AuroraMiddleware/v8
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Replace ad-hoc weakness in prototype transitions with WeakCell.

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BUG=

Review URL: https://codereview.chromium.org/1163073002

Cr-Commit-Position: refs/heads/master@{#28830}
This commit is contained in:
ulan 2015-06-08 03:20:34 -07:00 committed by Commit bot
parent 9c41204048
commit bfb81fbe0d
5 changed files with 27 additions and 28 deletions
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7
src/heap/mark-compact.cc
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@ -2404,11 +2404,10 @@ void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
const int header = TransitionArray::kProtoTransitionHeaderSize;
int new_number_of_transitions = 0;
for (int i = 0; i < number_of_transitions; i++) {
Object* cached_map = prototype_transitions->get(header + i);
if (IsMarked(cached_map)) {
Object* cell = prototype_transitions->get(header + i);
if (!WeakCell::cast(cell)->cleared()) {
if (new_number_of_transitions != i) {
prototype_transitions->set(header + new_number_of_transitions,
cached_map, SKIP_WRITE_BARRIER);
prototype_transitions->set(header + new_number_of_transitions, cell);
}
new_number_of_transitions++;
}

9
src/heap/objects-visiting-inl.h
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@ -571,13 +571,8 @@ void StaticMarkingVisitor<StaticVisitor>::MarkTransitionArray(
if (!StaticVisitor::MarkObjectWithoutPush(heap, transitions)) return;
if (transitions->HasPrototypeTransitions()) {
// Mark prototype transitions array but do not push it onto marking
// stack, this will make references from it weak. We will clean dead
// prototype transitions in ClearNonLiveReferences.
Object** slot = transitions->GetPrototypeTransitionsSlot();
HeapObject* obj = HeapObject::cast(*slot);
heap->mark_compact_collector()->RecordSlot(slot, slot, obj);
StaticVisitor::MarkObjectWithoutPush(heap, obj);
StaticVisitor::VisitPointer(heap,
transitions->GetPrototypeTransitionsSlot());
}
int num_transitions = TransitionArray::NumberOfTransitions(transitions);

31
src/transitions.cc
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@ -233,17 +233,19 @@ bool TransitionArray::CanHaveMoreTransitions(Handle<Map> map) {
// static
Handle<Map> TransitionArray::PutPrototypeTransition(Handle<Map> map,
Handle<Object> prototype,
Handle<Map> target_map) {
void TransitionArray::PutPrototypeTransition(Handle<Map> map,
Handle<Object> prototype,
Handle<Map> target_map) {
DCHECK(HeapObject::cast(*prototype)->map()->IsMap());
// Don't cache prototype transition if this map is either shared, or a map of
// a prototype.
if (map->is_prototype_map()) return map;
if (map->is_dictionary_map() || !FLAG_cache_prototype_transitions) return map;
if (map->is_prototype_map()) return;
if (map->is_dictionary_map() || !FLAG_cache_prototype_transitions) return;
const int header = kProtoTransitionHeaderSize;
Handle<WeakCell> target_cell = Map::WeakCellForMap(target_map);
Handle<FixedArray> cache(GetPrototypeTransitions(*map));
int capacity = cache->length() - header;
int transitions = NumberOfPrototypeTransitions(*cache) + 1;
@ -251,7 +253,7 @@ Handle<Map> TransitionArray::PutPrototypeTransition(Handle<Map> map,
if (transitions > capacity) {
// Grow array by factor 2 up to MaxCachedPrototypeTransitions.
int new_capacity = Min(kMaxCachedPrototypeTransitions, transitions * 2);
if (new_capacity == capacity) return map;
if (new_capacity == capacity) return;
cache = FixedArray::CopySize(cache, header + new_capacity);
if (capacity < 0) {
@ -267,10 +269,8 @@ Handle<Map> TransitionArray::PutPrototypeTransition(Handle<Map> map,
int last = NumberOfPrototypeTransitions(*cache);
int entry = header + last;
cache->set(entry, *target_map);
cache->set(entry, *target_cell);
SetNumberOfPrototypeTransitions(*cache, last + 1);
return map;
}
@ -281,8 +281,12 @@ Handle<Map> TransitionArray::GetPrototypeTransition(Handle<Map> map,
FixedArray* cache = GetPrototypeTransitions(*map);
int number_of_transitions = NumberOfPrototypeTransitions(cache);
for (int i = 0; i < number_of_transitions; i++) {
Map* target = Map::cast(cache->get(kProtoTransitionHeaderSize + i));
if (target->prototype() == *prototype) return handle(target);
WeakCell* target_cell =
WeakCell::cast(cache->get(kProtoTransitionHeaderSize + i));
if (!target_cell->cleared() &&
Map::cast(target_cell->value())->prototype() == *prototype) {
return handle(Map::cast(target_cell->value()));
}
}
return Handle<Map>();
}
@ -436,8 +440,9 @@ void TransitionArray::TraverseTransitionTreeInternal(Map* map,
FixedArray* proto_trans = transitions->GetPrototypeTransitions();
for (int i = 0; i < NumberOfPrototypeTransitions(proto_trans); ++i) {
int index = TransitionArray::kProtoTransitionHeaderSize + i;
TraverseTransitionTreeInternal(Map::cast(proto_trans->get(index)),
callback, data);
WeakCell* cell = WeakCell::cast(proto_trans->get(index));
TraverseTransitionTreeInternal(Map::cast(cell->value()), callback,
data);
}
}
for (int i = 0; i < transitions->number_of_transitions(); ++i) {

5
src/transitions.h
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@ -92,9 +92,8 @@ class TransitionArray: public FixedArray {
// 0: finger - index of the first free cell in the cache
// 1 + i: target map
static const int kMaxCachedPrototypeTransitions = 256;
static Handle<Map> PutPrototypeTransition(Handle<Map> map,
Handle<Object> prototype,
Handle<Map> target_map);
static void PutPrototypeTransition(Handle<Map> map, Handle<Object> prototype,
Handle<Map> target_map);
static Handle<Map> GetPrototypeTransition(Handle<Map> map,
Handle<Object> prototype);

3
test/cctest/test-heap.cc
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@ -2521,7 +2521,8 @@ TEST(PrototypeTransitionClearing) {
TransitionArray::GetPrototypeTransitions(baseObject->map());
for (int i = initialTransitions; i < initialTransitions + transitions; i++) {
int j = TransitionArray::kProtoTransitionHeaderSize + i;
CHECK(trans->get(j)->IsMap());
CHECK(trans->get(j)->IsWeakCell());
CHECK(WeakCell::cast(trans->get(j))->value()->IsMap());
}
// Make sure next prototype is placed on an old-space evacuation candidate.