Optimize clearing of map transitions.

src/heap/objects-visiting-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_VISITING_INL_H_
 #define V8_OBJECTS_VISITING_INL_H_
 
 #include "src/heap/array-buffer-tracker.h"
 #include "src/heap/objects-visiting.h"
 #include "src/ic/ic-state.h"
@@ skipping 328 matching lines @@
                           UPDATE_WEAK_WRITE_BARRIER);
       heap->set_encountered_weak_cells(weak_cell);
     }
   }
 }
 
 
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitTransitionArray(
     Map* map, HeapObject* object) {
-  typedef FlexibleBodyVisitor<StaticVisitor, TransitionArray::BodyDescriptor,
-                              int> TransitionArrayBodyVisitor;
   TransitionArray* array = TransitionArray::cast(object);
+  Heap* heap = array->GetHeap();
+  // Visit strong references.
+  if (array->HasPrototypeTransitions()) {
+    StaticVisitor::VisitPointer(heap, array,
+                                array->GetPrototypeTransitionsSlot());
+  }
+  int num_transitions = TransitionArray::NumberOfTransitions(array);
+  for (int i = 0; i < num_transitions; ++i) {
+    StaticVisitor::VisitPointer(heap, array, array->GetKeySlot(i));
+  }
   // Enqueue the array in linked list of encountered transition arrays if it is
   // not already in the list.
   if (array->next_link()->IsUndefined()) {
     Heap* heap = map->GetHeap();
     array->set_next_link(heap->encountered_transition_arrays(),
                          UPDATE_WEAK_WRITE_BARRIER);
     heap->set_encountered_transition_arrays(array);
   }
-  // TODO(ulan): Move MarkTransitionArray logic here.
-  TransitionArrayBodyVisitor::Visit(map, object);
 }
 
 
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitAllocationSite(
     Map* map, HeapObject* object) {
   Heap* heap = map->GetHeap();
 
   StaticVisitor::VisitPointers(
       heap, object,
@@ skipping 155 matching lines @@
   StaticVisitor::VisitPointers(
       map->GetHeap(), object,
       HeapObject::RawField(object, BytecodeArray::kConstantPoolOffset),
       HeapObject::RawField(object, BytecodeArray::kHeaderSize));
 }
 
 
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::MarkMapContents(Heap* heap,
                                                           Map* map) {
-  Object* raw_transitions = map->raw_transitions();
-  if (TransitionArray::IsFullTransitionArray(raw_transitions)) {
-    MarkTransitionArray(heap, TransitionArray::cast(raw_transitions));
-  }
-
   // Since descriptor arrays are potentially shared, ensure that only the
   // descriptors that belong to this map are marked. The first time a non-empty
   // descriptor array is marked, its header is also visited. The slot holding
   // the descriptor array will be implicitly recorded when the pointer fields of
   // this map are visited.  Prototype maps don't keep track of transitions, so
   // just mark the entire descriptor array.
   if (!map->is_prototype_map()) {
     DescriptorArray* descriptors = map->instance_descriptors();
     if (StaticVisitor::MarkObjectWithoutPush(heap, descriptors) &&
         descriptors->length() > 0) {
@@ skipping 13 matching lines @@
   // Mark the pointer fields of the Map. Since the transitions array has
   // been marked already, it is fine that one of these fields contains a
   // pointer to it.
   StaticVisitor::VisitPointers(
       heap, map, HeapObject::RawField(map, Map::kPointerFieldsBeginOffset),
       HeapObject::RawField(map, Map::kPointerFieldsEndOffset));
 }
 
 
 template <typename StaticVisitor>
-void StaticMarkingVisitor<StaticVisitor>::MarkTransitionArray(
-    Heap* heap, TransitionArray* transitions) {
-  if (!StaticVisitor::MarkObjectWithoutPush(heap, transitions)) return;
-
-  if (transitions->HasPrototypeTransitions()) {
-    StaticVisitor::VisitPointer(heap, transitions,
-                                transitions->GetPrototypeTransitionsSlot());
-  }
-
-  int num_transitions = TransitionArray::NumberOfTransitions(transitions);
-  for (int i = 0; i < num_transitions; ++i) {
-    StaticVisitor::VisitPointer(heap, transitions, transitions->GetKeySlot(i));
-  }
-}
-
-
-template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::MarkOptimizedCodeMap(
     Heap* heap, FixedArray* code_map) {
   if (!StaticVisitor::MarkObjectWithoutPush(heap, code_map)) return;
 
   // Mark the context-independent entry in the optimized code map. Depending on
   // the age of the code object, we treat it as a strong or a weak reference.
   Object* shared_object = code_map->get(SharedFunctionInfo::kSharedCodeIndex);
   if (FLAG_turbo_preserve_shared_code && shared_object->IsCode() &&
       FLAG_age_code && !Code::cast(shared_object)->IsOld()) {
     StaticVisitor::VisitPointer(
@@ skipping 171 matching lines @@
   typedef FlexibleBodyVisitor<StaticVisitor, JSFunction::BodyDescriptorWeakCode,
                               void> JSFunctionWeakCodeBodyVisitor;
   JSFunctionWeakCodeBodyVisitor::Visit(map, object);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_VISITING_INL_H_