src/derives.c

   1 /* Match rules with nonterminals for bison,
   2
   3    Copyright (C) 1984, 1989, 2000-2003, 2005, 2009-2015 Free Software
   4    Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include "getargs.h"
  25
  26 #include "derives.h"
  27 #include "gram.h"
  28 #include "reader.h"
  29 #include "symtab.h"
  30
  31 /* Linked list of rule numbers.  */
  32 typedef struct rule_list
  33 {
  34   struct rule_list *next;
  35   rule *value;
  36 } rule_list;
  37
  38 rule ***derives;
  39
  40 static void
  41 print_derives (void)
  42 {
  43   int i;
  44
  45   fputs ("DERIVES\n", stderr);
  46
  47   for (i = ntokens; i < nsyms; i++)
  48     {
  49       rule **rp;
  50       fprintf (stderr, "  %s derives\n", symbols[i]->tag);
  51       for (rp = derives[i - ntokens]; *rp; ++rp)
  52         {
  53           fprintf (stderr, "    %3d ", (*rp)->user_number);
  54           rule_rhs_print (*rp, stderr);
  55           fprintf (stderr, "\n");
  56         }
  57     }
  58
  59   fputs ("\n\n", stderr);
  60 }
  61
  62
  63 void
  64 derives_compute (void)
  65 {
  66   symbol_number i;
  67   rule_number r;
  68   rule **q;
  69
  70   /* DSET[NTERM - NTOKENS] -- A linked list of the numbers of the rules
  71      whose LHS is NTERM.  */
  72   rule_list **dset = xcalloc (nvars, sizeof *dset);
  73
  74   /* DELTS[RULE] -- There are NRULES rule number to attach to nterms.
  75      Instead of performing NRULES allocations for each, have an array
  76      indexed by rule numbers.  */
  77   rule_list *delts = xnmalloc (nrules, sizeof *delts);
  78
  79   for (r = nrules - 1; r >= 0; --r)
  80     {
  81       symbol_number lhs = rules[r].lhs->number;
  82       rule_list *p = &delts[r];
  83       /* A new LHS is found.  */
  84       p->next = dset[lhs - ntokens];
  85       p->value = &rules[r];
  86       dset[lhs - ntokens] = p;
  87     }
  88
  89   /* DSET contains what we need under the form of a linked list.  Make
  90      it a single array.  */
  91
  92   derives = xnmalloc (nvars, sizeof *derives);
  93   q = xnmalloc (nvars + nrules, sizeof *q);
  94
  95   for (i = ntokens; i < nsyms; i++)
  96     {
  97       rule_list *p = dset[i - ntokens];
  98       derives[i - ntokens] = q;
  99       while (p)
 100         {
 101           *q++ = p->value;
 102           p = p->next;
 103         }
 104       *q++ = NULL;
 105     }
 106
 107   if (trace_flag & trace_sets)
 108     print_derives ();
 109
 110   free (dset);
 111   free (delts);
 112 }
 113
 114
 115 void
 116 derives_free (void)
 117 {
 118   free (derives[0]);
 119   free (derives);
 120 }