Upstream version 9.38.207.0
[platform/framework/web/crosswalk.git] / src / v8 / src / objects.h
index 4f65328..fb4470e 100644 (file)
 // Copyright 2012 the V8 project authors. All rights reserved.
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-//       notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-//       copyright notice, this list of conditions and the following
-//       disclaimer in the documentation and/or other materials provided
-//       with the distribution.
-//     * Neither the name of Google Inc. nor the names of its
-//       contributors may be used to endorse or promote products derived
-//       from this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// 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 "allocation.h"
-#include "assert-scope.h"
-#include "builtins.h"
-#include "elements-kind.h"
-#include "flags.h"
-#include "list.h"
-#include "property-details.h"
-#include "smart-pointers.h"
-#include "unicode-inl.h"
+#include "src/allocation.h"
+#include "src/assert-scope.h"
+#include "src/builtins.h"
+#include "src/checks.h"
+#include "src/elements-kind.h"
+#include "src/field-index.h"
+#include "src/flags.h"
+#include "src/list.h"
+#include "src/property-details.h"
+#include "src/smart-pointers.h"
+#include "src/unicode-inl.h"
+#include "src/zone.h"
+
 #if V8_TARGET_ARCH_ARM
-#include "arm/constants-arm.h"
+#include "src/arm/constants-arm.h"  // NOLINT
+#elif V8_TARGET_ARCH_ARM64
+#include "src/arm64/constants-arm64.h"  // NOLINT
 #elif V8_TARGET_ARCH_MIPS
-#include "mips/constants-mips.h"
+#include "src/mips/constants-mips.h"  // NOLINT
+#elif V8_TARGET_ARCH_MIPS64
+#include "src/mips64/constants-mips64.h"  // NOLINT
 #endif
-#include "v8checks.h"
-#include "zone.h"
 
 
 //
 // Most object types in the V8 JavaScript are described in this file.
 //
 // Inheritance hierarchy:
-// - MaybeObject    (an object or a failure)
-//   - Failure      (immediate for marking failed operation)
-//   - Object
-//     - Smi          (immediate small integer)
-//     - HeapObject   (superclass for everything allocated in the heap)
-//       - JSReceiver  (suitable for property access)
-//         - JSObject
-//           - JSArray
-//           - JSArrayBuffer
-//           - JSArrayBufferView
-//             - JSTypedArray
-//             - JSDataView
+// - Object
+//   - Smi          (immediate small integer)
+//   - HeapObject   (superclass for everything allocated in the heap)
+//     - JSReceiver  (suitable for property access)
+//       - JSObject
+//         - JSArray
+//         - JSArrayBuffer
+//         - JSArrayBufferView
+//           - JSTypedArray
+//           - JSDataView
+//         - JSCollection
+//         - Float32x4
+//         - Float64x2
+//         - Int32x4
 //           - JSSet
 //           - JSMap
-//           - JSWeakCollection
-//             - JSWeakMap
-//             - JSWeakSet
-//           - JSRegExp
-//           - JSFunction
-//           - JSGeneratorObject
-//           - JSModule
-//           - GlobalObject
-//             - JSGlobalObject
-//             - JSBuiltinsObject
-//           - JSGlobalProxy
-//           - JSValue
-//             - JSDate
-//           - JSMessageObject
-//         - JSProxy
-//           - JSFunctionProxy
-//       - FixedArrayBase
-//         - ByteArray
-//         - FixedArray
-//           - DescriptorArray
-//           - HashTable
-//             - Dictionary
-//             - StringTable
-//             - CompilationCacheTable
-//             - CodeCacheHashTable
-//             - MapCache
-//           - Context
-//           - JSFunctionResultCache
-//           - ScopeInfo
-//           - TransitionArray
-//         - FixedDoubleArray
-//         - ExternalArray
-//           - ExternalUint8ClampedArray
-//           - ExternalInt8Array
-//           - ExternalUint8Array
-//           - ExternalInt16Array
-//           - ExternalUint16Array
-//           - ExternalInt32Array
-//           - ExternalUint32Array
-//           - ExternalFloat32Array
-//           - ExternalFloat32x4Array
-//           - ExternalInt32x4Array
-//       - Name
-//         - String
-//           - SeqString
-//             - SeqOneByteString
-//             - SeqTwoByteString
-//           - SlicedString
-//           - ConsString
-//           - ExternalString
-//             - ExternalAsciiString
-//             - ExternalTwoByteString
-//           - InternalizedString
-//             - SeqInternalizedString
-//               - SeqOneByteInternalizedString
-//               - SeqTwoByteInternalizedString
-//             - ConsInternalizedString
-//             - ExternalInternalizedString
-//               - ExternalAsciiInternalizedString
-//               - ExternalTwoByteInternalizedString
-//         - Symbol
-//       - HeapNumber
-//       - Float32x4
-//       - Int32x4
-//       - Cell
-//         - PropertyCell
-//       - Code
-//       - Map
-//       - Oddball
-//       - Foreign
-//       - SharedFunctionInfo
-//       - Struct
-//         - Box
-//         - DeclaredAccessorDescriptor
-//         - AccessorInfo
-//           - DeclaredAccessorInfo
-//           - ExecutableAccessorInfo
-//         - AccessorPair
-//         - AccessCheckInfo
-//         - InterceptorInfo
-//         - CallHandlerInfo
-//         - TemplateInfo
-//           - FunctionTemplateInfo
-//           - ObjectTemplateInfo
-//         - Script
-//         - SignatureInfo
-//         - TypeSwitchInfo
-//         - DebugInfo
-//         - BreakPointInfo
-//         - CodeCache
+//         - JSSetIterator
+//         - JSMapIterator
+//         - JSWeakCollection
+//           - JSWeakMap
+//           - JSWeakSet
+//         - JSRegExp
+//         - JSFunction
+//         - JSGeneratorObject
+//         - JSModule
+//         - GlobalObject
+//           - JSGlobalObject
+//           - JSBuiltinsObject
+//         - JSGlobalProxy
+//         - JSValue
+//           - JSDate
+//         - JSMessageObject
+//       - JSProxy
+//         - JSFunctionProxy
+//     - FixedArrayBase
+//       - ByteArray
+//       - FixedArray
+//         - DescriptorArray
+//         - HashTable
+//           - Dictionary
+//           - StringTable
+//           - CompilationCacheTable
+//           - CodeCacheHashTable
+//           - MapCache
+//         - OrderedHashTable
+//           - OrderedHashSet
+//           - OrderedHashMap
+//         - Context
+//         - JSFunctionResultCache
+//         - ScopeInfo
+//         - TransitionArray
+//       - FixedDoubleArray
+//       - ExternalArray
+//         - ExternalUint8ClampedArray
+//         - ExternalInt8Array
+//         - ExternalUint8Array
+//         - ExternalInt16Array
+//         - ExternalUint16Array
+//         - ExternalInt32Array
+//         - ExternalUint32Array
+//         - ExternalFloat32Array
+//         - ExternalFloat32x4Array
+//         - ExternalFloat64x2Array
+//         - ExternalInt32x4Array
+//     - Name
+//       - String
+//         - SeqString
+//           - SeqOneByteString
+//           - SeqTwoByteString
+//         - SlicedString
+//         - ConsString
+//         - ExternalString
+//           - ExternalAsciiString
+//           - ExternalTwoByteString
+//         - InternalizedString
+//           - SeqInternalizedString
+//             - SeqOneByteInternalizedString
+//             - SeqTwoByteInternalizedString
+//           - ConsInternalizedString
+//           - ExternalInternalizedString
+//             - ExternalAsciiInternalizedString
+//             - ExternalTwoByteInternalizedString
+//       - Symbol
+//     - HeapNumber
+//     - Cell
+//       - PropertyCell
+//     - Code
+//     - Map
+//     - Oddball
+//     - Foreign
+//     - SharedFunctionInfo
+//     - Struct
+//       - Box
+//       - DeclaredAccessorDescriptor
+//       - AccessorInfo
+//         - DeclaredAccessorInfo
+//         - ExecutableAccessorInfo
+//       - AccessorPair
+//       - AccessCheckInfo
+//       - InterceptorInfo
+//       - CallHandlerInfo
+//       - TemplateInfo
+//         - FunctionTemplateInfo
+//         - ObjectTemplateInfo
+//       - Script
+//       - SignatureInfo
+//       - TypeSwitchInfo
+//       - DebugInfo
+//       - BreakPointInfo
+//       - CodeCache
 //
 // Formats of Object*:
 //  Smi:        [31 bit signed int] 0
 //  HeapObject: [32 bit direct pointer] (4 byte aligned) | 01
-//  Failure:    [30 bit signed int] 11
 
 namespace v8 {
 namespace internal {
 
+class OStream;
+
 enum KeyedAccessStoreMode {
   STANDARD_STORE,
   STORE_TRANSITION_SMI_TO_OBJECT,
@@ -189,6 +179,12 @@ enum ContextualMode {
 };
 
 
+enum MutableMode {
+  MUTABLE,
+  IMMUTABLE
+};
+
+
 static const int kGrowICDelta = STORE_AND_GROW_NO_TRANSITION -
     STANDARD_STORE;
 STATIC_ASSERT(STANDARD_STORE == 0);
@@ -257,12 +253,12 @@ enum PropertyNormalizationMode {
 };
 
 
-// NormalizedMapSharingMode is used to specify whether a map may be shared
-// by different objects with normalized properties.
-enum NormalizedMapSharingMode {
-  UNIQUE_NORMALIZED_MAP,
-  SHARED_NORMALIZED_MAP
-};
+// Indicates how aggressively the prototype should be optimized. FAST_PROTOTYPE
+// will give the fastest result by tailoring the map to the prototype, but that
+// will cause polymorphism with other objects. REGULAR_PROTOTYPE is to be used
+// (at least for now) when dynamically modifying the prototype chain of an
+// object using __proto__ or Object.setPrototypeOf.
+enum PrototypeOptimizationMode { REGULAR_PROTOTYPE, FAST_PROTOTYPE };
 
 
 // Indicates whether transitions can be added to a source map or not.
@@ -315,8 +311,10 @@ static const ExtraICState kNoExtraICState = 0;
 // Instance size sentinel for objects of variable size.
 const int kVariableSizeSentinel = 0;
 
+// We may store the unsigned bit field as signed Smi value and do not
+// use the sign bit.
 const int kStubMajorKeyBits = 7;
-const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
+const int kStubMinorKeyBits = kSmiValueSize - kStubMajorKeyBits - 1;
 
 // All Maps have a field instance_type containing a InstanceType.
 // It describes the type of the instances.
@@ -357,8 +355,6 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
                                                                                \
   V(INTERNALIZED_STRING_TYPE)                                                  \
   V(ASCII_INTERNALIZED_STRING_TYPE)                                            \
-  V(CONS_INTERNALIZED_STRING_TYPE)                                             \
-  V(CONS_ASCII_INTERNALIZED_STRING_TYPE)                                       \
   V(EXTERNAL_INTERNALIZED_STRING_TYPE)                                         \
   V(EXTERNAL_ASCII_INTERNALIZED_STRING_TYPE)                                   \
   V(EXTERNAL_INTERNALIZED_STRING_WITH_ONE_BYTE_DATA_TYPE)                      \
@@ -375,8 +371,7 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
   V(PROPERTY_CELL_TYPE)                                                        \
                                                                                \
   V(HEAP_NUMBER_TYPE)                                                          \
-  V(FLOAT32x4_TYPE)                                                            \
-  V(INT32x4_TYPE)                                                              \
+  V(MUTABLE_HEAP_NUMBER_TYPE)                                                  \
   V(FOREIGN_TYPE)                                                              \
   V(BYTE_ARRAY_TYPE)                                                           \
   V(FREE_SPACE_TYPE)                                                           \
@@ -391,6 +386,7 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
   V(EXTERNAL_UINT32_ARRAY_TYPE)                                                \
   V(EXTERNAL_FLOAT32_ARRAY_TYPE)                                               \
   V(EXTERNAL_FLOAT32x4_ARRAY_TYPE)                                             \
+  V(EXTERNAL_FLOAT64x2_ARRAY_TYPE)                                             \
   V(EXTERNAL_INT32x4_ARRAY_TYPE)                                               \
   V(EXTERNAL_FLOAT64_ARRAY_TYPE)                                               \
   V(EXTERNAL_UINT8_CLAMPED_ARRAY_TYPE)                                         \
@@ -405,6 +401,7 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
   V(FIXED_FLOAT32_ARRAY_TYPE)                                                  \
   V(FIXED_FLOAT32x4_ARRAY_TYPE)                                                \
   V(FIXED_FLOAT64_ARRAY_TYPE)                                                  \
+  V(FIXED_FLOAT64x2_ARRAY_TYPE)                                                \
   V(FIXED_UINT8_CLAMPED_ARRAY_TYPE)                                            \
                                                                                \
   V(FILLER_TYPE)                                                               \
@@ -449,9 +446,14 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
   V(JS_ARRAY_BUFFER_TYPE)                                                      \
   V(JS_TYPED_ARRAY_TYPE)                                                       \
   V(JS_DATA_VIEW_TYPE)                                                         \
+  V(FLOAT32x4_TYPE)                                                            \
+  V(FLOAT64x2_TYPE)                                                            \
+  V(INT32x4_TYPE)                                                              \
   V(JS_PROXY_TYPE)                                                             \
   V(JS_SET_TYPE)                                                               \
   V(JS_MAP_TYPE)                                                               \
+  V(JS_SET_ITERATOR_TYPE)                                                      \
+  V(JS_MAP_ITERATOR_TYPE)                                                      \
   V(JS_WEAK_MAP_TYPE)                                                          \
   V(JS_WEAK_SET_TYPE)                                                          \
   V(JS_REGEXP_TYPE)                                                            \
@@ -522,14 +524,6 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
     kVariableSizeSentinel,                                                     \
     ascii_internalized_string,                                                 \
     AsciiInternalizedString)                                                   \
-  V(CONS_INTERNALIZED_STRING_TYPE,                                             \
-    ConsString::kSize,                                                         \
-    cons_internalized_string,                                                  \
-    ConsInternalizedString)                                                    \
-  V(CONS_ASCII_INTERNALIZED_STRING_TYPE,                                       \
-    ConsString::kSize,                                                         \
-    cons_ascii_internalized_string,                                            \
-    ConsAsciiInternalizedString)                                               \
   V(EXTERNAL_INTERNALIZED_STRING_TYPE,                                         \
     ExternalTwoByteString::kSize,                                              \
     external_internalized_string,                                              \
@@ -564,7 +558,7 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
 // Note that for subtle reasons related to the ordering or numerical values of
 // type tags, elements in this list have to be added to the INSTANCE_TYPE_LIST
 // manually.
-#define STRUCT_LIST_ALL(V)                                                     \
+#define STRUCT_LIST(V)                                                         \
   V(BOX, Box, box)                                                             \
   V(DECLARED_ACCESSOR_DESCRIPTOR,                                              \
     DeclaredAccessorDescriptor,                                                \
@@ -585,19 +579,9 @@ const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
   V(CODE_CACHE, CodeCache, code_cache)                                         \
   V(POLYMORPHIC_CODE_CACHE, PolymorphicCodeCache, polymorphic_code_cache)      \
   V(TYPE_FEEDBACK_INFO, TypeFeedbackInfo, type_feedback_info)                  \
-  V(ALIASED_ARGUMENTS_ENTRY, AliasedArgumentsEntry, aliased_arguments_entry)
-
-#ifdef ENABLE_DEBUGGER_SUPPORT
-#define STRUCT_LIST_DEBUGGER(V)                                                \
+  V(ALIASED_ARGUMENTS_ENTRY, AliasedArgumentsEntry, aliased_arguments_entry)   \
   V(DEBUG_INFO, DebugInfo, debug_info)                                         \
   V(BREAK_POINT_INFO, BreakPointInfo, break_point_info)
-#else
-#define STRUCT_LIST_DEBUGGER(V)
-#endif
-
-#define STRUCT_LIST(V)                                                         \
-  STRUCT_LIST_ALL(V)                                                           \
-  STRUCT_LIST_DEBUGGER(V)
 
 // We use the full 8 bits of the instance_type field to encode heap object
 // instance types.  The high-order bit (bit 7) is set if the object is not a
@@ -629,17 +613,17 @@ enum StringRepresentationTag {
 };
 const uint32_t kIsIndirectStringMask = 0x1;
 const uint32_t kIsIndirectStringTag = 0x1;
-STATIC_ASSERT((kSeqStringTag & kIsIndirectStringMask) == 0);
-STATIC_ASSERT((kExternalStringTag & kIsIndirectStringMask) == 0);
-STATIC_ASSERT(
-    (kConsStringTag & kIsIndirectStringMask) == kIsIndirectStringTag);
-STATIC_ASSERT(
-    (kSlicedStringTag & kIsIndirectStringMask) == kIsIndirectStringTag);
+STATIC_ASSERT((kSeqStringTag & kIsIndirectStringMask) == 0);  // NOLINT
+STATIC_ASSERT((kExternalStringTag & kIsIndirectStringMask) == 0);  // NOLINT
+STATIC_ASSERT((kConsStringTag &
+               kIsIndirectStringMask) == kIsIndirectStringTag);  // NOLINT
+STATIC_ASSERT((kSlicedStringTag &
+               kIsIndirectStringMask) == kIsIndirectStringTag);  // NOLINT
 
