Rename CurrentMapForDeprecated to TryUpdate, and introduce Map::Update which potentially deprecates

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/401243003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22510 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ast.h

@@ -265,7 +265,7 @@ class SmallMapList V8_FINAL {
   int length() const { return list_.length(); }
 
   void AddMapIfMissing(Handle<Map> map, Zone* zone) {
-    if (!Map::CurrentMapForDeprecated(map).ToHandle(&map)) return;
+    if (!Map::TryUpdate(map).ToHandle(&map)) return;
     for (int i = 0; i < length(); ++i) {
       if (at(i).is_identical_to(map)) return;
     }

src/objects.cc

@@ -2861,7 +2861,7 @@ Handle<Map> Map::GeneralizeAllFieldRepresentations(
 
 
 // static
-MaybeHandle<Map> Map::CurrentMapForDeprecated(Handle<Map> map) {
+MaybeHandle<Map> Map::TryUpdate(Handle<Map> map) {
   Handle<Map> proto_map(map);
   while (proto_map->prototype()->IsJSObject()) {
     Handle<JSObject> holder(JSObject::cast(proto_map->prototype()));
@@ -2870,12 +2870,20 @@ MaybeHandle<Map> Map::CurrentMapForDeprecated(Handle<Map> map) {
       proto_map = Handle<Map>(holder->map());
     }
   }
-  return CurrentMapForDeprecatedInternal(map);
+  return TryUpdateInternal(map);
 }
 
 
 // static
-MaybeHandle<Map> Map::CurrentMapForDeprecatedInternal(Handle<Map> old_map) {
+Handle<Map> Map::Update(Handle<Map> map) {
+  return GeneralizeRepresentation(map, 0, Representation::None(),
+                                  HeapType::None(map->GetIsolate()),
+                                  ALLOW_AS_CONSTANT);
+}
+
+
+// static
+MaybeHandle<Map> Map::TryUpdateInternal(Handle<Map> old_map) {
   DisallowHeapAllocation no_allocation;
   DisallowDeoptimization no_deoptimization(old_map->GetIsolate());
 
@@ -3940,17 +3948,12 @@ void JSObject::AllocateStorageForMap(Handle<JSObject> object, Handle<Map> map) {
 
 
 void JSObject::MigrateInstance(Handle<JSObject> object) {
-  // Converting any field to the most specific type will cause the
-  // GeneralizeFieldRepresentation algorithm to create the most general existing
-  // transition that matches the object. This achieves what is needed.
   Handle<Map> original_map(object->map());
-  GeneralizeFieldRepresentation(
-      object, 0, Representation::None(),
-      HeapType::None(object->GetIsolate()),
-      ALLOW_AS_CONSTANT);
-  object->map()->set_migration_target(true);
+  Handle<Map> map = Map::Update(original_map);
+  map->set_migration_target(true);
+  MigrateToMap(object, map);
   if (FLAG_trace_migration) {
-    object->PrintInstanceMigration(stdout, *original_map, object->map());
+    object->PrintInstanceMigration(stdout, *original_map, *map);
   }
 }
 
@@ -3961,7 +3964,7 @@ bool JSObject::TryMigrateInstance(Handle<JSObject> object) {
   DisallowDeoptimization no_deoptimization(isolate);
   Handle<Map> original_map(object->map(), isolate);
   Handle<Map> new_map;
-  if (!Map::CurrentMapForDeprecatedInternal(original_map).ToHandle(&new_map)) {
+  if (!Map::TryUpdate(original_map).ToHandle(&new_map)) {
     return false;
   }
   JSObject::MigrateToMap(object, new_map);
@@ -7326,11 +7329,7 @@ Handle<Map> Map::PrepareForDataProperty(Handle<Map> map, int descriptor,
   if (map->is_dictionary_map()) return map;
 
   // Migrate to the newest map before storing the property.
-  if (map->is_deprecated()) {
-    map = GeneralizeRepresentation(map, 0, Representation::None(),
-                                   HeapType::None(map->GetIsolate()),
-                                   ALLOW_AS_CONSTANT);
-  }
+  if (map->is_deprecated()) map = Update(map);
 
   Handle<DescriptorArray> descriptors(map->instance_descriptors());
 
@@ -7353,11 +7352,7 @@ Handle<Map> Map::TransitionToDataProperty(Handle<Map> map, Handle<Name> name,
   if (map->is_dictionary_map()) return map;
 
   // Migrate to the newest map before transitioning to the new property.
-  if (map->is_deprecated()) {
-    map = GeneralizeRepresentation(map, 0, Representation::None(),
-                                   HeapType::None(map->GetIsolate()),
-                                   ALLOW_AS_CONSTANT);
-  }
+  if (map->is_deprecated()) map = Update(map);
 
   int index = map->SearchTransition(*name);
   if (index != TransitionArray::kNotFound) {

src/objects.h

@@ -6451,12 +6451,16 @@ class Map: public HeapObject {
   // is found by re-transitioning from the root of the transition tree using the
   // descriptor array of the map. Returns NULL if no updated map is found.
   // This method also applies any pending migrations along the prototype chain.
-  static MaybeHandle<Map> CurrentMapForDeprecated(Handle<Map> map)
-      V8_WARN_UNUSED_RESULT;
+  static MaybeHandle<Map> TryUpdate(Handle<Map> map) V8_WARN_UNUSED_RESULT;
   // Same as above, but does not touch the prototype chain.
-  static MaybeHandle<Map> CurrentMapForDeprecatedInternal(Handle<Map> map)
+  static MaybeHandle<Map> TryUpdateInternal(Handle<Map> map)
       V8_WARN_UNUSED_RESULT;
 
+  // Returns a non-deprecated version of the input. This method may deprecate
+  // existing maps along the way if encodings conflict. Not for use while
+  // gathering type feedback. Use TryUpdate in those cases instead.
+  static Handle<Map> Update(Handle<Map> map);
+
   static Handle<Map> CopyDropDescriptors(Handle<Map> map);
   static Handle<Map> CopyInsertDescriptor(Handle<Map> map,
                                           Descriptor* descriptor,

src/type-info.cc

@@ -200,7 +200,7 @@ void TypeFeedbackOracle::CompareType(TypeFeedbackId id,
   Handle<Map> map;
   Map* raw_map = code->FindFirstMap();
   if (raw_map != NULL) {
-    if (Map::CurrentMapForDeprecated(handle(raw_map)).ToHandle(&map) &&
+    if (Map::TryUpdate(handle(raw_map)).ToHandle(&map) &&
         CanRetainOtherContext(*map, *native_context_)) {
       map = Handle<Map>::null();
     }