First take on custom call generators.

src/top.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 421 matching lines @@
 void Top::ReportFailedAccessCheck(JSObject* receiver, v8::AccessType type) {
   if (!thread_local_.failed_access_check_callback_) return;
 
   ASSERT(receiver->IsAccessCheckNeeded());
   ASSERT(Top::context());
   // The callers of this method are not expecting a GC.
   AssertNoAllocation no_gc;
 
   // Get the data object from access check info.
   JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());
-  Object* info = constructor->shared()->function_data();
-  if (info == Heap::undefined_value()) return;
-
-  Object* data_obj = FunctionTemplateInfo::cast(info)->access_check_info();
+  if (!constructor->shared()->IsApiFunction()) return;
+  Object* data_obj =
+      constructor->shared()->get_api_func_data()->access_check_info();
   if (data_obj == Heap::undefined_value()) return;
 
   HandleScope scope;
   Handle<JSObject> receiver_handle(receiver);
   Handle<Object> data(AccessCheckInfo::cast(data_obj)->data());
   thread_local_.failed_access_check_callback_(
     v8::Utils::ToLocal(receiver_handle),
     type,
     v8::Utils::ToLocal(data));
 }
@@ skipping 39 matching lines @@
 
   // Check for compatibility between the security tokens in the
   // current lexical context and the accessed object.
   ASSERT(Top::context());
 
   MayAccessDecision decision = MayAccessPreCheck(receiver, type);
   if (decision != UNKNOWN) return decision == YES;
 
   // Get named access check callback
   JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());
-  Object* info = constructor->shared()->function_data();
-  if (info == Heap::undefined_value()) return false;
+  if (!constructor->shared()->IsApiFunction()) return false;
 
-  Object* data_obj = FunctionTemplateInfo::cast(info)->access_check_info();
+  Object* data_obj =
+     constructor->shared()->get_api_func_data()->access_check_info();
   if (data_obj == Heap::undefined_value()) return false;
 
   Object* fun_obj = AccessCheckInfo::cast(data_obj)->named_callback();
   v8::NamedSecurityCallback callback =
       v8::ToCData<v8::NamedSecurityCallback>(fun_obj);
 
   if (!callback) return false;
 
   HandleScope scope;
   Handle<JSObject> receiver_handle(receiver);
@@ skipping 21 matching lines @@
   // current lexical context and the accessed object.
   ASSERT(Top::context());
   // The callers of this method are not expecting a GC.
   AssertNoAllocation no_gc;
 
   MayAccessDecision decision = MayAccessPreCheck(receiver, type);
   if (decision != UNKNOWN) return decision == YES;
 
   // Get indexed access check callback
   JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());
-  Object* info = constructor->shared()->function_data();
-  if (info == Heap::undefined_value()) return false;
+  if (!constructor->shared()->IsApiFunction()) return false;
 
-  Object* data_obj = FunctionTemplateInfo::cast(info)->access_check_info();
+  Object* data_obj =
+      constructor->shared()->get_api_func_data()->access_check_info();
   if (data_obj == Heap::undefined_value()) return false;
 
   Object* fun_obj = AccessCheckInfo::cast(data_obj)->indexed_callback();
   v8::IndexedSecurityCallback callback =
       v8::ToCData<v8::IndexedSecurityCallback>(fun_obj);
 
   if (!callback) return false;
 
   HandleScope scope;
   Handle<JSObject> receiver_handle(receiver);
@@ skipping 403 matching lines @@
   Top::break_access_->Lock();
 }
 
 
 ExecutionAccess::~ExecutionAccess() {
   Top::break_access_->Unlock();
 }
 
 
 } }  // namespace v8::internal