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Add fast path in MigrateFastToFast for following transitions that don't extend storage

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BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/588553002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24087 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
verwaest@chromium.org 2014-09-19 13:39:55 +00:00
parent f7329c62ea
commit 5d0b12db8e
1 changed files with 15 additions and 4 deletions
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19
src/objects.cc
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@ -1946,9 +1946,21 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
int total_size = number_of_fields + unused; int total_size = number_of_fields + unused;
int external = total_size - inobject; int external = total_size - inobject;
if ((old_map->unused_property_fields() == 0) && if (number_of_fields != old_number_of_fields &&
(number_of_fields != old_number_of_fields) && new_map->GetBackPointer() == *old_map) {
(new_map->GetBackPointer() == *old_map)) { PropertyDetails details = new_map->GetLastDescriptorDetails();
if (old_map->unused_property_fields() > 0) {
if (details.representation().IsDouble()) {
Handle<Object> value = isolate->factory()->NewHeapNumber(0, MUTABLE);
FieldIndex index =
FieldIndex::ForDescriptor(*new_map, new_map->LastAdded());
object->FastPropertyAtPut(index, *value);
}
object->synchronized_set_map(*new_map);
return;
}
DCHECK(number_of_fields == old_number_of_fields + 1); DCHECK(number_of_fields == old_number_of_fields + 1);
// This migration is a transition from a map that has run out out property // This migration is a transition from a map that has run out out property
// space. Therefore it could be done by extending the backing store. // space. Therefore it could be done by extending the backing store.
@ -1957,7 +1969,6 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
FixedArray::CopySize(old_storage, external); FixedArray::CopySize(old_storage, external);
// Properly initialize newly added property. // Properly initialize newly added property.
PropertyDetails details = new_map->GetLastDescriptorDetails();
Handle<Object> value; Handle<Object> value;
if (details.representation().IsDouble()) { if (details.representation().IsDouble()) {
value = isolate->factory()->NewHeapNumber(0, MUTABLE); value = isolate->factory()->NewHeapNumber(0, MUTABLE);