 // Use this mask to distinguish between cons and slice only after making
 // sure that the string is one of the two (an indirect string).
 const uint32_t kSlicedNotConsMask = kSlicedStringTag & ~kConsStringTag;
-STATIC_ASSERT(IS_POWER_OF_TWO(kSlicedNotConsMask) && kSlicedNotConsMask != 0);
+STATIC_ASSERT(IS_POWER_OF_TWO(kSlicedNotConsMask));
 
 // If bit 7 is clear, then bit 3 indicates whether this two-byte
 // string actually contains one byte data.
@@ -653,16 +637,21 @@ const uint32_t kShortExternalStringTag = 0x10;
 
 
 // A ConsString with an empty string as the right side is a candidate
-// for being shortcut by the garbage collector unless it is internalized.
-// It's not common to have non-flat internalized strings, so we do not
-// shortcut them thereby avoiding turning internalized strings into strings.
-// See heap.cc and mark-compact.cc.
+// for being shortcut by the garbage collector. We don't allocate any
+// non-flat internalized strings, so we do not shortcut them thereby
+// avoiding turning internalized strings into strings. The bit-masks
+// below contain the internalized bit as additional safety.
+// See heap.cc, mark-compact.cc and objects-visiting.cc.
 const uint32_t kShortcutTypeMask =
     kIsNotStringMask |
     kIsNotInternalizedMask |
     kStringRepresentationMask;
 const uint32_t kShortcutTypeTag = kConsStringTag | kNotInternalizedTag;
 
+static inline bool IsShortcutCandidate(int type) {
+  return ((type & kShortcutTypeMask) == kShortcutTypeTag);
+}
+
 
 enum InstanceType {
   // String types.
@@ -670,10 +659,6 @@ enum InstanceType {
       | kInternalizedTag,
   ASCII_INTERNALIZED_STRING_TYPE = kOneByteStringTag | kSeqStringTag
       | kInternalizedTag,
-  CONS_INTERNALIZED_STRING_TYPE = kTwoByteStringTag | kConsStringTag
-      | kInternalizedTag,
-  CONS_ASCII_INTERNALIZED_STRING_TYPE = kOneByteStringTag | kConsStringTag
-      | kInternalizedTag,
   EXTERNAL_INTERNALIZED_STRING_TYPE = kTwoByteStringTag | kExternalStringTag
       | kInternalizedTag,
   EXTERNAL_ASCII_INTERNALIZED_STRING_TYPE = kOneByteStringTag
@@ -693,9 +678,9 @@ enum InstanceType {
 
   STRING_TYPE = INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
   ASCII_STRING_TYPE = ASCII_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
-  CONS_STRING_TYPE = CONS_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
+  CONS_STRING_TYPE = kTwoByteStringTag | kConsStringTag | kNotInternalizedTag,
   CONS_ASCII_STRING_TYPE =
-      CONS_ASCII_INTERNALIZED_STRING_TYPE | kNotInternalizedTag,
+      kOneByteStringTag | kConsStringTag | kNotInternalizedTag,
 
   SLICED_STRING_TYPE =
       kTwoByteStringTag | kSlicedStringTag | kNotInternalizedTag,
@@ -729,8 +714,7 @@ enum InstanceType {
   // "Data", objects that cannot contain non-map-word pointers to heap
   // objects.
   HEAP_NUMBER_TYPE,
-  FLOAT32x4_TYPE,
-  INT32x4_TYPE,
+  MUTABLE_HEAP_NUMBER_TYPE,
   FOREIGN_TYPE,
   BYTE_ARRAY_TYPE,
   FREE_SPACE_TYPE,
@@ -743,6 +727,7 @@ enum InstanceType {
   EXTERNAL_UINT32_ARRAY_TYPE,
   EXTERNAL_FLOAT32_ARRAY_TYPE,
   EXTERNAL_FLOAT32x4_ARRAY_TYPE,
+  EXTERNAL_FLOAT64x2_ARRAY_TYPE,
   EXTERNAL_INT32x4_ARRAY_TYPE,
   EXTERNAL_FLOAT64_ARRAY_TYPE,
   EXTERNAL_UINT8_CLAMPED_ARRAY_TYPE,  // LAST_EXTERNAL_ARRAY_TYPE
@@ -756,6 +741,7 @@ enum InstanceType {
   FIXED_UINT32_ARRAY_TYPE,
   FIXED_FLOAT32_ARRAY_TYPE,
   FIXED_FLOAT32x4_ARRAY_TYPE,
+  FIXED_FLOAT64x2_ARRAY_TYPE,
   FIXED_FLOAT64_ARRAY_TYPE,
   FIXED_UINT8_CLAMPED_ARRAY_TYPE,  // LAST_FIXED_TYPED_ARRAY_TYPE
 
@@ -782,10 +768,6 @@ enum InstanceType {
   TYPE_FEEDBACK_INFO_TYPE,
   ALIASED_ARGUMENTS_ENTRY_TYPE,
   BOX_TYPE,
-  // The following two instance types are only used when ENABLE_DEBUGGER_SUPPORT
-  // is defined. However as include/v8.h contain some of the instance type
-  // constants always having them avoids them getting different numbers
-  // depending on whether ENABLE_DEBUGGER_SUPPORT is defined or not.
   DEBUG_INFO_TYPE,
   BREAK_POINT_INFO_TYPE,
 
@@ -793,8 +775,6 @@ enum InstanceType {
   CONSTANT_POOL_ARRAY_TYPE,
   SHARED_FUNCTION_INFO_TYPE,
 
-  JS_MESSAGE_OBJECT_TYPE,
-
   // All the following types are subtypes of JSReceiver, which corresponds to
   // objects in the JS sense. The first and the last type in this range are
   // the two forms of function. This organization enables using the same
@@ -804,6 +784,7 @@ enum InstanceType {
   JS_PROXY_TYPE,  // LAST_JS_PROXY_TYPE
 
   JS_VALUE_TYPE,  // FIRST_JS_OBJECT_TYPE
+  JS_MESSAGE_OBJECT_TYPE,
   JS_DATE_TYPE,
   JS_OBJECT_TYPE,
   JS_CONTEXT_EXTENSION_OBJECT_TYPE,
@@ -816,8 +797,13 @@ enum InstanceType {
   JS_ARRAY_BUFFER_TYPE,
   JS_TYPED_ARRAY_TYPE,
   JS_DATA_VIEW_TYPE,
+  FLOAT32x4_TYPE,
+  FLOAT64x2_TYPE,
+  INT32x4_TYPE,
   JS_SET_TYPE,
   JS_MAP_TYPE,
+  JS_SET_ITERATOR_TYPE,
+  JS_MAP_ITERATOR_TYPE,
   JS_WEAK_MAP_TYPE,
   JS_WEAK_SET_TYPE,
 
@@ -868,10 +854,10 @@ enum InstanceType {
 const int kExternalArrayTypeCount =
     LAST_EXTERNAL_ARRAY_TYPE - FIRST_EXTERNAL_ARRAY_TYPE + 1;
 
-STATIC_CHECK(JS_OBJECT_TYPE == Internals::kJSObjectType);
-STATIC_CHECK(FIRST_NONSTRING_TYPE == Internals::kFirstNonstringType);
-STATIC_CHECK(ODDBALL_TYPE == Internals::kOddballType);
-STATIC_CHECK(FOREIGN_TYPE == Internals::kForeignType);
+STATIC_ASSERT(JS_OBJECT_TYPE == Internals::kJSObjectType);
+STATIC_ASSERT(FIRST_NONSTRING_TYPE == Internals::kFirstNonstringType);
+STATIC_ASSERT(ODDBALL_TYPE == Internals::kOddballType);
+STATIC_ASSERT(FOREIGN_TYPE == Internals::kForeignType);
 
 
 #define FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(V) \
@@ -903,25 +889,31 @@ enum CompareResult {
 
 
 #define DECL_BOOLEAN_ACCESSORS(name)   \
-  inline bool name();                  \
+  inline bool name() const;            \
   inline void set_##name(bool value);  \
 
 
 #define DECL_ACCESSORS(name, type)                                      \
-  inline type* name();                                                  \
+  inline type* name() const;                                            \
   inline void set_##name(type* value,                                   \
                          WriteBarrierMode mode = UPDATE_WRITE_BARRIER); \
 
+
+#define DECLARE_CAST(type)                              \
+  INLINE(static type* cast(Object* object));            \
+  INLINE(static const type* cast(const Object* object));
+
+
 class AccessorPair;
 class AllocationSite;
 class AllocationSiteCreationContext;
 class AllocationSiteUsageContext;
 class DictionaryElementsAccessor;
 class ElementsAccessor;
-class Failure;
 class FixedArrayBase;
 class GlobalObject;
 class ObjectVisitor;
+class LookupIterator;
 class StringStream;
 // We cannot just say "class HeapType;" if it is created from a template... =8-?
 template<class> class TypeImpl;
@@ -939,66 +931,11 @@ template <class C> inline bool Is(Object* obj);
 #endif
 
 #ifdef OBJECT_PRINT
-#define DECLARE_PRINTER(Name) void Name##Print(FILE* out = stdout);
+#define DECLARE_PRINTER(Name) void Name##Print(OStream& os);  // NOLINT
 #else
 #define DECLARE_PRINTER(Name)
 #endif
 
-class MaybeObject BASE_EMBEDDED {
- public:
-  inline bool IsFailure();
-  inline bool IsRetryAfterGC();
-  inline bool IsOutOfMemory();
-  inline bool IsException();
-  INLINE(bool IsTheHole());
-  INLINE(bool IsUninitialized());
-  inline bool ToObject(Object** obj) {
-    if (IsFailure()) return false;
-    *obj = reinterpret_cast<Object*>(this);
-    return true;
-  }
-  inline Failure* ToFailureUnchecked() {
-    ASSERT(IsFailure());
-    return reinterpret_cast<Failure*>(this);
-  }
-  inline Object* ToObjectUnchecked() {
-    // TODO(jkummerow): Turn this back into an ASSERT when we can be certain
-    // that it never fires in Release mode in the wild.
-    CHECK(!IsFailure());
-    return reinterpret_cast<Object*>(this);
-  }
-  inline Object* ToObjectChecked() {
-    CHECK(!IsFailure());
-    return reinterpret_cast<Object*>(this);
-  }
-
-  template<typename T>
-  inline bool To(T** obj) {
-    if (IsFailure()) return false;
-    *obj = T::cast(reinterpret_cast<Object*>(this));
-    return true;
-  }
-
-  template<typename T>
-    inline bool ToHandle(Handle<T>* obj, Isolate* isolate) {
-    if (IsFailure()) return false;
-    *obj = handle(T::cast(reinterpret_cast<Object*>(this)), isolate);
-    return true;
-  }
-
-#ifdef OBJECT_PRINT
-  // Prints this object with details.
-  void Print();
-  void Print(FILE* out);
-  void PrintLn();
-  void PrintLn(FILE* out);
-#endif
-#ifdef VERIFY_HEAP
-  // Verifies the object.
-  void Verify();
-#endif
-};
-
 
 #define OBJECT_TYPE_LIST(V)                    \
   V(Smi)                                       \
@@ -1007,8 +944,7 @@ class MaybeObject BASE_EMBEDDED {
 
 #define HEAP_OBJECT_TYPE_LIST(V)               \
   V(HeapNumber)                                \
-  V(Float32x4)                                 \
-  V(Int32x4)                                  \
+  V(MutableHeapNumber)                         \
   V(Name)                                      \
   V(UniqueName)                                \
   V(String)                                    \
@@ -1032,6 +968,7 @@ class MaybeObject BASE_EMBEDDED {
   V(ExternalUint32Array)                       \
   V(ExternalFloat32Array)                      \
   V(ExternalFloat32x4Array)                    \
+  V(ExternalFloat64x2Array)                    \
   V(ExternalInt32x4Array)                      \
   V(ExternalFloat64Array)                      \
   V(ExternalUint8ClampedArray)                 \
@@ -1044,6 +981,7 @@ class MaybeObject BASE_EMBEDDED {
   V(FixedInt32Array)                           \
   V(FixedFloat32Array)                         \
   V(FixedFloat32x4Array)                       \
+  V(FixedFloat64x2Array)                       \
   V(FixedInt32x4Array)                         \
   V(FixedFloat64Array)                         \
   V(FixedUint8ClampedArray)                    \
@@ -1060,7 +998,6 @@ class MaybeObject BASE_EMBEDDED {
   V(DeoptimizationInputData)                   \
   V(DeoptimizationOutputData)                  \
   V(DependentCode)                             \
-  V(TypeFeedbackCells)                         \
   V(FixedArray)                                \
   V(FixedDoubleArray)                          \
   V(ConstantPoolArray)                         \
@@ -1082,10 +1019,15 @@ class MaybeObject BASE_EMBEDDED {
   V(JSArrayBufferView)                         \
   V(JSTypedArray)                              \
   V(JSDataView)                                \
+  V(Float32x4)                                 \
+  V(Float64x2)                                 \
+  V(Int32x4)                                   \
   V(JSProxy)                                   \
   V(JSFunctionProxy)                           \
   V(JSSet)                                     \
   V(JSMap)                                     \
+  V(JSSetIterator)                             \
+  V(JSMapIterator)                             \
   V(JSWeakCollection)                          \
   V(JSWeakMap)                                 \
   V(JSWeakSet)                                 \
@@ -1109,7 +1051,8 @@ class MaybeObject BASE_EMBEDDED {
   V(Cell)                                      \
   V(PropertyCell)                              \
   V(ObjectHashTable)                           \
-  V(WeakHashTable)
+  V(WeakHashTable)                             \
+  V(OrderedHashTable)
 
