In-object double fields unboxing (for 64-bit only).

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index fbe06c70286654161b6de8b58c639e3f2613cb31..2dc33e2458d3722d7d5cdc1bb785a1ea02c6c96b 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -857,6 +857,7 @@ class ElementsAccessor;
 class FixedArrayBase;
 class GlobalObject;
 class ObjectVisitor;

[Hannes Payer (out of office), 2014/11/06 12:29:46]

Can we fix the alphabetic order here. Move ObjectVisitor down.

[Igor Sheludko, 2014/11/07 08:03:53]

Done.

+class LayoutDescriptor;
 class LookupIterator;
 class StringStream;
 class TypeFeedbackVector;
@@ -932,6 +933,7 @@ template <class C> inline bool Is(Object* obj);
   V(JSContextExtensionObject)      \
   V(JSGeneratorObject)             \
   V(JSModule)                      \
+  V(LayoutDescriptor)              \
   V(Map)                           \
   V(DescriptorArray)               \
   V(TransitionArray)               \
@@ -2059,12 +2061,18 @@ class JSObject: public JSReceiver {
   static void MigrateSlowToFast(Handle<JSObject> object,
                                 int unused_property_fields);
 
+  inline bool IsUnboxedDoubleField(FieldIndex index);
+
   // Access fast-case object properties at index.
   static Handle<Object> FastPropertyAt(Handle<JSObject> object,
                                        Representation representation,
                                        FieldIndex index);
   inline Object* RawFastPropertyAt(FieldIndex index);
+  inline double RawFastDoublePropertyAt(FieldIndex index);
+
   inline void FastPropertyAtPut(FieldIndex index, Object* value);
+  inline void RawFastPropertyAtPut(FieldIndex index, Object* value);
+  inline void RawFastDoublePropertyAtPut(FieldIndex index, double value);
   void WriteToField(int descriptor, Object* value);
 
   // Access to in object properties.
@@ -3128,9 +3136,7 @@ class DescriptorArray: public FixedArray {
 
   // Transfer a complete descriptor from the src descriptor array to this
   // descriptor array.
-  void CopyFrom(int index,
-                DescriptorArray* src,
-                const WhitenessWitness&);
+  void CopyFrom(int index, DescriptorArray* src, const WhitenessWitness&);
 
   inline void Set(int descriptor_number,
                   Descriptor* desc,
@@ -4813,6 +4819,7 @@ TYPED_ARRAYS(FIXED_TYPED_ARRAY_TRAITS)
 
 #undef FIXED_TYPED_ARRAY_TRAITS
 
+
 // DeoptimizationInputData is a fixed array used to hold the deoptimization
 // data for code generated by the Hydrogen/Lithium compiler.  It also
 // contains information about functions that were inlined.  If N different
@@ -5903,7 +5910,19 @@ class Map: public HeapObject {
 
   // [instance descriptors]: describes the object.
   DECL_ACCESSORS(instance_descriptors, DescriptorArray)
-  inline void InitializeDescriptors(DescriptorArray* descriptors);
+
+  // [layout descriptor]: describes the object layout.
+  DECL_ACCESSORS(layout_descriptor, LayoutDescriptor)
+  // |layout descriptor| accessor which can be used from GC.
+  inline LayoutDescriptor* layout_descriptor_gc_safe();
+
+  // |layout descriptor| accessor that returns a handle.
+  inline Handle<LayoutDescriptor> GetLayoutDescriptor();
+
+  inline void UpdateDescriptors(DescriptorArray* descriptors,
+                                LayoutDescriptor* layout_descriptor);
+  inline void InitializeDescriptors(DescriptorArray* descriptors,
+                                    LayoutDescriptor* layout_descriptor);
 
   // [stub cache]: contains stubs compiled for this map.
   DECL_ACCESSORS(code_cache, Object)
@@ -6231,7 +6250,13 @@ class Map: public HeapObject {
       kConstructorOffset + kPointerSize;
   static const int kDescriptorsOffset =
       kTransitionsOrBackPointerOffset + kPointerSize;
+#if V8_DOUBLE_FIELDS_UNBOXING
+  static const int kLayoutDecriptorOffset = kDescriptorsOffset + kPointerSize;
+  static const int kCodeCacheOffset = kLayoutDecriptorOffset + kPointerSize;
+#else
+  static const int kLayoutDecriptorOffset = 1;  // Must not be ever accessed.
   static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
+#endif
   static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;
   static const int kSize = kDependentCodeOffset + kPointerSize;
 
@@ -6309,6 +6334,9 @@ class Map: public HeapObject {
   // The "shared" flags of both this map and |other| are ignored.
   bool EquivalentToForNormalization(Map* other, PropertyNormalizationMode mode);
 
+  // Returns true if given field is unboxed double.
+  inline bool IsUnboxedDoubleField(FieldIndex index);
+
  private:
   static void ConnectElementsTransition(Handle<Map> parent, Handle<Map> child);
   static void ConnectTransition(Handle<Map> parent, Handle<Map> child,
@@ -6320,16 +6348,14 @@ class Map: public HeapObject {
                                      Handle<DescriptorArray> descriptors,
                                      Descriptor* descriptor);
   static Handle<Map> CopyInstallDescriptors(
-      Handle<Map> map,
-      int new_descriptor,
-      Handle<DescriptorArray> descriptors);
+      Handle<Map> map, int new_descriptor, Handle<DescriptorArray> descriptors,
+      Handle<LayoutDescriptor> layout_descriptor);
   static Handle<Map> CopyAddDescriptor(Handle<Map> map,
                                        Descriptor* descriptor,
                                        TransitionFlag flag);
   static Handle<Map> CopyReplaceDescriptors(
-      Handle<Map> map,
-      Handle<DescriptorArray> descriptors,
-      TransitionFlag flag,
+      Handle<Map> map, Handle<DescriptorArray> descriptors,
+      Handle<LayoutDescriptor> layout_descriptor, TransitionFlag flag,
       MaybeHandle<Name> maybe_name,
       SimpleTransitionFlag simple_flag = FULL_TRANSITION);
   static Handle<Map> CopyReplaceDescriptor(Handle<Map> map,
@@ -6359,7 +6385,9 @@ class Map: public HeapObject {
   void ZapTransitions();
 
   void DeprecateTransitionTree();
-  void DeprecateTarget(Name* key, DescriptorArray* new_descriptors);
+  void DeprecateTarget(Handle<Name> key,
+                       Handle<DescriptorArray> new_descriptors,
+                       Handle<LayoutDescriptor> new_layout_descriptor);
 
   Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);
 
@@ -6390,6 +6418,7 @@ class Map: public HeapObject {
   static const int kFastPropertiesSoftLimit = 12;
   static const int kMaxFastProperties = 128;
 
+  friend class TestAccessor;

[Hannes Payer (out of office), 2014/11/06 12:29:46]

Uff, do we really have to add test dependencies to the code?

[Igor Sheludko, 2014/11/07 08:03:53]

Done.

   DISALLOW_IMPLICIT_CONSTRUCTORS(Map);
 };