src/derives.c

   1 /* Match rules with nonterminals 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
   7    it 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,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU 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
  18    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21
  22 /* set_derives finds, for each variable (nonterminal), which rules can
  23    derive it.  It sets up the value of derives so that derives[i -
  24    ntokens] points to a vector of rule numbers, terminated with -1.
  25    */
  26
  27 #include "system.h"
  28 #include "types.h"
  29 #include "reader.h"
  30 #include "gram.h"
  31 #include "derives.h"
  32
  33 short **derives;
  34
  35 #if TRACE
  36
  37 static void
  38 print_derives (void)
  39 {
  40   int i;
  41   short *sp;
  42
  43   fputs ("\n\n\nDERIVES\n\n", stderr);
  44
  45   for (i = ntokens; i < nsyms; i++)
  46     {
  47       fprintf (stderr, "%s derives", tags[i]);
  48       for (sp = derives[i]; *sp > 0; sp++)
  49         fprintf (stderr, "  %d", *sp);
  50       putc ('\n', stderr);
  51     }
  52
  53   putc ('\n', stderr);
  54 }
  55
  56 #endif
  57
  58 void
  59 set_derives (void)
  60 {
  61   int i;
  62   int lhs;
  63   shorts *p;
  64   short *q;
  65   shorts **dset;
  66   shorts *delts;
  67
  68   dset = XCALLOC (shorts *, nvars) - ntokens;
  69   delts = XCALLOC (shorts, nrules + 1);
  70
  71   p = delts;
  72   for (i = nrules; i > 0; i--)
  73     {
  74       lhs = rule_table[i].lhs;
  75       if (lhs >= 0)
  76         {
  77           p->next = dset[lhs];
  78           p->value = i;
  79           dset[lhs] = p;
  80           p++;
  81         }
  82     }
  83
  84   derives = XCALLOC (short *, nvars) - ntokens;
  85   q = XCALLOC (short, nvars + nrules);
  86
  87   for (i = ntokens; i < nsyms; i++)
  88     {
  89       derives[i] = q;
  90       p = dset[i];
  91       while (p)
  92         {
  93           *q++ = p->value;
  94           p = p->next;
  95         }
  96       *q++ = -1;
  97     }
  98
  99 #if TRACE
 100   print_derives ();
 101 #endif
 102
 103   XFREE (dset + ntokens);
 104   XFREE (delts);
 105 }
 106
 107 void
 108 free_derives (void)
 109 {
 110   XFREE (derives[ntokens]);
 111   XFREE (derives + ntokens);
 112 }