 
 #define ERROR_MESSAGES_LIST(V) \
@@ -1151,7 +1094,10 @@ class MaybeObject BASE_EMBEDDED {
   V(kCodeObjectNotProperlyPatched, "Code object not properly patched")        \
   V(kCompoundAssignmentToLookupSlot, "Compound assignment to lookup slot")    \
   V(kContextAllocatedArguments, "Context-allocated arguments")                \
-  V(kDebuggerIsActive, "Debugger is active")                                  \
+  V(kCopyBuffersOverlap, "Copy buffers overlap")                              \
+  V(kCouldNotGenerateZero, "Could not generate +0.0")                         \
+  V(kCouldNotGenerateNegativeZero, "Could not generate -0.0")                 \
+  V(kDebuggerHasBreakPoints, "Debugger has break points")                     \
   V(kDebuggerStatement, "DebuggerStatement")                                  \
   V(kDeclarationInCatchContext, "Declaration in catch context")               \
   V(kDeclarationInWithContext, "Declaration in with context")                 \
@@ -1163,18 +1109,35 @@ class MaybeObject BASE_EMBEDDED {
     "DontDelete cells can't contain the hole")                                \
   V(kDoPushArgumentNotImplementedForDoubleType,                               \
     "DoPushArgument not implemented for double type")                         \
+  V(kEliminatedBoundsCheckFailed, "Eliminated bounds check failed")           \
   V(kEmitLoadRegisterUnsupportedDoubleImmediate,                              \
     "EmitLoadRegister: Unsupported double immediate")                         \
   V(kEval, "eval")                                                            \
   V(kExpected0AsASmiSentinel, "Expected 0 as a Smi sentinel")                 \
-  V(kExpectedAlignmentMarker, "expected alignment marker")                    \
-  V(kExpectedAllocationSite, "expected allocation site")                      \
-  V(kExpectedPropertyCellInRegisterA2,                                        \
-    "Expected property cell in register a2")                                  \
-  V(kExpectedPropertyCellInRegisterEbx,                                       \
-    "Expected property cell in register ebx")                                 \
-  V(kExpectedPropertyCellInRegisterRbx,                                       \
-    "Expected property cell in register rbx")                                 \
+  V(kExpectedAlignmentMarker, "Expected alignment marker")                    \
+  V(kExpectedAllocationSite, "Expected allocation site")                      \
+  V(kExpectedFunctionObject, "Expected function object in register")          \
+  V(kExpectedHeapNumber, "Expected HeapNumber")                               \
+  V(kExpectedNativeContext, "Expected native context")                        \
+  V(kExpectedNonIdenticalObjects, "Expected non-identical objects")           \
+  V(kExpectedNonNullContext, "Expected non-null context")                     \
+  V(kExpectedPositiveZero, "Expected +0.0")                                   \
+  V(kExpectedAllocationSiteInCell,                                            \
+    "Expected AllocationSite in property cell")                               \
+  V(kExpectedFixedArrayInFeedbackVector,                                      \
+    "Expected fixed array in feedback vector")                                \
+  V(kExpectedFixedArrayInRegisterA2,                                          \
+    "Expected fixed array in register a2")                                    \
+  V(kExpectedFixedArrayInRegisterEbx,                                         \
+    "Expected fixed array in register ebx")                                   \
+  V(kExpectedFixedArrayInRegisterR2,                                          \
+    "Expected fixed array in register r2")                                    \
+  V(kExpectedFixedArrayInRegisterRbx,                                         \
+    "Expected fixed array in register rbx")                                   \
+  V(kExpectedNewSpaceObject, "Expected new space object")                     \
+  V(kExpectedSmiOrHeapNumber, "Expected smi or HeapNumber")                   \
+  V(kExpectedUndefinedOrCell,                                                 \
+    "Expected undefined or cell in register")                                 \
   V(kExpectingAlignmentForCopyBytes,                                          \
     "Expecting alignment for CopyBytes")                                      \
   V(kExportDeclaration, "Export declaration")                                 \
@@ -1219,6 +1182,7 @@ class MaybeObject BASE_EMBEDDED {
   V(kInliningBailedOut, "Inlining bailed out")                                \
   V(kInputGPRIsExpectedToHaveUpper32Cleared,                                  \
     "Input GPR is expected to have upper32 cleared")                          \
+  V(kInputStringTooLong, "Input string too long")                             \
   V(kInstanceofStubUnexpectedCallSiteCacheCheck,                              \
     "InstanceofStub unexpected call site cache (check)")                      \
   V(kInstanceofStubUnexpectedCallSiteCacheCmp1,                               \
@@ -1232,6 +1196,7 @@ class MaybeObject BASE_EMBEDDED {
   V(kInvalidCaptureReferenced, "Invalid capture referenced")                  \
   V(kInvalidElementsKindForInternalArrayOrInternalPackedArray,                \
     "Invalid ElementsKind for InternalArray or InternalPackedArray")          \
+  V(kInvalidFullCodegenState, "invalid full-codegen state")                   \
   V(kInvalidHandleScopeLevel, "Invalid HandleScope level")                    \
   V(kInvalidLeftHandSideInAssignment, "Invalid left-hand side in assignment") \
   V(kInvalidLhsInCompoundAssignment, "Invalid lhs in compound assignment")    \
@@ -1244,14 +1209,13 @@ class MaybeObject BASE_EMBEDDED {
   V(kJSObjectWithFastElementsMapHasSlowElements,                              \
     "JSObject with fast elements map has slow elements")                      \
   V(kLetBindingReInitialization, "Let binding re-initialization")             \
+  V(kLhsHasBeenClobbered, "lhs has been clobbered")                           \
   V(kLiveBytesCountOverflowChunkSize, "Live Bytes Count overflow chunk size") \
-  V(kLiveEditFrameDroppingIsNotSupportedOnArm,                                \
-    "LiveEdit frame dropping is not supported on arm")                        \
-  V(kLiveEditFrameDroppingIsNotSupportedOnMips,                               \
-    "LiveEdit frame dropping is not supported on mips")                       \
   V(kLiveEdit, "LiveEdit")                                                    \
   V(kLookupVariableInCountOperation,                                          \
     "Lookup variable in count operation")                                     \
+  V(kMapBecameDeprecated, "Map became deprecated")                            \
+  V(kMapBecameUnstable, "Map became unstable")                                \
   V(kMapIsNoLongerInEax, "Map is no longer in eax")                           \
   V(kModuleDeclaration, "Module declaration")                                 \
   V(kModuleLiteral, "Module literal")                                         \
@@ -1260,6 +1224,7 @@ class MaybeObject BASE_EMBEDDED {
   V(kModuleVariable, "Module variable")                                       \
   V(kModuleUrl, "Module url")                                                 \
   V(kNativeFunctionLiteral, "Native function literal")                        \
+  V(kNeedSmiLiteral, "Need a Smi literal here")                               \
   V(kNoCasesLeft, "No cases left")                                            \
   V(kNoEmptyArraysHereInEmitFastAsciiArrayJoin,                               \
     "No empty arrays here in EmitFastAsciiArrayJoin")                         \
@@ -1280,6 +1245,7 @@ class MaybeObject BASE_EMBEDDED {
     "Object literal with complex property")                                   \
   V(kOddballInStringTableIsNotUndefinedOrTheHole,                             \
     "Oddball in string table is not undefined or the hole")                   \
+  V(kOffsetOutOfRange, "Offset out of range")                                 \
   V(kOperandIsASmiAndNotAName, "Operand is a smi and not a name")             \
   V(kOperandIsASmiAndNotAString, "Operand is a smi and not a string")         \
   V(kOperandIsASmi, "Operand is a smi")                                       \
@@ -1289,12 +1255,15 @@ class MaybeObject BASE_EMBEDDED {
   V(kOperandIsNotAString, "Operand is not a string")                          \
   V(kOperandIsNotSmi, "Operand is not smi")                                   \
   V(kOperandNotANumber, "Operand not a number")                               \
+  V(kObjectTagged, "The object is tagged")                                    \
+  V(kObjectNotTagged, "The object is not tagged")                             \
   V(kOptimizationDisabled, "Optimization is disabled")                        \
   V(kOptimizedTooManyTimes, "Optimized too many times")                       \
   V(kOutOfVirtualRegistersWhileTryingToAllocateTempRegister,                  \
     "Out of virtual registers while trying to allocate temp register")        \
   V(kParseScopeError, "Parse/scope error")                                    \
   V(kPossibleDirectCallToEval, "Possible direct call to eval")                \
+  V(kPreconditionsWereNotMet, "Preconditions were not met")                   \
   V(kPropertyAllocationCountFailed, "Property allocation count failed")       \
   V(kReceivedInvalidReturnAddress, "Received invalid return address")         \
   V(kReferenceToAVariableWhichRequiresDynamicLookup,                          \
@@ -1304,24 +1273,38 @@ class MaybeObject BASE_EMBEDDED {
   V(kReferenceToUninitializedVariable, "Reference to uninitialized variable") \
   V(kRegisterDidNotMatchExpectedRoot, "Register did not match expected root") \
   V(kRegisterWasClobbered, "Register was clobbered")                          \
+  V(kRememberedSetPointerInNewSpace, "Remembered set pointer is in new space") \
+  V(kReturnAddressNotFoundInFrame, "Return address not found in frame")       \
+  V(kRhsHasBeenClobbered, "Rhs has been clobbered")                           \
   V(kScopedBlock, "ScopedBlock")                                              \
   V(kSmiAdditionOverflow, "Smi addition overflow")                            \
   V(kSmiSubtractionOverflow, "Smi subtraction overflow")                      \
+  V(kStackAccessBelowStackPointer, "Stack access below stack pointer")        \
   V(kStackFrameTypesMustMatch, "Stack frame types must match")                \
   V(kSwitchStatementMixedOrNonLiteralSwitchLabels,                            \
     "SwitchStatement: mixed or non-literal switch labels")                    \
   V(kSwitchStatementTooManyClauses, "SwitchStatement: too many clauses")      \
+  V(kTheCurrentStackPointerIsBelowCsp,                                        \
+    "The current stack pointer is below csp")                                 \
   V(kTheInstructionShouldBeALui, "The instruction should be a lui")           \
   V(kTheInstructionShouldBeAnOri, "The instruction should be an ori")         \
-  V(kTheInstructionToPatchShouldBeALoadFromPc,                                \
-    "The instruction to patch should be a load from pc")                      \
+  V(kTheInstructionToPatchShouldBeALoadFromConstantPool,                      \
+    "The instruction to patch should be a load from the constant pool")       \
+  V(kTheInstructionToPatchShouldBeAnLdrLiteral,                               \
+    "The instruction to patch should be a ldr literal")                       \
   V(kTheInstructionToPatchShouldBeALui,                                       \
     "The instruction to patch should be a lui")                               \
   V(kTheInstructionToPatchShouldBeAnOri,                                      \
     "The instruction to patch should be an ori")                              \
+  V(kTheSourceAndDestinationAreTheSame,                                       \
+    "The source and destination are the same")                                \
+  V(kTheStackPointerIsNotAligned, "The stack pointer is not aligned.")        \
+  V(kTheStackWasCorruptedByMacroAssemblerCall,                                \
+    "The stack was corrupted by MacroAssembler::Call()")                      \
   V(kTooManyParametersLocals, "Too many parameters/locals")                   \
   V(kTooManyParameters, "Too many parameters")                                \
   V(kTooManySpillSlotsNeededForOSR, "Too many spill slots needed for OSR")    \
+  V(kToOperand32UnsupportedImmediate, "ToOperand32 unsupported immediate.")   \
   V(kToOperandIsDoubleRegisterUnimplemented,                                  \
     "ToOperand IsDoubleRegister unimplemented")                               \
   V(kToOperandUnsupportedDoubleImmediate,                                     \
@@ -1330,10 +1313,12 @@ class MaybeObject BASE_EMBEDDED {
   V(kTryFinallyStatement, "TryFinallyStatement")                              \
   V(kUnableToEncodeValueAsSmi, "Unable to encode value as smi")               \
   V(kUnalignedAllocationInNewSpace, "Unaligned allocation in new space")      \
+  V(kUnalignedCellInWriteBarrier, "Unaligned cell in write barrier")          \
   V(kUndefinedValueNotLoaded, "Undefined value not loaded")                   \
   V(kUndoAllocationOfNonAllocatedMemory,                                      \
     "Undo allocation of non allocated memory")                                \
   V(kUnexpectedAllocationTop, "Unexpected allocation top")                    \
+  V(kUnexpectedColorFound, "Unexpected color bit pattern found")              \
   V(kUnexpectedElementsKindInArrayConstructor,                                \
     "Unexpected ElementsKind in array constructor")                           \
   V(kUnexpectedFallthroughFromCharCodeAtSlowCase,                             \
@@ -1360,16 +1345,21 @@ class MaybeObject BASE_EMBEDDED {
     "Unexpected initial map for InternalArray function")                      \
   V(kUnexpectedLevelAfterReturnFromApiCall,                                   \
     "Unexpected level after return from api call")                            \
+  V(kUnexpectedNegativeValue, "Unexpected negative value")                    \
   V(kUnexpectedNumberOfPreAllocatedPropertyFields,                            \
     "Unexpected number of pre-allocated property fields")                     \
+  V(kUnexpectedFPCRMode, "Unexpected FPCR mode.")                             \
+  V(kUnexpectedSmi, "Unexpected smi value")                                   \
   V(kUnexpectedStringFunction, "Unexpected String function")                  \
   V(kUnexpectedStringType, "Unexpected string type")                          \
   V(kUnexpectedStringWrapperInstanceSize,                                     \
     "Unexpected string wrapper instance size")                                \
   V(kUnexpectedTypeForRegExpDataFixedArrayExpected,                           \
     "Unexpected type for RegExp data, FixedArray expected")                   \
+  V(kUnexpectedValue, "Unexpected value")                                     \
   V(kUnexpectedUnusedPropertiesOfStringWrapper,                               \
     "Unexpected unused properties of string wrapper")                         \
+  V(kUnimplemented, "unimplemented")                                          \
   V(kUninitializedKSmiConstantRegister, "Uninitialized kSmiConstantRegister") \
   V(kUnknown, "Unknown")                                                      \
   V(kUnsupportedConstCompoundAssignment,                                      \
@@ -1409,61 +1399,67 @@ const char* GetBailoutReason(BailoutReason reason);
 // object hierarchy.
 // Object does not use any virtual functions to avoid the
 // allocation of the C++ vtable.
-// Since Smi and Failure are subclasses of Object no
+// Since both Smi and HeapObject are subclasses of Object no
 // data members can be present in Object.
-class Object : public MaybeObject {
+class Object {
  public:
   // Type testing.
-  bool IsObject() { return true; }
+  bool IsObject() const { return true; }
 
-#define IS_TYPE_FUNCTION_DECL(type_)  inline bool Is##type_();
+#define IS_TYPE_FUNCTION_DECL(type_)  INLINE(bool Is##type_() const);
   OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
   HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
 #undef IS_TYPE_FUNCTION_DECL
 
-  inline bool IsFixedArrayBase();
-  inline bool IsExternal();
-  inline bool IsAccessorInfo();
+  // A non-keyed store is of the form a.x = foo or a["x"] = foo whereas
+  // a keyed store is of the form a[expression] = foo.
+  enum StoreFromKeyed {
+    MAY_BE_STORE_FROM_KEYED,
+    CERTAINLY_NOT_STORE_FROM_KEYED
+  };
+
+  INLINE(bool IsFixedArrayBase() const);
+  INLINE(bool IsExternal() const);
+  INLINE(bool IsAccessorInfo() const);
 
-  inline bool IsStruct();
-#define DECLARE_STRUCT_PREDICATE(NAME, Name, name) inline bool Is##Name();
+  INLINE(bool IsStruct() const);
+#define DECLARE_STRUCT_PREDICATE(NAME, Name, name) \
+  INLINE(bool Is##Name() const);
   STRUCT_LIST(DECLARE_STRUCT_PREDICATE)
 #undef DECLARE_STRUCT_PREDICATE
 
-  INLINE(bool IsSpecObject());
-  INLINE(bool IsSpecFunction());
-  bool IsCallable();
+  INLINE(bool IsSpecObject()) const;
+  INLINE(bool IsSpecFunction()) const;
+  INLINE(bool IsTemplateInfo()) const;
+  INLINE(bool IsNameDictionary() const);
+  INLINE(bool IsSeededNumberDictionary() const);
+  INLINE(bool IsUnseededNumberDictionary() const);
+  INLINE(bool IsOrderedHashSet() const);
+  INLINE(bool IsOrderedHashMap() const);
+  bool IsCallable() const;
 
   // Oddball testing.
-  INLINE(bool IsUndefined());
-  INLINE(bool IsNull());
-  INLINE(bool IsTheHole());  // Shadows MaybeObject's implementation.
-  INLINE(bool IsUninitialized());
-  INLINE(bool IsTrue());
-  INLINE(bool IsFalse());
-  inline bool IsArgumentsMarker();
-  inline bool NonFailureIsHeapObject();
+  INLINE(bool IsUndefined() const);
+  INLINE(bool IsNull() const);
+  INLINE(bool IsTheHole() const);
+  INLINE(bool IsException() const);
+  INLINE(bool IsUninitialized() const);
+  INLINE(bool IsTrue() const);
+  INLINE(bool IsFalse() const);
+  INLINE(bool IsArgumentsMarker() const);
 
   // Filler objects (fillers and free space objects).
-  inline bool IsFiller();
+  INLINE(bool IsFiller() const);
 
   // Extract the number.
   inline double Number();
-  inline bool IsNaN();
+  INLINE(bool IsNaN() const);
+  INLINE(bool IsMinusZero() const);
   bool ToInt32(int32_t* value);
   bool ToUint32(uint32_t* value);
 
-  // Indicates whether OptimalRepresentation can do its work, or whether it
-  // always has to return Representation::Tagged().
-  enum ValueType {
-    OPTIMAL_REPRESENTATION,
-    FORCE_TAGGED
-  };
-
-  inline Representation OptimalRepresentation(
-      ValueType type = OPTIMAL_REPRESENTATION) {
+  inline Representation OptimalRepresentation() {
     if (!FLAG_track_fields) return Representation::Tagged();
-    if (type == FORCE_TAGGED) return Representation::Tagged();
     if (IsSmi()) {
       return Representation::Smi();
     } else if (FLAG_track_double_fields && IsHeapNumber()) {
@@ -1471,7 +1467,7 @@ class Object : public MaybeObject {
     } else if (FLAG_track_computed_fields && IsUninitialized()) {
       return Representation::None();
     } else if (FLAG_track_heap_object_fields) {
-      ASSERT(IsHeapObject());
+      DCHECK(IsHeapObject());
       return Representation::HeapObject();
     } else {
       return Representation::Tagged();
@@ -1484,15 +1480,22 @@ class Object : public MaybeObject {
     } else if (FLAG_track_fields && representation.IsSmi()) {
       return IsSmi();
     } else if (FLAG_track_double_fields && representation.IsDouble()) {
-      return IsNumber();
+      return IsMutableHeapNumber() || IsNumber();
     } else if (FLAG_track_heap_object_fields && representation.IsHeapObject()) {
       return IsHeapObject();
     }
     return true;
   }
 
-  inline MaybeObject* AllocateNewStorageFor(Heap* heap,
-                                            Representation representation);
+  Handle<HeapType> OptimalType(Isolate* isolate, Representation representation);
+
+  inline static Handle<Object> NewStorageFor(Isolate* isolate,
+                                             Handle<Object> object,
+                                             Representation representation);
+
+  inline static Handle<Object> WrapForRead(Isolate* isolate,
+                                           Handle<Object> object,
+                                           Representation representation);
 
   // Returns true if the object is of the correct type to be used as a
   // implementation of a JSObject's elements.
@@ -1500,72 +1503,79 @@ class Object : public MaybeObject {
 
   inline bool HasSpecificClassOf(String* name);
 
-  MUST_USE_RESULT MaybeObject* ToObject(Isolate* isolate);  // ECMA-262 9.9.
   bool BooleanValue();                                      // ECMA-262 9.2.
 
   // Convert to a JSObject if needed.
   // native_context is used when creating wrapper object.
-  MUST_USE_RESULT MaybeObject* ToObject(Context* native_context);
+  static inline MaybeHandle<JSReceiver> ToObject(Isolate* isolate,
+                                                 Handle<Object> object);
+  static MaybeHandle<JSReceiver> ToObject(Isolate* isolate,
+                                          Handle<Object> object,
+                                          Handle<Context> context);
 
   // Converts this to a Smi if possible.
-  // Failure is returned otherwise.
-  MUST_USE_RESULT inline MaybeObject* ToSmi();
-
-  void Lookup(Name* name, LookupResult* result);
-
-  // Property access.
-  MUST_USE_RESULT inline MaybeObject* GetProperty(Name* key);
-  MUST_USE_RESULT inline MaybeObject* GetProperty(
-      Name* key,
-      PropertyAttributes* attributes);
-
-  // TODO(yangguo): this should eventually replace the non-handlified version.
-  static Handle<Object> GetPropertyWithReceiver(Handle<Object> object,
-                                                Handle<Object> receiver,
-                                                Handle<Name> name,
-                                                PropertyAttributes* attributes);
-  MUST_USE_RESULT MaybeObject* GetPropertyWithReceiver(
-      Object* receiver,
-      Name* key,
-      PropertyAttributes* attributes);
-
-  static Handle<Object> GetProperty(Handle<Object> object,
-                                    Handle<Name> key);
-  static Handle<Object> GetProperty(Handle<Object> object,
-                                    Handle<Object> receiver,
-                                    LookupResult* result,
-                                    Handle<Name> key,
-                                    PropertyAttributes* attributes);
+  static MUST_USE_RESULT inline MaybeHandle<Smi> ToSmi(Isolate* isolate,
+                                                       Handle<Object> object);
+
+  void Lookup(Handle<Name> name, LookupResult* result);
+
+  MUST_USE_RESULT static MaybeHandle<Object> GetProperty(LookupIterator* it);
+
+  // Implementation of [[Put]], ECMA-262 5th edition, section 8.12.5.
+  MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
+      Handle<Object> object, Handle<Name> key, Handle<Object> value,
+      StrictMode strict_mode,
+      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
 
-  MUST_USE_RESULT static MaybeObject* GetPropertyOrFail(
+  MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
+      LookupIterator* it, Handle<Object> value, StrictMode strict_mode,
+      StoreFromKeyed store_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> WriteToReadOnlyProperty(
+      LookupIterator* it, Handle<Object> value, StrictMode strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetDataProperty(
+      LookupIterator* it, Handle<Object> value);
+  MUST_USE_RESULT static MaybeHandle<Object> AddDataProperty(
+      LookupIterator* it, Handle<Object> value, PropertyAttributes attributes,
+      StrictMode strict_mode, StoreFromKeyed store_mode);
+  MUST_USE_RESULT static inline MaybeHandle<Object> GetPropertyOrElement(
+      Handle<Object> object,
+      Handle<Name> key);
+  MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
+      Isolate* isolate,
       Handle<Object> object,
+      const char* key);
+  MUST_USE_RESULT static inline MaybeHandle<Object> GetProperty(
+      Handle<Object> object,
+      Handle<Name> key);
+
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithAccessor(
       Handle<Object> receiver,
-      LookupResult* result,
-      Handle<Name> key,
-      PropertyAttributes* attributes);
-
-  MUST_USE_RESULT MaybeObject* GetProperty(Object* receiver,
-                                           LookupResult* result,
-                                           Name* key,
-                                           PropertyAttributes* attributes);
-
-  MUST_USE_RESULT MaybeObject* GetPropertyWithDefinedGetter(Object* receiver,
-                                                            JSReceiver* getter);
-
-  static Handle<Object> GetElement(Isolate* isolate,
-                                   Handle<Object> object,
-                                   uint32_t index);
-  MUST_USE_RESULT inline MaybeObject* GetElement(Isolate* isolate,
-                                                 uint32_t index);
-  // For use when we know that no exception can be thrown.
-  inline Object* GetElementNoExceptionThrown(Isolate* isolate, uint32_t index);
-  MUST_USE_RESULT MaybeObject* GetElementWithReceiver(Isolate* isolate,
-                                                      Object* receiver,
-                                                      uint32_t index);
-
-  // Return the object's prototype (might be Heap::null_value()).
-  Object* GetPrototype(Isolate* isolate);
-  Map* GetMarkerMap(Isolate* isolate);
+      Handle<Name> name,
+      Handle<JSObject> holder,
+      Handle<Object> structure);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithAccessor(
+      Handle<Object> receiver, Handle<Name> name, Handle<Object> value,
+      Handle<JSObject> holder, Handle<Object> structure,
+      StrictMode strict_mode);
+
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithDefinedGetter(
+      Handle<Object> receiver,
+      Handle<JSReceiver> getter);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithDefinedSetter(
+      Handle<Object> receiver,
+      Handle<JSReceiver> setter,
+      Handle<Object> value);
+
+  MUST_USE_RESULT static inline MaybeHandle<Object> GetElement(
+      Isolate* isolate,
+      Handle<Object> object,
+      uint32_t index);
+
+  MUST_USE_RESULT static MaybeHandle<Object> GetElementWithReceiver(
+      Isolate* isolate,
+      Handle<Object> object,
+      Handle<Object> receiver,
+      uint32_t index);
 
   // Returns the permanent hash code associated with this object. May return
   // undefined if not yet created.
@@ -1574,16 +1584,19 @@ class Object : public MaybeObject {
   // Returns the permanent hash code associated with this object depending on
   // the actual object type. May create and store a hash code if needed and none
   // exists.
-  // TODO(rafaelw): Remove isolate parameter when objects.cc is fully
-  // handlified.
-  static Handle<Object> GetOrCreateHash(Handle<Object> object,
-                                        Isolate* isolate);
+  static Handle<Smi> GetOrCreateHash(Isolate* isolate, Handle<Object> object);
 
   // Checks whether this object has the same value as the given one.  This
   // function is implemented according to ES5, section 9.12 and can be used
   // to implement the Harmony "egal" function.
   bool SameValue(Object* other);
 
+  // Checks whether this object has the same value as the given one.
+  // +0 and -0 are treated equal. Everything else is the same as SameValue.
+  // This function is implemented according to ES6, section 7.2.4 and is used
+  // by ES6 Map and Set.
+  bool SameValueZero(Object* other);
+
   // 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);
@@ -1592,6 +1605,7 @@ class Object : public MaybeObject {
   // < the length of the string.  Used to implement [] on strings.
   inline bool IsStringObjectWithCharacterAt(uint32_t index);
 
+  DECLARE_VERIFIER(Object)
 #ifdef VERIFY_HEAP
   // Verify a pointer is a valid object pointer.
   static void VerifyPointer(Object* p);
@@ -1605,17 +1619,39 @@ class Object : public MaybeObject {
   // Prints this object without details to a message accumulator.
   void ShortPrint(StringStream* accumulator);
 
-  // Casting: This cast is only needed to satisfy macros in objects-inl.h.
-  static Object* cast(Object* value) { return value; }
+  DECLARE_CAST(Object)
 
   // Layout description.
   static const int kHeaderSize = 0;  // Object does not take up any space.
 
+#ifdef OBJECT_PRINT
+  // For our gdb macros, we should perhaps change these in the future.
+  void Print();
+
+  // Prints this object with details.
+  void Print(OStream& os);  // NOLINT
+#endif
+
  private:
+  friend class LookupIterator;
+  friend class PrototypeIterator;
+
+  // Return the map of the root of object's prototype chain.
+  Map* GetRootMap(Isolate* isolate);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(Object);
 };
 
 
+struct Brief {
+  explicit Brief(const Object* const v) : value(v) {}
+  const Object* value;
+};
+
+
+OStream& operator<<(OStream& os, const Brief& v);
+
+
 // Smi represents integer Numbers that can be stored in 31 bits.
 // Smis are immediate which means they are NOT allocated in the heap.
 // The this pointer has the following format: [31 bit signed int] 0
@@ -1625,7 +1661,7 @@ class Object : public MaybeObject {
 class Smi: public Object {
  public:
   // Returns the integer value.
-  inline int value();
+  inline int value() const;
 
   // Convert a value to a Smi object.
   static inline Smi* FromInt(int value);
@@ -1635,13 +1671,10 @@ class Smi: public Object {
   // Returns whether value can be represented in a Smi.
   static inline bool IsValid(intptr_t value);
 
-  // Casting.
-  static inline Smi* cast(Object* object);
+  DECLARE_CAST(Smi)
 
   // Dispatched behavior.
-  void SmiPrint(FILE* out = stdout);
-  void SmiPrint(StringStream* accumulator);
-
+  void SmiPrint(OStream& os) const;  // NOLINT
   DECLARE_VERIFIER(Smi)
 
   static const int kMinValue =
@@ -1653,76 +1686,6 @@ class Smi: public Object {
 };
 
 
-// Failure is used for reporting out of memory situations and
-// propagating exceptions through the runtime system.  Failure objects
-// are transient and cannot occur as part of the object graph.
-//
-// Failures are a single word, encoded as follows:
-// +-------------------------+---+--+--+
-// |.........unused..........|sss|tt|11|
-// +-------------------------+---+--+--+
-//                          7 6 4 32 10
-//
-//
-// The low two bits, 0-1, are the failure tag, 11.  The next two bits,
-// 2-3, are a failure type tag 'tt' with possible values:
-//   00 RETRY_AFTER_GC
-//   01 EXCEPTION
-//   10 INTERNAL_ERROR
-//   11 OUT_OF_MEMORY_EXCEPTION
-//
-// The next three bits, 4-6, are an allocation space tag 'sss'.  The
-// allocation space tag is 000 for all failure types except
-// RETRY_AFTER_GC.  For RETRY_AFTER_GC, the possible values are the
-// allocation spaces (the encoding is found in globals.h).
-
-// Failure type tag info.
-const int kFailureTypeTagSize = 2;
-const int kFailureTypeTagMask = (1 << kFailureTypeTagSize) - 1;
-
-class Failure: public MaybeObject {
- public:
-  // RuntimeStubs assumes EXCEPTION = 1 in the compiler-generated code.
-  enum Type {
-    RETRY_AFTER_GC = 0,
-    EXCEPTION = 1,       // Returning this marker tells the real exception
-                         // is in Isolate::pending_exception.
-    INTERNAL_ERROR = 2,
-    OUT_OF_MEMORY_EXCEPTION = 3
-  };
-
-  inline Type type() const;
-
-  // Returns the space that needs to be collected for RetryAfterGC failures.
-  inline AllocationSpace allocation_space() const;
-
-  inline bool IsInternalError() const;
-  inline bool IsOutOfMemoryException() const;
-
-  static inline Failure* RetryAfterGC(AllocationSpace space);
-  static inline Failure* RetryAfterGC();  // NEW_SPACE
-  static inline Failure* Exception();
-  static inline Failure* InternalError();
-  // TODO(jkummerow): The value is temporary instrumentation. Remove it
-  // when it has served its purpose.
-  static inline Failure* OutOfMemoryException(intptr_t value);
-  // Casting.
-  static inline Failure* cast(MaybeObject* object);
-
-  // Dispatched behavior.
-  void FailurePrint(FILE* out = stdout);
-  void FailurePrint(StringStream* accumulator);
-
-  DECLARE_VERIFIER(Failure)
-
- private:
-  inline intptr_t value() const;
-  static inline Failure* Construct(Type type, intptr_t value = 0);
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(Failure);
-};
-
-
 // Heap objects typically have a map pointer in their first word.  However,
 // during GC other data (e.g. mark bits, forwarding addresses) is sometimes
 // encoded in the first word.  The class MapWord is an abstraction of the
@@ -1732,7 +1695,7 @@ class MapWord BASE_EMBEDDED {
   // Normal state: the map word contains a map pointer.
 
   // Create a map word from a map pointer.
-  static inline MapWord FromMap(Map* map);
+  static inline MapWord FromMap(const Map* map);
 
   // View this map word as a map pointer.
   inline Map* ToMap();
@@ -1776,23 +1739,32 @@ class HeapObject: public Object {
  public:
   // [map]: Contains a map which contains the object's reflective
   // information.
-  inline Map* map();
+  inline Map* map() const;
   inline void set_map(Map* value);
   // The no-write-barrier version.  This is OK if the object is white and in
   // new space, or if the value is an immortal immutable object, like the maps
   // of primitive (non-JS) objects like strings, heap numbers etc.
   inline void set_map_no_write_barrier(Map* value);
 
+  // Get the map using acquire load.
+  inline Map* synchronized_map();
+  inline MapWord synchronized_map_word() const;
+
+  // Set the map using release store
+  inline void synchronized_set_map(Map* value);
+  inline void synchronized_set_map_no_write_barrier(Map* value);
+  inline void synchronized_set_map_word(MapWord map_word);
+
   // During garbage collection, the map word of a heap object does not
   // necessarily contain a map pointer.
-  inline MapWord map_word();
+  inline MapWord map_word() const;
   inline void set_map_word(MapWord map_word);
 
   // The Heap the object was allocated in. Used also to access Isolate.
-  inline Heap* GetHeap();
+  inline Heap* GetHeap() const;
 
   // Convenience method to get current isolate.
-  inline Isolate* GetIsolate();
+  inline Isolate* GetIsolate() const;
 
   // Converts an address to a HeapObject pointer.
   static inline HeapObject* FromAddress(Address address);
@@ -1812,6 +1784,10 @@ class HeapObject: public Object {
   // Returns the heap object's size in bytes
   inline int Size();
 
+  // Returns true if this heap object may contain pointers to objects in new
+  // space.
+  inline bool MayContainNewSpacePointers();
+
   // 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.
@@ -1830,8 +1806,7 @@ class HeapObject: public Object {
                                  Handle<Name> name,
                                  Handle<Code> code);
 
-  // Casting.
-  static inline HeapObject* cast(Object* obj);
+  DECLARE_CAST(HeapObject)
 
   // Return the write barrier mode for this. Callers of this function
   // must be able to present a reference to an DisallowHeapAllocation
@@ -1842,9 +1817,9 @@ class HeapObject: public Object {
       const DisallowHeapAllocation& promise);
 
   // Dispatched behavior.
-  void HeapObjectShortPrint(StringStream* accumulator);
+  void HeapObjectShortPrint(OStream& os);  // NOLINT
 #ifdef OBJECT_PRINT
-  void PrintHeader(FILE* out, const char* id);
+  void PrintHeader(OStream& os, const char* id);  // NOLINT
 #endif
   DECLARE_PRINTER(HeapObject)
   DECLARE_VERIFIER(HeapObject)
@@ -1862,7 +1837,7 @@ class HeapObject: public Object {
   static const int kMapOffset = Object::kHeaderSize;
   static const int kHeaderSize = kMapOffset + kPointerSize;
 
-  STATIC_CHECK(kMapOffset == Internals::kHeapObjectMapOffset);
+  STATIC_ASSERT(kMapOffset == Internals::kHeapObjectMapOffset);
 
  protected:
   // helpers for calling an ObjectVisitor to iterate over pointers in the
@@ -1870,6 +1845,8 @@ class HeapObject: public Object {
   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);
@@ -1921,17 +1898,15 @@ class FlexibleBodyDescriptor {
 class HeapNumber: public HeapObject {
  public:
   // [value]: number value.
-  inline double value();
+  inline double value() const;
   inline void set_value(double value);
 
-  // Casting.
-  static inline HeapNumber* cast(Object* obj);
+  DECLARE_CAST(HeapNumber)
 
   // Dispatched behavior.
   bool HeapNumberBooleanValue();
 
-  void HeapNumberPrint(FILE* out = stdout);
-  void HeapNumberPrint(StringStream* accumulator);
+  void HeapNumberPrint(OStream& os);  // NOLINT
   DECLARE_VERIFIER(HeapNumber)
 
   inline int get_exponent();
@@ -1940,11 +1915,18 @@ class HeapNumber: public HeapObject {
   // Layout description.
   static const int kValueOffset = HeapObject::kHeaderSize;
   // IEEE doubles are two 32 bit words.  The first is just mantissa, the second
-  // is a mixture of sign, exponent and mantissa.  Our current platforms are all
-  // little endian apart from non-EABI arm which is little endian with big
-  // endian floating point word ordering!
+  // is a mixture of sign, exponent and mantissa. The offsets of two 32 bit
+  // words within double numbers are endian dependent and they are set
+  // accordingly.
+#if defined(V8_TARGET_LITTLE_ENDIAN)
   static const int kMantissaOffset = kValueOffset;
   static const int kExponentOffset = kValueOffset + 4;
+#elif defined(V8_TARGET_BIG_ENDIAN)
+  static const int kMantissaOffset = kValueOffset + 4;
+  static const int kExponentOffset = kValueOffset;
+#else
+#error Unknown byte ordering
+#endif
 
   static const int kSize = kValueOffset + kDoubleSize;
   static const uint32_t kSignMask = 0x80000000u;
@@ -1964,84 +1946,6 @@ class HeapNumber: public HeapObject {
 };
 
 
-class Float32x4: public HeapObject {
- public:
-  typedef float32x4_value_t value_t;
-  static const int kLanes = 4;
-  static const int kValueSize = kFloat32x4Size;
-  static const InstanceType kInstanceType = FLOAT32x4_TYPE;
-  static inline const char* Name();
-  static inline int kRuntimeAllocatorId();
-  static inline int kMapRootIndex();
-
-  // [value]: float32x4 value.
-  inline float32x4_value_t value();
-  inline void set_value(float32x4_value_t value);
-
-  // Casting.
-  static inline Float32x4* cast(Object* obj);
-
-  inline void Float32x4Print() {
-    Float32x4Print(stdout);
-  }
-  void Float32x4Print(FILE* out);
-  void Float32x4Print(StringStream* accumulator);
-  DECLARE_VERIFIER(Float32x4)
-
-  inline float getAt(int index);
-  inline float x() { return getAt(0); }
-  inline float y() { return getAt(1); }
-  inline float z() { return getAt(2); }
-  inline float w() { return getAt(3); }
-
-  // Layout description.
-  static const int kValueOffset = HeapObject::kHeaderSize;
-  static const int kSize = kValueOffset + kValueSize;
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(Float32x4);
-};
-
-
-class Int32x4: public HeapObject {
- public:
-  typedef int32x4_value_t value_t;
-  static const int kValueSize = kInt32x4Size;
-  static const InstanceType kInstanceType = INT32x4_TYPE;
-  static inline const char* Name();
-  static inline int kRuntimeAllocatorId();
-  static inline int kMapRootIndex();
-
-  // [value]: int32x4 value.
-  inline int32x4_value_t value();
-  inline void set_value(int32x4_value_t value);
-
-  // Casting.
-  static inline Int32x4* cast(Object* obj);
-
-  inline void Int32x4Print() {
-    Int32x4Print(stdout);
-  }
-  void Int32x4Print(FILE* out);
-  void Int32x4Print(StringStream* accumulator);
-  DECLARE_VERIFIER(Int32x4)
-
-  static const int kLanes = 4;
-  inline int32_t getAt(int32_t index);
-  inline int32_t x() { return getAt(0); }
-  inline int32_t y() { return getAt(1); }
-  inline int32_t z() { return getAt(2); }
-  inline int32_t w() { return getAt(3); }
-
-  // Layout description.
-  static const int kValueOffset = HeapObject::kHeaderSize;
-  static const int kSize = kValueOffset + kValueSize;
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(Int32x4);
-};
-
-
 enum EnsureElementsMode {
   DONT_ALLOW_DOUBLE_ELEMENTS,
   ALLOW_COPIED_DOUBLE_ELEMENTS,
@@ -2076,13 +1980,6 @@ class JSReceiver: public HeapObject {
     FORCE_DELETION
   };
 
-  // A non-keyed store is of the form a.x = foo or a["x"] = foo whereas
-  // a keyed store is of the form a[expression] = foo.
-  enum StoreFromKeyed {
-    MAY_BE_STORE_FROM_KEYED,
-    CERTAINLY_NOT_STORE_FROM_KEYED
-  };
-
   // Internal properties (e.g. the hidden properties dictionary) might
   // be added even though the receiver is non-extensible.
   enum ExtensibilityCheck {
@@ -2090,36 +1987,34 @@ class JSReceiver: public HeapObject {
     OMIT_EXTENSIBILITY_CHECK
   };
 
-  // Casting.
-  static inline JSReceiver* cast(Object* obj);
+  DECLARE_CAST(JSReceiver)
 
-  // Implementation of [[Put]], ECMA-262 5th edition, section 8.12.5.
-  static Handle<Object> SetProperty(Handle<JSReceiver> object,
-                                    Handle<Name> key,
-                                    Handle<Object> value,
-                                    PropertyAttributes attributes,
-                                    StrictModeFlag strict_mode,
-                                    StoreFromKeyed store_mode =
-                                        MAY_BE_STORE_FROM_KEYED);
-  static Handle<Object> SetElement(Handle<JSReceiver> object,
-                                   uint32_t index,
-                                   Handle<Object> value,
-                                   PropertyAttributes attributes,
-                                   StrictModeFlag strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetElement(
+      Handle<JSReceiver> object,
+      uint32_t index,
+      Handle<Object> value,
+      PropertyAttributes attributes,
+      StrictMode strict_mode);
 
   // Implementation of [[HasProperty]], ECMA-262 5th edition, section 8.12.6.
-  static inline bool HasProperty(Handle<JSReceiver> object, Handle<Name> name);
-  static inline bool HasLocalProperty(Handle<JSReceiver>, Handle<Name> name);
-  static inline bool HasElement(Handle<JSReceiver> object, uint32_t index);
-  static inline bool HasLocalElement(Handle<JSReceiver> object, uint32_t index);
+  MUST_USE_RESULT static inline Maybe<bool> HasProperty(
+      Handle<JSReceiver> object, Handle<Name> name);
+  MUST_USE_RESULT static inline Maybe<bool> HasOwnProperty(Handle<JSReceiver>,
+                                                           Handle<Name> name);
+  MUST_USE_RESULT static inline Maybe<bool> HasElement(
+      Handle<JSReceiver> object, uint32_t index);
+  MUST_USE_RESULT static inline Maybe<bool> HasOwnElement(
+      Handle<JSReceiver> object, uint32_t index);
 
   // Implementation of [[Delete]], ECMA-262 5th edition, section 8.12.7.
-  static Handle<Object> DeleteProperty(Handle<JSReceiver> object,
-                                       Handle<Name> name,
-                                       DeleteMode mode = NORMAL_DELETION);
-  static Handle<Object> DeleteElement(Handle<JSReceiver> object,
-                                      uint32_t index,
-                                      DeleteMode mode = NORMAL_DELETION);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteProperty(
+      Handle<JSReceiver> object,
+      Handle<Name> name,
+      DeleteMode mode = NORMAL_DELETION);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteElement(
+      Handle<JSReceiver> object,
+      uint32_t index,
+      DeleteMode mode = NORMAL_DELETION);
 
   // Tests for the fast common case for property enumeration.
   bool IsSimpleEnum();
@@ -2131,16 +2026,17 @@ class JSReceiver: public HeapObject {
   // function that was used to instantiate the object).
   String* constructor_name();
 
-  inline PropertyAttributes GetPropertyAttribute(Name* name);
-  PropertyAttributes GetPropertyAttributeWithReceiver(JSReceiver* receiver,
-                                                      Name* name);
-  PropertyAttributes GetLocalPropertyAttribute(Name* name);
+  MUST_USE_RESULT static inline Maybe<PropertyAttributes> GetPropertyAttributes(
+      Handle<JSReceiver> object, Handle<Name> name);
+  MUST_USE_RESULT static Maybe<PropertyAttributes> GetPropertyAttributes(
+      LookupIterator* it);
+  MUST_USE_RESULT static Maybe<PropertyAttributes> GetOwnPropertyAttributes(
+      Handle<JSReceiver> object, Handle<Name> name);
 
-  inline PropertyAttributes GetElementAttribute(uint32_t index);
-  inline PropertyAttributes GetLocalElementAttribute(uint32_t index);
-
-  // Return the object's prototype (might be Heap::null_value()).
-  inline Object* GetPrototype();
+  MUST_USE_RESULT static inline Maybe<PropertyAttributes> GetElementAttribute(
+      Handle<JSReceiver> object, uint32_t index);
+  MUST_USE_RESULT static inline Maybe<PropertyAttributes>
+      GetOwnElementAttribute(Handle<JSReceiver> object, uint32_t index);
 
   // Return the constructor function (may be Heap::null_value()).
   inline Object* GetConstructor();
@@ -2151,42 +2047,34 @@ class JSReceiver: public HeapObject {
 
   // Retrieves a permanent object identity hash code. May create and store a
   // hash code if needed and none exists.
-  inline static Handle<Object> GetOrCreateIdentityHash(
+  inline static Handle<Smi> GetOrCreateIdentityHash(
       Handle<JSReceiver> object);
 
   // Lookup a property.  If found, the result is valid and has
   // detailed information.
-  void LocalLookup(Name* name, LookupResult* result,
-                   bool search_hidden_prototypes = false);
-  void Lookup(Name* name, LookupResult* result);
+  void LookupOwn(Handle<Name> name, LookupResult* result,
+                 bool search_hidden_prototypes = false);
+  void Lookup(Handle<Name> name, LookupResult* result);
 
- protected:
-  Smi* GenerateIdentityHash();
+  enum KeyCollectionType { OWN_ONLY, INCLUDE_PROTOS };
 
-  static Handle<Object> SetPropertyWithDefinedSetter(Handle<JSReceiver> object,
-                                                     Handle<JSReceiver> setter,
-                                                     Handle<Object> value);
+  // Computes the enumerable keys for a JSObject. Used for implementing
+  // "for (n in object) { }".
+  MUST_USE_RESULT static MaybeHandle<FixedArray> GetKeys(
+      Handle<JSReceiver> object,
+      KeyCollectionType type);
 
  private:
-  PropertyAttributes GetPropertyAttributeForResult(JSReceiver* receiver,
-                                                   LookupResult* result,
-                                                   Name* name,
-                                                   bool continue_search);
-
-  static Handle<Object> SetProperty(Handle<JSReceiver> receiver,
-                                    LookupResult* result,
-                                    Handle<Name> key,
-                                    Handle<Object> value,
-                                    PropertyAttributes attributes,
-                                    StrictModeFlag strict_mode,
-                                    StoreFromKeyed store_from_keyed);
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSReceiver);
 };
 
 // Forward declaration for JSObject::GetOrCreateHiddenPropertiesHashTable.
 class ObjectHashTable;
 
+// Forward declaration for JSObject::Copy.
+class AllocationSite;
+
+
 // The JSObject describes real heap allocated JavaScript objects with
 // properties.
 // Note that the map of JSObject changes during execution to enable inline
@@ -2210,18 +2098,21 @@ class JSObject: public JSReceiver {
   // In the fast mode elements is a FixedArray and so each element can
   // be quickly accessed. This fact is used in the generated code. The
   // elements array can have one of three maps in this mode:
-  // fixed_array_map, non_strict_arguments_elements_map or
+  // fixed_array_map, sloppy_arguments_elements_map or
   // fixed_cow_array_map (for copy-on-write arrays). In the latter case
   // the elements array may be shared by a few objects and so before
   // writing to any element the array must be copied. Use
   // EnsureWritableFastElements in this case.
   //
   // In the slow mode the elements is either a NumberDictionary, an
-  // ExternalArray, or a FixedArray parameter map for a (non-strict)
+  // ExternalArray, or a FixedArray parameter map for a (sloppy)
   // arguments object.
   DECL_ACCESSORS(elements, FixedArrayBase)
   inline void initialize_elements();
-  MUST_USE_RESULT inline MaybeObject* ResetElements();
+  static void ResetElements(Handle<JSObject> object);
+  static inline void SetMapAndElements(Handle<JSObject> object,
+                                       Handle<Map> map,
+                                       Handle<FixedArrayBase> elements);
   inline ElementsKind GetElementsKind();
   inline ElementsAccessor* GetElementsAccessor();
   // Returns true if an object has elements of FAST_SMI_ELEMENTS ElementsKind.
@@ -2239,7 +2130,7 @@ class JSObject: public JSReceiver {
   // Returns true if an object has elements of FAST_HOLEY_*_ELEMENTS
   // ElementsKind.
   inline bool HasFastHoleyElements();
-  inline bool HasNonStrictArgumentsElements();
+  inline bool HasSloppyArgumentsElements();
   inline bool HasDictionaryElements();
 
   inline bool HasExternalUint8ClampedElements();
@@ -2252,24 +2143,33 @@ class JSObject: public JSReceiver {
   inline bool HasExternalUint32Elements();
   inline bool HasExternalFloat32Elements();
   inline bool HasExternalFloat32x4Elements();
+  inline bool HasExternalFloat64x2Elements();
   inline bool HasExternalInt32x4Elements();
   inline bool HasExternalFloat64Elements();
 
   inline bool HasFixedTypedArrayElements();
 
+  inline bool HasFixedUint8ClampedElements();
+  inline bool HasFixedArrayElements();
+  inline bool HasFixedInt8Elements();
+  inline bool HasFixedUint8Elements();
+  inline bool HasFixedInt16Elements();
+  inline bool HasFixedUint16Elements();
+  inline bool HasFixedInt32Elements();
+  inline bool HasFixedUint32Elements();
+  inline bool HasFixedFloat32Elements();
+  inline bool HasFixedFloat64Elements();
+  inline bool HasFixedFloat32x4Elements();
+  inline bool HasFixedFloat64x2Elements();
+  inline bool HasFixedInt32x4Elements();
+
   bool HasFastArgumentsElements();
   bool HasDictionaryArgumentsElements();
   inline SeededNumberDictionary* element_dictionary();  // Gets slow elements.
 
-  inline void set_map_and_elements(
-      Map* map,
-      FixedArrayBase* value,
-      WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-
   // Requires: HasFastElements().
   static Handle<FixedArray> EnsureWritableFastElements(
       Handle<JSObject> object);
-  MUST_USE_RESULT inline MaybeObject* EnsureWritableFastElements();
 
   // Collects elements starting at index 0.
   // Undefined values are placed after non-undefined values.
@@ -2277,56 +2177,32 @@ class JSObject: public JSReceiver {
   static Handle<Object> PrepareElementsForSort(Handle<JSObject> object,
                                                uint32_t limit);
   // As PrepareElementsForSort, but only on objects where elements is
-  // a dictionary, and it will stay a dictionary.
+  // a dictionary, and it will stay a dictionary.  Collates undefined and
+  // unexisting elements below limit from position zero of the elements.
   static Handle<Object> PrepareSlowElementsForSort(Handle<JSObject> object,
                                                    uint32_t limit);
-  MUST_USE_RESULT MaybeObject* PrepareSlowElementsForSort(uint32_t limit);
-
-  static Handle<Object> GetPropertyWithCallback(Handle<JSObject> object,
-                                                Handle<Object> receiver,
-                                                Handle<Object> structure,
-                                                Handle<Name> name);
-
-  static Handle<Object> SetPropertyWithCallback(
-      Handle<JSObject> object,
-      Handle<Object> structure,
-      Handle<Name> name,
-      Handle<Object> value,
-      Handle<JSObject> holder,
-      StrictModeFlag strict_mode);
 
-  static Handle<Object> SetPropertyWithInterceptor(
-      Handle<JSObject> object,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithInterceptor(
+      LookupIterator* it, Handle<Object> value);
 
-  static Handle<Object> SetPropertyForResult(
-      Handle<JSObject> object,
-      LookupResult* result,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
-      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
+  // SetLocalPropertyIgnoreAttributes converts callbacks to fields. We need to
+  // grant an exemption to ExecutableAccessor callbacks in some cases.
+  enum ExecutableAccessorInfoHandling {
+    DEFAULT_HANDLING,
+    DONT_FORCE_FIELD
+  };
 
-  static Handle<Object> SetLocalPropertyIgnoreAttributes(
+  MUST_USE_RESULT static MaybeHandle<Object> SetOwnPropertyIgnoreAttributes(
       Handle<JSObject> object,
       Handle<Name> key,
       Handle<Object> value,
       PropertyAttributes attributes,
-      ValueType value_type = OPTIMAL_REPRESENTATION,
-      StoreMode mode = ALLOW_AS_CONSTANT,
-      ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK);
-
-  static inline Handle<String> ExpectedTransitionKey(Handle<Map> map);
-  static inline Handle<Map> ExpectedTransitionTarget(Handle<Map> map);
+      ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK,
+      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED,
+      ExecutableAccessorInfoHandling handling = DEFAULT_HANDLING);
 
-  // Try to follow an existing transition to a field with attributes NONE. The
-  // return value indicates whether the transition was successful.
-  static inline Handle<Map> FindTransitionToField(Handle<Map> map,
-                                                  Handle<Name> key);
+  static void AddProperty(Handle<JSObject> object, Handle<Name> key,
+                          Handle<Object> value, PropertyAttributes attributes);
 
   // Extend the receiver with a single fast property appeared first in the
   // passed map. This also extends the property backing store if necessary.
@@ -2337,17 +2213,19 @@ class JSObject: public JSReceiver {
   static void MigrateInstance(Handle<JSObject> instance);
 
   // Migrates the given object only if the target map is already available,
-  // or returns an empty handle if such a map is not yet available.
-  static Handle<Object> TryMigrateInstance(Handle<JSObject> instance);
+  // or returns false if such a map is not yet available.
+  static bool TryMigrateInstance(Handle<JSObject> instance);
 
