src/closure.c

   1 /* Subroutines for bison
   2    Copyright (C) 1984, 1989, 2000, 2001, 2002 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 "quotearg.h"
  23 #include "bitset.h"
  24 #include "bitsetv.h"
  25 #include "getargs.h"
  26 #include "symtab.h"
  27 #include "gram.h"
  28 #include "reader.h"
  29 #include "closure.h"
  30 #include "derives.h"
  31
  32 /* NITEMSET is the size of the array ITEMSET.  */
  33 short *itemset;
  34 int nritemset;
  35
  36 static bitset ruleset;
  37
  38 /* internal data.  See comments before set_fderives and set_firsts.  */
  39 static bitsetv fderives = NULL;
  40 static bitsetv firsts = NULL;
  41
  42 /* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var.  */
  43 #define FDERIVES(Var)   fderives[(Var) - ntokens]
  44 #define   FIRSTS(Var)   firsts[(Var) - ntokens]
  45 \f
  46
  47 /*-----------------.
  48 | Debugging code.  |
  49 `-----------------*/
  50
  51 static void
  52 print_closure (const char *title, short *array, size_t size)
  53 {
  54   size_t i;
  55   fprintf (stderr, "Closure: %s\n", title);
  56   for (i = 0; i < size; ++i)
  57     {
  58       short *rp;
  59       fprintf (stderr, "  %2d: .", array[i]);
  60       for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
  61         fprintf (stderr, " %s",
  62                  quotearg_style (escape_quoting_style, symbols[*rp]->tag));
  63       fprintf (stderr, "  (rule %d)\n", -*rp - 1);
  64     }
  65   fputs ("\n\n", stderr);
  66 }
  67
  68
  69 static void
  70 print_firsts (void)
  71 {
  72   int i, j;
  73
  74   fprintf (stderr, "FIRSTS\n");
  75   for (i = ntokens; i < nsyms; i++)
  76     {
  77       fprintf (stderr, "\t%s firsts\n",
  78                quotearg_style (escape_quoting_style, symbols[i]->tag));
  79       for (j = 0; j < nvars; j++)
  80         if (bitset_test (FIRSTS (i), j))
  81           fprintf (stderr, "\t\t%d (%s)\n",
  82                    j + ntokens,
  83                    quotearg_style (escape_quoting_style,
  84                                    symbols[j + ntokens]->tag));
  85     }
  86   fprintf (stderr, "\n\n");
  87 }
  88
  89
  90 static void
  91 print_fderives (void)
  92 {
  93   int i, j;
  94
  95   fprintf (stderr, "FDERIVES\n");
  96   for (i = ntokens; i < nsyms; i++)
  97     {
  98       fprintf (stderr, "\t%s derives\n",
  99                quotearg_style (escape_quoting_style, symbols[i]->tag));
 100       for (j = 0; j < nrules + 1; j++)
 101         if (bitset_test (FDERIVES (i), j))
 102           {
 103             short *rhsp;
 104             fprintf (stderr, "\t\t%d:", j - 1);
 105             for (rhsp = rules[j].rhs; *rhsp >= 0; ++rhsp)
 106               fprintf (stderr, " %s",
 107                        quotearg_style (escape_quoting_style,
 108                                        symbols[*rhsp]->tag));
 109             fputc ('\n', stderr);
 110           }
 111     }
 112   fprintf (stderr, "\n\n");
 113 }
 114
 115 /*--------------------------------------------------------.
 116 | Display the MATRIX array of SIZE bitsets of size SIZE.  |
 117 `--------------------------------------------------------*/
 118
 119 static void
 120 bitmatrix_print (const char *title, bitsetv matrix)
 121 {
 122   size_t i, j;
 123   size_t size = bitset_size (matrix[0]);
 124
 125   /* Title. */
 126   fprintf (stderr, "%s BEGIN\n", title);
 127
 128   /* Column numbers. */
 129   fputs ("   ", stderr);
 130   for (i = 0; i < size; ++i)
 131     putc (i / 10 ? '0' + i / 10 : ' ', stderr);
 132   putc ('\n', stderr);
 133   fputs ("   ", stderr);
 134   for (i = 0; i < size; ++i)
 135     fprintf (stderr, "%d", i % 10);
 136   putc ('\n', stderr);
 137
 138   /* Bar. */
 139   fputs ("  .", stderr);
 140   for (i = 0; i < size; ++i)
 141     putc ('-', stderr);
 142   fputs (".\n", stderr);
 143
 144   /* Contents. */
 145   for (i = 0; i < size; ++i)
 146     {
 147       fprintf (stderr, "%2d|", i);
 148       for (j = 0; j < size; ++j)
 149         fputs (bitset_test (matrix[i], j) ? "1" : " ", stderr);
 150       fputs ("|\n", stderr);
 151     }
 152
 153   /* Bar. */
 154   fputs ("  `", stderr);
 155   for (i = 0; i < size; ++i)
 156     putc ('-', stderr);
 157   fputs ("'\n", stderr);
 158
 159   /* End title. */
 160   fprintf (stderr, "%s END\n\n", title);
 161 }
 162 \f
 163 /*------------------------------------------------------------------.
 164 | Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
 165 | items can represent the beginning of the input corresponding to   |
 166 | which other items.                                                |
 167 |                                                                   |
 168 | For example, if some rule expands symbol 5 into the sequence of   |
 169 | symbols 8 3 20, the symbol 8 can be the beginning of the data for |
 170 | symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
 171 | (5)) is set.                                                      |
 172 `------------------------------------------------------------------*/
 173
 174 static void
 175 set_firsts (void)
 176 {
 177   int i, j;
 178
 179   firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
 180
 181   for (i = ntokens; i < nsyms; i++)
 182     for (j = 0; derives[i][j] >= 0; ++j)
 183       {
 184         int symbol = rules[derives[i][j]].rhs[0];
 185         if (ISVAR (symbol))
 186           bitset_set (FIRSTS (i), symbol - ntokens);
 187       }
 188
 189   if (trace_flag)
 190     bitmatrix_print ("RTC: Input", firsts);
 191   bitsetv_reflexive_transitive_closure (firsts);
 192   if (trace_flag)
 193     bitmatrix_print ("RTC: Output", firsts);
 194
 195   if (trace_flag)
 196     print_firsts ();
 197 }
 198
 199 /*-------------------------------------------------------------------.
 200 | Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
 201 | rules can help derive the beginning of the data for each           |
 202 | nonterminal.                                                       |
 203 |                                                                    |
 204 | For example, if symbol 5 can be derived as the sequence of symbols |
 205 | 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
 206 | the [5 - NTOKENS, 4] bit in FDERIVES is set.                       |
 207 `-------------------------------------------------------------------*/
 208
 209 static void
 210 set_fderives (void)
 211 {
 212   int i, j, k;
 213
 214   fderives = bitsetv_create (nvars, nrules + 1, BITSET_FIXED);
 215
 216   set_firsts ();
 217
 218   for (i = ntokens; i < nsyms; ++i)
 219     for (j = ntokens; j < nsyms; ++j)
 220       if (bitset_test (FIRSTS (i), j - ntokens))
 221         for (k = 0; derives[j][k] > 0; ++k)
 222           bitset_set (FDERIVES (i), derives[j][k]);
 223
 224   if (trace_flag)
 225     print_fderives ();
 226
 227   bitsetv_free (firsts);
 228 }
 229 \f
 230
 231 void
 232 new_closure (int n)
 233 {
 234   itemset = XCALLOC (short, n);
 235
 236   ruleset = bitset_create (nrules + 1, BITSET_FIXED);
 237
 238   set_fderives ();
 239 }
 240
 241
 242
 243 void
 244 closure (short *core, int n)
 245 {
 246   /* Index over CORE. */
 247   int c;
 248
 249   /* A bit index over RULESET. */
 250   int ruleno;
 251
 252   if (trace_flag)
 253     print_closure ("input", core, n);
 254
 255   bitset_zero (ruleset);
 256
 257   for (c = 0; c < n; ++c)
 258     if (ISVAR (ritem[core[c]]))
 259       bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
 260
 261   nritemset = 0;
 262   c = 0;
 263   for (ruleno = 0; ruleno < nrules + 1; ++ruleno)
 264     if (bitset_test (ruleset, ruleno))
 265       {
 266         int itemno = rules[ruleno].rhs - ritem;
 267         while (c < n && core[c] < itemno)
 268           {
 269             itemset[nritemset] = core[c];
 270             nritemset++;
 271             c++;
 272           }
 273         itemset[nritemset] = itemno;
 274         nritemset++;
 275       }
 276
 277   while (c < n)
 278     {
 279       itemset[nritemset] = core[c];
 280       nritemset++;
 281       c++;
 282     }
 283
 284   if (trace_flag)
 285     print_closure ("output", itemset, nritemset);
 286 }
 287
 288
 289 void
 290 free_closure (void)
 291 {
 292   XFREE (itemset);
 293   bitset_free (ruleset);
 294   bitsetv_free (fderives);
 295 }