[runtime] Avoid prefix PrepareForDataProperty in TransitionToDataProperty

BUG=

Review URL: https://codereview.chromium.org/1700903002

Cr-Commit-Position: refs/heads/master@{#34018}

src/objects.cc

@@ -3164,8 +3164,14 @@ void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
   // respective prototypes.
   UpdatePrototypeUserRegistration(old_map, new_map, new_map->GetIsolate());
 
-  if (object->HasFastProperties()) {
-    if (!new_map->is_dictionary_map()) {
+  if (old_map->is_dictionary_map()) {
+    // For slow-to-fast migrations JSObject::MigrateSlowToFast()
+    // must be used instead.
+    CHECK(new_map->is_dictionary_map());
+
+    // Slow-to-slow migration is trivial.
+    object->set_map(*new_map);
+  } else if (!new_map->is_dictionary_map()) {
     MigrateFastToFast(object, new_map);
     if (old_map->is_prototype_map()) {
       DCHECK(!old_map->is_stable());
@@ -3176,21 +3182,13 @@ void JSObject::MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
           old_map->GetHeap()->empty_descriptor_array(),
           LayoutDescriptor::FastPointerLayout());
       // Ensure that no transition was inserted for prototype migrations.
-        DCHECK_EQ(0, TransitionArray::NumberOfTransitions(
-                         old_map->raw_transitions()));
+      DCHECK_EQ(
+          0, TransitionArray::NumberOfTransitions(old_map->raw_transitions()));
       DCHECK(new_map->GetBackPointer()->IsUndefined());
     }
   } else {
     MigrateFastToSlow(object, new_map, expected_additional_properties);
   }
-  } else {
-    // For slow-to-fast migrations JSObject::MigrateSlowToFast()
-    // must be used instead.
-    CHECK(new_map->is_dictionary_map());
-
-    // Slow-to-slow migration is trivial.
-    object->set_map(*new_map);
-  }
 
   // Careful: Don't allocate here!
   // For some callers of this method, |object| might be in an inconsistent
@@ -9930,28 +9928,32 @@ bool DescriptorArray::CanHoldValue(int descriptor, Object* value) {
   return false;
 }
 
+namespace {
 
-// static
-Handle<Map> Map::PrepareForDataProperty(Handle<Map> map, int descriptor,
+Handle<Map> UpdateDescriptorForValue(Handle<Map> map, int descriptor,
                                      Handle<Object> value) {
-  // Dictionaries can store any property value.
-  if (map->is_dictionary_map()) return map;
-
-  // Migrate to the newest map before storing the property.
-  map = Update(map);
-
-  Handle<DescriptorArray> descriptors(map->instance_descriptors());
-
-  if (descriptors->CanHoldValue(descriptor, *value)) return map;
+  if (map->instance_descriptors()->CanHoldValue(descriptor, *value)) return map;
 
   Isolate* isolate = map->GetIsolate();
   PropertyAttributes attributes =
-      descriptors->GetDetails(descriptor).attributes();
+      map->instance_descriptors()->GetDetails(descriptor).attributes();
   Representation representation = value->OptimalRepresentation();
   Handle<FieldType> type = value->OptimalType(isolate, representation);
 
-  return ReconfigureProperty(map, descriptor, kData, attributes, representation,
-                             type, FORCE_FIELD);
+  return Map::ReconfigureProperty(map, descriptor, kData, attributes,
+                                  representation, type, FORCE_FIELD);
+}
+
+}  // namespace
+
+// static
+Handle<Map> Map::PrepareForDataProperty(Handle<Map> map, int descriptor,
+                                        Handle<Object> value) {
+  // Dictionaries can store any property value.
+  if (map->is_dictionary_map()) return map;
+
+  // Update to the newest map before storing the property.
+  return UpdateDescriptorForValue(Update(map), descriptor, value);
 }
 
 
@@ -9975,7 +9977,7 @@ Handle<Map> Map::TransitionToDataProperty(Handle<Map> map, Handle<Name> name,
                               ->GetDetails(descriptor)
                               .attributes());
 
-    return Map::PrepareForDataProperty(transition, descriptor, value);
+    return UpdateDescriptorForValue(transition, descriptor, value);
   }
 
   TransitionFlag flag = INSERT_TRANSITION;