   // Retrieve a value in a normalized object given a lookup result.
   // Handles the special representation of JS global objects.
-  Object* GetNormalizedProperty(LookupResult* result);
+  Object* GetNormalizedProperty(const LookupResult* result);
+  static Handle<Object> GetNormalizedProperty(Handle<JSObject> object,
+                                              const LookupResult* result);
 
   // Sets the property value in a normalized object given a lookup result.
   // Handles the special representation of JS global objects.
   static void SetNormalizedProperty(Handle<JSObject> object,
-                                    LookupResult* result,
+                                    const LookupResult* result,
                                     Handle<Object> value);
 
   // Sets the property value in a normalized object given (key, value, details).
@@ -2357,75 +2235,59 @@ class JSObject: public JSReceiver {
                                     Handle<Object> value,
                                     PropertyDetails details);
 
-  static void OptimizeAsPrototype(Handle<JSObject> object);
+  static void OptimizeAsPrototype(Handle<JSObject> object,
+                                  PrototypeOptimizationMode mode);
+  static void ReoptimizeIfPrototype(Handle<JSObject> object);
 
   // Retrieve interceptors.
   InterceptorInfo* GetNamedInterceptor();
   InterceptorInfo* GetIndexedInterceptor();
 
   // Used from JSReceiver.
-  PropertyAttributes GetPropertyAttributePostInterceptor(JSObject* receiver,
-                                                         Name* name,
-                                                         bool continue_search);
-  PropertyAttributes GetPropertyAttributeWithInterceptor(JSObject* receiver,
-                                                         Name* name,
-                                                         bool continue_search);
-  PropertyAttributes GetPropertyAttributeWithFailedAccessCheck(
-      Object* receiver,
-      LookupResult* result,
-      Name* name,
-      bool continue_search);
-  PropertyAttributes GetElementAttributeWithReceiver(JSReceiver* receiver,
-                                                     uint32_t index,
-                                                     bool continue_search);
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetPropertyAttributesWithInterceptor(Handle<JSObject> holder,
+                                           Handle<Object> receiver,
+                                           Handle<Name> name);
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetPropertyAttributesWithFailedAccessCheck(LookupIterator* it);
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetElementAttributeWithReceiver(Handle<JSObject> object,
+                                      Handle<JSReceiver> receiver,
+                                      uint32_t index, bool check_prototype);
 
   // Retrieves an AccessorPair property from the given object. Might return
   // undefined if the property doesn't exist or is of a different kind.
-  static Handle<Object> GetAccessor(Handle<JSObject> object,
-                                    Handle<Name> name,
-                                    AccessorComponent component);
+  MUST_USE_RESULT static MaybeHandle<Object> GetAccessor(
+      Handle<JSObject> object,
+      Handle<Name> name,
+      AccessorComponent component);
 
   // Defines an AccessorPair property on the given object.
-  // TODO(mstarzinger): Rename to SetAccessor() and return empty handle on
-  // exception instead of letting callers check for scheduled exception.
-  static void DefineAccessor(Handle<JSObject> object,
-                             Handle<Name> name,
-                             Handle<Object> getter,
-                             Handle<Object> setter,
-                             PropertyAttributes attributes,
-                             v8::AccessControl access_control = v8::DEFAULT);
+  // TODO(mstarzinger): Rename to SetAccessor().
+  static MaybeHandle<Object> DefineAccessor(Handle<JSObject> object,
+                                            Handle<Name> name,
+                                            Handle<Object> getter,
+                                            Handle<Object> setter,
+                                            PropertyAttributes attributes);
 
   // Defines an AccessorInfo property on the given object.
-  static Handle<Object> SetAccessor(Handle<JSObject> object,
-                                    Handle<AccessorInfo> info);
+  MUST_USE_RESULT static MaybeHandle<Object> SetAccessor(
+      Handle<JSObject> object,
+      Handle<AccessorInfo> info);
 
-  static Handle<Object> GetPropertyWithInterceptor(
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithInterceptor(
       Handle<JSObject> object,
       Handle<Object> receiver,
-      Handle<Name> name,
-      PropertyAttributes* attributes);
-  static Handle<Object> GetPropertyPostInterceptor(
-      Handle<JSObject> object,
-      Handle<Object> receiver,
-      Handle<Name> name,
-      PropertyAttributes* attributes);
-  MUST_USE_RESULT MaybeObject* GetLocalPropertyPostInterceptor(
-      Object* receiver,
-      Name* name,
-      PropertyAttributes* attributes);
+      Handle<Name> name);
 
   // Returns true if this is an instance of an api function and has
   // been modified since it was created.  May give false positives.
   bool IsDirty();
 
-  // If the receiver is a JSGlobalProxy this method will return its prototype,
-  // otherwise the result is the receiver itself.
-  inline Object* BypassGlobalProxy();
-
   // Accessors for hidden properties object.
   //
-  // Hidden properties are not local properties of the object itself.
-  // Instead they are stored in an auxiliary structure kept as a local
+  // Hidden properties are not own properties of the object itself.
+  // Instead they are stored in an auxiliary structure kept as an own
   // property with a special name Heap::hidden_string(). But if the
   // receiver is a JSGlobalProxy then the auxiliary object is a property
   // of its prototype, and if it's a detached proxy, then you can't have
@@ -2439,36 +2301,42 @@ class JSObject: public JSReceiver {
   // Gets the value of a hidden property with the given key. Returns the hole
   // if the property doesn't exist (or if called on a detached proxy),
   // otherwise returns the value set for the key.
-  Object* GetHiddenProperty(Name* key);
+  Object* GetHiddenProperty(Handle<Name> key);
   // Deletes a hidden property. Deleting a non-existing property is
   // considered successful.
   static void DeleteHiddenProperty(Handle<JSObject> object,
                                    Handle<Name> key);
   // Returns true if the object has a property with the hidden string as name.
-  bool HasHiddenProperties();
+  static bool HasHiddenProperties(Handle<JSObject> object);
 
   static void SetIdentityHash(Handle<JSObject> object, Handle<Smi> hash);
 
-  inline void ValidateElements();
+  static inline void ValidateElements(Handle<JSObject> object);
 
   // Makes sure that this object can contain HeapObject as elements.
   static inline void EnsureCanContainHeapObjectElements(Handle<JSObject> obj);
 
   // Makes sure that this object can contain the specified elements.
-  MUST_USE_RESULT inline MaybeObject* EnsureCanContainElements(
+  static inline void EnsureCanContainElements(
+      Handle<JSObject> object,
       Object** elements,
       uint32_t count,
       EnsureElementsMode mode);
-  MUST_USE_RESULT inline MaybeObject* EnsureCanContainElements(
-      FixedArrayBase* elements,
+  static inline void EnsureCanContainElements(
+      Handle<JSObject> object,
+      Handle<FixedArrayBase> elements,
       uint32_t length,
       EnsureElementsMode mode);
-  MUST_USE_RESULT MaybeObject* EnsureCanContainElements(
+  static void EnsureCanContainElements(
+      Handle<JSObject> object,
       Arguments* arguments,
       uint32_t first_arg,
       uint32_t arg_count,
       EnsureElementsMode mode);
 
+  // Would we convert a fast elements array to dictionary mode given
+  // an access at key?
+  bool WouldConvertToSlowElements(Handle<Object> key);
   // Do we want to keep the elements in fast case when increasing the
   // capacity?
   bool ShouldConvertToSlowElements(int new_capacity);
@@ -2489,33 +2357,39 @@ class JSObject: public JSReceiver {
   }
 
   // These methods do not perform access checks!
-  AccessorPair* GetLocalPropertyAccessorPair(Name* name);
-  AccessorPair* GetLocalElementAccessorPair(uint32_t index);
+  MUST_USE_RESULT static MaybeHandle<AccessorPair> GetOwnElementAccessorPair(
+      Handle<JSObject> object,
+      uint32_t index);
 
-  static Handle<Object> SetFastElement(Handle<JSObject> object, uint32_t index,
-                                       Handle<Object> value,
-                                       StrictModeFlag strict_mode,
-                                       bool check_prototype);
+  MUST_USE_RESULT static MaybeHandle<Object> SetFastElement(
+      Handle<JSObject> object,
+      uint32_t index,
+      Handle<Object> value,
+      StrictMode strict_mode,
+      bool check_prototype);
 
-  static Handle<Object> SetOwnElement(Handle<JSObject> object,
-                                      uint32_t index,
-                                      Handle<Object> value,
-                                      StrictModeFlag strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetOwnElement(
+      Handle<JSObject> object,
+      uint32_t index,
+      Handle<Object> value,
+      StrictMode strict_mode);
 
   // Empty handle is returned if the element cannot be set to the given value.
-  static Handle<Object> SetElement(
+  MUST_USE_RESULT static MaybeHandle<Object> SetElement(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
       PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
+      StrictMode strict_mode,
       bool check_prototype = true,
       SetPropertyMode set_mode = SET_PROPERTY);
 
   // Returns the index'th element.
   // The undefined object if index is out of bounds.
-  MUST_USE_RESULT MaybeObject* GetElementWithInterceptor(Object* receiver,
-                                                         uint32_t index);
+  MUST_USE_RESULT static MaybeHandle<Object> GetElementWithInterceptor(
+      Handle<JSObject> object,
+      Handle<Object> receiver,
+      uint32_t index);
 
   enum SetFastElementsCapacitySmiMode {
     kAllowSmiElements,
@@ -2523,15 +2397,11 @@ class JSObject: public JSReceiver {
     kDontAllowSmiElements
   };
 
-  static Handle<FixedArray> SetFastElementsCapacityAndLength(
-      Handle<JSObject> object,
-      int capacity,
-      int length,
-      SetFastElementsCapacitySmiMode smi_mode);
   // Replace the elements' backing store with fast elements of the given
   // capacity.  Update the length for JSArrays.  Returns the new backing
   // store.
-  MUST_USE_RESULT MaybeObject* SetFastElementsCapacityAndLength(
+  static Handle<FixedArray> SetFastElementsCapacityAndLength(
+      Handle<JSObject> object,
       int capacity,
       int length,
       SetFastElementsCapacitySmiMode smi_mode);
@@ -2539,21 +2409,28 @@ class JSObject: public JSReceiver {
       Handle<JSObject> object,
       int capacity,
       int length);
-  MUST_USE_RESULT MaybeObject* SetFastDoubleElementsCapacityAndLength(
-      int capacity,
-      int length);
 
   // Lookup interceptors are used for handling properties controlled by host
   // objects.
   inline bool HasNamedInterceptor();
   inline bool HasIndexedInterceptor();
 
+  // Computes the enumerable keys from interceptors. Used for debug mirrors and
+  // by JSReceiver::GetKeys.
+  MUST_USE_RESULT static MaybeHandle<JSObject> GetKeysForNamedInterceptor(
+      Handle<JSObject> object,
+      Handle<JSReceiver> receiver);
+  MUST_USE_RESULT static MaybeHandle<JSObject> GetKeysForIndexedInterceptor(
+      Handle<JSObject> object,
+      Handle<JSReceiver> receiver);
+
   // Support functions for v8 api (needed for correct interceptor behavior).
-  static bool HasRealNamedProperty(Handle<JSObject> object,
-                                   Handle<Name> key);
-  static bool HasRealElementProperty(Handle<JSObject> object, uint32_t index);
-  static bool HasRealNamedCallbackProperty(Handle<JSObject> object,
-                                           Handle<Name> key);
+  MUST_USE_RESULT static Maybe<bool> HasRealNamedProperty(
+      Handle<JSObject> object, Handle<Name> key);
+  MUST_USE_RESULT static Maybe<bool> HasRealElementProperty(
+      Handle<JSObject> object, uint32_t index);
+  MUST_USE_RESULT static Maybe<bool> HasRealNamedCallbackProperty(
+      Handle<JSObject> object, Handle<Name> key);
 
   // Get the header size for a JSObject.  Used to compute the index of
   // internal fields as well as the number of internal fields.
@@ -2566,27 +2443,27 @@ class JSObject: public JSReceiver {
   inline void SetInternalField(int index, Smi* value);
 
   // The following lookup functions skip interceptors.
-  void LocalLookupRealNamedProperty(Name* name, LookupResult* result);
-  void LookupRealNamedProperty(Name* name, LookupResult* result);
-  void LookupRealNamedPropertyInPrototypes(Name* name, LookupResult* result);
-  void LookupCallbackProperty(Name* name, LookupResult* result);
+  void LookupOwnRealNamedProperty(Handle<Name> name, LookupResult* result);
+  void LookupRealNamedProperty(Handle<Name> name, LookupResult* result);
+  void LookupRealNamedPropertyInPrototypes(Handle<Name> name,
+                                           LookupResult* result);
 
   // Returns the number of properties on this object filtering out properties
   // with the specified attributes (ignoring interceptors).
-  int NumberOfLocalProperties(PropertyAttributes filter = NONE);
+  int NumberOfOwnProperties(PropertyAttributes filter = NONE);
   // Fill in details for properties into storage starting at the specified
   // index.
-  void GetLocalPropertyNames(
+  void GetOwnPropertyNames(
       FixedArray* storage, int index, PropertyAttributes filter = NONE);
 
   // Returns the number of properties on this object filtering out properties
   // with the specified attributes (ignoring interceptors).
-  int NumberOfLocalElements(PropertyAttributes filter);
+  int NumberOfOwnElements(PropertyAttributes filter);
   // Returns the number of enumerable elements (ignoring interceptors).
   int NumberOfEnumElements();
   // Returns the number of elements on this object filtering out elements
   // with the specified attributes (ignoring interceptors).
-  int GetLocalElementKeys(FixedArray* storage, PropertyAttributes filter);
+  int GetOwnElementKeys(FixedArray* storage, PropertyAttributes filter);
   // Count and fill in the enumerable elements into storage.
   // (storage->length() == NumberOfEnumElements()).
   // If storage is NULL, will count the elements without adding
@@ -2598,23 +2475,10 @@ class JSObject: public JSReceiver {
   // map and the ElementsKind set.
   static Handle<Map> GetElementsTransitionMap(Handle<JSObject> object,
                                               ElementsKind to_kind);
-  inline MUST_USE_RESULT MaybeObject* GetElementsTransitionMap(
-      Isolate* isolate,
-      ElementsKind elements_kind);
-  MUST_USE_RESULT MaybeObject* GetElementsTransitionMapSlow(
-      ElementsKind elements_kind);
-
   static void TransitionElementsKind(Handle<JSObject> object,
                                      ElementsKind to_kind);
 
-  MUST_USE_RESULT MaybeObject* TransitionElementsKind(ElementsKind to_kind);
-
-  // TODO(mstarzinger): Both public because of ConvertAnsSetLocalProperty().
   static void MigrateToMap(Handle<JSObject> object, Handle<Map> new_map);
-  static void GeneralizeFieldRepresentation(Handle<JSObject> object,
-                                            int modify_index,
-                                            Representation new_representation,
-                                            StoreMode store_mode);
 
   // Convert the object to use the canonical dictionary
   // representation. If the object is expected to have additional properties
@@ -2629,18 +2493,17 @@ class JSObject: public JSReceiver {
   static Handle<SeededNumberDictionary> NormalizeElements(
       Handle<JSObject> object);
 
-  MUST_USE_RESULT MaybeObject* NormalizeElements();
-
   // Transform slow named properties to fast variants.
-  static void TransformToFastProperties(Handle<JSObject> object,
-                                        int unused_property_fields);
+  static void MigrateSlowToFast(Handle<JSObject> object,
+                                int unused_property_fields);
 
   // Access fast-case object properties at index.
-  MUST_USE_RESULT inline MaybeObject* FastPropertyAt(
-      Representation representation,
-      int index);
-  inline Object* RawFastPropertyAt(int index);
-  inline void FastPropertyAtPut(int index, Object* value);
+  static Handle<Object> FastPropertyAt(Handle<JSObject> object,
+                                       Representation representation,
+                                       FieldIndex index);
+  inline Object* RawFastPropertyAt(FieldIndex index);
+  inline void FastPropertyAtPut(FieldIndex index, Object* value);
+  void WriteToField(int descriptor, Object* value);
 
   // Access to in object properties.
   inline int GetInObjectPropertyOffset(int index);
@@ -2651,9 +2514,8 @@ class JSObject: public JSReceiver {
                                        = UPDATE_WRITE_BARRIER);
 
   // Set the object's prototype (only JSReceiver and null are allowed values).
-  static Handle<Object> SetPrototype(Handle<JSObject> object,
-                                     Handle<Object> value,
-                                     bool skip_hidden_prototypes = false);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPrototype(
+      Handle<JSObject> object, Handle<Object> value, bool from_javascript);
 
   // Initializes the body after properties slot, properties slot is
   // initialized by set_properties.  Fill the pre-allocated fields with
@@ -2668,43 +2530,46 @@ class JSObject: public JSReceiver {
   bool ReferencesObject(Object* obj);
 
   // Disalow further properties to be added to the object.
-  static Handle<Object> PreventExtensions(Handle<JSObject> object);
+  MUST_USE_RESULT static MaybeHandle<Object> PreventExtensions(
+      Handle<JSObject> object);
 
