1  /* Match rules with nonterminals for bison,
       2  
       3     Copyright (C) 1984, 1989, 2000-2003, 2005, 2009-2015, 2018-2021 Free
       4     Software 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 <https://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    fputs ("DERIVES\n", stderr);
      44  
      45    for (symbol_number i = ntokens; i < nsyms; ++i)
      46      {
      47        fprintf (stderr, "  %s derives\n", symbols[i]->tag);
      48        for (rule **rp = derives[i - ntokens]; *rp; ++rp)
      49          {
      50            fprintf (stderr, "    %3d ", (*rp)->code);
      51            rule_rhs_print (*rp, stderr);
      52            fprintf (stderr, "\n");
      53          }
      54      }
      55  
      56    fputs ("\n\n", stderr);
      57  }
      58  
      59  
      60  void
      61  derives_compute (void)
      62  {
      63    /* DSET[NTERM - NTOKENS] -- A linked list of the numbers of the rules
      64       whose LHS is NTERM.  */
      65    rule_list **dset = xcalloc (nnterms, sizeof *dset);
      66  
      67    /* DELTS[RULE] -- There are NRULES rule number to attach to nterms.
      68       Instead of performing NRULES allocations for each, have an array
      69       indexed by rule numbers.  */
      70    rule_list *delts = xnmalloc (nrules, sizeof *delts);
      71  
      72    for (rule_number r = nrules - 1; r >= 0; --r)
      73      {
      74        symbol_number lhs = rules[r].lhs->number;
      75        rule_list *p = &delts[r];
      76        /* A new LHS is found.  */
      77        p->next = dset[lhs - ntokens];
      78        p->value = &rules[r];
      79        dset[lhs - ntokens] = p;
      80      }
      81  
      82    /* DSET contains what we need under the form of a linked list.  Make
      83       it a single array.  */
      84  
      85    derives = xnmalloc (nnterms, sizeof *derives);
      86    /* Q is the storage for DERIVES[...] (DERIVES[0] = q).  */
      87    rule **q = xnmalloc (nnterms + nrules, sizeof *q);
      88  
      89    for (symbol_number i = ntokens; i < nsyms; ++i)
      90      {
      91        rule_list *p = dset[i - ntokens];
      92        derives[i - ntokens] = q;
      93        while (p)
      94          {
      95            *q++ = p->value;
      96            p = p->next;
      97          }
      98        *q++ = NULL;
      99      }
     100  
     101    if (trace_flag & trace_sets)
     102      print_derives ();
     103  
     104    free (dset);
     105    free (delts);
     106  }
     107  
     108  
     109  void
     110  derives_free (void)
     111  {
     112    if (derives)
     113      {
     114        free (derives[0]);
     115        free (derives);
     116      }
     117  }