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 31d0a16dfb827b7fa14fcab61f14350d1fb48e15..822dc048d33b33ac5198a4f81a1c1b4d54fa8c9d 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -858,8 +858,9 @@ class DictionaryElementsAccessor;
 class ElementsAccessor;
 class FixedArrayBase;
 class GlobalObject;
-class ObjectVisitor;
+class LayoutDescriptor;
 class LookupIterator;
+class ObjectVisitor;
 class StringStream;
 class TypeFeedbackVector;
 class WeakCell;
@@ -934,6 +935,7 @@ template <class C> inline bool Is(Object* obj);
   V(JSContextExtensionObject)      \
   V(JSGeneratorObject)             \
   V(JSModule)                      \
+  V(LayoutDescriptor)              \
   V(Map)                           \
   V(DescriptorArray)               \
   V(TransitionArray)               \
@@ -2063,12 +2065,18 @@ class JSObject: public JSReceiver {
   static void MigrateSlowToFast(Handle<JSObject> object,
                                 int unused_property_fields, const char* reason);
 
+  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.
@@ -3132,9 +3140,7 @@ 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,
@@ -4814,6 +4820,7 @@ 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
@@ -5911,7 +5918,19 @@ 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)
@@ -6241,7 +6260,13 @@ 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;
 
@@ -6319,11 +6344,18 @@ 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);
+
 #if TRACE_MAPS
   static void TraceTransition(const char* what, Map* from, Map* to, Name* name);
   static void TraceAllTransitions(Map* map);
 #endif
 
+  static inline Handle<Map> CopyInstallDescriptorsForTesting(
+      Handle<Map> map, int new_descriptor, Handle<DescriptorArray> descriptors,
+      Handle<LayoutDescriptor> layout_descriptor);
+
  private:
   static void ConnectElementsTransition(Handle<Map> parent, Handle<Map> child);
   static void ConnectTransition(Handle<Map> parent, Handle<Map> child,
@@ -6335,18 +6367,17 @@ 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,
-                                            MaybeHandle<Name> maybe_name,
-                                            const char* reason,
-                                            SimpleTransitionFlag simple_flag);
+  static Handle<Map> CopyReplaceDescriptors(
+      Handle<Map> map, Handle<DescriptorArray> descriptors,
+      Handle<LayoutDescriptor> layout_descriptor, TransitionFlag flag,
+      MaybeHandle<Name> maybe_name, const char* reason,
+      SimpleTransitionFlag simple_flag);
+
   static Handle<Map> CopyReplaceDescriptor(Handle<Map> map,
                                            Handle<DescriptorArray> descriptors,
                                            Descriptor* descriptor,
@@ -6376,7 +6407,8 @@ class Map: public HeapObject {
   void DeprecateTransitionTree();
   void DeprecateTarget(PropertyType type, Name* key,
                        PropertyAttributes attributes,
-                       DescriptorArray* new_descriptors);
+                       DescriptorArray* new_descriptors,
+                       LayoutDescriptor* new_layout_descriptor);
 
   Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);