   // ES5 Object.freeze
-  static Handle<Object> Freeze(Handle<JSObject> object);
+  MUST_USE_RESULT static MaybeHandle<Object> Freeze(Handle<JSObject> object);
 
   // Called the first time an object is observed with ES7 Object.observe.
   static void SetObserved(Handle<JSObject> object);
 
   // Copy object.
-  enum DeepCopyHints {
-    kNoHints = 0,
-    kObjectIsShallowArray = 1
-  };
+  enum DeepCopyHints { kNoHints = 0, kObjectIsShallow = 1 };
 
   static Handle<JSObject> Copy(Handle<JSObject> object);
-  static Handle<JSObject> DeepCopy(Handle<JSObject> object,
-                                   AllocationSiteUsageContext* site_context,
-                                   DeepCopyHints hints = kNoHints);
-  static Handle<JSObject> DeepWalk(Handle<JSObject> object,
-                                   AllocationSiteCreationContext* site_context);
+  MUST_USE_RESULT static MaybeHandle<JSObject> DeepCopy(
+      Handle<JSObject> object,
+      AllocationSiteUsageContext* site_context,
+      DeepCopyHints hints = kNoHints);
+  MUST_USE_RESULT static MaybeHandle<JSObject> DeepWalk(
+      Handle<JSObject> object,
+      AllocationSiteCreationContext* site_context);
 
-  // Casting.
-  static inline JSObject* cast(Object* obj);
+  static Handle<Object> GetDataProperty(Handle<JSObject> object,
+                                        Handle<Name> key);
+
+  DECLARE_CAST(JSObject)
 
   // Dispatched behavior.
   void JSObjectShortPrint(StringStream* accumulator);
   DECLARE_PRINTER(JSObject)
   DECLARE_VERIFIER(JSObject)
 #ifdef OBJECT_PRINT
-  void PrintProperties(FILE* out = stdout);
-  void PrintElements(FILE* out = stdout);
-  void PrintTransitions(FILE* out = stdout);
+  void PrintProperties(OStream& os);   // NOLINT
+  void PrintElements(OStream& os);     // NOLINT
+  void PrintTransitions(OStream& os);  // NOLINT
 #endif
 
-  void PrintElementsTransition(
-      FILE* file, ElementsKind from_kind, FixedArrayBase* from_elements,
-      ElementsKind to_kind, FixedArrayBase* to_elements);
+  static void PrintElementsTransition(
+      FILE* file, Handle<JSObject> object,
+      ElementsKind from_kind, Handle<FixedArrayBase> from_elements,
+      ElementsKind to_kind, Handle<FixedArrayBase> to_elements);
 
   void PrintInstanceMigration(FILE* file, Map* original_map, Map* new_map);
 
@@ -2739,12 +2604,6 @@ class JSObject: public JSReceiver {
 
   Object* SlowReverseLookup(Object* value);
 
-  // Maximal number of fast properties for the JSObject. Used to
-  // restrict the number of map transitions to avoid an explosion in
-  // the number of maps for objects used as dictionaries.
-  inline bool TooManyFastProperties(
-      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
-
   // Maximal number of elements (numbered 0 .. kMaxElementCount - 1).
   // Also maximal value of JSArray's length property.
   static const uint32_t kMaxElementCount = 0xffffffffu;
@@ -2765,11 +2624,13 @@ class JSObject: public JSReceiver {
   static const int kMaxUncheckedOldFastElementsLength = 500;
 
   // Note that Page::kMaxRegularHeapObjectSize puts a limit on
-  // permissible values (see the ASSERT in heap.cc).
+  // permissible values (see the DCHECK in heap.cc).
   static const int kInitialMaxFastElementArray = 100000;
 
-  static const int kFastPropertiesSoftLimit = 12;
-  static const int kMaxFastProperties = 64;
+  // This constant applies only to the initial map of "$Object" aka
+  // "global.Object" and not to arbitrary other JSObject maps.
+  static const int kInitialGlobalObjectUnusedPropertiesCount = 4;
+
   static const int kMaxInstanceSize = 255 * kPointerSize;
   // When extending the backing storage for property values, we increase
   // its size by more than the 1 entry necessary, so sequentially adding fields
@@ -2781,147 +2642,133 @@ class JSObject: public JSReceiver {
   static const int kElementsOffset = kPropertiesOffset + kPointerSize;
   static const int kHeaderSize = kElementsOffset + kPointerSize;
 
-  STATIC_CHECK(kHeaderSize == Internals::kJSObjectHeaderSize);
+  STATIC_ASSERT(kHeaderSize == Internals::kJSObjectHeaderSize);
 
   class BodyDescriptor : public FlexibleBodyDescriptor<kPropertiesOffset> {
    public:
     static inline int SizeOf(Map* map, HeapObject* object);
   };
 
+  Context* GetCreationContext();
+
   // Enqueue change record for Object.observe. May cause GC.
   static void EnqueueChangeRecord(Handle<JSObject> object,
                                   const char* type,
                                   Handle<Name> name,
                                   Handle<Object> old_value);
 
+  static void MigrateToNewProperty(Handle<JSObject> object,
+                                   Handle<Map> transition,
+                                   Handle<Object> value);
+
  private:
   friend class DictionaryElementsAccessor;
   friend class JSReceiver;
   friend class Object;
 
+  static void MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map);
+  static void MigrateFastToSlow(Handle<JSObject> object,
+                                Handle<Map> new_map,
+                                int expected_additional_properties);
+
+  static void SetPropertyToField(LookupResult* lookup, Handle<Object> value);
+
+  static void ConvertAndSetOwnProperty(LookupResult* lookup,
+                                       Handle<Name> name,
+                                       Handle<Object> value,
+                                       PropertyAttributes attributes);
+
+  static void SetPropertyToFieldWithAttributes(LookupResult* lookup,
+                                               Handle<Name> name,
+                                               Handle<Object> value,
+                                               PropertyAttributes attributes);
+  static void GeneralizeFieldRepresentation(Handle<JSObject> object,
+                                            int modify_index,
+                                            Representation new_representation,
+                                            Handle<HeapType> new_field_type);
+
   static void UpdateAllocationSite(Handle<JSObject> object,
                                    ElementsKind to_kind);
-  MUST_USE_RESULT MaybeObject* UpdateAllocationSite(ElementsKind to_kind);
 
   // Used from Object::GetProperty().
-  static Handle<Object> GetPropertyWithFailedAccessCheck(
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithFailedAccessCheck(
+      LookupIterator* it);
+
+  MUST_USE_RESULT static MaybeHandle<Object> GetElementWithCallback(
       Handle<JSObject> object,
       Handle<Object> receiver,
-      LookupResult* result,
-      Handle<Name> name,
-      PropertyAttributes* attributes);
-
-  MUST_USE_RESULT MaybeObject* GetElementWithCallback(Object* receiver,
-                                                      Object* structure,
-                                                      uint32_t index,
-                                                      Object* holder);
-  MUST_USE_RESULT PropertyAttributes GetElementAttributeWithInterceptor(
-      JSReceiver* receiver,
-      uint32_t index,
-      bool continue_search);
-  MUST_USE_RESULT PropertyAttributes GetElementAttributeWithoutInterceptor(
-      JSReceiver* receiver,
+      Handle<Object> structure,
       uint32_t index,
-      bool continue_search);
-  static Handle<Object> SetElementWithCallback(
+      Handle<Object> holder);
+
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetElementAttributeWithInterceptor(Handle<JSObject> object,
+                                         Handle<JSReceiver> receiver,
+                                         uint32_t index, bool continue_search);
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetElementAttributeWithoutInterceptor(Handle<JSObject> object,
+                                            Handle<JSReceiver> receiver,
+                                            uint32_t index,
+                                            bool continue_search);
+  MUST_USE_RESULT static MaybeHandle<Object> SetElementWithCallback(
       Handle<JSObject> object,
       Handle<Object> structure,
       uint32_t index,
       Handle<Object> value,
       Handle<JSObject> holder,
-      StrictModeFlag strict_mode);
-  static Handle<Object> SetElementWithInterceptor(
+      StrictMode strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetElementWithInterceptor(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
       PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
+      StrictMode strict_mode,
       bool check_prototype,
       SetPropertyMode set_mode);
-  static Handle<Object> SetElementWithoutInterceptor(
+  MUST_USE_RESULT static MaybeHandle<Object> SetElementWithoutInterceptor(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
       PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
+      StrictMode strict_mode,
       bool check_prototype,
       SetPropertyMode set_mode);
-  static Handle<Object> SetElementWithCallbackSetterInPrototypes(
+  MUST_USE_RESULT
+  static MaybeHandle<Object> SetElementWithCallbackSetterInPrototypes(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
       bool* found,
-      StrictModeFlag strict_mode);
-  static Handle<Object> SetDictionaryElement(
+      StrictMode strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetDictionaryElement(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
       PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
+      StrictMode strict_mode,
       bool check_prototype,
       SetPropertyMode set_mode = SET_PROPERTY);
-  static Handle<Object> SetFastDoubleElement(
+  MUST_USE_RESULT static MaybeHandle<Object> SetFastDoubleElement(
       Handle<JSObject> object,
       uint32_t index,
       Handle<Object> value,
-      StrictModeFlag strict_mode,
+      StrictMode strict_mode,
       bool check_prototype = true);
 
-  // Searches the prototype chain for property 'name'. If it is found and
-  // has a setter, invoke it and set '*done' to true. If it is found and is
-  // read-only, reject and set '*done' to true. Otherwise, set '*done' to
-  // false. Can throw and return an empty handle with '*done==true'.
-  static Handle<Object> SetPropertyViaPrototypes(
-      Handle<JSObject> object,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
-      bool* done);
-  static Handle<Object> SetPropertyPostInterceptor(
-      Handle<JSObject> object,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode);
-  static Handle<Object> SetPropertyUsingTransition(
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyUsingTransition(
       Handle<JSObject> object,
       LookupResult* lookup,
       Handle<Name> name,
       Handle<Object> value,
       PropertyAttributes attributes);
-  static Handle<Object> SetPropertyWithFailedAccessCheck(
-      Handle<JSObject> object,
-      LookupResult* result,
-      Handle<Name> name,
-      Handle<Object> value,
-      bool check_prototype,
-      StrictModeFlag strict_mode);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithFailedAccessCheck(
+      LookupIterator* it, Handle<Object> value, StrictMode strict_mode);
 
   // Add a property to an object.
-  static Handle<Object> AddProperty(
-      Handle<JSObject> object,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
-      StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED,
-      ExtensibilityCheck extensibility_check = PERFORM_EXTENSIBILITY_CHECK,
-      ValueType value_type = OPTIMAL_REPRESENTATION,
-      StoreMode mode = ALLOW_AS_CONSTANT,
-      TransitionFlag flag = INSERT_TRANSITION);
-
-  // Add a constant function property to a fast-case object.
-  // This leaves a CONSTANT_TRANSITION in the old map, and
-  // if it is called on a second object with this map, a
-  // normal property is added instead, with a map transition.
-  // This avoids the creation of many maps with the same constant
-  // function, all orphaned.
-  static void AddConstantProperty(Handle<JSObject> object,
-                                  Handle<Name> name,
-                                  Handle<Object> constant,
-                                  PropertyAttributes attributes,
-                                  TransitionFlag flag);
+  MUST_USE_RESULT static MaybeHandle<Object> AddPropertyInternal(
+      Handle<JSObject> object, Handle<Name> name, Handle<Object> value,
+      PropertyAttributes attributes, StoreFromKeyed store_mode,
+      ExtensibilityCheck extensibility_check, TransitionFlag flag);
 
   // Add a property to a fast-case object.
   static void AddFastProperty(Handle<JSObject> object,
@@ -2929,43 +2776,37 @@ class JSObject: public JSReceiver {
                               Handle<Object> value,
                               PropertyAttributes attributes,
                               StoreFromKeyed store_mode,
-                              ValueType value_type,
                               TransitionFlag flag);
 
-  // Add a property to a fast-case object using a map transition to
-  // new_map.
-  static void AddFastPropertyUsingMap(Handle<JSObject> object,
-                                      Handle<Map> new_map,
-                                      Handle<Name> name,
-                                      Handle<Object> value,
-                                      int field_index,
-                                      Representation representation);
-
   // Add a property to a slow-case object.
   static void AddSlowProperty(Handle<JSObject> object,
                               Handle<Name> name,
                               Handle<Object> value,
                               PropertyAttributes attributes);
 
-  static Handle<Object> DeleteProperty(Handle<JSObject> object,
-                                       Handle<Name> name,
-                                       DeleteMode mode);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteProperty(
+      Handle<JSObject> object,
+      Handle<Name> name,
+      DeleteMode mode);
   static Handle<Object> DeletePropertyPostInterceptor(Handle<JSObject> object,
                                                       Handle<Name> name,
                                                       DeleteMode mode);
-  static Handle<Object> DeletePropertyWithInterceptor(Handle<JSObject> object,
-                                                      Handle<Name> name);
+  MUST_USE_RESULT static MaybeHandle<Object> DeletePropertyWithInterceptor(
+      Handle<JSObject> object,
+      Handle<Name> name);
 
   // Deletes the named property in a normalized object.
   static Handle<Object> DeleteNormalizedProperty(Handle<JSObject> object,
                                                  Handle<Name> name,
                                                  DeleteMode mode);
 
-  static Handle<Object> DeleteElement(Handle<JSObject> object,
-                                      uint32_t index,
-                                      DeleteMode mode);
-  static Handle<Object> DeleteElementWithInterceptor(Handle<JSObject> object,
-                                                     uint32_t index);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteElement(
+      Handle<JSObject> object,
+      uint32_t index,
+      DeleteMode mode);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteElementWithInterceptor(
+      Handle<JSObject> object,
+      uint32_t index);
 
   bool ReferencesObjectFromElements(FixedArray* elements,
                                     ElementsKind kind,
@@ -2977,7 +2818,7 @@ class JSObject: public JSReceiver {
   // Gets the current elements capacity and the number of used elements.
   void GetElementsCapacityAndUsage(int* capacity, int* used);
 
-  bool CanSetCallback(Name* name);
+  static bool CanSetCallback(Handle<JSObject> object, Handle<Name> name);
   static void SetElementCallback(Handle<JSObject> object,
                                  uint32_t index,
                                  Handle<Object> structure,
@@ -2990,16 +2831,14 @@ class JSObject: public JSReceiver {
                                     uint32_t index,
                                     Handle<Object> getter,
                                     Handle<Object> setter,
-                                    PropertyAttributes attributes,
-                                    v8::AccessControl access_control);
+                                    PropertyAttributes attributes);
   static Handle<AccessorPair> CreateAccessorPairFor(Handle<JSObject> object,
                                                     Handle<Name> name);
   static void DefinePropertyAccessor(Handle<JSObject> object,
                                      Handle<Name> name,
                                      Handle<Object> getter,
                                      Handle<Object> setter,
-                                     PropertyAttributes attributes,
-                                     v8::AccessControl access_control);
+                                     PropertyAttributes attributes);
 
   // Try to define a single accessor paying attention to map transitions.
   // Returns false if this was not possible and we have to use the slow case.
@@ -3027,7 +2866,7 @@ class JSObject: public JSReceiver {
 
   MUST_USE_RESULT Object* GetIdentityHash();
 
-  static Handle<Object> GetOrCreateIdentityHash(Handle<JSObject> object);
+  static Handle<Smi> GetOrCreateIdentityHash(Handle<JSObject> object);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSObject);
 };
@@ -3038,10 +2877,14 @@ class JSObject: public JSReceiver {
 class FixedArrayBase: public HeapObject {
  public:
   // [length]: length of the array.
-  inline int length();
+  inline int length() const;
   inline void set_length(int value);
 
-  inline static FixedArrayBase* cast(Object* object);
+  // Get and set the length using acquire loads and release stores.
+  inline int synchronized_length() const;
+  inline void synchronized_set_length(int value);
+
+  DECLARE_CAST(FixedArrayBase)
 
   // Layout description.
   // Length is smi tagged when it is stored.
@@ -3059,6 +2902,7 @@ class FixedArray: public FixedArrayBase {
  public:
   // Setter and getter for elements.
   inline Object* get(int index);
+  static inline Handle<Object> get(Handle<FixedArray> array, int index);
   // Setter that uses write barrier.
   inline void set(int index, Object* value);
   inline bool is_the_hole(int index);
@@ -3079,19 +2923,26 @@ class FixedArray: public FixedArrayBase {
   // Gives access to raw memory which stores the array's data.
   inline Object** data_start();
 
+  inline void FillWithHoles(int from, int to);
+
   // Shrink length and insert filler objects.
   void Shrink(int length);
 
-  // Copy operations.
-  MUST_USE_RESULT inline MaybeObject* Copy();
-  MUST_USE_RESULT MaybeObject* CopySize(int new_length,
-                                        PretenureFlag pretenure = NOT_TENURED);
+  // Copy operation.
+  static Handle<FixedArray> CopySize(Handle<FixedArray> array,
+                                     int new_length,
+                                     PretenureFlag pretenure = NOT_TENURED);
 
