Revert of Fix memory leak caused by field type in descriptor array. (patchset...

Revert of Fix memory leak caused by field type in descriptor array. (patchset #3 id:40001 of https://codereview.chromium.org/955063002/)

Reason for revert:
Breaks test/mjsunit/debug-clearbreakpointgroup.js on arm64.debug.

Original issue's description:
> Fix memory leak caused by field type in descriptor array.
>
> When a field type is a map, it is wrapped in a weak cell upon storing to the descriptor array.
>
> Map::GetFieldType(i) does the unwrapping.
>
> BUG=v8:3877
> LOG=N
> TEST=cctest/test-heap/Regress3877
>
> Committed: https://crrev.com/77d3ae0e119893ac8d34ea6ca090cddd5bbf987e
> Cr-Commit-Position: refs/heads/master@{#26879}

TBR=verwaest@chromium.org,ulan@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:3877

Review URL: https://codereview.chromium.org/960103003

Cr-Commit-Position: refs/heads/master@{#26883}

src/objects-inl.h

@@ -3136,12 +3136,7 @@ int DescriptorArray::GetFieldIndex(int descriptor_number) {
 
 HeapType* DescriptorArray::GetFieldType(int descriptor_number) {
   DCHECK(GetDetails(descriptor_number).location() == kField);
-  Object* value = GetValue(descriptor_number);
-  if (value->IsWeakCell()) {
-    if (WeakCell::cast(value)->cleared()) return HeapType::Any();
-    value = WeakCell::cast(value)->value();
-  }
-  return HeapType::cast(value);
+  return HeapType::cast(GetValue(descriptor_number));
 }
 
 

src/objects.cc

@@ -1704,12 +1704,6 @@ String* JSReceiver::constructor_name() {
 }
 
 
-static Handle<Object> WrapType(Handle<HeapType> type) {
-  if (type->IsClass()) return Map::WeakCellForMap(type->AsClass()->Map());
-  return type;
-}
-
-
 MaybeHandle<Map> Map::CopyWithField(Handle<Map> map,
                                     Handle<Name> name,
                                     Handle<HeapType> type,
@@ -1735,10 +1729,7 @@ MaybeHandle<Map> Map::CopyWithField(Handle<Map> map,
     type = HeapType::Any(isolate);
   }
 
-  Handle<Object> wrapped_type(WrapType(type));
-
-  DataDescriptor new_field_desc(name, index, wrapped_type, attributes,
-                                representation);
+  DataDescriptor new_field_desc(name, index, type, attributes, representation);
   Handle<Map> new_map = Map::CopyAddDescriptor(map, &new_field_desc, flag);
   int unused_property_fields = new_map->unused_property_fields() - 1;
   if (unused_property_fields < 0) {
@@ -2314,16 +2305,15 @@ Map* Map::FindFieldOwner(int descriptor) {
 
 void Map::UpdateFieldType(int descriptor, Handle<Name> name,
                           Representation new_representation,
-                          Handle<Object> new_wrapped_type) {
-  DCHECK(new_wrapped_type->IsSmi() || new_wrapped_type->IsWeakCell());
+                          Handle<HeapType> new_type) {
   DisallowHeapAllocation no_allocation;
   PropertyDetails details = instance_descriptors()->GetDetails(descriptor);
   if (details.type() != DATA) return;
   if (HasTransitionArray()) {
     TransitionArray* transitions = this->transitions();
     for (int i = 0; i < transitions->number_of_transitions(); ++i) {
-      transitions->GetTarget(i)->UpdateFieldType(
-          descriptor, name, new_representation, new_wrapped_type);
+      transitions->GetTarget(i)
+          ->UpdateFieldType(descriptor, name, new_representation, new_type);
     }
   }
   // It is allowed to change representation here only from None to something.
@@ -2331,9 +2321,9 @@ void Map::UpdateFieldType(int descriptor, Handle<Name> name,
          details.representation().IsNone());
 
