Move prototype metadata from internal properties to prototype maps

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 706c06496fef1313552ecea4387cf3970db95eea..2fe600d5236e0cc0c898649e8ce520096db431b0 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -144,6 +144,7 @@
 //       - DebugInfo
 //       - BreakPointInfo
 //       - CodeCache
+//       - PrototypeInfo
 //     - WeakCell
 //
 // Formats of Object*:
@@ -420,6 +421,7 @@ const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
   V(TYPE_FEEDBACK_INFO_TYPE)                                    \
   V(ALIASED_ARGUMENTS_ENTRY_TYPE)                               \
   V(BOX_TYPE)                                                   \
+  V(PROTOTYPE_INFO_TYPE)                                        \
                                                                 \
   V(FIXED_ARRAY_TYPE)                                           \
   V(FIXED_DOUBLE_ARRAY_TYPE)                                    \
@@ -517,25 +519,27 @@ const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
 // Note that for subtle reasons related to the ordering or numerical values of
 // type tags, elements in this list have to be added to the INSTANCE_TYPE_LIST
 // manually.
-#define STRUCT_LIST(V)                                                         \
-  V(BOX, Box, box)                                                             \
-  V(EXECUTABLE_ACCESSOR_INFO, ExecutableAccessorInfo, executable_accessor_info)\
-  V(ACCESSOR_PAIR, AccessorPair, accessor_pair)                                \
-  V(ACCESS_CHECK_INFO, AccessCheckInfo, access_check_info)                     \
-  V(INTERCEPTOR_INFO, InterceptorInfo, interceptor_info)                       \
-  V(CALL_HANDLER_INFO, CallHandlerInfo, call_handler_info)                     \
-  V(FUNCTION_TEMPLATE_INFO, FunctionTemplateInfo, function_template_info)      \
-  V(OBJECT_TEMPLATE_INFO, ObjectTemplateInfo, object_template_info)            \
-  V(TYPE_SWITCH_INFO, TypeSwitchInfo, type_switch_info)                        \
-  V(SCRIPT, Script, script)                                                    \
-  V(ALLOCATION_SITE, AllocationSite, allocation_site)                          \
-  V(ALLOCATION_MEMENTO, AllocationMemento, allocation_memento)                 \
-  V(CODE_CACHE, CodeCache, code_cache)                                         \
-  V(POLYMORPHIC_CODE_CACHE, PolymorphicCodeCache, polymorphic_code_cache)      \
-  V(TYPE_FEEDBACK_INFO, TypeFeedbackInfo, type_feedback_info)                  \
-  V(ALIASED_ARGUMENTS_ENTRY, AliasedArgumentsEntry, aliased_arguments_entry)   \
-  V(DEBUG_INFO, DebugInfo, debug_info)                                         \
-  V(BREAK_POINT_INFO, BreakPointInfo, break_point_info)
+#define STRUCT_LIST(V)                                                       \

[Jakob Kummerow, 2015/03/24 10:40:14]

clang-format...

+  V(BOX, Box, box)                                                           \
+  V(EXECUTABLE_ACCESSOR_INFO, ExecutableAccessorInfo,                        \
+    executable_accessor_info)                                                \
+  V(ACCESSOR_PAIR, AccessorPair, accessor_pair)                              \
+  V(ACCESS_CHECK_INFO, AccessCheckInfo, access_check_info)                   \
+  V(INTERCEPTOR_INFO, InterceptorInfo, interceptor_info)                     \
+  V(CALL_HANDLER_INFO, CallHandlerInfo, call_handler_info)                   \
+  V(FUNCTION_TEMPLATE_INFO, FunctionTemplateInfo, function_template_info)    \
+  V(OBJECT_TEMPLATE_INFO, ObjectTemplateInfo, object_template_info)          \
+  V(TYPE_SWITCH_INFO, TypeSwitchInfo, type_switch_info)                      \
+  V(SCRIPT, Script, script)                                                  \
+  V(ALLOCATION_SITE, AllocationSite, allocation_site)                        \
+  V(ALLOCATION_MEMENTO, AllocationMemento, allocation_memento)               \
+  V(CODE_CACHE, CodeCache, code_cache)                                       \
+  V(POLYMORPHIC_CODE_CACHE, PolymorphicCodeCache, polymorphic_code_cache)    \
+  V(TYPE_FEEDBACK_INFO, TypeFeedbackInfo, type_feedback_info)                \
+  V(ALIASED_ARGUMENTS_ENTRY, AliasedArgumentsEntry, aliased_arguments_entry) \
+  V(DEBUG_INFO, DebugInfo, debug_info)                                       \
+  V(BREAK_POINT_INFO, BreakPointInfo, break_point_info)                      \
+  V(PROTOTYPE_INFO, PrototypeInfo, prototype_info)
 
