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Clear Map::constructor to object_function from the same context for prototype maps. This avoids keeping small pockets of memory alive for the common pattern where prototypes are used to emulate classes:

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function inherit(parent, child) {
  function p() {}
  p.prototype = parent.prototype;
  child.prototype = new p();
}

Otherwise child.prototype[constructor] keeps alive p, p's context, the
initial map attached to p, and the (now empty) transition array of the
initial map.

BUG=

Review URL: https://codereview.chromium.org/942493002

Cr-Commit-Position: refs/heads/master@{#26747}
This commit is contained in:
verwaest 2015-02-19 05:01:52 -08:00 committed by Commit bot
parent 8e241468ed
commit e758a36b02
1 changed files with 13 additions and 0 deletions
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13
src/objects.cc
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@ -9976,6 +9976,19 @@ void JSObject::OptimizeAsPrototype(Handle<JSObject> object,
Handle<Map> new_map = Map::Copy(handle(object->map()), "CopyAsPrototype");
JSObject::MigrateToMap(object, new_map);
}
if (object->map()->constructor()->IsJSFunction()) {
JSFunction* constructor = JSFunction::cast(object->map()->constructor());
// Replace the pointer to the exact constructor with the Object function
// from the same context if undetectable from JS. This is to avoid keeping
// memory alive unnecessarily.
if (!constructor->shared()->IsApiFunction() &&
object->class_name() ==
object->GetIsolate()->heap()->Object_string()) {
Context* context = constructor->context()->native_context();
JSFunction* object_function = context->object_function();
object->map()->set_constructor(object_function);
}
}
object->map()->set_is_prototype_map(true);
}
}