Object's body descriptors refactoring.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 1537 matching lines @@
   static inline HeapObject* FromAddress(Address address) {
     DCHECK_TAG_ALIGNED(address);
     return reinterpret_cast<HeapObject*>(address + kHeapObjectTag);
   }
 
   // Returns the address of this HeapObject.
   inline Address address() {
     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();
 
   // Indicates what type of values this heap object may contain.
   inline HeapObjectContents ContentType();
 
   // Given a heap object's map pointer, returns the heap size in bytes
   // Useful when the map pointer field is used for other purposes.
   // GC internal.
   inline int SizeFromMap(Map* map);
@@ skipping 39 matching lines @@
 
   inline AllocationAlignment RequiredAlignment();
 
   // Layout description.
   // First field in a heap object is map.
   static const int kMapOffset = Object::kHeaderSize;
   static const int kHeaderSize = kMapOffset + kPointerSize;
 
   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);
-};
+template <int start_offset, int end_offset, int size>
+class FixedBodyDescriptor;
 
 
-// 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;
-
-  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
 // represented in a Smi (small integer)
 class HeapNumber: public HeapObject {
  public:
   // [value]: number value.
   inline double value() const;
   inline void set_value(double value);
 
@@ skipping 961 matching lines @@
   // Swap two elements in a pair of arrays.  If this array and the
   // numbers array are the same object, the elements are only swapped
   // once.
   void SwapPairs(FixedArray* numbers, int i, int j);
 
   // Sort prefix of this array and the numbers array as pairs wrt. the
   // numbers.  If the numbers array and the this array are the same
   // 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
   // only be used for storing old space objects or smis.
   static inline void NoWriteBarrierSet(FixedArray* array,
                                        int index,
                                        Object* value);
 
   // Set operation on FixedArray without incremental write barrier. Can
   // only be used if the object is guaranteed to be white (whiteness witness
@@ skipping 1711 matching lines @@
   inline int parameter_count() const;
   inline void set_parameter_count(int number_of_parameters);
 
   // Accessors for the constant pool.
   DECL_ACCESSORS(constant_pool, FixedArray)
 
   DECLARE_CAST(BytecodeArray)
 
   // Dispatched behavior.
   inline int BytecodeArraySize();
-  inline void BytecodeArrayIterateBody(ObjectVisitor* v);
 
   DECLARE_PRINTER(BytecodeArray)
   DECLARE_VERIFIER(BytecodeArray)
 
   void Disassemble(std::ostream& os);
 
   // Layout description.
   static const int kFrameSizeOffset = FixedArrayBase::kHeaderSize;
   static const int kParameterSizeOffset = kFrameSizeOffset + kIntSize;
   static const int kConstantPoolOffset = kParameterSizeOffset + kIntSize;
   static const int kHeaderSize = kConstantPoolOffset + kPointerSize;
 
   static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
 
   // Maximal memory consumption for a single BytecodeArray.
   static const int kMaxSize = 512 * MB;
   // Maximal length of a single BytecodeArray.
   static const int kMaxLength = kMaxSize - kHeaderSize;
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(BytecodeArray);
 };
 
 
 // FreeSpace are fixed-size free memory blocks used by the heap and GC.
 // They look like heap objects (are heap object tagged and have a map) so that
 // the heap remains iterable.  They have a size and a next pointer.
 // The next pointer is the raw address of the next FreeSpace object (or NULL)
 // in the free list.
@@ skipping 45 matching lines @@
  public:
   // [base_pointer]: Either points to the FixedTypedArrayBase itself or nullptr.
   DECL_ACCESSORS(base_pointer, Object)
 
   // [external_pointer]: Contains the offset between base_pointer and the start
   // of the data. If the base_pointer is a nullptr, the external_pointer
   // therefore points to the actual backing store.
   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;
   static const int kExternalPointerOffset = kBasePointerOffset + kPointerSize;
   static const int kHeaderSize =
       DOUBLE_POINTER_ALIGN(kExternalPointerOffset + kPointerSize);
 
   static const int kDataOffset = kHeaderSize;
 
+  class BodyDescriptor;
+
   inline int size();
 
   static inline int TypedArraySize(InstanceType type, int length);
   inline int TypedArraySize(InstanceType type);
 
   // Use with care: returns raw pointer into heap.
   inline void* DataPtr();
 
   inline int DataSize();
 
@@ skipping 650 matching lines @@
   inline int ExecutableSize();
 
   // Locating source position.
   int SourcePosition(Address pc);
   int SourceStatementPosition(Address pc);
 
   DECLARE_CAST(Code)
 
   // Dispatched behavior.
   inline int CodeSize();
-  inline void CodeIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void CodeIterateBody(Heap* heap);
 
   DECLARE_PRINTER(Code)
   DECLARE_VERIFIER(Code)
 
   void ClearInlineCaches();
   void ClearInlineCaches(Kind kind);
 
   BailoutId TranslatePcOffsetToAstId(uint32_t pc_offset);
   uint32_t TranslateAstIdToPcOffset(BailoutId ast_id);
 
@@ skipping 78 matching lines @@
   static const int kPrologueOffset = kKindSpecificFlags2Offset + kIntSize;
   static const int kConstantPoolOffset = kPrologueOffset + kIntSize;
   static const int kHeaderPaddingStart =
       kConstantPoolOffset + kConstantPoolSize;
 
   // Add padding to align the instruction start following right after
   // the Code object header.
   static const int kHeaderSize =
       (kHeaderPaddingStart + kCodeAlignmentMask) & ~kCodeAlignmentMask;
 
+  class BodyDescriptor;
+
   // Byte offsets within kKindSpecificFlags1Offset.
   static const int kFullCodeFlags = kKindSpecificFlags1Offset;
   class FullCodeFlagsHasDeoptimizationSupportField:
       public BitField<bool, 0, 1> {};  // NOLINT
   class FullCodeFlagsHasDebugBreakSlotsField: public BitField<bool, 1, 1> {};
   class FullCodeFlagsHasRelocInfoForSerialization
       : public BitField<bool, 2, 1> {};
   // Bit 3 in this bitfield is unused.
   class ProfilerTicksField : public BitField<int, 4, 28> {};
 
@@ skipping 3890 matching lines @@
   // which the pointer cache has to be refreshed.
   inline void update_data_cache();
 
   inline const uint8_t* GetChars();
 
   // Dispatched behavior.
   inline uint16_t ExternalOneByteStringGet(int index);
 
   DECLARE_CAST(ExternalOneByteString)
 
-  // Garbage collection support.
-  inline void ExternalOneByteStringIterateBody(ObjectVisitor* v);
-
-  template <typename StaticVisitor>
-  inline void ExternalOneByteStringIterateBody();
+  class BodyDescriptor;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalOneByteString);
 };
 
 
 // The ExternalTwoByteString class is an external string backed by a UTF-16
 // encoded string.
 class ExternalTwoByteString: public ExternalString {
  public:
@@ skipping 14 matching lines @@
   inline const uint16_t* GetChars();
 
   // Dispatched behavior.
   inline uint16_t ExternalTwoByteStringGet(int index);
 
   // For regexp code.
   inline const uint16_t* ExternalTwoByteStringGetData(unsigned start);
 
   DECLARE_CAST(ExternalTwoByteString)
 
-  // Garbage collection support.
-  inline void ExternalTwoByteStringIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void ExternalTwoByteStringIterateBody();
+  class BodyDescriptor;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalTwoByteString);
 };
 
 
 // Utility superclass for stack-allocated objects that must be updated
 // on gc.  It provides two ways for the gc to update instances, either
 // iterating or updating after gc.
 class Relocatable BASE_EMBEDDED {
@@ skipping 618 matching lines @@
   static void Initialize(Handle<JSWeakCollection> collection, Isolate* isolate);
   static void Set(Handle<JSWeakCollection> collection, Handle<Object> key,
                   Handle<Object> value, int32_t hash);
   static bool Delete(Handle<JSWeakCollection> collection, Handle<Object> key,
                      int32_t hash);
 
   static const int kTableOffset = JSObject::kHeaderSize;
   static const int kNextOffset = kTableOffset + kPointerSize;
   static const int kSize = kNextOffset + kPointerSize;
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSWeakCollection);
 };
 
 
 // The JSWeakMap describes EcmaScript Harmony weak maps
 class JSWeakMap: public JSWeakCollection {
  public:
   DECLARE_CAST(JSWeakMap)
 
@@ skipping 58 matching lines @@
   static bool SetupAllocatingData(Handle<JSArrayBuffer> array_buffer,
                                   Isolate* isolate, size_t allocated_length,
                                   bool initialize = true,
                                   SharedFlag shared = SharedFlag::kNotShared);
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSArrayBuffer)
   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
   static const int kBitFieldOffset = kBitFieldSlot;
 #else
   static const int kBitFieldOffset = kBitFieldSlot + kIntSize;
 #endif
   static const int kSize = kBitFieldSlot + kPointerSize;
 
   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> {};
   class WasNeutered : public BitField<bool, 3, 1> {};
   class IsShared : public BitField<bool, 4, 1> {};
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSArrayBuffer);
 };
 
@@ skipping 85 matching lines @@
 // Foreign describes objects pointing from JavaScript to C structures.
 class Foreign: public HeapObject {
  public:
   // [address]: field containing the address.
   inline Address foreign_address();
   inline void set_foreign_address(Address value);
 
   DECLARE_CAST(Foreign)
 
   // Dispatched behavior.
-  inline void ForeignIterateBody(ObjectVisitor* v);
-
-  template<typename StaticVisitor>
-  inline void ForeignIterateBody();
-
-  // Dispatched behavior.
   DECLARE_PRINTER(Foreign)
   DECLARE_VERIFIER(Foreign)
 
   // Layout description.
 
   static const int kForeignAddressOffset = HeapObject::kHeaderSize;
   static const int kSize = kForeignAddressOffset + kPointerSize;
 
   STATIC_ASSERT(kForeignAddressOffset == Internals::kForeignAddressOffset);
 
+  class BodyDescriptor;
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Foreign);
 };
 
 
 // The JSArray describes JavaScript Arrays
 //  Such an array can be in one of two modes:
 //    - fast, backing storage is a FixedArray and length <= elements.length();
 //       Please note: push and pop can be used to grow and shrink the array.
 //    - slow, backing storage is a HashTable with numbers as keys.
@@ skipping 643 matching lines @@
   // Visits a handle that has an embedder-assigned class ID.
   virtual void VisitEmbedderReference(Object** p, uint16_t class_id) {}
 
   // Intended for serialization/deserialization checking: insert, or
   // check for the presence of, a tag at this position in the stream.
   // Also used for marking up GC roots in heap snapshots.
   virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
 };
 
 
-typedef FlexibleBodyDescriptor<HeapObject::kHeaderSize> StructBodyDescriptor;
-
-
 // BooleanBit is a helper class for setting and getting a bit in an integer.
 class BooleanBit : public AllStatic {
  public:
   static inline bool get(int value, int bit_position) {
     return (value & (1 << bit_position)) != 0;
   }
 
   static inline int set(int value, int bit_position, bool v) {
     if (v) {
       value |= (1 << bit_position);
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_