Elide hole checks on KeyedLoads of holey double arrays.

src/isolate.cc

 // Copyright 2012 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 2425 matching lines @@
   return hstatistics();
 }
 
 
 HTracer* Isolate::GetHTracer() {
   if (htracer() == NULL) set_htracer(new HTracer(id()));
   return htracer();
 }
 
 
+Map* Isolate::get_initial_js_array_map(ElementsKind kind) {
+  Context* native_context = context()->native_context();
+  Object* maybe_map_array = native_context->js_array_maps();
+  if (!maybe_map_array->IsUndefined()) {
+    Object* maybe_transitioned_map =
+        FixedArray::cast(maybe_map_array)->get(kind);
+    if (!maybe_transitioned_map->IsUndefined()) {
+      return Map::cast(maybe_transitioned_map);
+    }
+  }
+  return NULL;
+}
+
+
+bool Isolate::IsFastArrayConstructorPrototypeChainIntact() {
+  Map* root_array_map =

[ulan, 2013/05/10 14:34:25]

Can root_array_map be NULL here?

[danno, 2013/05/10 14:40:12]

Done.

+      get_initial_js_array_map(GetInitialFastElementsKind());
+  JSObject* initial_array_proto = JSObject::cast(*initial_array_prototype());
+
+  // Check that the array prototype hasn't been altered WRT empty elements.
+  if (root_array_map->prototype() != initial_array_proto) return false;
+  if (initial_array_proto->elements() != heap()->empty_fixed_array()) {
+    return false;
+  }
+
+  // Check that the object prototype hasn't been altered WRT empty elements.
+  JSObject* initial_object_proto = JSObject::cast(*initial_object_prototype());
+  Object* root_array_map_proto = initial_array_proto->GetPrototype();
+  if (root_array_map_proto != initial_object_proto) return false;
+  if (initial_object_proto->elements() != heap()->empty_fixed_array()) {
+    return false;
+  }
+
+  return initial_object_proto->GetPrototype()->IsNull();
+}
+
+
 CodeStubInterfaceDescriptor*
     Isolate::code_stub_interface_descriptor(int index) {
   return code_stub_interface_descriptors_ + index;
 }
 
 
 #ifdef DEBUG
 #define ISOLATE_FIELD_OFFSET(type, name, ignored)                       \
 const intptr_t Isolate::name##_debug_offset_ = OFFSET_OF(Isolate, name##_);
 ISOLATE_INIT_LIST(ISOLATE_FIELD_OFFSET)
 ISOLATE_INIT_ARRAY_LIST(ISOLATE_FIELD_OFFSET)
 #undef ISOLATE_FIELD_OFFSET
 #endif
 
 } }  // namespace v8::internal