Introduce a PrototypeIterator template and use it all over the place

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/bootstrapper.h"
@@ skipping 983 matching lines @@
 
 bool Isolate::IsErrorObject(Handle<Object> obj) {
   if (!obj->IsJSObject()) return false;
 
   Handle<String> error_key =
       factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("$Error"));
   Handle<Object> error_constructor = Object::GetProperty(
       js_builtins_object(), error_key).ToHandleChecked();
 
   DisallowHeapAllocation no_gc;
-  for (Object* prototype = *obj; !prototype->IsNull();
-       prototype = prototype->GetPrototype(this)) {
-    if (!prototype->IsJSObject()) return false;
-    if (JSObject::cast(prototype)->map()->constructor() ==
+  for (PrototypeIterator<STORE_AS_POINTER, TYPE_BASED_WALK, END_AT_NULL_VALUE>
+           iter(this, *obj); !iter.IsAtEnd(); iter.Advance()) {
+    if (!iter.GetCurrent()->IsJSObject()) return false;
+    if (JSObject::cast(iter.GetCurrent())->map()->constructor() ==
         *error_constructor) {
       return true;
     }
   }
   return false;
 }
 
 static int fatal_exception_depth = 0;
 
 void Isolate::DoThrow(Object* exception, MessageLocation* location) {
@@ skipping 1158 matching lines @@
   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();
+  Object* root_array_map_proto = SAFE_GET_PROTOTYPE_FAST(initial_array_proto);
   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();
+  return SAFE_GET_PROTOTYPE_FAST(initial_object_proto)->IsNull();
 }
 
 
 CodeStubInterfaceDescriptor*
     Isolate::code_stub_interface_descriptor(int index) {
   return code_stub_interface_descriptors_ + index;
 }
 
 
 CallInterfaceDescriptor*
@@ skipping 159 matching lines @@
   // The simulator uses a separate JS stack.
   Address jssp_address = Simulator::current(isolate_)->get_sp();
   uintptr_t jssp = reinterpret_cast<uintptr_t>(jssp_address);
   if (jssp < stack_guard->real_jslimit()) return true;
 #endif  // USE_SIMULATOR
   return reinterpret_cast<uintptr_t>(this) < stack_guard->real_climit();
 }
 
 
 } }  // namespace v8::internal