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