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 extern char **tags;
  29
  30 extern void RTC PARAMS ((unsigned *, int));
  31
  32 short *itemset;
  33 short *itemsetend;
  34 static unsigned *ruleset;
  35
  36 /* internal data.  See comments before set_fderives and set_firsts.  */
  37 static unsigned *fderives;
  38 static unsigned *firsts;
  39
  40 /* number of words required to hold a bit for each rule */
  41 static int rulesetsize;
  42
  43 /* number of words required to hold a bit for each variable */
  44 static int varsetsize;
  45 \f
  46 #if DEBUG
  47
  48 /*-----------------.
  49 | Debugging code.  |
  50 `-----------------*/
  51
  52 static void
  53 print_closure (int n)
  54 {
  55   short *isp;
  56
  57   printf ("\n\nn = %d\n\n", n);
  58   for (isp = itemset; isp < itemsetend; isp++)
  59     printf ("   %d\n", *isp);
  60 }
  61
  62
  63 static void
  64 print_firsts (void)
  65 {
  66   int i;
  67   int j;
  68   unsigned *rowp;
  69
  70   printf ("\n\n\nFIRSTS\n\n");
  71
  72   for (i = ntokens; i < nsyms; i++)
  73     {
  74       printf ("\n\n%s firsts\n\n", tags[i]);
  75
  76       rowp = firsts + ((i - ntokens) * varsetsize);
  77
  78       for (j = 0; j < nvars; j++)
  79         if (BITISSET (rowp, j))
  80           printf ("   %s\n", tags[j + ntokens]);
  81     }
  82 }
  83
  84
  85 static void
  86 print_fderives (void)
  87 {
  88   int i;
  89   int j;
  90   unsigned *rp;
  91
  92   printf ("\n\n\nFDERIVES\n");
  93
  94   for (i = ntokens; i < nsyms; i++)
  95     {
  96       printf ("\n\n%s derives\n\n", tags[i]);
  97       rp = fderives + i * rulesetsize;
  98
  99       for (j = 0; j <= nrules; j++)
 100         if (BITISSET (rp, j))
 101           printf ("   %d\n", j);
 102     }
 103
 104   fflush (stdout);
 105 }
 106 #endif
 107 \f
 108 /*-------------------------------------------------------------------.
 109 | Set FIRSTS to be an NVARS by NVARS bit matrix indicating which     |
 110 | items can represent the beginning of the input corresponding to    |
 111 | which other items.                                                 |
 112 |                                                                    |
 113 | For example, if some rule expands symbol 5 into the sequence of    |
 114 | symbols 8 3 20, the symbol 8 can be the beginning of the data for  |
 115 | symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is set.  |
 116 `-------------------------------------------------------------------*/
 117
 118 static void
 119 set_firsts (void)
 120 {
 121   unsigned *row;
 122   int symbol;
 123   short *sp;
 124   int rowsize;
 125
 126   int i;
 127
 128   varsetsize = rowsize = WORDSIZE (nvars);
 129
 130   firsts = NEW2 (nvars * rowsize, unsigned);
 131
 132   row = firsts;
 133   for (i = ntokens; i < nsyms; i++)
 134     {
 135       sp = derives[i];
 136       while (*sp >= 0)
 137         {
 138           symbol = ritem[rrhs[*sp++]];
 139           if (ISVAR (symbol))
 140             {
 141               symbol -= ntokens;
 142               SETBIT (row, symbol);
 143             }
 144         }
 145
 146       row += rowsize;
 147     }
 148
 149   RTC (firsts, nvars);
 150
 151 #ifdef  DEBUG
 152   print_firsts ();
 153 #endif
 154 }
 155
 156 /*-------------------------------------------------------------------.
