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Unified Diff: src/heap/mark-compact.cc

Issue 988703002: Revert of Revert of Simplify and compact transitions storage (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: fix extra ';', again Created 5 years, 9 months ago
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Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 741414a1eff5db98378708b496fa0e2793cbb5cc..44262e42b162b58974cf7b2092ea141047856d2a 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -1470,8 +1470,9 @@ class MarkCompactMarkingVisitor::ObjectStatsTracker<
heap->RecordFixedArraySubTypeStats(DESCRIPTOR_ARRAY_SUB_TYPE,
fixed_array_size);
}
- if (map_obj->HasTransitionArray()) {
- int fixed_array_size = map_obj->transitions()->Size();
+ if (TransitionArray::IsFullTransitionArray(map_obj->raw_transitions())) {
+ int fixed_array_size =
+ TransitionArray::cast(map_obj->raw_transitions())->Size();
heap->RecordFixedArraySubTypeStats(TRANSITION_ARRAY_SUB_TYPE,
fixed_array_size);
}
@@ -2406,10 +2407,12 @@ void MarkCompactCollector::ClearNonLiveReferences() {
void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
- int number_of_transitions = map->NumberOfProtoTransitions();
- FixedArray* prototype_transitions = map->GetPrototypeTransitions();
+ FixedArray* prototype_transitions =
+ TransitionArray::GetPrototypeTransitions(map);
+ int number_of_transitions =
+ TransitionArray::NumberOfPrototypeTransitions(prototype_transitions);
- const int header = Map::kProtoTransitionHeaderSize;
+ 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);
@@ -2423,7 +2426,8 @@ void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
}
if (new_number_of_transitions != number_of_transitions) {
- map->SetNumberOfProtoTransitions(new_number_of_transitions);
+ TransitionArray::SetNumberOfPrototypeTransitions(prototype_transitions,
+ new_number_of_transitions);
}
// Fill slots that became free with undefined value.
@@ -2444,7 +2448,7 @@ void MarkCompactCollector::ClearNonLiveMapTransitions(Map* map,
bool current_is_alive = map_mark.Get();
bool parent_is_alive = Marking::MarkBitFrom(parent).Get();
if (!current_is_alive && parent_is_alive) {
- ClearMapTransitions(parent);
+ ClearMapTransitions(parent, map);
}
}
@@ -2458,28 +2462,43 @@ bool MarkCompactCollector::ClearMapBackPointer(Map* target) {
}
-void MarkCompactCollector::ClearMapTransitions(Map* map) {
- // If there are no transitions to be cleared, return.
- // TODO(verwaest) Should be an assert, otherwise back pointers are not
- // properly cleared.
- if (!map->HasTransitionArray()) return;
+void MarkCompactCollector::ClearMapTransitions(Map* map, Map* dead_transition) {
+ Object* transitions = map->raw_transitions();
+ int num_transitions = TransitionArray::NumberOfTransitions(transitions);
- TransitionArray* t = map->transitions();
+ int number_of_own_descriptors = map->NumberOfOwnDescriptors();
+ DescriptorArray* descriptors = map->instance_descriptors();
+
+ // A previously existing simple transition (stored in a WeakCell) may have
+ // been cleared. Clear the useless cell pointer, and take ownership
+ // of the descriptor array.
+ if (transitions->IsWeakCell() && WeakCell::cast(transitions)->cleared()) {
+ map->set_raw_transitions(Smi::FromInt(0));
+ }
+ if (num_transitions == 0 &&
+ descriptors == dead_transition->instance_descriptors() &&
+ number_of_own_descriptors > 0) {
+ TrimDescriptorArray(map, descriptors, number_of_own_descriptors);
+ DCHECK(descriptors->number_of_descriptors() == number_of_own_descriptors);
+ map->set_owns_descriptors(true);
+ return;
+ }
int transition_index = 0;
- DescriptorArray* descriptors = map->instance_descriptors();
bool descriptors_owner_died = false;
// Compact all live descriptors to the left.
- for (int i = 0; i < t->number_of_transitions(); ++i) {
- Map* target = t->GetTarget(i);
+ for (int i = 0; i < num_transitions; ++i) {
+ Map* target = TransitionArray::GetTarget(transitions, i);
if (ClearMapBackPointer(target)) {
if (target->instance_descriptors() == descriptors) {
descriptors_owner_died = true;
}
} else {
if (i != transition_index) {
+ DCHECK(TransitionArray::IsFullTransitionArray(transitions));
+ TransitionArray* t = TransitionArray::cast(transitions);
Name* key = t->GetKey(i);
t->SetKey(transition_index, key);
Object** key_slot = t->GetKeySlot(transition_index);
@@ -2494,9 +2513,7 @@ void MarkCompactCollector::ClearMapTransitions(Map* map) {
// If there are no transitions to be cleared, return.
// TODO(verwaest) Should be an assert, otherwise back pointers are not
// properly cleared.
- if (transition_index == t->number_of_transitions()) return;
-
- int number_of_own_descriptors = map->NumberOfOwnDescriptors();
+ if (transition_index == num_transitions) return;
if (descriptors_owner_died) {
if (number_of_own_descriptors > 0) {
@@ -2512,14 +2529,17 @@ void MarkCompactCollector::ClearMapTransitions(Map* map) {
// such that number_of_transitions() == 0. If this assumption changes,
// TransitionArray::Insert() will need to deal with the case that a transition
// array disappeared during GC.
- int trim = t->number_of_transitions_storage() - transition_index;
+ int trim = TransitionArray::Capacity(transitions) - transition_index;
if (trim > 0) {
+ // Non-full-TransitionArray cases can never reach this point.
+ DCHECK(TransitionArray::IsFullTransitionArray(transitions));
+ TransitionArray* t = TransitionArray::cast(transitions);
heap_->RightTrimFixedArray<Heap::FROM_GC>(
- t, t->IsSimpleTransition() ? trim
- : trim * TransitionArray::kTransitionSize);
+ t, trim * TransitionArray::kTransitionSize);
t->SetNumberOfTransitions(transition_index);
+ // The map still has a full transition array.
+ DCHECK(TransitionArray::IsFullTransitionArray(map->raw_transitions()));
}
- DCHECK(map->HasTransitionArray());
}
@@ -4231,7 +4251,7 @@ void MarkCompactCollector::SweepSpaces() {
EvacuateNewSpaceAndCandidates();
- // ClearNonLiveTransitions depends on precise sweeping of map space to
+ // ClearNonLiveReferences depends on precise sweeping of map space to
// detect whether unmarked map became dead in this collection or in one
// of the previous ones.
{
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