Add fast path in MigrateFastToFast for following transitions that don't extend storage
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
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@ -1946,9 +1946,21 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
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int total_size = number_of_fields + unused;
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int external = total_size - inobject;
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if ((old_map->unused_property_fields() == 0) &&
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(number_of_fields != old_number_of_fields) &&
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(new_map->GetBackPointer() == *old_map)) {
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if (number_of_fields != old_number_of_fields &&
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new_map->GetBackPointer() == *old_map) {
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PropertyDetails details = new_map->GetLastDescriptorDetails();
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if (old_map->unused_property_fields() > 0) {
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if (details.representation().IsDouble()) {
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Handle<Object> value = isolate->factory()->NewHeapNumber(0, MUTABLE);
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FieldIndex index =
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FieldIndex::ForDescriptor(*new_map, new_map->LastAdded());
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object->FastPropertyAtPut(index, *value);
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}
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object->synchronized_set_map(*new_map);
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return;
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}
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DCHECK(number_of_fields == old_number_of_fields + 1);
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// This migration is a transition from a map that has run out out property
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// space. Therefore it could be done by extending the backing store.
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@ -1957,7 +1969,6 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
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FixedArray::CopySize(old_storage, external);
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// Properly initialize newly added property.
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PropertyDetails details = new_map->GetLastDescriptorDetails();
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Handle<Object> value;
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if (details.representation().IsDouble()) {
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value = isolate->factory()->NewHeapNumber(0, MUTABLE);
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