Reviewers: Hannes Payer,
Message:
PTAL
Description:
Avoid adjusting live bytes in JSObject::MigrateFastToFast() if the size
delta is
zero.
BUG=chromium:388880
LOG=N
Please review this at https://codereview.chromium.org/333903003/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+11, -8 lines):
M src/objects.cc
Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index
6a437d6b0a8b04d671ad493d1111e84af8dafdbe..aab918e231badf963241cf7e08c564180bdb5e86
100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2248,12 +2248,6 @@ void JSObject::MigrateFastToFast(Handle<JSObject>
object, Handle<Map> new_map) {
object->FastPropertyAtPut(index, array->get(external + i));
}
- // Create filler object past the new instance size.
- int new_instance_size = new_map->instance_size();
- int instance_size_delta = old_map->instance_size() - new_instance_size;
- ASSERT(instance_size_delta >= 0);
- Address address = object->address() + new_instance_size;
-
Heap* heap = isolate->heap();
// If there are properties in the new backing store, trim it to the
correct
@@ -2263,8 +2257,17 @@ void JSObject::MigrateFastToFast(Handle<JSObject>
object, Handle<Map> new_map) {
object->set_properties(*array);
}
- heap->CreateFillerObjectAt(address, instance_size_delta);
- heap->AdjustLiveBytes(address, -instance_size_delta, Heap::FROM_MUTATOR);
+ // Create filler object past the new instance size.
+ int new_instance_size = new_map->instance_size();
+ int instance_size_delta = old_map->instance_size() - new_instance_size;
+ ASSERT(instance_size_delta >= 0);
+
+ if (instance_size_delta > 0) {
+ Address address = object->address();
+ heap->CreateFillerObjectAt(
+ address + new_instance_size, instance_size_delta);
+ heap->AdjustLiveBytes(address, -instance_size_delta,
Heap::FROM_MUTATOR);
+ }
// We are storing the new map using release store after creating a
filler for
// the left-over space to avoid races with the sweeper thread.
--
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