Update from Bruno Haible's 2003-04-14 patch to gnulib.

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index c207924dc8328a9770263d2313451c8e38b66748..cf6cfd68c0831b370c7693e3ddca1c1057ae1ab6 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -1,5 +1,7 @@
-/* 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, 2001, 2002, 2003 Free Software
+   Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -24,13 +26,21 @@
    do so.  */
 
 #include "system.h"
+
 #include "getargs.h"
-#include "reader.h"
-#include "types.h"
 #include "gram.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)
@@ -38,107 +48,96 @@ nullable_print (FILE *out)
   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
-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");
+  rule_number ruleno;
+  symbol_number *s1;
+  symbol_number *s2;
+  rule_list *p;
+
+  symbol_number *squeue = CALLOC (squeue, nvars);
+  short *rcount = CALLOC (rcount, nrules);
+  /* RITEM contains all the rules, including useless productions.
+     Hence we must allocate room for useless nonterminals too.  */
+  rule_list **rsets = CALLOC (rsets, nvars);
+  /* This is said to be more elements than we actually use.
+     Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
+  rule_list *relts = CALLOC (relts, nritems + nvars + 1);
 
-  nullable = XCALLOC (char, nvars) - ntokens;
+  CALLOC (nullable, nvars);
 
-  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)
-       {
-         int symbol = rule_table[-(*r++)].lhs;
-         if (symbol >= 0 && !nullable[symbol])
-           {
-             nullable[symbol] = 1;
-             *s2++ = symbol;
-           }
-       }
-      else
-       {
-         int any_tokens = 0;
-         int symbol;
-         short *r1 = r;
-         for (symbol = *r++; symbol > 0; symbol = *r++)
-           if (ISTOKEN (symbol))
-             any_tokens = 1;
-
-         if (!any_tokens)
-           {
-             int ruleno = -symbol;
-             r = r1;
-             for (symbol = *r++; symbol > 0; symbol = *r++)
+  for (ruleno = 0; ruleno < nrules; ++ruleno)
+    if (rules[ruleno].useful)
+      {
+       rule *rules_ruleno = &rules[ruleno];
+       if (rules_ruleno->rhs[0] >= 0)
+         {
+           /* This rule has a non empty RHS. */
+           item_number *rp = NULL;
+           int any_tokens = 0;
+           for (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
+             if (ISTOKEN (*rp))
+               any_tokens = 1;
+
+           /* 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[symbol];
-                 p->value = ruleno;
-                 rsets[symbol] = p;
+                 p->next = rsets[*rp - ntokens];
+                 p->value = rules_ruleno;
+                 rsets[*rp - ntokens] = p;
                  p++;
                }
-           }
-       }
-    }
+         }
+       else
+         {
+           /* This rule has an empty RHS. */
+           if (item_number_as_rule_number (rules_ruleno->rhs[0]) != ruleno)
+             abort ();
+           if (rules_ruleno->useful
+               && ! nullable[rules_ruleno->lhs->number - ntokens])
+             {
+               nullable[rules_ruleno->lhs->number - ntokens] = 1;
+               *s2++ = rules_ruleno->lhs->number;
+             }
+         }
+      }
 
   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] = 1;
+             *s2++ = r->lhs->number;
            }
-       }
-    }
+      }
 
   XFREE (squeue);
   XFREE (rcount);
-  XFREE (rsets + ntokens);
+  XFREE (rsets);
   XFREE (relts);
 
-  if (trace_flag)
+  if (trace_flag & trace_sets)
     nullable_print (stderr);
 }
 
 
 void
-free_nullable (void)
+nullable_free (void)
 {
-  XFREE (nullable + ntokens);
+  XFREE (nullable);
 }