Avoid incremental marking write-barrier when constructing descriptor arrays.

src/objects.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5378 matching lines @@
 void DescriptorArray::SetEnumCache(FixedArray* bridge_storage,
                                    FixedArray* new_cache) {
   ASSERT(bridge_storage->length() >= kEnumCacheBridgeLength);
   if (HasEnumCache()) {
     FixedArray::cast(get(kEnumerationIndexIndex))->
       set(kEnumCacheBridgeCacheIndex, new_cache);
   } else {
     if (IsEmpty()) return;  // Do nothing for empty descriptor array.
     FixedArray::cast(bridge_storage)->
       set(kEnumCacheBridgeCacheIndex, new_cache);
-    fast_set(FixedArray::cast(bridge_storage),
-             kEnumCacheBridgeEnumIndex,
-             get(kEnumerationIndexIndex));
+    NoWriteBarrierSet(FixedArray::cast(bridge_storage),
+                      kEnumCacheBridgeEnumIndex,
+                      get(kEnumerationIndexIndex));
     set(kEnumerationIndexIndex, bridge_storage);
   }
 }
 
 
 MaybeObject* DescriptorArray::CopyInsert(Descriptor* descriptor,
                                          TransitionFlag transition_flag) {
   // Transitions are only kept when inserting another transition.
   // This precondition is not required by this function's implementation, but
   // is currently required by the semantics of maps, so we check it.
@@ skipping 40 matching lines @@
         t == FIELD ||
         t == CALLBACKS ||
         t == INTERCEPTOR) {
       keep_enumeration_index = true;
     } else if (remove_transitions) {
      // Replaced descriptor has been counted as removed if it is
      // a transition that will be replaced.  Adjust count in this case.
       ++new_size;
     }
   }
+
+  DescriptorArray* new_descriptors;
   { MaybeObject* maybe_result = Allocate(new_size);
-    if (!maybe_result->ToObject(&result)) return maybe_result;
+    if (!maybe_result->To<DescriptorArray>(&new_descriptors)) {
+      return maybe_result;
+    }
   }
-  DescriptorArray* new_descriptors = DescriptorArray::cast(result);
+
+  DescriptorArray::WhitenessWitness witness(new_descriptors);
+
   // Set the enumeration index in the descriptors and set the enumeration index
   // in the result.
   int enumeration_index = NextEnumerationIndex();
   if (!descriptor->GetDetails().IsTransition()) {
     if (keep_enumeration_index) {
       descriptor->SetEnumerationIndex(
           PropertyDetails(GetDetails(index)).index());
     } else {
       descriptor->SetEnumerationIndex(enumeration_index);
       ++enumeration_index;
     }
   }
   new_descriptors->SetNextEnumerationIndex(enumeration_index);
 
   // Copy the descriptors, filtering out transitions and null descriptors,
   // and inserting or replacing a descriptor.
   uint32_t descriptor_hash = descriptor->GetKey()->Hash();
   int from_index = 0;
   int to_index = 0;
 
   for (; from_index < number_of_descriptors(); from_index++) {
     String* key = GetKey(from_index);
     if (key->Hash() > descriptor_hash || key == descriptor->GetKey()) {
       break;
     }
     if (IsNullDescriptor(from_index)) continue;
     if (remove_transitions && IsTransition(from_index)) continue;
-    new_descriptors->CopyFrom(to_index++, this, from_index);
+    new_descriptors->CopyFrom(to_index++, this, from_index, witness);
   }
 
-  new_descriptors->Set(to_index++, descriptor);
+  new_descriptors->Set(to_index++, descriptor, witness);
   if (replacing) from_index++;
 
   for (; from_index < number_of_descriptors(); from_index++) {
     if (IsNullDescriptor(from_index)) continue;
     if (remove_transitions && IsTransition(from_index)) continue;
-    new_descriptors->CopyFrom(to_index++, this, from_index);
+    new_descriptors->CopyFrom(to_index++, this, from_index, witness);
   }
 
   ASSERT(to_index == new_descriptors->number_of_descriptors());
   SLOW_ASSERT(new_descriptors->IsSortedNoDuplicates());
 
   return new_descriptors;
 }
 
 
 MaybeObject* DescriptorArray::RemoveTransitions() {
   // Remove all transitions and null descriptors. Return a copy of the array
   // with all transitions removed, or a Failure object if the new array could
   // not be allocated.
 
   // Compute the size of the map transition entries to be removed.
   int num_removed = 0;
   for (int i = 0; i < number_of_descriptors(); i++) {
     if (!IsProperty(i)) num_removed++;
   }
 
   // Allocate the new descriptor array.
-  Object* result;
+  DescriptorArray* new_descriptors;
   { MaybeObject* maybe_result = Allocate(number_of_descriptors() - num_removed);
-    if (!maybe_result->ToObject(&result)) return maybe_result;
+    if (!maybe_result->To<DescriptorArray>(&new_descriptors)) {
+      return maybe_result;
+    }
   }
-  DescriptorArray* new_descriptors = DescriptorArray::cast(result);
+
+  DescriptorArray::WhitenessWitness witness(new_descriptors);
 
   // Copy the content.
   int next_descriptor = 0;
   for (int i = 0; i < number_of_descriptors(); i++) {
-    if (IsProperty(i)) new_descriptors->CopyFrom(next_descriptor++, this, i);
+    if (IsProperty(i)) {
+      new_descriptors->CopyFrom(next_descriptor++, this, i, witness);
+    }
   }
   ASSERT(next_descriptor == new_descriptors->number_of_descriptors());
 
   return new_descriptors;
 }
 
 
-void DescriptorArray::SortUnchecked() {
+void DescriptorArray::SortUnchecked(const WhitenessWitness& witness) {
   // In-place heap sort.
   int len = number_of_descriptors();
 
   // Bottom-up max-heap construction.
   // Index of the last node with children
   const int max_parent_index = (len / 2) - 1;
   for (int i = max_parent_index; i >= 0; --i) {
     int parent_index = i;
     const uint32_t parent_hash = GetKey(i)->Hash();
     while (parent_index <= max_parent_index) {
       int child_index = 2 * parent_index + 1;
       uint32_t child_hash = GetKey(child_index)->Hash();
       if (child_index + 1 < len) {
         uint32_t right_child_hash = GetKey(child_index + 1)->Hash();
         if (right_child_hash > child_hash) {
           child_index++;
           child_hash = right_child_hash;
         }
       }
       if (child_hash <= parent_hash) break;
-      Swap(parent_index, child_index);
+      NoWriteBarrierSwapDescriptors(parent_index, child_index);
       // Now element at child_index could be < its children.
       parent_index = child_index;  // parent_hash remains correct.
     }
   }
 
   // Extract elements and create sorted array.
   for (int i = len - 1; i > 0; --i) {
     // Put max element at the back of the array.
-    Swap(0, i);
-    // Sift down the new top element.
+    NoWriteBarrierSwapDescriptors(0, i);
+    // Shift down the new top element.
     int parent_index = 0;
     const uint32_t parent_hash = GetKey(parent_index)->Hash();
     const int max_parent_index = (i / 2) - 1;
     while (parent_index <= max_parent_index) {
       int child_index = parent_index * 2 + 1;
       uint32_t child_hash = GetKey(child_index)->Hash();
       if (child_index + 1 < i) {
         uint32_t right_child_hash = GetKey(child_index + 1)->Hash();
         if (right_child_hash > child_hash) {
           child_index++;
           child_hash = right_child_hash;
         }
       }
       if (child_hash <= parent_hash) break;
-      Swap(parent_index, child_index);
+      NoWriteBarrierSwapDescriptors(parent_index, child_index);
       parent_index = child_index;
     }
   }
 }
 