 157 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 158 | rules can help derive the beginning of the data for each           |
 159 | nonterminal.                                                       |
 160 |                                                                    |
 161 | For example, if symbol 5 can be derived as the sequence of symbols |
 162 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 163 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 164 `-------------------------------------------------------------------*/
 165
 166 static void
 167 set_fderives (void)
 168 {
 169   unsigned *rrow;
 170   unsigned *vrow;
 171   int j;
 172   unsigned cword;
 173   short *rp;
 174   int b;
 175
 176   int ruleno;
 177   int i;
 178
 179   fderives = NEW2 (nvars * rulesetsize, unsigned) - ntokens * rulesetsize;
 180
 181   set_firsts ();
 182
 183   rrow = fderives + ntokens * rulesetsize;
 184
 185   for (i = ntokens; i < nsyms; i++)
 186     {
 187       vrow = firsts + ((i - ntokens) * varsetsize);
 188       cword = *vrow++;
 189       b = 0;
 190       for (j = ntokens; j < nsyms; j++)
 191         {
 192           if (cword & (1 << b))
 193             {
 194               rp = derives[j];
 195               while ((ruleno = *rp++) > 0)
 196                 {
 197                   SETBIT (rrow, ruleno);
 198                 }
 199             }
 200
 201           b++;
 202           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 203             {
 204               cword = *vrow++;
 205               b = 0;
 206             }
 207         }
 208
 209       rrow += rulesetsize;
 210     }
 211
 212 #ifdef  DEBUG
 213   print_fderives ();
 214 #endif
 215
 216   FREE (firsts);
 217 }
 218 \f
 219
 220 void
 221 new_closure (int n)
 222 {
 223   itemset = NEW2 (n, short);
 224
 225   rulesetsize = WORDSIZE (nrules + 1);
 226   ruleset = NEW2 (rulesetsize, unsigned);
 227
 228   set_fderives ();
 229 }
 230
 231
 232
 233 void
 234 closure (short *core, int n)
 235 {
 236   int ruleno;
 237   unsigned word;
 238   short *csp;
 239   unsigned *dsp;
 240   unsigned *rsp;
 241
 242   short *csend;
 243   unsigned *rsend;
 244   int symbol;
 245   int itemno;
 246
 247   rsp = ruleset;
 248   rsend = ruleset + rulesetsize;
 249   csend = core + n;
 250
 251   if (n == 0)
 252     {
 253       dsp = fderives + start_symbol * rulesetsize;
 254       while (rsp < rsend)
 255         *rsp++ = *dsp++;
 256     }
 257   else
 258     {
 259       while (rsp < rsend)
 260         *rsp++ = 0;
 261
 262       csp = core;
 263       while (csp < csend)
 264         {
 265           symbol = ritem[*csp++];
 266           if (ISVAR (symbol))
 267             {
 268               dsp = fderives + symbol * rulesetsize;
 269               rsp = ruleset;
 270               while (rsp < rsend)
 271                 *rsp++ |= *dsp++;
 272             }
 273         }
 274     }
 275
 276   ruleno = 0;
 277   itemsetend = itemset;
 278   csp = core;
 279   rsp = ruleset;
 280   while (rsp < rsend)
 281     {
 282       word = *rsp++;
 283       if (word == 0)
 284         {
 285           ruleno += BITS_PER_WORD;
 286         }
 287       else
 288         {
 289           int b;
 290
 291           for (b = 0; b < BITS_PER_WORD; b++)
 292             {
 293               if (word & (1 << b))
 294                 {
 295                   itemno = rrhs[ruleno];
 296                   while (csp < csend && *csp < itemno)
 297                     *itemsetend++ = *csp++;
 298                   *itemsetend++ = itemno;
 299                 }
 300
 301               ruleno++;
 302             }
 303         }
 304     }
 305
 306   while (csp < csend)
 307     *itemsetend++ = *csp++;
 308
 309 #if DEBUG
 310   print_closure (n);
 311 #endif
 312 }
 313
 314
 315 void
 316 free_closure (void)
 317 {
 318   FREE (itemset);
 319   FREE (ruleset);
 320   FREE (fderives + ntokens * rulesetsize);
 321 }