ObjC: get rid of another unnecessary, temporary copy of instance variables

["Nicola Pero" <nicola dot pero at meta-innovation dot com>]

This patch for the Objective-C compiler gets rid of another case where
we'd create a temporary tree chain with a copy of all the instance variables
of a class just to do a simple check on them.

The check is the one to check the scope of the instance variable that is
being accessed; without this patch, the check requires copying all the
instance variables for the class on a temporary tree chain.  With this
patch, the check is done (as you'd expect) on the instance variables
themselves, without copying them.

This is obviously faster; on the other hand, the typical GNUstep-based ObjC file
has classes with few instance variables (maybe 10 or 20) and only accesses instance
variables up to a few hundred times per file, so the speedup is only of the order
of 0.1% to 0.2% even with -fsyntax-only.  Of course, in unusual cases (ie, classes
with many instance variables, and a big file accessing instance variables lots of
times) the speedup may be bigger.

Ok to commit ?

Thanks

Index: ChangeLog
===================================================================
--- ChangeLog   (revision 172511)
+++ ChangeLog   (working copy)
@@ -1,5 +1,10 @@
 2011-04-15  Nicola Pero  <nicola.pero@meta-innovation.com>
 
+       * objc-act.c (ivar_of_class): New.
+       (objc_is_public): Use ivar_of_class.
+
+2011-04-15  Nicola Pero  <nicola.pero@meta-innovation.com>
+
        * objc-act.c (objc_get_interface_ivars): Removed.
        (objc_detect_field_duplicates): New.
        (hash_instance_variable): New.
Index: objc-act.c
===================================================================
--- objc-act.c  (revision 172511)
+++ objc-act.c  (working copy)
@@ -6367,6 +6367,35 @@ is_private (tree decl)
                        DECL_NAME (decl)));
 }
 
+/* Searches all the instance variables of 'klass' and of its
+   superclasses for an instance variable whose name (identifier) is
+   'ivar_name_ident'.  Return the declaration (DECL) of the instance
+   variable, if found, or NULL_TREE, if not found.  */
+static inline tree
+ivar_of_class (tree klass, tree ivar_name_ident)
+{
+  /* First, look up the ivar in CLASS_RAW_IVARS.  */
+  tree decl_chain = CLASS_RAW_IVARS (klass);
+
+  for ( ; decl_chain; decl_chain = DECL_CHAIN (decl_chain))
+    if (DECL_NAME (decl_chain) == ivar_name_ident)
+      return decl_chain;
+
+  /* If not found, search up the class hierarchy.  */
+  while (CLASS_SUPER_NAME (klass))
+    {
+      klass = lookup_interface (CLASS_SUPER_NAME (klass));
+      
+      decl_chain = CLASS_RAW_IVARS (klass);
+  
+      for ( ; decl_chain; decl_chain = DECL_CHAIN (decl_chain))
+       if (DECL_NAME (decl_chain) == ivar_name_ident)
+         return decl_chain;
+    }
+
+  return NULL_TREE;
+}
+
 /* We have an instance variable reference;, check to see if it is public.  */
 
 int
@@ -6397,7 +6426,7 @@ objc_is_public (tree expr, tree identifier)
              return 0;
            }
 
-         if ((decl = is_ivar (get_class_ivars (klass, true), identifier)))
+         if ((decl = ivar_of_class (klass, identifier)))
            {
              if (TREE_PUBLIC (decl))
                return 1;