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 "gram.h"
  23 #include "reader.h"
  24 #include "closure.h"
  25 #include "derives.h"
  26 #include "warshall.h"
  27
  28 short *itemset;
  29 short *itemsetend;
  30 static unsigned *ruleset;
  31
  32 /* internal data.  See comments before set_fderives and set_firsts.  */
  33 static unsigned *fderives;
  34 static unsigned *firsts;
  35
  36 /* number of words required to hold a bit for each rule */
  37 static int rulesetsize;
  38
  39 /* number of words required to hold a bit for each variable */
  40 static int varsetsize;
  41 \f
  42 #if TRACE
  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 #endif
 101 \f
 102 /*-------------------------------------------------------------------.
 103 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 104 | items can represent the beginning of the input corresponding to    |
 105 | which other items.                                                 |
 106 |                                                                    |
 107 | For example, if some rule expands symbol 5 into the sequence of    |
 108 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 109 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 110 `-------------------------------------------------------------------*/
 111
 112 static void
 113 set_firsts (void)
 114 {
 115   unsigned *row;
 116   int symbol;
 117   short *sp;
 118   int rowsize;
 119
 120   int i;
 121
 122   varsetsize = rowsize = WORDSIZE (nvars);
 123
 124   firsts = XCALLOC (unsigned, nvars * rowsize);
 125
 126   row = firsts;
 127   for (i = ntokens; i < nsyms; i++)
 128     {
 129       sp = derives[i];
 130       while (*sp >= 0)
 131         {
 132           symbol = ritem[rule_table[*sp++].rhs];
 133           if (ISVAR (symbol))
 134             {
 135               symbol -= ntokens;
 136               SETBIT (row, symbol);
 137             }
 138         }
 139
 140       row += rowsize;
 141     }
 142
 143   RTC (firsts, nvars);
 144
 145 #ifdef TRACE
 146   print_firsts ();
 147 #endif
 148 }
 149
 150 /*-------------------------------------------------------------------.
 151 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 152 | rules can help derive the beginning of the data for each           |
 153 | nonterminal.                                                       |
 154 |                                                                    |
 155 | For example, if symbol 5 can be derived as the sequence of symbols |
 156 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 157 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 158 `-------------------------------------------------------------------*/
 159
 160 static void
 161 set_fderives (void)
 162 {
 163   unsigned *rrow;
 164   unsigned *vrow;
 165   int j;
 166   unsigned cword;
 167   short *rp;
 168   int b;
 169
 170   int ruleno;
 171   int i;
 172
 173   fderives = XCALLOC (unsigned, nvars * rulesetsize) - ntokens * rulesetsize;
 174
 175   set_firsts ();
 176
 177   rrow = fderives + ntokens * rulesetsize;
 178
 179   for (i = ntokens; i < nsyms; i++)
 180     {
 181       vrow = firsts + ((i - ntokens) * varsetsize);
 182       cword = *vrow++;
 183       b = 0;
 184       for (j = ntokens; j < nsyms; j++)
 185         {
 186           if (cword & (1 << b))
 187             {
 188               rp = derives[j];
 189               while ((ruleno = *rp++) > 0)
 190                 {
 191                   SETBIT (rrow, ruleno);
 192                 }
 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 #ifdef TRACE
 207   print_fderives ();
 208 #endif
 209
 210   XFREE (firsts);
 211 }
 212 \f
 213
 214 void
 215 new_closure (int n)
 216 {
 217   itemset = XCALLOC (short, n);
 218
 219   rulesetsize = WORDSIZE (nrules + 1);
 220   ruleset = XCALLOC (unsigned, rulesetsize);
 221
 222   set_fderives ();
 223 }
 224
 225
 226
 227 void
 228 closure (short *core, int n)
 229 {
 230   int ruleno;
 231   unsigned word;
 232   short *csp;
 233   unsigned *dsp;
 234   unsigned *rsp;
 235
 236   short *csend;
 237   unsigned *rsend;
 238   int symbol;
 239   int itemno;
 240
 241   rsp = ruleset;
 242   rsend = ruleset + rulesetsize;
 243   csend = core + n;
 244
 245   if (n == 0)
 246     {
 247       dsp = fderives + start_symbol * rulesetsize;
 248       while (rsp < rsend)
 249         *rsp++ = *dsp++;
 250     }
 251   else
 252     {
 253       while (rsp < rsend)
 254         *rsp++ = 0;
 255
 256       csp = core;
 257       while (csp < csend)
 258         {
 259           symbol = ritem[*csp++];
 260           if (ISVAR (symbol))
 261             {
 262               dsp = fderives + symbol * rulesetsize;
 263               rsp = ruleset;
 264               while (rsp < rsend)
 265                 *rsp++ |= *dsp++;
 266             }
 267         }
 268     }
 269
 270   ruleno = 0;
 271   itemsetend = itemset;
 272   csp = core;
 273   rsp = ruleset;
 274   while (rsp < rsend)
 275     {
 276       word = *rsp++;
 277       if (word == 0)
 278         {
 279           ruleno += BITS_PER_WORD;
 280         }
 281       else
 282         {
 283           int b;
 284
 285           for (b = 0; b < BITS_PER_WORD; b++)
 286             {
 287               if (word & (1 << b))
 288                 {
 289                   itemno = rule_table[ruleno].rhs;
 290                   while (csp < csend && *csp < itemno)
 291                     *itemsetend++ = *csp++;
 292                   *itemsetend++ = itemno;
 293                 }
 294
 295               ruleno++;
 296             }
 297         }
 298     }
 299
 300   while (csp < csend)
 301     *itemsetend++ = *csp++;
 302
 303 #if TRACE
 304   print_closure (n);
 305 #endif
 306 }
 307
 308
 309 void
 310 free_closure (void)
 311 {
 312   XFREE (itemset);
 313   XFREE (ruleset);
 314   XFREE (fderives + ntokens * rulesetsize);
 315 }