 
-void DescriptorArray::Sort() {
-  SortUnchecked();
+void DescriptorArray::Sort(const WhitenessWitness& witness) {
+  SortUnchecked(witness);
   SLOW_ASSERT(IsSortedNoDuplicates());
 }
 
 
 int DescriptorArray::BinarySearch(String* name, int low, int high) {
   uint32_t hash = name->Hash();
 
   while (low <= high) {
     int mid = (low + high) / 2;
     String* mid_name = GetKey(mid);
@@ skipping 6096 matching lines @@
   return cache;
 }
 
 
 void CompilationCacheTable::Remove(Object* value) {
   Object* null_value = GetHeap()->null_value();
   for (int entry = 0, size = Capacity(); entry < size; entry++) {
     int entry_index = EntryToIndex(entry);
     int value_index = entry_index + 1;
     if (get(value_index) == value) {
-      fast_set(this, entry_index, null_value);
-      fast_set(this, value_index, null_value);
+      NoWriteBarrierSet(this, entry_index, null_value);
+      NoWriteBarrierSet(this, value_index, null_value);
       ElementRemoved();
     }
   }
   return;
 }
 
 
 // SymbolsKey used for HashTable where key is array of symbols.
 class SymbolsKey : public HashTableKey {
  public:
@@ skipping 451 matching lines @@
       ASSERT(type != FIELD);
       instance_descriptor_length++;
       if (type == NORMAL &&
           (!value->IsJSFunction() || heap->InNewSpace(value))) {
         number_of_fields += 1;
       }
     }
   }
 
   // Allocate the instance descriptor.
-  Object* descriptors_unchecked;
-  { MaybeObject* maybe_descriptors_unchecked =
+  DescriptorArray* descriptors;
+  { MaybeObject* maybe_descriptors =
         DescriptorArray::Allocate(instance_descriptor_length);
-    if (!maybe_descriptors_unchecked->ToObject(&descriptors_unchecked)) {
-      return maybe_descriptors_unchecked;
+    if (!maybe_descriptors->To<DescriptorArray>(&descriptors)) {
+      return maybe_descriptors;
     }
   }
-  DescriptorArray* descriptors = DescriptorArray::cast(descriptors_unchecked);
+
+  DescriptorArray::WhitenessWitness witness(descriptors);
 
   int inobject_props = obj->map()->inobject_properties();
   int number_of_allocated_fields =
       number_of_fields + unused_property_fields - inobject_props;
   if (number_of_allocated_fields < 0) {
     // There is enough inobject space for all fields (including unused).
     number_of_allocated_fields = 0;
     unused_property_fields = inobject_props - number_of_fields;
   }
 
@@ skipping 17 matching lines @@
         if (!maybe_key->ToObject(&key)) return maybe_key;
       }
       PropertyDetails details = DetailsAt(i);
       PropertyType type = details.type();
 
       if (value->IsJSFunction() && !heap->InNewSpace(value)) {
         ConstantFunctionDescriptor d(String::cast(key),
                                      JSFunction::cast(value),
                                      details.attributes(),
                                      details.index());
-        descriptors->Set(next_descriptor++, &d);
+        descriptors->Set(next_descriptor++, &d, witness);
       } else if (type == NORMAL) {
         if (current_offset < inobject_props) {
           obj->InObjectPropertyAtPut(current_offset,
                                      value,
                                      UPDATE_WRITE_BARRIER);
         } else {
           int offset = current_offset - inobject_props;
           FixedArray::cast(fields)->set(offset, value);
         }
         FieldDescriptor d(String::cast(key),
                           current_offset++,
                           details.attributes(),
                           details.index());
-        descriptors->Set(next_descriptor++, &d);
+        descriptors->Set(next_descriptor++, &d, witness);
       } else if (type == CALLBACKS) {
         CallbacksDescriptor d(String::cast(key),
                               value,
                               details.attributes(),
                               details.index());
-        descriptors->Set(next_descriptor++, &d);
+        descriptors->Set(next_descriptor++, &d, witness);
       } else {
         UNREACHABLE();
       }
     }
   }
   ASSERT(current_offset == number_of_fields);
 
-  descriptors->Sort();
+  descriptors->Sort(witness);
   // Allocate new map.
   Object* new_map;
   { MaybeObject* maybe_new_map = obj->map()->CopyDropDescriptors();
     if (!maybe_new_map->ToObject(&new_map)) return maybe_new_map;
   }
 
   // Transform the object.
   obj->set_map(Map::cast(new_map));
   obj->map()->set_instance_descriptors(descriptors);
   obj->map()->set_unused_property_fields(unused_property_fields);
@@ skipping 313 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single break point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 } }  // namespace v8::internal