Version 1.75a.

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index 7240132f526e04914b81d359c23252211d3a7032..c0b60f64d40235e653e2f9b7033030341d0d0580 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -1,5 +1,5 @@
 /* Part of the bison parser generator,
-   Copyright 1984, 1989, 2000 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.
 
@@ -24,113 +24,114 @@
    do so.  */
 
 #include "system.h"
-#include "types.h"
+#include "getargs.h"
+#include "symtab.h"
 #include "gram.h"
-#include "xalloc.h"
+#include "reduce.h"
 #include "nullable.h"
 
-char *nullable = NULL;
+/* Linked list of rules.  */
+typedef struct rule_list_s
+{
+  struct rule_list_s *next;
+  rule_t *value;
+} rule_list_t;
 
-void
-set_nullable (void)
+bool *nullable = NULL;
+
+static void
+nullable_print (FILE *out)
 {
-  short *r;
-  short *s1;
-  short *s2;
-  int ruleno;
-  int symbol;
-  shorts *p;
-
-  short *squeue;
-  short *rcount;
-  shorts **rsets;
-  shorts *relts;
-  char any_tokens;
-  short *r1;
-
-#ifdef TRACE
-  fprintf (stderr, _("Entering set_nullable"));
-#endif
-
-  nullable = XCALLOC (char, nvars) - ntokens;
-
-  squeue = XCALLOC (short, nvars);
-  s1 = s2 = squeue;
+  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);
+}
 
-  rcount = XCALLOC (short, nrules + 1);
-  rsets = XCALLOC (shorts *, nvars) - ntokens;
+void
+nullable_compute (void)
+{
+  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.
-     Supposedly nitems - nrules is enough.
-     But why take the risk?  */
-  relts = XCALLOC (shorts, nitems + nvars + 1);
+     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;
 
-  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;
-           }
 
-         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]++;
-                 p->next = rsets[symbol];
-                 p->value = ruleno;
-                 rsets[symbol] = p;
+                 p->next = rsets[*r];
+                 p->value = rule;
+                 rsets[*r] = 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)
-    {
-      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);
+
+  if (trace_flag & trace_sets)
+    nullable_print (stderr);
 }
 
 
 void
-free_nullable (void)
+nullable_free (void)
 {
   XFREE (nullable + ntokens);
 }