* src/LR0.c, src/derives.c, src/gram.c, src/gram.h, src/lalr.c,

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index 4568114f9f84b3f64f92c8c50f8895f5746327c3..42e398b34624b92f865f1ba86019bd5385ef30ca 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -24,107 +24,105 @@
    do so.  */
 
 #include "system.h"
+#include "getargs.h"
+#include "symtab.h"
 #include "types.h"
 #include "gram.h"
+#include "reduce.h"
 #include "nullable.h"
 
 char *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
 set_nullable (void)
 {
-  short *r;
-  short *s1;
-  short *s2;
   int ruleno;
-  int symbol;
+  symbol_number_t *s1;
+  symbol_number_t *s2;
   shorts *p;
 
-  short *squeue;
-  short *rcount;
-  shorts **rsets;
-  shorts *relts;
-  char any_tokens;
-  short *r1;
+  symbol_number_t *squeue = XCALLOC (symbol_number_t, nvars);
+  short *rcount = XCALLOC (short, nrules + 1);
+  /* RITEM contains all the rules, including useless productions.
+     Hence we must allocate room for useless nonterminals too.  */
+  shorts **rsets = XCALLOC (shorts *, nvars) - ntokens;
+  /* This is said to be more elements than we actually use.
+     Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
+  shorts *relts = XCALLOC (shorts, nritems + nvars + 1);
 
-#ifdef TRACE
-  fprintf (stderr, "Entering set_nullable\n");
-#endif
+  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);
-  rsets = XCALLOC (shorts *, 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);
   p = relts;
 
-  r = ritem;
-  while (*r)
-    {
-      if (*r < 0)
-       {
-         symbol = rule_table[-(*r++)].lhs;
-         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 = 1; ruleno < nrules + 1; ++ruleno)
+    if (rules[ruleno].useful)
+      {
+       if (rules[ruleno].rhs[0] >= 0)
+         {
+           /* This rule has a non empty RHS. */
+           item_number_t *r;
+           int any_tokens = 0;
+           for (r = rules[ruleno].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 = rules[ruleno].rhs; *r >= 0; ++r)
                {
                  rcount[ruleno]++;
-                 p->next = rsets[symbol];
+                 p->next = rsets[*r];
                  p->value = ruleno;
-                 rsets[symbol] = p;
+                 rsets[*r] = p;
                  p++;
                }
-           }
-       }
-    }
+         }
+       else
+         {
+           /* This rule has an empty RHS. */
+           assert (rules[ruleno].rhs[0] == -ruleno);
+           if (rules[ruleno].useful && !nullable[rules[ruleno].lhs->number])
+             {
+               nullable[rules[ruleno].lhs->number] = 1;
+               *s2++ = rules[ruleno].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)
+      {
+       ruleno = p->value;
+       if (--rcount[ruleno] == 0)
+         if (rules[ruleno].useful && !nullable[rules[ruleno].lhs->number])
            {
-             symbol = rule_table[ruleno].lhs;
-             if (symbol >= 0 && !nullable[symbol])
-               {
-                 nullable[symbol] = 1;
-                 *s2++ = symbol;
-               }
+             nullable[rules[ruleno].lhs->number] = 1;
+             *s2++ = rules[ruleno].lhs->number;
            }
-       }
-    }
+      }
 
   XFREE (squeue);
   XFREE (rcount);
   XFREE (rsets + ntokens);
   XFREE (relts);
+
+  if (trace_flag)
+    nullable_print (stderr);
 }