 // We use the full 8 bits of the instance_type field to encode heap object
 // instance types.  The high-order bit (bit 7) is set if the object is not a
@@ -718,6 +722,7 @@ enum InstanceType {
   SHARED_FUNCTION_INFO_TYPE,
   WEAK_CELL_TYPE,
   PROPERTY_CELL_TYPE,
+  PROTOTYPE_INFO_TYPE,
 
   // All the following types are subtypes of JSReceiver, which corresponds to
   // objects in the JS sense. The first and the last type in this range are
@@ -2049,7 +2054,11 @@ class JSObject: public JSReceiver {
   static void TransitionElementsKind(Handle<JSObject> object,
                                      ElementsKind to_kind);
 
-  static void MigrateToMap(Handle<JSObject> object, Handle<Map> new_map);
+  // Always use this to migrate an object to a new map.
+  // |expected_additional_properties| is only used for fast-to-slow transitions
+  // and ignored otherwise.
+  static void MigrateToMap(Handle<JSObject> object, Handle<Map> new_map,
+                           int expected_additional_properties = 0);
 
   // Convert the object to use the canonical dictionary
   // representation. If the object is expected to have additional properties
@@ -5796,15 +5805,15 @@ class Map: public HeapObject {
   inline void set_unused_property_fields(int value);
 
   // Bit field.
-  inline byte bit_field();
+  inline byte bit_field() const;
   inline void set_bit_field(byte value);
 
   // Bit field 2.
-  inline byte bit_field2();
+  inline byte bit_field2() const;
   inline void set_bit_field2(byte value);
 
   // Bit field 3.
-  inline uint32_t bit_field3();
+  inline uint32_t bit_field3() const;
   inline void set_bit_field3(uint32_t bits);
 
   class EnumLengthBits:             public BitField<int,
@@ -5899,7 +5908,7 @@ class Map: public HeapObject {
   inline void set_is_extensible(bool value);
   inline bool is_extensible();
   inline void set_is_prototype_map(bool value);
-  inline bool is_prototype_map();
+  inline bool is_prototype_map() const;
 
   inline void set_elements_kind(ElementsKind elements_kind) {
     DCHECK(static_cast<int>(elements_kind) < kElementsKindCount);
@@ -5970,6 +5979,9 @@ class Map: public HeapObject {
   // Don't call set_raw_transitions() directly to overwrite transitions, use
   // the TransitionArray::ReplaceTransitions() wrapper instead!
   DECL_ACCESSORS(raw_transitions, Object)
+  // [prototype_info]: Per-prototype metadata. Aliased with transitions
+  // (which prototype maps don't have).
+  DECL_ACCESSORS(prototype_info, Object)
 
   Map* FindRootMap();
   Map* FindFieldOwner(int descriptor);
@@ -6328,9 +6340,10 @@ class Map: public HeapObject {
   // otherwise a transition array is used.
   // For prototype maps, this slot is used to store a pointer to the prototype
   // object using this map.
-  static const int kTransitionsOffset =
+  static const int kTransitionsOrPrototypeInfoOffset =
       kConstructorOrBackPointerOffset + kPointerSize;
-  static const int kDescriptorsOffset = kTransitionsOffset + kPointerSize;
+  static const int kDescriptorsOffset =
+      kTransitionsOrPrototypeInfoOffset + kPointerSize;
 #if V8_DOUBLE_FIELDS_UNBOXING
   static const int kLayoutDecriptorOffset = kDescriptorsOffset + kPointerSize;
   static const int kCodeCacheOffset = kLayoutDecriptorOffset + kPointerSize;
@@ -6532,6 +6545,35 @@ class Box : public Struct {
 };
 
 
+// Container for metadata stored on each prototype map.
+class PrototypeInfo : public Struct {
+ public:
+  // [prototype_object]: The object using the map holding this PrototypeInfo.
+  DECL_ACCESSORS(prototype_object, JSObject)
+  // [prototype_users]: WeakFixedArray containing maps using this prototype,
+  // or Smi(0) if uninitialized.
+  DECL_ACCESSORS(prototype_users, Object)
+  // [validity_cell]: Cell containing the validity bit for prototype chains
+  // going through this object, or Smi(0) if uninitialized.
+  DECL_ACCESSORS(validity_cell, Object)
+
+  DECLARE_CAST(PrototypeInfo)
+
+  // Dispatched behavior.
+  DECLARE_PRINTER(PrototypeInfo)
+  DECLARE_VERIFIER(PrototypeInfo)
+
+  static const int kPrototypeObjectOffset = HeapObject::kHeaderSize;
+  static const int kPrototypeUsersOffset =
+      kPrototypeObjectOffset + kPointerSize;
+  static const int kValidityCellOffset = kPrototypeUsersOffset + kPointerSize;
+  static const int kSize = kValidityCellOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(PrototypeInfo);
+};
+
+
 // Script describes a script which has been added to the VM.
 class Script: public Struct {
  public: