Refactor copying of maps and descriptor arrays.

src/runtime.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 2162 matching lines @@
     // Construct a new field descriptor with updated attributes.
     DescriptorArray* instance_desc = function->map()->instance_descriptors();
     int index = instance_desc->Search(name);
     ASSERT(index != DescriptorArray::kNotFound);
     PropertyDetails details = instance_desc->GetDetails(index);
     CallbacksDescriptor new_desc(name,
         instance_desc->GetValue(index),
         static_cast<PropertyAttributes>(details.attributes() | READ_ONLY),
         details.index());
     // Construct a new field descriptors array containing the new descriptor.
-    Object* descriptors_unchecked;
-    { MaybeObject* maybe_descriptors_unchecked =
-        instance_desc->CopyInsert(&new_desc);
-      if (!maybe_descriptors_unchecked->ToObject(&descriptors_unchecked)) {
-        return maybe_descriptors_unchecked;
-      }
+    DescriptorArray* new_descriptors;
+    { MaybeObject* maybe_descriptors = instance_desc->CopyInsert(&new_desc);
+      if (!maybe_descriptors->To(&new_descriptors)) return maybe_descriptors;
     }
-    DescriptorArray* new_descriptors =
-        DescriptorArray::cast(descriptors_unchecked);
     // Create a new map featuring the new field descriptors array.
     Map* new_map;
-    { MaybeObject* maybe_map_unchecked =
-          function->map()->CopyDropDescriptors();
-      if (!maybe_map_unchecked->To(&new_map)) {
-        return maybe_map_unchecked;
-      }
+    { MaybeObject* maybe_map =
+          function->map()->CopyReplaceDescriptors(new_descriptors);
+      if (!maybe_map->To(&new_map)) return maybe_map;
     }
-    new_map->set_instance_descriptors(new_descriptors);
     function->set_map(new_map);
   } else {  // Dictionary properties.
     // Directly manipulate the property details.
     int entry = function->property_dictionary()->FindEntry(name);
     ASSERT(entry != StringDictionary::kNotFound);
     PropertyDetails details = function->property_dictionary()->DetailsAt(entry);
     PropertyDetails new_details(
         static_cast<PropertyAttributes>(details.attributes() | READ_ONLY),
         details.type(),
         details.index());
@@ skipping 11508 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal