Version 1.75a.

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index c3c96d7def4a7ae00c105ff94da3abc4f3ddd6ed..c0b60f64d40235e653e2f9b7033030341d0d0580 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -1,136 +1,137 @@
 /* Part of the bison parser generator,
 /* Part of the bison parser generator,

-   Copyright (C) 1984, 1989 Free Software Foundation, Inc.
+   Copyright (C) 1984, 1989, 2000, 2001, 2002 Free Software Foundation, Inc.

 
 

-This file is part of Bison, the GNU Compiler Compiler.
+   This file is part of Bison, the GNU Compiler Compiler.

 
 

-Bison is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
+   Bison is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.

 
 

-Bison is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
+   Bison is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.

 
 

-You should have received a copy of the GNU General Public License
-along with Bison; see the file COPYING.  If not, write to
-the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+   You should have received a copy of the GNU General Public License
+   along with Bison; see the file COPYING.  If not, write to
+   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */

 
 
 
 

-/* set up nullable, a vector saying which nonterminals can expand into the null string.
-   nullable[i - ntokens] is nonzero if symbol i can do so.  */
+/* Set up NULLABLE, a vector saying which nonterminals can expand into
+   the null string.  NULLABLE[I - NTOKENS] is nonzero if symbol I can
+   do so.  */

 
 

-#include <stdio.h>

 #include "system.h"
 #include "system.h"

-#include "types.h"
+#include "getargs.h"
+#include "symtab.h"

 #include "gram.h"
 #include "gram.h"

-#include "alloc.h"
+#include "reduce.h"
+#include "nullable.h"

 
 

+/* Linked list of rules.  */
+typedef struct rule_list_s
+{
+  struct rule_list_s *next;
+  rule_t *value;
+} rule_list_t;

 
 

-char *nullable;
+bool *nullable = NULL;

 
 

+static void
+nullable_print (FILE *out)
+{
+  int i;
+  fputs ("NULLABLE\n", out);
+  for (i = ntokens; i < nsyms; i++)
+    fprintf (out, "\t%s: %s\n", symbols[i]->tag, nullable[i] ? "yes" : "no");
+  fputs ("\n\n", out);
+}

 
 void
 
 void

-set_nullable()
+nullable_compute (void)

 {
 {

-  register short *r;
-  register short *s1;
-  register short *s2;
-  register int ruleno;
-  register int symbol;
-  register shorts *p;
-
-  short *squeue;
-  short *rcount;
-  shorts **rsets;
-  shorts *relts;
-  char any_tokens;
-  short *r1;
-
-#ifdef TRACE
-  fprintf(stderr, _("Entering set_nullable"));
-#endif
-
-  nullable = NEW2(nvars, char) - ntokens;
-
-  squeue = NEW2(nvars, short);
-  s1 = s2 = squeue;
-
-  rcount = NEW2(nrules + 1, short);
-  rsets = NEW2(nvars, shorts *) - ntokens;
+  rule_number_t ruleno;
+  symbol_number_t *s1;
+  symbol_number_t *s2;
+  rule_list_t *p;
+
+  symbol_number_t *squeue = XCALLOC (symbol_number_t, nvars);
+  short *rcount = XCALLOC (short, nrules);
+  /* RITEM contains all the rules, including useless productions.
+     Hence we must allocate room for useless nonterminals too.  */
+  rule_list_t **rsets = XCALLOC (rule_list_t *, nvars) - ntokens;

   /* This is said to be more elements than we actually use.
   /* This is said to be more elements than we actually use.

-     Supposedly nitems - nrules is enough.
-     But why take the risk?  */
-  relts = NEW2(nitems + nvars + 1, shorts);
+     Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
+  rule_list_t *relts = XCALLOC (rule_list_t, nritems + nvars + 1);
+
+  nullable = XCALLOC (bool, nvars) - ntokens;
+
+  s1 = s2 = squeue;

   p = relts;
 
   p = relts;
 

-  r = ritem;
-  while (*r)
-    {
-      if (*r < 0)
-       {
-         symbol = rlhs[-(*r++)];
-         if (symbol >= 0 && !nullable[symbol])
-           {
-             nullable[symbol] = 1;
-             *s2++ = symbol;
-           }
-       }
-      else
-       {
-         r1 = r;
-         any_tokens = 0;
-         for (symbol = *r++; symbol > 0; symbol = *r++)
-           {
-             if (ISTOKEN(symbol))
+  for (ruleno = 0; ruleno < nrules; ++ruleno)
+    if (rules[ruleno].useful)
+      {
+       rule_t *rule = &rules[ruleno];
+       if (rule->rhs[0] >= 0)
+         {
+           /* This rule has a non empty RHS. */
+           item_number_t *r = NULL;
+           int any_tokens = 0;
+           for (r = rule->rhs; *r >= 0; ++r)
+             if (ISTOKEN (*r))

                any_tokens = 1;
                any_tokens = 1;

-           }

 
 

-         if (!any_tokens)
-           {
-             ruleno = -symbol;
-             r = r1;
-             for (symbol = *r++; symbol > 0; symbol = *r++)
+           /* This rule has only nonterminals: schedule it for the second
+              pass.  */
+           if (!any_tokens)
+             for (r = rule->rhs; *r >= 0; ++r)

                {
                  rcount[ruleno]++;
                {
                  rcount[ruleno]++;

-                 p->next = rsets[symbol];
-                 p->value = ruleno;
-                 rsets[symbol] = p;
+                 p->next = rsets[*r];
+                 p->value = rule;
+                 rsets[*r] = p;

                  p++;
                }
                  p++;
                }

-           }
-       }
-    }
+         }
+       else
+         {
+           /* This rule has an empty RHS. */
+           assert (item_number_as_rule_number (rule->rhs[0]) == ruleno);
+           if (rule->useful && !nullable[rule->lhs->number])
+             {
+               nullable[rule->lhs->number] = 1;
+               *s2++ = rule->lhs->number;
+             }
+         }
+      }

 
   while (s1 < s2)
 
   while (s1 < s2)

-    {
-      p = rsets[*s1++];
-      while (p)
-       {
-         ruleno = p->value;
-         p = p->next;
-         if (--rcount[ruleno] == 0)
+    for (p = rsets[*s1++]; p; p = p->next)
+      {
+       rule_t *rule = p->value;
+       if (--rcount[rule->number] == 0)
+         if (rule->useful && !nullable[rule->lhs->number])

            {
            {

-             symbol = rlhs[ruleno];
-             if (symbol >= 0 && !nullable[symbol])
-               {
-                 nullable[symbol] = 1;
-                 *s2++ = symbol;
-               }
+             nullable[rule->lhs->number] = 1;
+             *s2++ = rule->lhs->number;

            }
            }

-       }
-    }
+      }
+
+  XFREE (squeue);
+  XFREE (rcount);
+  XFREE (rsets + ntokens);
+  XFREE (relts);

 
 

-  FREE(squeue);
-  FREE(rcount);
-  FREE(rsets + ntokens);
-  FREE(relts);
+  if (trace_flag & trace_sets)
+    nullable_print (stderr);

 }
 
 
 void
 }
 
 
 void

-free_nullable()
+nullable_free (void)

 {
 {

-  FREE(nullable + ntokens);
+  XFREE (nullable + ntokens);

 }
 }