Optimize Object.seal and Object.preventExtensions

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index bb9ecee0172d71b6348f4e90ed0ee3c7bc5e5850..38d05d311387757d1a7e6aa44041042bc7e88840 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2106,6 +2106,9 @@ class JSObject: public JSReceiver {
   MUST_USE_RESULT static MaybeHandle<Object> PreventExtensions(
       Handle<JSObject> object);
 
+  // ES5 Object.seal
+  MUST_USE_RESULT static MaybeHandle<Object> Seal(Handle<JSObject> object);
+
   // ES5 Object.freeze
   MUST_USE_RESULT static MaybeHandle<Object> Freeze(Handle<JSObject> object);
 
@@ -2393,6 +2396,15 @@ class JSObject: public JSReceiver {
 
   static Handle<Smi> GetOrCreateIdentityHash(Handle<JSObject> object);
 
+  static Handle<SeededNumberDictionary> GetNormalizedElementDictionary(
+      Handle<JSObject> object);
+
+  // Helper for fast versions of preventExtensions, seal, and freeze.
+  // attrs is one of NONE, SEALED, or FROZEN (depending on the operation).
+  template <PropertyAttributes attrs>
+  MUST_USE_RESULT static MaybeHandle<Object> PreventExtensionsWithTransition(
+      Handle<JSObject> object);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSObject);
 };
 
@@ -5612,6 +5624,9 @@ class DependentCode: public FixedArray {
 };
 
 
+class Symbol;

[Igor Sheludko, 2014/12/10 10:36:14]

I think src/globals.h is a better place for this.

[adamk, 2014/12/10 18:46:01]

Thanks for the pointer, I didn't know about that list of forward-decls. String
and Name are already there, added Symbol.

+
+
 // All heap objects have a Map that describes their structure.
 //  A Map contains information about:
 //  - Size information about the object
@@ -5662,11 +5677,10 @@ class Map: public HeapObject {
   class OwnsDescriptors : public BitField<bool, 21, 1> {};
   class HasInstanceCallHandler : public BitField<bool, 22, 1> {};
   class Deprecated : public BitField<bool, 23, 1> {};
-  class IsFrozen : public BitField<bool, 24, 1> {};
-  class IsUnstable : public BitField<bool, 25, 1> {};
-  class IsMigrationTarget : public BitField<bool, 26, 1> {};
-  class DoneInobjectSlackTracking : public BitField<bool, 27, 1> {};
-  // Bit 28 is free.
+  class IsUnstable : public BitField<bool, 24, 1> {};
+  class IsMigrationTarget : public BitField<bool, 25, 1> {};
+  class DoneInobjectSlackTracking : public BitField<bool, 26, 1> {};
+  // Bits 27 and 28 are free.
 
   // Keep this bit field at the very end for better code in
   // Builtins::kJSConstructStubGeneric stub.
@@ -6006,8 +6020,6 @@ class Map: public HeapObject {
   inline void set_owns_descriptors(bool owns_descriptors);
   inline bool has_instance_call_handler();
   inline void set_has_instance_call_handler();
-  inline void freeze();
-  inline bool is_frozen();
   inline void mark_unstable();
   inline bool is_stable();
   inline void set_migration_target(bool value);
@@ -6067,7 +6079,10 @@ class Map: public HeapObject {
 
   static Handle<Map> CopyForObserved(Handle<Map> map);
 
-  static Handle<Map> CopyForFreeze(Handle<Map> map);
+  static Handle<Map> CopyForPreventExtensions(Handle<Map> map,
+                                              PropertyAttributes attrs_to_add,
+                                              Handle<Symbol> transition_marker,
+                                              const char* reason);
   // Maximal number of fast properties. Used to restrict the number of map
   // transitions to avoid an explosion in the number of maps for objects used as
   // dictionaries.