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 /* ITEMSETSIZE is the size of the array ITEMSET.  */
  30 short *itemset;
  31 size_t itemsetsize;
  32
  33 static unsigned *ruleset;
  34
  35 /* internal data.  See comments before set_fderives and set_firsts.  */
  36 static unsigned *fderives;
  37 static unsigned *firsts;
  38
  39 #define FDERIVES(Symbol)   (fderives + (Symbol) * rulesetsize)
  40 #define   FIRSTS(Symbol)   (firsts   + (Symbol) * varsetsize)
  41
  42 /* number of words required to hold a bit for each rule */
  43 static int rulesetsize;
  44
  45 /* number of words required to hold a bit for each variable */
  46 static int varsetsize;
  47 \f
  48
  49 /*-----------------.
  50 | Debugging code.  |
  51 `-----------------*/
  52
  53 static void
  54 print_closure (int n)
  55 {
  56   int i;
  57   fprintf (stderr, "n = %d\n", n);
  58   for (i = 0; i < itemsetsize; ++i)
  59     fprintf (stderr, "   %d\n", itemset[i]);
  60   fprintf (stderr, "\n\n");
  61 }
  62
  63
  64 static void
  65 print_firsts (void)
  66 {
  67   int i;
  68   int j;
  69   unsigned *rowp;
  70
  71   fprintf (stderr, "FIRSTS\n");
  72
  73   for (i = ntokens; i < nsyms; i++)
  74     {
  75       fprintf (stderr, "\t%s firsts\n", tags[i]);
  76
  77       rowp = FIRSTS (i - ntokens);
  78
  79       for (j = 0; j < nvars; j++)
  80         if (BITISSET (rowp, j))
  81           fprintf (stderr, "\t\t%d (%s)\n", j + ntokens, tags[j + ntokens]);
  82     }
  83   fprintf (stderr, "\n\n");
  84 }
  85
  86
  87 static void
  88 print_fderives (void)
  89 {
  90   int i;
  91   int j;
  92   unsigned *rp;
  93
  94   fprintf (stderr, "FDERIVES\n");
  95
  96   for (i = ntokens; i < nsyms; i++)
  97     {
  98       fprintf (stderr, "\t%s derives\n", tags[i]);
  99       rp = FDERIVES (i);
 100
 101       for (j = 0; j <= nrules; j++)
 102         if (BITISSET (rp, j))
 103           fprintf (stderr, "\t\t%d (%s)\n", j, tags[j]);
 104     }
 105   fprintf (stderr, "\n\n");
 106 }
 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 = XCALLOC (unsigned, nvars * rowsize);
 131
 132   row = firsts;
 133   for (i = ntokens; i < nsyms; i++)
 134     {
 135       sp = derives[i];
 136       while (*sp >= 0)
 137         {
 138           symbol = ritem[rule_table[*sp++].rhs];
 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   if (trace_flag)
 152     print_firsts ();
 153 }
 154
 155 /*-------------------------------------------------------------------.
 156 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 157 | rules can help derive the beginning of the data for each           |
 158 | nonterminal.                                                       |
 159 |                                                                    |
 160 | For example, if symbol 5 can be derived as the sequence of symbols |
 161 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 162 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 163 `-------------------------------------------------------------------*/
 164
 165 static void
 166 set_fderives (void)
 167 {
 168   unsigned *rrow;
 169   unsigned *vrow;
 170   int j;
 171   unsigned cword;
 172   short *rp;
 173   int b;
 174
 175   int ruleno;
 176   int i;
 177
 178   fderives = XCALLOC (unsigned, nvars * rulesetsize) - ntokens * rulesetsize;
 179
 180   set_firsts ();
 181
 182   rrow = FDERIVES (ntokens);
 183
 184   for (i = ntokens; i < nsyms; i++)
 185     {
 186       vrow = FIRSTS (i - ntokens);
 187       cword = *vrow++;
 188       b = 0;
 189       for (j = ntokens; j < nsyms; j++)
 190         {
 191           if (cword & (1 << b))
 192             {
 193               rp = derives[j];
 194               while ((ruleno = *rp++) > 0)
 195                 SETBIT (rrow, ruleno);
 196             }
 197
 198           b++;
 199           if (b >= BITS_PER_WORD && j + 1 < nsyms)
 200             {
 201               cword = *vrow++;
 202               b = 0;
 203             }
 204         }
 205
 206       rrow += rulesetsize;
 207     }
 208
 209   if (trace_flag)
 210     print_fderives ();
 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   short *csp;
 234
 235   int itemno;
 236   int i;
 237
 238   if (trace_flag)
 239     {
 240       fprintf (stderr, "Entering closure (items = {");
 241       for (i = 0; i < n; ++i)
 242         fprintf (stderr, " %d ", core[i]);
 243       fprintf (stderr, "}, nitems = %d)\n", n);
 244     }
 245
 246   if (n == 0)
 247     {
 248       for (i = 0; i < rulesetsize; ++i)
 249         ruleset[i] = FDERIVES (start_symbol)[i];
 250     }
 251   else
 252     {
 253       for (i = 0; i < rulesetsize; ++i)
 254         ruleset[i] = 0;
 255
 256       for (i = 0; i < n; ++i)
 257         {
 258           int symbol = ritem[core[i]];
 259           if (ISVAR (symbol))
 260             {
 261               int j;
 262               for (j = 0; j < rulesetsize; ++j)
 263                 ruleset[j] |= FDERIVES (symbol)[j];
 264             }
 265         }
 266     }
 267
 268   ruleno = 0;
 269   itemsetsize = 0;
 270   csp = core;
 271   for (i = 0; i < rulesetsize; ++i)
 272     {
 273       int word = ruleset[i];
 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 < (core + n) && *csp < itemno)
 288                     itemset[itemsetsize++] = *csp++;
 289                   itemset[itemsetsize++] = itemno;
 290                 }
 291
 292               ruleno++;
 293             }
 294         }
 295     }
 296
 297   while (csp < (core + n))
 298     itemset[itemsetsize++] = *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 }