src/relation.c

   1 /* Binary relations.
   2
   3    Copyright (C) 2002, 2004-2005, 2009-2015, 2018-2021 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 <https://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include <bitsetv.h>
  25
  26 #include "getargs.h"
  27 #include "relation.h"
  28
  29 void
  30 relation_print (const char *title,
  31                 relation r, relation_node size,
  32                 relation_node_print print, FILE *out)
  33 {
  34   if (title)
  35     fprintf (out, "%s:\n", title);
  36   for (relation_node i = 0; i < size; ++i)
  37     if (r[i])
  38       {
  39         fputs ("    ", out);
  40         if (print)
  41           print (i, out);
  42         else
  43           fprintf (out, "%3ld", (long) i);
  44         fputc (':', out);
  45         for (relation_node j = 0; r[i][j] != END_NODE; ++j)
  46           {
  47             fputc (' ', out);
  48             if (print)
  49               print (r[i][j], out);
  50             else
  51               fprintf (out, "%3ld", (long) r[i][j]);
  52           }
  53         fputc ('\n', out);
  54       }
  55   fputc ('\n', out);
  56 }
  57
  58
  59 /*---------------------------------------------------------------.
  60 | digraph & traverse.                                            |
  61 |                                                                |
  62 | The following variables are used as common storage between the |
  63 | two.                                                           |
  64 `---------------------------------------------------------------*/
  65
  66 static relation R;
  67 static relation_nodes indexes;
  68 static relation_nodes vertices;
  69 static relation_node top;
  70 static relation_node infinity;
  71 static bitsetv F;
  72
  73 static void
  74 traverse (relation_node i)
  75 {
  76   vertices[++top] = i;
  77   relation_node height = indexes[i] = top;
  78
  79   if (R[i])
  80     for (relation_node j = 0; R[i][j] != END_NODE; ++j)
  81       {
  82         if (indexes[R[i][j]] == 0)
  83           traverse (R[i][j]);
  84
  85         if (indexes[i] > indexes[R[i][j]])
  86           indexes[i] = indexes[R[i][j]];
  87
  88         bitset_or (F[i], F[i], F[R[i][j]]);
  89       }
  90
  91   if (indexes[i] == height)
  92     for (;;)
  93       {
  94         relation_node j = vertices[top--];
  95         indexes[j] = infinity;
  96
  97         if (i == j)
  98           break;
  99
 100         bitset_copy (F[j], F[i]);
 101       }
 102 }
 103
 104
 105 void
 106 relation_digraph (relation r, relation_node size, bitsetv function)
 107 {
 108   infinity = size + 2;
 109   indexes = xcalloc (size + 1, sizeof *indexes);
 110   vertices = xnmalloc (size + 1, sizeof *vertices);
 111   top = 0;
 112
 113   R = r;
 114   F = function;
 115
 116   for (relation_node i = 0; i < size; i++)
 117     if (indexes[i] == 0 && R[i])
 118       traverse (i);
 119
 120   free (indexes);
 121   free (vertices);
 122
 123   function = F;
 124 }
 125
 126
 127 /*-------------------------------------------.
 128 | Destructively transpose R_ARG, of size N.  |
 129 `-------------------------------------------*/
 130
 131 void
 132 relation_transpose (relation *R_arg, relation_node size)
 133 {
 134   relation r = *R_arg;
 135
 136   if (trace_flag & trace_sets)
 137     relation_print ("relation_transpose", r, size, NULL, stderr);
 138
 139   /* Count. */
 140   /* NEDGES[I] -- total size of NEW_R[I]. */
 141   size_t *nedges = xcalloc (size, sizeof *nedges);
 142   for (relation_node i = 0; i < size; i++)
 143     if (r[i])
 144       for (relation_node j = 0; r[i][j] != END_NODE; ++j)
 145         ++nedges[r[i][j]];
 146
 147   /* Allocate. */
 148   /* The result. */
 149   relation new_R = xnmalloc (size, sizeof *new_R);
 150   /* END_R[I] -- next entry of NEW_R[I]. */
 151   relation end_R = xnmalloc (size, sizeof *end_R);
 152   for (relation_node i = 0; i < size; i++)
 153     {
 154       relation_node *sp = NULL;
 155       if (nedges[i] > 0)
 156         {
 157           sp = xnmalloc (nedges[i] + 1, sizeof *sp);
 158           sp[nedges[i]] = END_NODE;
 159         }
 160       new_R[i] = sp;
 161       end_R[i] = sp;
 162     }
 163
 164   /* Store. */
 165   for (relation_node i = 0; i < size; i++)
 166     if (r[i])
 167       for (relation_node j = 0; r[i][j] != END_NODE; ++j)
 168         *end_R[r[i][j]]++ = i;
 169
 170   free (nedges);
 171   free (end_R);
 172
 173   /* Free the input: it is replaced with the result. */
 174   for (relation_node i = 0; i < size; i++)
 175     free (r[i]);
 176   free (r);
 177
 178   if (trace_flag & trace_sets)
 179     relation_print ("relation_transpose: output", new_R, size, NULL, stderr);
 180
 181   *R_arg = new_R;
 182 }