Perform local label lookup

This patch fix the sparse breakage triggered by
rcu_read_lock() lockdep annotations.

Now sparse look up the local label in symbol node
name space as well, just like looking up a normal
symbol node. Now a lable symbol can be both
type SYM_LABEL or SYM_NODE with MOD_LABEL.

Singed-Off-By: Christopher Li <sparse@chrisli.org>

Index: sparse/parse.c
===================================================================
--- sparse.orig/parse.c	2007-10-19 13:52:37.000000000 -0700
+++ sparse/parse.c	2007-10-19 13:55:23.000000000 -0700
@@ -459,6 +459,16 @@ static struct symbol *lookup_or_create_s
 	return sym;
 }
 
+static struct symbol * local_label(struct token *token)
+{
+	struct symbol *sym = lookup_symbol(token->ident, NS_SYMBOL);
+
+	if (sym && sym->ctype.modifiers & MOD_LABEL)
+		return sym;
+
+	return NULL;
+}
+
 /*
  * NOTE! NS_LABEL is not just a different namespace,
  * it also ends up using function scope instead of the
@@ -466,6 +476,9 @@ static struct symbol *lookup_or_create_s
  */
 struct symbol *label_symbol(struct token *token)
 {
+	struct symbol *sym = local_label(token);
+	if (sym)
+		return sym;
 	return lookup_or_create_symbol(NS_LABEL, SYM_LABEL, token);
 }
 
Index: sparse/validation/local-label.c
===================================================================
--- sparse.orig/validation/local-label.c	2007-10-19 13:52:40.000000000 -0700
+++ sparse/validation/local-label.c	2007-10-19 13:52:40.000000000 -0700
@@ -0,0 +1,8 @@
+void f(unsigned long ip);
+static void g(void)
+{
+       if (1) {
+	     f(({ __label__ x; x: (unsigned long)&&x; }));
+       }
+       f(({ __label__ x; x: (unsigned long)&&x; }));
+}