ObjC: do not prepare instance variables for output unless there is an actual error message to print

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

This is another very small optimization.  Whenever the ObjC compiler
found an instance variable, it was preparing it for printing it
in error messages.

Of course, in the typical ObjC compilation run with Foundation and AppKit
the compiler will see about 1.5k instance variables, none of which will
generate any error message (in most cases), so this patch changes the
compiler to only do the work for pretty printing when there is an actual
error message to print.

The speedup is tiny.

Ok to commit ?

Thanks

Index: ChangeLog
===================================================================
--- ChangeLog   (revision 172254)
+++ ChangeLog   (working copy)
@@ -1,3 +1,10 @@
+2011-04-11  Nicola Pero  <nicola.pero@meta-innovation.com>
+
+       * objc-act.c (printable_ivar_name): New.
+       (add_instance_variable): Call printable_ivar_name() when an error
+       message needs to be printed.  Do not prepare the instance variable
+       for printing unless there is an actual error.
+
 2011-04-06  Joseph Myers  <joseph@codesourcery.com>
 
        * objc-act.c: Include c-target.h instead of target.h.
Index: objc-act.c
===================================================================
--- objc-act.c  (revision 172254)
+++ objc-act.c  (working copy)
@@ -5974,6 +5974,17 @@ flexible_array_type_p (tree type)
 }
 #endif
 
+/* Produce a printable version of an ivar name.  This is only used
+   inside add_instance_variable.  */
+static const char *
+printable_ivar_name (tree field_decl)
+{
+  if (DECL_NAME (field_decl))
+    return identifier_to_locale (IDENTIFIER_POINTER (DECL_NAME (field_decl)));
+  else
+    return _("<unnamed>");
+}
+
 /* Called after parsing each instance variable declaration. Necessary to
    preserve typedefs and implement public/private...
 
@@ -5984,15 +5995,12 @@ add_instance_variable (tree klass, objc_ivar_visib
                       tree field_decl)
 {
   tree field_type = TREE_TYPE (field_decl);
-  const char *ivar_name = DECL_NAME (field_decl)
-                         ? identifier_to_locale (IDENTIFIER_POINTER (DECL_NAME (field_decl)))
-                         : _("<unnamed>");
 
 #ifdef OBJCPLUS
   if (TREE_CODE (field_type) == REFERENCE_TYPE)
     {
       error ("illegal reference type specified for instance variable %qs",
-            ivar_name);
+            printable_ivar_name (field_decl));
       /* Return class as is without adding this ivar.  */
       return klass;
     }
@@ -6002,7 +6010,8 @@ add_instance_variable (tree klass, objc_ivar_visib
       || TYPE_SIZE (field_type) == error_mark_node)
       /* 'type[0]' is allowed, but 'type[]' is not! */
     {
-      error ("instance variable %qs has unknown size", ivar_name);
+      error ("instance variable %qs has unknown size",
+            printable_ivar_name (field_decl));
       /* Return class as is without adding this ivar.  */
       return klass;
     }
@@ -6022,7 +6031,8 @@ add_instance_variable (tree klass, objc_ivar_visib
        to calculate the offset of the next instance variable.  */
   if (flexible_array_type_p (field_type))
     {
-      error ("instance variable %qs uses flexible array member", ivar_name);
+      error ("instance variable %qs uses flexible array member",
+            printable_ivar_name (field_decl));
       /* Return class as is without adding this ivar.  */
       return klass;      
     }
@@ -6069,7 +6079,7 @@ add_instance_variable (tree klass, objc_ivar_visib
              error ("type %qE has virtual member functions", type_name);
              error ("illegal aggregate type %qE specified "
                     "for instance variable %qs",
-                    type_name, ivar_name);
+                    type_name, printable_ivar_name (field_decl));
              /* Return class as is without adding this ivar.  */
              return klass;
            }