void)
  60 {
  61   int i;
  62   int j;
  63   unsigned *rowp;
  64
  65   printf ("\n\n\nFIRSTS\n\n");
  66
  67   for (i = ntokens; i < nsyms; i++)
  68     {
  69       printf ("\n\n%s firsts\n\n", tags[i]);
  70
  71       rowp = firsts + ((i - ntokens) * varsetsize);
  72
  73       for (j = 0; j < nvars; j++)
  74         if (BITISSET (rowp, j))
  75           printf ("   %s\n", tags[j + ntokens]);
  76     }
  77 }
  78
  79
  80 static void
  81 print_fderives (void)
  82 {
  83   int i;
  84   int j;
  85   unsigned *rp;
  86
  87   printf ("\n\n\nFDERIVES\n");
  88
  89   for (i = ntokens; i < nsyms; i++)
  90     {
  91       printf ("\n\n%s derives\n\n", tags[i]);
  92       rp = fderives + i * rulesetsize;
  93
  94       for (j = 0; j <= nrules; j++)
  95         if (BITISSET (rp, j))
  96           printf ("   %d\n", j);
  97     }
  98
  99   fflush (stdout);
 100 }
 101 #endif
 102 \f
 103 /*-------------------------------------------------------------------.
 104 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 105 | items can represent the beginning of the input corresponding to    |
 106 | which other items.                                                 |
 107 |                                                                    |
 108 | For example, if some rule expands symbol 5 into the sequence of    |
 109 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 110 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 111 `-------------------------------------------------------------------*/
 112
 113 static void
 114 set_firsts (void)
 115 {
 116   unsigned *row;
 117   int symbol;
 118   short *sp;
 119   int rowsize;
 120
 121   int i;
 122
 123   varsetsize = rowsize = WORDSIZE (nvars);
 124
 125   firsts = NEW2 (nvars * rowsize, unsigned);
 126
 127   row = firsts;
 128   for (i = ntokens; i < nsyms; i++)
 129     {
 130       sp = derives[i];
 131       while (*sp >= 0)
 132         {
 133           symbol = ritem[rrhs[*sp++]];
 134           if (ISVAR (symbol))
 135             {
 136               symbol -= ntokens;
 137               SETBIT (row, symbol);
 138             }
 139         }
 140
 141       row += rowsize;
 142     }
 143
 144   RTC (firsts, nvars);
 145
 146 #ifdef  DEBUG
 147   print_firsts ();
 148 #endif
 149 }
 150
 151 /*-------------------------------------------------------------------.
 152 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 153 | rules can help derive the beginning of the data for each           |
 154 | nonterminal.                                                       |
 155 |                                                                    |
 156 | For example, if symbol 5 can be derived as the sequence of symbols |
 157 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 158 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 159 `-------------------------------------------------------------------*/
 160
 161 static void
 162 set_fderives (void)
 163 {
 164   unsigned *rrow;
 165   unsigned *vrow;
 166   int j;
 167   unsigned cword;
 168   short *rp;
 169   int b;
 170
 171   int ruleno;
 172   int i;
 173
 174   fderives = NEW2 (nvars * rulesetsize, unsigned) - ntokens * rulesetsize;
 175
 176   set_firsts ();
 177
 178   rrow = fderives + ntokens * rulesetsize;
 179
 180   for (i = ntokens; i < nsyms; i++)
 181     {
 182       vrow = firsts + ((i - ntokens) * varsetsize);
 183       cword = *vrow++;
 184       b = 0;
 185       for (j = ntokens; j < nsyms; j++)
 186         {
 187           if (cword & (1 << b))
 188             {
 189               rp = derives[j];
 190               while ((ruleno = *rp++) > 0)
 191                 {
 192                   SETBIT (rrow, ruleno);
 193                 }
 194             }
 195
 196           b++;
 197           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 198             {
 199               cword = *vrow++;
 200               b = 0;
 201             }
 202         }
 203
 204       rrow += rulesetsize;
 205     }
 206
 207 #ifdef  DEBUG
 208   print_fderives ();
 209 #endif
 210
 211   FREE (firsts);
 212 }
 213 \f
 214
 215 void
 216 new_closure (int n)
 217 {
 218   itemset = NEW2 (n, short);
 219
 220   rulesetsize = WORDSIZE (nrules + 1);
 221   ruleset = NEW2 (rulesetsize, unsigned);
 222
 223   set_fderives ();
 224 }
 225
 226
 227
 228 void
 229 closure (short *core, int n)
 230 {
 231   int ruleno;
 232   unsigned word;
 233   short *csp;
 234   unsigned *dsp;
 235   unsigned *rsp;
 236
 237   short *csend;
 238   unsigned *rsend;
 239   int symbol;
 240   int itemno;
 241
 242   rsp = ruleset;
 243   rsend = ruleset + rulesetsize;
 244   csend = core + n;
 245
 246   if (n == 0)
 247     {
 248       dsp = fderives + start_symbol * rulesetsize;
 249       while (rsp < rsend)
 250         *rsp++ = *dsp++;
 251     }
 252   else
 253     {
 254       while (rsp < rsend)
 255         *rsp++ = 0;
 256
 257       csp = core;
 258       while (csp < csend)
 259         {
 260           symbol = ritem[*csp++];
 261           if (ISVAR (symbol))
 262             {
 263               dsp = fderives + symbol * rulesetsize;
 264               rsp = ruleset;
 265               while (rsp < rsend)
 266                 *rsp++ |= *dsp++;
 267             }
 268         }
 269     }
 270
 271   ruleno = 0;
 272   itemsetend = itemset;
 273   csp = core;
 274   rsp = ruleset;
 275   while (rsp < rsend)
 276     {
 277       word = *rsp++;
 278       if (word == 0)
 279         {
 280           ruleno += BITS_PER_WORD;
 281         }
 282       else
 283         {
 284           int b;
 285
 286           for (b = 0; b < BITS_PER_WORD; b++)
 287             {
 288               if (word & (1 << b))
 289                 {
 290                   itemno = rrhs[ruleno];
 291                   while (csp < csend && *csp < itemno)
 292                     *itemsetend++ = *csp++;
 293                   *itemsetend++ = itemno;
 294                 }
 295
 296               ruleno++;
 297             }
 298         }
 299     }
 300
 301   while (csp < csend)
 302     *itemsetend++ = *csp++;
 303
 304 #if DEBUG
 305   print_closure (n);
 306 #endif
 307 }
 308
 309
 310 void
 311 free_closure (void)
 312 {
 313   FREE (itemset);
 314   FREE (ruleset);
 315   FREE (fderives + ntokens * rulesetsize);
 316 }