Improved version of LookupForRead (tnx to Kasper) + some faster paths....

src/ic.cc

 // Copyright 2006-2009 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 255 matching lines @@
 
 
 static bool HasInterceptorGetter(JSObject* object) {
   return !object->GetNamedInterceptor()->getter()->IsUndefined();
 }
 
 
 static void LookupForRead(Object* object,
                           String* name,
                           LookupResult* lookup) {
-  object->Lookup(name, lookup);
-  if (lookup->IsNotFound() || lookup->type() != INTERCEPTOR) {
-    return;
+  AssertNoAllocation no_gc;  // pointers must stay valid
+
+  // Skip all the objects with named interceptors, but
+  // without actual getter.
+  while (true) {
+    object->Lookup(name, lookup);
+    // Besides normal conditions (property not found or it's not
+    // an interceptor), bail out of lookup is not cacheable: we won't
+    // be able to IC it anyway and regular lookup should work fine.
+    if (lookup->IsNotFound() || lookup->type() != INTERCEPTOR ||
+        !lookup->IsCacheable()) {
+      return;
+    }
+
+    JSObject* holder = lookup->holder();
+    if (HasInterceptorGetter(holder)) {
+      return;
+    }
+
+    holder->LocalLookupRealNamedProperty(name, lookup);
+    if (lookup->IsValid()) {
+      ASSERT(lookup->type() != INTERCEPTOR);
+      return;
+    }
+
+    Object* proto = holder->GetPrototype();
+    if (proto->IsNull()) {
+      lookup->NotFound();
+      return;
+    }
+
+    object = proto;
   }
-
-  JSObject* holder = lookup->holder();
-  if (HasInterceptorGetter(holder)) {
-    return;
-  }
-
-  // There is no getter, just skip it and lookup down the proto chain
-  holder->LocalLookupRealNamedProperty(name, lookup);
-  if (lookup->IsValid()) {
-    return;
-  }
-
-  Object* proto = holder->GetPrototype();
-  if (proto == Heap::null_value()) {
-    return;
-  }
-
-  LookupForRead(proto, name, lookup);
 }
 
 
 Object* CallIC::TryCallAsFunction(Object* object) {
   HandleScope scope;
   Handle<Object> target(object);
   Handle<Object> delegate = Execution::GetFunctionDelegate(target);
 
   if (delegate->IsJSFunction()) {
     // Patch the receiver and use the delegate as the function to
@@ skipping 1047 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal