Revert r4715.

src/objects.h

Index: src/objects.h
===================================================================
--- src/objects.h	(revision 4722)
+++ src/objects.h	(working copy)
@@ -54,28 +54,29 @@
 //           - JSGlobalObject
 //           - JSBuiltinsObject
 //         - JSGlobalProxy
-//        - JSValue
-//       - ByteArray
-//       - PixelArray
-//       - ExternalArray
-//         - ExternalByteArray
-//         - ExternalUnsignedByteArray
-//         - ExternalShortArray
-//         - ExternalUnsignedShortArray
-//         - ExternalIntArray
-//         - ExternalUnsignedIntArray
-//         - ExternalFloatArray
-//       - FixedArray
-//         - DescriptorArray
-//         - HashTable
-//           - Dictionary
-//           - SymbolTable
-//           - CompilationCacheTable
-//           - CodeCacheHashTable
-//           - MapCache
-//         - Context
-//         - GlobalContext
-//         - JSFunctionResultCache
+//         - JSValue
+//       - Array
+//         - ByteArray
+//         - PixelArray
+//         - ExternalArray
+//           - ExternalByteArray
+//           - ExternalUnsignedByteArray
+//           - ExternalShortArray
+//           - ExternalUnsignedShortArray
+//           - ExternalIntArray
+//           - ExternalUnsignedIntArray
+//           - ExternalFloatArray
+//         - FixedArray
+//           - DescriptorArray
+//           - HashTable
+//             - Dictionary
+//             - SymbolTable
+//             - CompilationCacheTable
+//             - CodeCacheHashTable
+//             - MapCache
+//           - Context
+//           - GlobalContext
+//           - JSFunctionResultCache
 //       - String
 //         - SeqString
 //           - SeqAsciiString
@@ -675,10 +676,6 @@
   // Return the object's prototype (might be Heap::null_value()).
   Object* GetPrototype();
 
-  // Tries to convert an object to an array index.  Returns true and sets
-  // the output parameter if it succeeds.
-  inline bool ToArrayIndex(uint32_t* index);
-
   // Returns true if this is a JSValue containing a string and the index is
   // < the length of the string.  Used to implement [] on strings.
   inline bool IsStringObjectWithCharacterAt(uint32_t index);
@@ -1029,7 +1026,7 @@
 
   // Returns the field at offset in obj, as a read/write Object* reference.
   // Does no checking, and is safe to use during GC, while maps are invalid.
-  // Does not invoke write barrier, so should only be assigned to
+  // Does not update remembered sets, so should only be assigned to
   // during marking GC.
   static inline Object** RawField(HeapObject* obj, int offset);
 
@@ -1049,7 +1046,6 @@
   void HeapObjectPrint();
   void HeapObjectVerify();
   inline void VerifyObjectField(int offset);
-  inline void VerifySmiField(int offset);
 
   void PrintHeader(const char* id);
 
@@ -1154,7 +1150,7 @@
   };
 
   // [properties]: Backing storage for properties.
-  // properties is a FixedArray in the fast case and a Dictionary in the
+  // properties is a FixedArray in the fast case, and a Dictionary in the
   // slow case.
   DECL_ACCESSORS(properties, FixedArray)  // Get and set fast properties.
   inline void initialize_properties();
@@ -1162,9 +1158,9 @@
   inline StringDictionary* property_dictionary();  // Gets slow properties.
 
   // [elements]: The elements (properties with names that are integers).
-  // elements is a FixedArray in the fast case, a Dictionary in the slow
-  // case, and a PixelArray or ExternalArray in special cases.
-  DECL_ACCESSORS(elements, HeapObject)
+  // elements is a FixedArray in the fast case, and a Dictionary in the slow
+  // case or a PixelArray in a special case.
+  DECL_ACCESSORS(elements, Array)  // Get and set fast elements.
   inline void initialize_elements();
   inline ElementsKind GetElementsKind();
   inline bool HasFastElements();
@@ -1598,13 +1594,37 @@
 };
 
 
-// FixedArray describes fixed-sized arrays with element type Object*.
-class FixedArray: public HeapObject {
+// Abstract super class arrays. It provides length behavior.
+class Array: public HeapObject {
  public:
   // [length]: length of the array.
   inline int length();
   inline void set_length(int value);
 
+  // Convert an object to an array index.
+  // Returns true if the conversion succeeded.
+  static inline bool IndexFromObject(Object* object, uint32_t* index);
+
+  // Layout descriptor.
+  static const int kLengthOffset = HeapObject::kHeaderSize;
+
+ protected:
+  // No code should use the Array class directly, only its subclasses.
+  // Use the kHeaderSize of the appropriate subclass, which may be aligned.
+  static const int kHeaderSize = kLengthOffset + kIntSize;
+  static const int kAlignedSize = POINTER_SIZE_ALIGN(kHeaderSize);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Array);
+};
+
+
+// FixedArray describes fixed sized arrays where element
+// type is Object*.
+
+class FixedArray: public Array {
+ public:
+
   // Setter and getter for elements.
   inline Object* get(int index);
   // Setter that uses write barrier.
@@ -1645,10 +1665,7 @@
   // Casting.
   static inline FixedArray* cast(Object* obj);
 
-  // Layout description.
-  // Length is smi tagged when it is stored.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
-  static const int kHeaderSize = kLengthOffset + kPointerSize;
+  static const int kHeaderSize = Array::kAlignedSize;
 
   // Maximal allowed size, in bytes, of a single FixedArray.
   // Prevents overflowing size computations, as well as extreme memory
@@ -2347,12 +2364,8 @@
 // ByteArray represents fixed sized byte arrays.  Used by the outside world,
 // such as PCRE, and also by the memory allocator and garbage collector to
 // fill in free blocks in the heap.
-class ByteArray: public HeapObject {
+class ByteArray: public Array {
  public:
-  // [length]: length of the array.
-  inline int length();
-  inline void set_length(int value);
-
   // Setter and getter.
   inline byte get(int index);
   inline void set(int index, byte value);
@@ -2361,7 +2374,7 @@
   inline int get_int(int index);
 
   static int SizeFor(int length) {
-    return OBJECT_POINTER_ALIGN(kHeaderSize + length);
+    return OBJECT_SIZE_ALIGN(kHeaderSize + length);
   }
   // We use byte arrays for free blocks in the heap.  Given a desired size in
   // bytes that is a multiple of the word size and big enough to hold a byte
@@ -2389,13 +2402,10 @@
   void ByteArrayVerify();
 #endif
 
-  // Layout description.
-  // Length is smi tagged when it is stored.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
-  static const int kHeaderSize = kLengthOffset + kPointerSize;
+  // ByteArray headers are not quadword aligned.
+  static const int kHeaderSize = Array::kHeaderSize;
+  static const int kAlignedSize = Array::kAlignedSize;
 
-  static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
-
   // Maximal memory consumption for a single ByteArray.
   static const int kMaxSize = 512 * MB;
   // Maximal length of a single ByteArray.
@@ -2413,12 +2423,8 @@
 //                      multipage/the-canvas-element.html#canvaspixelarray
 // In particular, write access clamps the value written to 0 or 255 if the
 // value written is outside this range.
-class PixelArray: public HeapObject {
+class PixelArray: public Array {
  public:
-  // [length]: length of the array.
-  inline int length();
-  inline void set_length(int value);
-
   // [external_pointer]: The pointer to the external memory area backing this
   // pixel array.
   DECL_ACCESSORS(external_pointer, uint8_t)  // Pointer to the data store.
@@ -2443,11 +2449,9 @@
   static const int kMaxLength = 0x3fffffff;
 
   // PixelArray headers are not quadword aligned.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
-  static const int kExternalPointerOffset =
-      POINTER_SIZE_ALIGN(kLengthOffset + kIntSize);
+  static const int kExternalPointerOffset = Array::kAlignedSize;
   static const int kHeaderSize = kExternalPointerOffset + kPointerSize;
-  static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
+  static const int kAlignedSize = OBJECT_SIZE_ALIGN(kHeaderSize);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PixelArray);
@@ -2465,12 +2469,8 @@
 // Out-of-range values passed to the setter are converted via a C
 // cast, not clamping. Out-of-range indices cause exceptions to be
 // raised rather than being silently ignored.
-class ExternalArray: public HeapObject {
+class ExternalArray: public Array {
  public:
-  // [length]: length of the array.
-  inline int length();
-  inline void set_length(int value);
-
   // [external_pointer]: The pointer to the external memory area backing this
   // external array.
   DECL_ACCESSORS(external_pointer, void)  // Pointer to the data store.
@@ -2482,11 +2482,9 @@
   static const int kMaxLength = 0x3fffffff;
 
   // ExternalArray headers are not quadword aligned.
-  static const int kLengthOffset = HeapObject::kHeaderSize;
-  static const int kExternalPointerOffset =
-      POINTER_SIZE_ALIGN(kLengthOffset + kIntSize);
+  static const int kExternalPointerOffset = Array::kAlignedSize;
   static const int kHeaderSize = kExternalPointerOffset + kPointerSize;
-  static const int kAlignedSize = OBJECT_POINTER_ALIGN(kHeaderSize);
+  static const int kAlignedSize = OBJECT_SIZE_ALIGN(kHeaderSize);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalArray);
@@ -3040,14 +3038,8 @@
       kConstructorOffset + kPointerSize;
   static const int kCodeCacheOffset = kInstanceDescriptorsOffset + kPointerSize;
   static const int kPadStart = kCodeCacheOffset + kPointerSize;
-  static const int kSize = MAP_POINTER_ALIGN(kPadStart);
+  static const int kSize = MAP_SIZE_ALIGN(kPadStart);
 
-  // Layout of pointer fields. Heap iteration code relies on them
-  // being continiously allocated.
-  static const int kPointerFieldsBeginOffset = Map::kPrototypeOffset;
-  static const int kPointerFieldsEndOffset =
-      Map::kCodeCacheOffset + kPointerSize;
-
   // Byte offsets within kInstanceSizesOffset.
   static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;
   static const int kInObjectPropertiesByte = 1;
@@ -3358,64 +3350,23 @@
   static const int kInferredNameOffset = kDebugInfoOffset + kPointerSize;
   static const int kThisPropertyAssignmentsOffset =
       kInferredNameOffset + kPointerSize;
-#if V8_HOST_ARCH_32_BIT
-  // Smi fields.
+  // Integer fields.
   static const int kLengthOffset =
       kThisPropertyAssignmentsOffset + kPointerSize;
-  static const int kFormalParameterCountOffset = kLengthOffset + kPointerSize;
+  static const int kFormalParameterCountOffset = kLengthOffset + kIntSize;
   static const int kExpectedNofPropertiesOffset =
-      kFormalParameterCountOffset + kPointerSize;
-  static const int kNumLiteralsOffset =
-      kExpectedNofPropertiesOffset + kPointerSize;
-  static const int kStartPositionAndTypeOffset =
-      kNumLiteralsOffset + kPointerSize;
-  static const int kEndPositionOffset =
-      kStartPositionAndTypeOffset + kPointerSize;
-  static const int kFunctionTokenPositionOffset =
-      kEndPositionOffset + kPointerSize;
-  static const int kCompilerHintsOffset =
-      kFunctionTokenPositionOffset + kPointerSize;
-  static const int kThisPropertyAssignmentsCountOffset =
-      kCompilerHintsOffset + kPointerSize;
-  // Total size.
-  static const int kSize = kThisPropertyAssignmentsCountOffset + kPointerSize;
-#else
-  // The only reason to use smi fields instead of int fields
-  // is to allow interation without maps decoding during
-  // garbage collections.
-  // To avoid wasting space on 64-bit architectures we use
-  // the following trick: we group integer fields into pairs
-  // First integer in each pair is shifted left by 1.
-  // By doing this we guarantee that LSB of each kPointerSize aligned
-  // word is not set and thus this word cannot be treated as pointer
-  // to HeapObject during old space traversal.
-  static const int kLengthOffset =
-      kThisPropertyAssignmentsOffset + kPointerSize;
-  static const int kFormalParameterCountOffset =
-      kLengthOffset + kIntSize;
-
-  static const int kExpectedNofPropertiesOffset =
       kFormalParameterCountOffset + kIntSize;
-  static const int kNumLiteralsOffset =
-      kExpectedNofPropertiesOffset + kIntSize;
-
-  static const int kEndPositionOffset =
-      kNumLiteralsOffset + kIntSize;
+  static const int kNumLiteralsOffset = kExpectedNofPropertiesOffset + kIntSize;
   static const int kStartPositionAndTypeOffset =
-      kEndPositionOffset + kIntSize;
-
-  static const int kFunctionTokenPositionOffset =
-      kStartPositionAndTypeOffset + kIntSize;
+      kNumLiteralsOffset + kIntSize;
+  static const int kEndPositionOffset = kStartPositionAndTypeOffset + kIntSize;
+  static const int kFunctionTokenPositionOffset = kEndPositionOffset + kIntSize;
   static const int kCompilerHintsOffset =
       kFunctionTokenPositionOffset + kIntSize;
-
   static const int kThisPropertyAssignmentsCountOffset =
       kCompilerHintsOffset + kIntSize;
-
   // Total size.
   static const int kSize = kThisPropertyAssignmentsCountOffset + kIntSize;
-
-#endif
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kSize);
 
  private:
@@ -4171,7 +4122,8 @@
   // Layout description.
   static const int kLengthOffset = HeapObject::kHeaderSize;
   static const int kHashFieldOffset = kLengthOffset + kPointerSize;
-  static const int kSize = kHashFieldOffset + kPointerSize;
+  static const int kSize = kHashFieldOffset + kIntSize;
+  // Notice: kSize is not pointer-size aligned if pointers are 64-bit.
 
   // Maximum number of characters to consider when trying to convert a string
   // value into an array index.
@@ -4190,7 +4142,7 @@
   // whether a hash code has been computed.  If the hash code has been
   // computed the 2nd bit tells whether the string can be used as an
   // array index.
-  static const int kHashNotComputedMask = 1;
+  static const int kHashComputedMask = 1;
   static const int kIsArrayIndexMask = 1 << 1;
   static const int kNofLengthBitFields = 2;
 
@@ -4208,15 +4160,10 @@
   static const int kArrayIndexHashMask = (1 << kArrayIndexHashLengthShift) - 1;
   static const int kArrayIndexValueBits =
       kArrayIndexHashLengthShift - kHashShift;
-  static const int kArrayIndexValueMask =
-      ((1 << kArrayIndexValueBits) - 1) << kHashShift;
 
   // Value of empty hash field indicating that the hash is not computed.
-  static const int kEmptyHashField = kHashNotComputedMask;
+  static const int kEmptyHashField = 0;
 
-  // Value of hash field containing computed hash equal to zero.
-  static const int kZeroHash = 0;
-
   // Maximal string length.
   static const int kMaxLength = (1 << (32 - 2)) - 1;
 
@@ -4283,8 +4230,6 @@
   // mutates the ConsString and might return a failure.
   Object* SlowTryFlatten(PretenureFlag pretenure);
 
-  static inline bool IsHashFieldComputed(uint32_t field);
-
   // Slow case of String::Equals.  This implementation works on any strings
   // but it is most efficient on strings that are almost flat.
   bool SlowEquals(String* other);
@@ -4334,7 +4279,7 @@
 
   // Computes the size for an AsciiString instance of a given length.
   static int SizeFor(int length) {
-    return OBJECT_POINTER_ALIGN(kHeaderSize + length * kCharSize);
+    return OBJECT_SIZE_ALIGN(kHeaderSize + length * kCharSize);
   }
 
   // Layout description.
@@ -4386,7 +4331,7 @@
 
   // Computes the size for a TwoByteString instance of a given length.
   static int SizeFor(int length) {
-    return OBJECT_POINTER_ALIGN(kHeaderSize + length * kShortSize);
+    return OBJECT_SIZE_ALIGN(kHeaderSize + length * kShortSize);
   }
 
   // Layout description.