   // Skip if already updated the shared descriptor.
-  if (instance_descriptors()->GetValue(descriptor) == *new_wrapped_type) return;
+  if (instance_descriptors()->GetFieldType(descriptor) == *new_type) return;
   DataDescriptor d(name, instance_descriptors()->GetFieldIndex(descriptor),
-                   new_wrapped_type, details.attributes(), new_representation);
+                   new_type, details.attributes(), new_representation);
   instance_descriptors()->Replace(descriptor, &d);
 }
 
@@ -2381,10 +2371,8 @@ void Map::GeneralizeFieldType(Handle<Map> map, int modify_index,
 
   PropertyDetails details = descriptors->GetDetails(modify_index);
   Handle<Name> name(descriptors->GetKey(modify_index));
-
-  Handle<Object> wrapped_type(WrapType(new_field_type));
   field_owner->UpdateFieldType(modify_index, name, new_representation,
-                               wrapped_type);
+                               new_field_type);
   field_owner->dependent_code()->DeoptimizeDependentCodeGroup(
       isolate, DependentCode::kFieldTypeGroup);
 
@@ -2776,8 +2764,7 @@ Handle<Map> Map::ReconfigureProperty(Handle<Map> old_map, int modify_index,
           next_field_type =
               GeneralizeFieldType(target_field_type, old_field_type, isolate);
         }
-        Handle<Object> wrapped_type(WrapType(next_field_type));
-        DataDescriptor d(target_key, current_offset, wrapped_type,
+        DataDescriptor d(target_key, current_offset, next_field_type,
                          next_attributes, next_representation);
         current_offset += d.GetDetails().field_width_in_words();
         new_descriptors->Set(i, &d);
@@ -2845,10 +2832,8 @@ Handle<Map> Map::ReconfigureProperty(Handle<Map> old_map, int modify_index,
           next_field_type = old_field_type;
         }
 
-        Handle<Object> wrapped_type(WrapType(next_field_type));
-
-        DataDescriptor d(old_key, current_offset, wrapped_type, next_attributes,
-                         next_representation);
+        DataDescriptor d(old_key, current_offset, next_field_type,
+                         next_attributes, next_representation);
         current_offset += d.GetDetails().field_width_in_words();
         new_descriptors->Set(i, &d);
       } else {
@@ -2979,41 +2964,33 @@ MaybeHandle<Map> Map::TryUpdate(Handle<Map> old_map) {
     if (!old_details.representation().fits_into(new_details.representation())) {
       return MaybeHandle<Map>();
     }
+    Object* new_value = new_descriptors->GetValue(i);
+    Object* old_value = old_descriptors->GetValue(i);
     switch (new_details.type()) {
       case DATA: {
-        HeapType* new_type = new_descriptors->GetFieldType(i);
-        PropertyType old_property_type = old_details.type();
-        if (old_property_type == DATA) {
-          HeapType* old_type = old_descriptors->GetFieldType(i);
-          if (!old_type->NowIs(new_type)) {
+        PropertyType old_type = old_details.type();
+        if (old_type == DATA) {
+          if (!HeapType::cast(old_value)->NowIs(HeapType::cast(new_value))) {
             return MaybeHandle<Map>();
           }
         } else {
-          DCHECK(old_property_type == DATA_CONSTANT);
-          Object* old_value = old_descriptors->GetValue(i);
-          if (!new_type->NowContains(old_value)) {
+          DCHECK(old_type == DATA_CONSTANT);
+          if (!HeapType::cast(new_value)->NowContains(old_value)) {
             return MaybeHandle<Map>();
           }
         }
         break;
       }
-      case ACCESSOR: {
-#ifdef DEBUG
-        HeapType* new_type = new_descriptors->GetFieldType(i);
-        DCHECK(HeapType::Any()->Is(new_type));
-#endif
+      case ACCESSOR:
+        DCHECK(HeapType::Any()->Is(HeapType::cast(new_value)));
         break;
-      }
 
       case DATA_CONSTANT:
-      case ACCESSOR_CONSTANT: {
-        Object* old_value = old_descriptors->GetValue(i);
-        Object* new_value = new_descriptors->GetValue(i);
+      case ACCESSOR_CONSTANT:
         if (old_details.location() == kField || old_value != new_value) {
           return MaybeHandle<Map>();
         }
         break;
-      }
     }
   }
   if (new_map->NumberOfOwnDescriptors() != old_nof) return MaybeHandle<Map>();

src/objects.h

@@ -6443,12 +6443,9 @@ class Map: public HeapObject {
 
   Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);
 
-  // Update field type of the given descriptor to new representation and new
-  // type. The type must be prepared for storing in descriptor array:
-  // it must be either a simple type or a map wrapped in a weak cell.
   void UpdateFieldType(int descriptor_number, Handle<Name> name,
                        Representation new_representation,
-                       Handle<Object> new_wrapped_type);
+                       Handle<HeapType> new_type);
 
   void PrintReconfiguration(FILE* file, int modify_index, PropertyKind kind,
                             PropertyAttributes attributes);

src/property.h

@@ -79,14 +79,10 @@ class DataDescriptor FINAL : public Descriptor {
                  PropertyAttributes attributes, Representation representation)
       : Descriptor(key, HeapType::Any(key->GetIsolate()), attributes, DATA,
                    representation, field_index) {}
-  // The field type is either a simple type or a map wrapped in a weak cell.
-  DataDescriptor(Handle<Name> key, int field_index,
-                 Handle<Object> wrapped_field_type,
+  DataDescriptor(Handle<Name> key, int field_index, Handle<HeapType> field_type,
                  PropertyAttributes attributes, Representation representation)
-      : Descriptor(key, wrapped_field_type, attributes, DATA, representation,
-                   field_index) {
-    DCHECK(wrapped_field_type->IsSmi() || wrapped_field_type->IsWeakCell());
-  }
+      : Descriptor(key, field_type, attributes, DATA, representation,
+                   field_index) {}
 };
 
 

test/cctest/test-heap.cc

@@ -5083,40 +5083,6 @@ TEST(NumberStringCacheSize) {
 }
 
 
-TEST(Regress3877) {
-  CcTest::InitializeVM();
-  Isolate* isolate = CcTest::i_isolate();
-  Heap* heap = isolate->heap();
-  Factory* factory = isolate->factory();
-  HandleScope scope(isolate);
-  CompileRun("function cls() { this.x = 10; }");
-  Handle<WeakCell> weak_prototype;
-  {
-    HandleScope inner_scope(isolate);
-    v8::Local<v8::Value> result = CompileRun("cls.prototype");
-    Handle<JSObject> proto =
-        v8::Utils::OpenHandle(*v8::Handle<v8::Object>::Cast(result));
-    weak_prototype = inner_scope.CloseAndEscape(factory->NewWeakCell(proto));
-  }
-  CHECK(!weak_prototype->cleared());
-  CompileRun(
-      "var a = { };"
-      "a.x = new cls();"
-      "cls.prototype = null;");
-  for (int i = 0; i < 4; i++) {
-    heap->CollectAllGarbage(Heap::kNoGCFlags);
-  }
-  // The map of a.x keeps prototype alive
-  CHECK(!weak_prototype->cleared());
-  // Change the map of a.x and make the previous map garbage collectable.
-  CompileRun("a.x.__proto__ = {};");
-  for (int i = 0; i < 4; i++) {
-    heap->CollectAllGarbage(Heap::kNoGCFlags);
-  }
-  CHECK(weak_prototype->cleared());
-}
-
-
 #ifdef DEBUG
 TEST(PathTracer) {
   CcTest::InitializeVM();

test/cctest/test-migrations.cc

@@ -233,14 +233,12 @@ class Expectations {
                       representations_[descriptor])) {
       return false;
     }
-    Object* value = descriptors->GetValue(descriptor);
     Object* expected_value = *values_[descriptor];
+    Object* value = descriptors->GetValue(descriptor);
     switch (type) {
       case DATA:
-      case ACCESSOR: {
-        HeapType* type = descriptors->GetFieldType(descriptor);
-        return HeapType::cast(expected_value)->Equals(type);
-      }
+      case ACCESSOR:
+        return HeapType::cast(expected_value)->Equals(HeapType::cast(value));
 
       case DATA_CONSTANT:
         return value == expected_value;