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