regen

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index 2797180c4496e51341627394bbb84bb352c36831..209b3d29143c8f806babf7968150ccad3f4bd993 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -1,37 +1,45 @@
-/* Part of the bison parser generator,
-   Copyright 1984, 1989, 2000, 2001 Free Software Foundation, Inc.
+/* Calculate which nonterminals can expand into the null string for Bison.
+
+   Copyright (C) 1984, 1989, 2000-2006, 2009-2013 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
+   This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by
    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.
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.

 
 

-   Bison is distributed in the hope that it will be useful,
+   This program 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
    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, Inc., 59 Temple Place - Suite 330,
-   Boston, MA 02111-1307, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 
 
 /* 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 <config.h>

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

+

 #include "getargs.h"
 #include "getargs.h"

-#include "reader.h"
-#include "types.h"

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

-#include "reduce.h"

 #include "nullable.h"
 #include "nullable.h"

+#include "reduce.h"
+#include "symtab.h"
+
+/* Linked list of rules.  */
+typedef struct rule_list
+{
+  struct rule_list *next;
+  rule *value;
+} rule_list;

 
 

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

 
 static void
 nullable_print (FILE *out)
 
 static void
 nullable_print (FILE *out)


@@ -39,104 +47,96 @@ nullable_print (FILE *out)
   int i;
   fputs ("NULLABLE\n", out);
   for (i = ntokens; i < nsyms; i++)
   int i;
   fputs ("NULLABLE\n", out);
   for (i = ntokens; i < nsyms; i++)

-    fprintf (out, "\t%s: %s\n", tags[i], nullable[i] ? "yes" : "no");
+    fprintf (out, "\t%s: %s\n", symbols[i]->tag,
+            nullable[i - ntokens] ? "yes" : "no");

   fputs ("\n\n", out);
 }
 
 void
   fputs ("\n\n", out);
 }
 
 void

-set_nullable (void)
+nullable_compute (void)

 {
 {

-  short *r;
-  short *s1;
-  short *s2;
-  shorts *p;
-
-  short *squeue;
-  short *rcount;
-  shorts **rsets;
-  shorts *relts;
-
-  if (trace_flag)
-    fprintf (stderr, "Entering set_nullable\n");
-
-  nullable = XCALLOC (char, nvars) - ntokens;
-
-  squeue = XCALLOC (short, nvars);
-  s1 = s2 = squeue;
-
-  rcount = XCALLOC (short, nrules + 1);
+  rule_number ruleno;
+  symbol_number *s1;
+  symbol_number *s2;
+  rule_list *p;

 
 

+  symbol_number *squeue = xnmalloc (nvars, sizeof *squeue);
+  size_t *rcount = xcalloc (nrules, sizeof *rcount);

   /* RITEM contains all the rules, including useless productions.
      Hence we must allocate room for useless nonterminals too.  */
   /* RITEM contains all the rules, including useless productions.
      Hence we must allocate room for useless nonterminals too.  */

-  rsets = XCALLOC (shorts *, nvars + nuseless_nonterminals) - ntokens;
+  rule_list **rsets = xcalloc (nvars, sizeof *rsets);

   /* 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 = XCALLOC (shorts, nitems + nvars + nuseless_nonterminals + 1);
+     Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
+  rule_list *relts = xnmalloc (nritems + nvars + 1, sizeof *relts);
+
+  nullable = xcalloc (nvars, sizeof *nullable);
+
+  s1 = s2 = squeue;

   p = relts;
 
   p = relts;
 

-  for (r = ritem; *r; ++r)
-    {
-      /* Walk RITEM to find (i), if there are any tokens in the
-        RHS, and (ii), to find RULENO. */
-      int ruleno;
-      int any_tokens = 0;
-      short *r1;
-      for (r1 = r; *r1 > 0; ++r1)
-       if (ISTOKEN (*r1))
-         any_tokens = 1;
-      ruleno = -*r1;
-
-      /* Examine the RHS of the rule.  */
-      if (!any_tokens)
-       for (/* Nothing. */; *r > 0; ++r)
+  for (ruleno = 0; ruleno < nrules; ++ruleno)
+    if (rules[ruleno].useful)
+      {
+       rule *rules_ruleno = &rules[ruleno];
+       if (rules_ruleno->rhs[0] >= 0)

          {
          {

-           rcount[ruleno]++;
-           p->next = rsets[*r];
-           p->value = ruleno;
-           rsets[*r] = p;
-           p++;
+           /* This rule has a non empty RHS. */
+           item_number *rp = NULL;
+           bool any_tokens = false;
+           for (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
+             if (ISTOKEN (*rp))
+               any_tokens = true;
+
+           /* This rule has only nonterminals: schedule it for the second
+              pass.  */
+           if (!any_tokens)
+             for (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
+               {
+                 rcount[ruleno]++;
+                 p->next = rsets[*rp - ntokens];
+                 p->value = rules_ruleno;
+                 rsets[*rp - ntokens] = p;
+                 p++;
+               }

          }
          }

-
-      /* Examine its LHS. */
-      if (rule_table[ruleno].useful && !nullable[rule_table[ruleno].lhs])
-       {
-         nullable[rule_table[ruleno].lhs] = 1;
-         *s2++ = rule_table[ruleno].lhs;
-        }
-    }
+       else
+         {
+           /* This rule has an empty RHS. */
+           aver (item_number_as_rule_number (rules_ruleno->rhs[0])
+                 == ruleno);
+           if (rules_ruleno->useful
+               && ! nullable[rules_ruleno->lhs->number - ntokens])
+             {
+               nullable[rules_ruleno->lhs->number - ntokens] = true;
+               *s2++ = rules_ruleno->lhs->number;
+             }
+         }
+      }

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

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

            {
            {

-             int symbol = rule_table[ruleno].lhs;
-             if (symbol >= 0 && !nullable[symbol])
-               {
-                 nullable[symbol] = 1;
-                 *s2++ = symbol;
-               }
+             nullable[r->lhs->number - ntokens] = true;
+             *s2++ = r->lhs->number;

            }
            }

-       }
-    }
+      }

 
 

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

 
 

-  if (trace_flag)
+  if (trace_flag & trace_sets)

     nullable_print (stderr);
 }
 
 
 void
     nullable_print (stderr);
 }
 
 
 void

-free_nullable (void)
+nullable_free (void)

 {
 {

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

 }
 }