Object's body descriptors refactoring.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 93f57333a150498810f73f264c74082e2147ff3b..12f220f144c2214e1b7695d0c749ae64cad55f17 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1555,15 +1555,35 @@ class HeapObject: public Object {
     return reinterpret_cast<Address>(this) - kHeapObjectTag;
   }
 
-  // Iterates over pointers contained in the object (including the Map)
+  // Iterates over pointers contained in the object (including the Map).
+  // If it's not performance critical iteration use the non-templatized
+  // version.
   void Iterate(ObjectVisitor* v);
 
+  template <typename ObjectVisitor>
+  inline void IterateFast(ObjectVisitor* v);
+
   // Iterates over all pointers contained in the object except the
   // first map pointer.  The object type is given in the first
   // parameter. This function does not access the map pointer in the
   // object, and so is safe to call while the map pointer is modified.
+  // If it's not performance critical iteration use the non-templatized
+  // version.
+  void IterateBody(ObjectVisitor* v);
   void IterateBody(InstanceType type, int object_size, ObjectVisitor* v);
 
+  template <typename ObjectVisitor>
+  inline void IterateBodyFast(ObjectVisitor* v);
+
+  template <typename ObjectVisitor>
+  inline void IterateBodyFast(InstanceType type, int object_size,
+                              ObjectVisitor* v);
+
+  // Returns true if the object contains a tagged value at given offset.
+  // It is used for invalid slots filtering. If the offset points outside
+  // of the object or to the map word, the result is UNDEFINED (!!!).
+  bool IsValidSlot(int offset);
+
   // Returns the heap object's size in bytes
   inline int Size();
 
@@ -1623,90 +1643,17 @@ class HeapObject: public Object {
 
   STATIC_ASSERT(kMapOffset == Internals::kHeapObjectMapOffset);
 
- protected:
-  // helpers for calling an ObjectVisitor to iterate over pointers in the
-  // half-open range [start, end) specified as integer offsets
-  inline void IteratePointers(ObjectVisitor* v, int start, int end);
-  // as above, for the single element at "offset"
-  inline void IteratePointer(ObjectVisitor* v, int offset);
-  // as above, for the next code link of a code object.
-  inline void IterateNextCodeLink(ObjectVisitor* v, int offset);
-
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(HeapObject);
 };
 
 
-// This is the base class for object's body descriptors.
-class BodyDescriptorBase {
- protected:
-  static inline void IterateBodyImpl(HeapObject* obj, int start_offset,
-                                     int end_offset, ObjectVisitor* v);
-
-  template <typename StaticVisitor>
-  static inline void IterateBodyImpl(Heap* heap, HeapObject* obj,
-                                     int start_offset, int end_offset);
-
-  static inline void IteratePointers(HeapObject* obj, int start_offset,
-                                     int end_offset, ObjectVisitor* v);
-
-  template <typename StaticVisitor>
-  static inline void IteratePointers(Heap* heap, HeapObject* obj,
-                                     int start_offset, int end_offset);
-};
-
-
-// This class describes a body of an object of a fixed size
-// in which all pointer fields are located in the [start_offset, end_offset)
-// interval.
 template <int start_offset, int end_offset, int size>
-class FixedBodyDescriptor : public BodyDescriptorBase {
- public:
-  static const int kStartOffset = start_offset;
-  static const int kEndOffset = end_offset;
-  static const int kSize = size;
+class FixedBodyDescriptor;
 
-  static inline void IterateBody(HeapObject* obj, ObjectVisitor* v) {
-    IterateBodyImpl(obj, start_offset, end_offset, v);
-  }
 
-  template <typename StaticVisitor>
-  static inline void IterateBody(HeapObject* obj) {
-    Heap* heap = obj->GetHeap();
-    IterateBodyImpl<StaticVisitor>(heap, obj, start_offset, end_offset);
-  }
-};
-
-
-// This base class describes a body of an object of a variable size
-// in which all pointer fields are located in the [start_offset, object_size)
-// interval.
 template <int start_offset>
-class FlexibleBodyDescriptorBase : public BodyDescriptorBase {
- public:
-  static const int kStartOffset = start_offset;
-
-  static inline void IterateBody(HeapObject* obj, int object_size,
-                                 ObjectVisitor* v) {
-    IterateBodyImpl(obj, start_offset, object_size, v);
-  }
-
-  template <typename StaticVisitor>
-  static inline void IterateBody(HeapObject* obj, int object_size) {
-    Heap* heap = obj->GetHeap();
-    IterateBodyImpl<StaticVisitor>(heap, obj, start_offset, object_size);
-  }
-};
-
-
-// This class describes a body of an object of a variable size
-// in which all pointer fields are located in the [start_offset, object_size)
-// interval. The size of the object is taken from the map.
-template <int start_offset>
-class FlexibleBodyDescriptor : public FlexibleBodyDescriptorBase<start_offset> {
- public:
-  static inline int SizeOf(Map* map, HeapObject* object);
-};
+class FlexibleBodyDescriptor;
 
 
 // The HeapNumber class describes heap allocated numbers that cannot be
@@ -2688,10 +2635,7 @@ class FixedArray: public FixedArrayBase {
   // object, the prefix of this array is sorted.
   void SortPairs(FixedArray* numbers, uint32_t len);
 
-  class BodyDescriptor : public FlexibleBodyDescriptorBase<kHeaderSize> {
-   public:
-    static inline int SizeOf(Map* map, HeapObject* object);
-  };
+  typedef FlexibleBodyDescriptor<kHeaderSize> BodyDescriptor;
 
  protected:
   // Set operation on FixedArray without using write barriers. Can
@@ -4423,7 +4367,6 @@ class BytecodeArray : public FixedArrayBase {
 
   // Dispatched behavior.
   inline int BytecodeArraySize();
-  inline void BytecodeArrayIterateBody(ObjectVisitor* v);
 
   DECLARE_PRINTER(BytecodeArray)
   DECLARE_VERIFIER(BytecodeArray)
@@ -4443,6 +4386,8 @@ class BytecodeArray : public FixedArrayBase {
   // Maximal length of a single BytecodeArray.
   static const int kMaxLength = kMaxSize - kHeaderSize;
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(BytecodeArray);
 };
@@ -4508,11 +4453,6 @@ class FixedTypedArrayBase: public FixedArrayBase {
   DECL_ACCESSORS(external_pointer, void)
 
   // Dispatched behavior.
-  inline void FixedTypedArrayBaseIterateBody(ObjectVisitor* v);
-
-  template <typename StaticVisitor>
-  inline void FixedTypedArrayBaseIterateBody();
-
   DECLARE_CAST(FixedTypedArrayBase)
 
   static const int kBasePointerOffset = FixedArrayBase::kHeaderSize;
@@ -4522,6 +4462,8 @@ class FixedTypedArrayBase: public FixedArrayBase {
 
   static const int kDataOffset = kHeaderSize;
 
+  class BodyDescriptor;
+
   inline int size();
 
   static inline int TypedArraySize(InstanceType type, int length);
@@ -5192,10 +5134,6 @@ class Code: public HeapObject {
 
   // Dispatched behavior.
   inline int CodeSize();
-  inline void CodeIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void CodeIterateBody(Heap* heap);
 
   DECLARE_PRINTER(Code)
   DECLARE_VERIFIER(Code)
@@ -5294,6 +5232,8 @@ class Code: public HeapObject {
   static const int kHeaderSize =
       (kHeaderPaddingStart + kCodeAlignmentMask) & ~kCodeAlignmentMask;
 
+  class BodyDescriptor;
+
   // Byte offsets within kKindSpecificFlags1Offset.
   static const int kFullCodeFlags = kKindSpecificFlags1Offset;
   class FullCodeFlagsHasDeoptimizationSupportField:
@@ -9204,11 +9144,7 @@ class ExternalOneByteString : public ExternalString {
 
   DECLARE_CAST(ExternalOneByteString)
 
-  // Garbage collection support.
-  inline void ExternalOneByteStringIterateBody(ObjectVisitor* v);
-
-  template <typename StaticVisitor>
-  inline void ExternalOneByteStringIterateBody();
+  class BodyDescriptor;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalOneByteString);
@@ -9243,11 +9179,7 @@ class ExternalTwoByteString: public ExternalString {
 
   DECLARE_CAST(ExternalTwoByteString)
 
-  // Garbage collection support.
-  inline void ExternalTwoByteStringIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void ExternalTwoByteStringIterateBody();
+  class BodyDescriptor;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalTwoByteString);
@@ -9886,6 +9818,8 @@ class JSWeakCollection: public JSObject {
   static const int kNextOffset = kTableOffset + kPointerSize;
   static const int kSize = kNextOffset + kPointerSize;
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakCollection);
 };
@@ -9964,11 +9898,6 @@ class JSArrayBuffer: public JSObject {
   DECLARE_VERIFIER(JSArrayBuffer)
 
   static const int kByteLengthOffset = JSObject::kHeaderSize;
-
-  // NOTE: GC will visit objects fields:
-  // 1. From JSObject::BodyDescriptor::kStartOffset to kByteLengthOffset +
-  //    kPointerSize
-  // 2. From start of the internal fields and up to the end of them
   static const int kBackingStoreOffset = kByteLengthOffset + kPointerSize;
   static const int kBitFieldSlot = kBackingStoreOffset + kPointerSize;
 #if V8_TARGET_LITTLE_ENDIAN || !V8_HOST_ARCH_64_BIT
@@ -9981,11 +9910,9 @@ class JSArrayBuffer: public JSObject {
   static const int kSizeWithInternalFields =
       kSize + v8::ArrayBuffer::kInternalFieldCount * kPointerSize;
 
-  template <typename StaticVisitor>
-  static inline void JSArrayBufferIterateBody(Heap* heap, HeapObject* obj);
-
-  static inline void JSArrayBufferIterateBody(HeapObject* obj,
-                                              ObjectVisitor* v);
+  // Iterates all fields in the object including internal ones except
+  // kBackingStoreOffset and kBitFieldSlot.
+  class BodyDescriptor;
 
   class IsExternal : public BitField<bool, 1, 1> {};
   class IsNeuterable : public BitField<bool, 2, 1> {};
@@ -10091,12 +10018,6 @@ class Foreign: public HeapObject {
   DECLARE_CAST(Foreign)
 
   // Dispatched behavior.
-  inline void ForeignIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void ForeignIterateBody();
-
-  // Dispatched behavior.
   DECLARE_PRINTER(Foreign)
   DECLARE_VERIFIER(Foreign)
 
@@ -10107,6 +10028,8 @@ class Foreign: public HeapObject {
 
   STATIC_ASSERT(kForeignAddressOffset == Internals::kForeignAddressOffset);
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Foreign);
 };
@@ -10770,9 +10693,6 @@ class ObjectVisitor BASE_EMBEDDED {
 };
 
 
-typedef FlexibleBodyDescriptor<HeapObject::kHeaderSize> StructBodyDescriptor;
-
-
 // BooleanBit is a helper class for setting and getting a bit in an integer.
 class BooleanBit : public AllStatic {
  public: