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