   // Add the elements of a JSArray to this FixedArray.
-  MUST_USE_RESULT MaybeObject* AddKeysFromJSArray(JSArray* array);
+  MUST_USE_RESULT static MaybeHandle<FixedArray> AddKeysFromArrayLike(
+      Handle<FixedArray> content,
+      Handle<JSObject> array);
 
-  // Compute the union of this and other.
-  MUST_USE_RESULT MaybeObject* UnionOfKeys(FixedArray* other);
+  // Computes the union of keys and return the result.
+  // Used for implementing "for (n in object) { }"
+  MUST_USE_RESULT static MaybeHandle<FixedArray> UnionOfKeys(
+      Handle<FixedArray> first,
+      Handle<FixedArray> second);
 
   // Copy a sub array from the receiver to dest.
   void CopyTo(int pos, FixedArray* dest, int dest_pos, int len);
@@ -3107,8 +2958,7 @@ class FixedArray: public FixedArrayBase {
     return HeapObject::RawField(this, OffsetOfElementAt(index));
   }
 
-  // Casting.
-  static inline FixedArray* cast(Object* obj);
+  DECLARE_CAST(FixedArray)
 
   // Maximal allowed size, in bytes, of a single FixedArray.
   // Prevents overflowing size computations, as well as extreme memory
@@ -3157,7 +3007,7 @@ class FixedArray: public FixedArrayBase {
                                                   Object* value);
 
  private:
-  STATIC_CHECK(kHeaderSize == Internals::kFixedArrayHeaderSize);
+  STATIC_ASSERT(kHeaderSize == Internals::kFixedArrayHeaderSize);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedArray);
 };
@@ -3169,16 +3019,13 @@ class FixedDoubleArray: public FixedArrayBase {
   // Setter and getter for elements.
   inline double get_scalar(int index);
   inline int64_t get_representation(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<FixedDoubleArray> array, int index);
   inline void set(int index, double value);
   inline void set_the_hole(int index);
 
   // Checking for the hole.
   inline bool is_the_hole(int index);
 
-  // Copy operations
-  MUST_USE_RESULT inline MaybeObject* Copy();
-
   // Garbage collection support.
   inline static int SizeFor(int length) {
     return kHeaderSize + length * kDoubleSize;
@@ -3187,6 +3034,8 @@ class FixedDoubleArray: public FixedArrayBase {
   // Gives access to raw memory which stores the array's data.
   inline double* data_start();
 
+  inline void FillWithHoles(int from, int to);
+
   // Code Generation support.
   static int OffsetOfElementAt(int index) { return SizeFor(index); }
 
@@ -3194,8 +3043,7 @@ class FixedDoubleArray: public FixedArrayBase {
   inline static double hole_nan_as_double();
   inline static double canonical_not_the_hole_nan_as_double();
 
-  // Casting.
-  static inline FixedDoubleArray* cast(Object* obj);
+  DECLARE_CAST(FixedDoubleArray)
 
   // Maximal allowed size, in bytes, of a single FixedDoubleArray.
   // Prevents overflowing size computations, as well as extreme memory
@@ -3214,75 +3062,294 @@ class FixedDoubleArray: public FixedArrayBase {
 
 
 // ConstantPoolArray describes a fixed-sized array containing constant pool
-// entires.
-// The format of the pool is:
-//   [0]: Field holding the first index which is a pointer entry
-//   [1]: Field holding the first index which is a int32 entry
-//   [2] ... [first_ptr_index() - 1]: 64 bit entries
-//   [first_ptr_index()] ... [first_int32_index() - 1]: pointer entries
-//   [first_int32_index()] ... [length - 1]: 32 bit entries
-class ConstantPoolArray: public FixedArrayBase {
- public:
-  // Getters for the field storing the first index for different type entries.
-  inline int first_ptr_index();
-  inline int first_int64_index();
-  inline int first_int32_index();
-
-  // Getters for counts of different type entries.
-  inline int count_of_ptr_entries();
-  inline int count_of_int64_entries();
-  inline int count_of_int32_entries();
+// entries.
+//
+// A ConstantPoolArray can be structured in two different ways depending upon
+// whether it is extended or small. The is_extended_layout() method can be used
+// to discover which layout the constant pool has.
+//
+// The format of a small constant pool is:
+//   [kSmallLayout1Offset]                    : Small section layout bitmap 1
+//   [kSmallLayout2Offset]                    : Small section layout bitmap 2
+//   [first_index(INT64, SMALL_SECTION)]      : 64 bit entries
+//    ...                                     :  ...
+//   [first_index(CODE_PTR, SMALL_SECTION)]   : code pointer entries
+//    ...                                     :  ...
+//   [first_index(HEAP_PTR, SMALL_SECTION)]   : heap pointer entries
+//    ...                                     :  ...
+//   [first_index(INT32, SMALL_SECTION)]      : 32 bit entries
+//    ...                                     :  ...
+//
+// If the constant pool has an extended layout, the extended section constant
+// pool also contains an extended section, which has the following format at
+// location get_extended_section_header_offset():
+//   [kExtendedInt64CountOffset]              : count of extended 64 bit entries
+//   [kExtendedCodePtrCountOffset]            : count of extended code pointers
+//   [kExtendedHeapPtrCountOffset]            : count of extended heap pointers
+//   [kExtendedInt32CountOffset]              : count of extended 32 bit entries
+//   [first_index(INT64, EXTENDED_SECTION)]   : 64 bit entries
+//    ...                                     :  ...
+//   [first_index(CODE_PTR, EXTENDED_SECTION)]: code pointer entries
+//    ...                                     :  ...
+//   [first_index(HEAP_PTR, EXTENDED_SECTION)]: heap pointer entries
+//    ...                                     :  ...
+//   [first_index(INT32, EXTENDED_SECTION)]   : 32 bit entries
+//    ...                                     :  ...
+//
+class ConstantPoolArray: public HeapObject {
+ public:
+  enum WeakObjectState {
+    NO_WEAK_OBJECTS,
+    WEAK_OBJECTS_IN_OPTIMIZED_CODE,
+    WEAK_OBJECTS_IN_IC
+  };
+
+  enum Type {
+    INT64 = 0,
+    CODE_PTR,
+    HEAP_PTR,
+    INT32,
+    // Number of types stored by the ConstantPoolArrays.
+    NUMBER_OF_TYPES,
+    FIRST_TYPE = INT64,
+    LAST_TYPE = INT32
+  };
+
+  enum LayoutSection {
+    SMALL_SECTION = 0,
+    EXTENDED_SECTION,
+    NUMBER_OF_LAYOUT_SECTIONS
+  };
+
+  class NumberOfEntries BASE_EMBEDDED {
+   public:
+    inline NumberOfEntries() {
+      for (int i = 0; i < NUMBER_OF_TYPES; i++) {
+        element_counts_[i] = 0;
+      }
+    }
+
+    inline NumberOfEntries(int int64_count, int code_ptr_count,
+                           int heap_ptr_count, int int32_count) {
+      element_counts_[INT64] = int64_count;
+      element_counts_[CODE_PTR] = code_ptr_count;
+      element_counts_[HEAP_PTR] = heap_ptr_count;
+      element_counts_[INT32] = int32_count;
+    }
+
+    inline NumberOfEntries(ConstantPoolArray* array, LayoutSection section) {
+      element_counts_[INT64] = array->number_of_entries(INT64, section);
+      element_counts_[CODE_PTR] = array->number_of_entries(CODE_PTR, section);
+      element_counts_[HEAP_PTR] = array->number_of_entries(HEAP_PTR, section);
+      element_counts_[INT32] = array->number_of_entries(INT32, section);
+    }
+
+    inline void increment(Type type);
+    inline int equals(const NumberOfEntries& other) const;
+    inline bool is_empty() const;
+    inline int count_of(Type type) const;
+    inline int base_of(Type type) const;
+    inline int total_count() const;
+    inline int are_in_range(int min, int max) const;
+
+   private:
+    int element_counts_[NUMBER_OF_TYPES];
+  };
+
+  class Iterator BASE_EMBEDDED {
+   public:
+    inline Iterator(ConstantPoolArray* array, Type type)
+        : array_(array),
+          type_(type),
+          final_section_(array->final_section()),
+          current_section_(SMALL_SECTION),
+          next_index_(array->first_index(type, SMALL_SECTION)) {
+      update_section();
+    }
+
+    inline Iterator(ConstantPoolArray* array, Type type, LayoutSection section)
+        : array_(array),
+          type_(type),
+          final_section_(section),
+          current_section_(section),
+          next_index_(array->first_index(type, section)) {
+      update_section();
+    }
+
+    inline int next_index();
+    inline bool is_finished();
+
+   private:
+    inline void update_section();
+    ConstantPoolArray* array_;
+    const Type type_;
+    const LayoutSection final_section_;
+
+    LayoutSection current_section_;
+    int next_index_;
+  };
+
+  // Getters for the first index, the last index and the count of entries of
+  // a given type for a given layout section.
+  inline int first_index(Type type, LayoutSection layout_section);
+  inline int last_index(Type type, LayoutSection layout_section);
+  inline int number_of_entries(Type type, LayoutSection layout_section);
+
+  // Returns the type of the entry at the given index.
+  inline Type get_type(int index);
+  inline bool offset_is_type(int offset, Type type);
 
   // Setter and getter for pool elements.
-  inline Object* get_ptr_entry(int index);
+  inline Address get_code_ptr_entry(int index);
+  inline Object* get_heap_ptr_entry(int index);
   inline int64_t get_int64_entry(int index);
   inline int32_t get_int32_entry(int index);
   inline double get_int64_entry_as_double(int index);
 
+  inline void set(int index, Address value);
   inline void set(int index, Object* value);
   inline void set(int index, int64_t value);
   inline void set(int index, double value);
   inline void set(int index, int32_t value);
 
-  // Set up initial state.
-  inline void SetEntryCounts(int number_of_int64_entries,
-                             int number_of_ptr_entries,
-                             int number_of_int32_entries);
+  // Setters which take a raw offset rather than an index (for code generation).
+  inline void set_at_offset(int offset, int32_t value);
+  inline void set_at_offset(int offset, int64_t value);
+  inline void set_at_offset(int offset, double value);
+  inline void set_at_offset(int offset, Address value);
+  inline void set_at_offset(int offset, Object* value);
 
-  // Copy operations
-  MUST_USE_RESULT inline MaybeObject* Copy();
+  // Setter and getter for weak objects state
+  inline void set_weak_object_state(WeakObjectState state);
+  inline WeakObjectState get_weak_object_state();
+
+  // Returns true if the constant pool has an extended layout, false if it has
+  // only the small layout.
+  inline bool is_extended_layout();
+
+  // Returns the last LayoutSection in this constant pool array.
+  inline LayoutSection final_section();
+
+  // Set up initial state for a small layout constant pool array.
+  inline void Init(const NumberOfEntries& small);
+
+  // Set up initial state for an extended layout constant pool array.
+  inline void InitExtended(const NumberOfEntries& small,
+                           const NumberOfEntries& extended);
+
+  // Clears the pointer entries with GC safe values.
+  void ClearPtrEntries(Isolate* isolate);
+
+  // returns the total number of entries in the constant pool array.
+  inline int length();
 
   // Garbage collection support.
-  inline static int SizeFor(int number_of_int64_entries,
-                            int number_of_ptr_entries,
-                            int number_of_int32_entries) {
-    return RoundUp(OffsetAt(number_of_int64_entries,
-                            number_of_ptr_entries,
-                            number_of_int32_entries),
-                   kPointerSize);
+  inline int size();
+
+
+  inline static int MaxInt64Offset(int number_of_int64) {
+    return kFirstEntryOffset + (number_of_int64 * kInt64Size);
+  }
+
+  inline static int SizeFor(const NumberOfEntries& small) {
+    int size = kFirstEntryOffset +
+        (small.count_of(INT64)  * kInt64Size) +
+        (small.count_of(CODE_PTR) * kPointerSize) +
+        (small.count_of(HEAP_PTR) * kPointerSize) +
+        (small.count_of(INT32) * kInt32Size);
+    return RoundUp(size, kPointerSize);
+  }
+
+  inline static int SizeForExtended(const NumberOfEntries& small,
+                                    const NumberOfEntries& extended) {
+    int size = SizeFor(small);
+    size = RoundUp(size, kInt64Size);  // Align extended header to 64 bits.
+    size += kExtendedFirstOffset +
+        (extended.count_of(INT64) * kInt64Size) +
+        (extended.count_of(CODE_PTR) * kPointerSize) +
+        (extended.count_of(HEAP_PTR) * kPointerSize) +
+        (extended.count_of(INT32) * kInt32Size);
+    return RoundUp(size, kPointerSize);
+  }
+
+  inline static int entry_size(Type type) {
+    switch (type) {
+      case INT32:
+        return kInt32Size;
+      case INT64:
+        return kInt64Size;
+      case CODE_PTR:
+      case HEAP_PTR:
+        return kPointerSize;
+      default:
+        UNREACHABLE();
+        return 0;
+    }
   }
 
   // Code Generation support.
   inline int OffsetOfElementAt(int index) {
-    ASSERT(index < length());
-    if (index >= first_int32_index()) {
-      return OffsetAt(count_of_int64_entries(), count_of_ptr_entries(),
-                      index - first_int32_index());
-    } else if (index >= first_ptr_index()) {
-      return OffsetAt(count_of_int64_entries(), index - first_ptr_index(), 0);
+    int offset;
+    LayoutSection section;
+    if (is_extended_layout() && index >= first_extended_section_index()) {
+      section = EXTENDED_SECTION;
+      offset = get_extended_section_header_offset() + kExtendedFirstOffset;
     } else {
-      return OffsetAt(index, 0, 0);
+      section = SMALL_SECTION;
+      offset = kFirstEntryOffset;
     }
+
+    // Add offsets for the preceding type sections.
+    DCHECK(index <= last_index(LAST_TYPE, section));
+    for (Type type = FIRST_TYPE; index > last_index(type, section);
+         type = next_type(type)) {
+      offset += entry_size(type) * number_of_entries(type, section);
+    }
+
+    // Add offset for the index in it's type.
+    Type type = get_type(index);
+    offset += entry_size(type) * (index - first_index(type, section));
+    return offset;
   }
 
-  // Casting.
-  static inline ConstantPoolArray* cast(Object* obj);
+  DECLARE_CAST(ConstantPoolArray)
 
-  // Layout description.
-  static const int kFirstPointerIndexOffset = FixedArray::kHeaderSize;
-  static const int kFirstInt32IndexOffset =
-      kFirstPointerIndexOffset + kPointerSize;
-  static const int kFirstOffset = kFirstInt32IndexOffset + kPointerSize;
+  // Garbage collection support.
+  Object** RawFieldOfElementAt(int index) {
+    return HeapObject::RawField(this, OffsetOfElementAt(index));
+  }
+
+  // Small Layout description.
+  static const int kSmallLayout1Offset = HeapObject::kHeaderSize;
+  static const int kSmallLayout2Offset = kSmallLayout1Offset + kInt32Size;
+  static const int kHeaderSize = kSmallLayout2Offset + kInt32Size;
+  static const int kFirstEntryOffset = ROUND_UP(kHeaderSize, kInt64Size);
+
+  static const int kSmallLayoutCountBits = 10;
+  static const int kMaxSmallEntriesPerType = (1 << kSmallLayoutCountBits) - 1;
+
+  // Fields in kSmallLayout1Offset.
+  class Int64CountField: public BitField<int, 1, kSmallLayoutCountBits> {};
+  class CodePtrCountField: public BitField<int, 11, kSmallLayoutCountBits> {};
+  class HeapPtrCountField: public BitField<int, 21, kSmallLayoutCountBits> {};
+  class IsExtendedField: public BitField<bool, 31, 1> {};
+
+  // Fields in kSmallLayout2Offset.
+  class Int32CountField: public BitField<int, 1, kSmallLayoutCountBits> {};
+  class TotalCountField: public BitField<int, 11, 12> {};
+  class WeakObjectStateField: public BitField<WeakObjectState, 23, 2> {};
+
+  // Extended layout description, which starts at
+  // get_extended_section_header_offset().
+  static const int kExtendedInt64CountOffset = 0;
+  static const int kExtendedCodePtrCountOffset =
+      kExtendedInt64CountOffset + kPointerSize;
+  static const int kExtendedHeapPtrCountOffset =
+      kExtendedCodePtrCountOffset + kPointerSize;
+  static const int kExtendedInt32CountOffset =
+      kExtendedHeapPtrCountOffset + kPointerSize;
+  static const int kExtendedFirstOffset =
+      kExtendedInt32CountOffset + kPointerSize;
 
   // Dispatched behavior.
   void ConstantPoolIterateBody(ObjectVisitor* v);
@@ -3291,16 +3358,13 @@ class ConstantPoolArray: public FixedArrayBase {
   DECLARE_VERIFIER(ConstantPoolArray)
 
  private:
-  inline void set_first_ptr_index(int value);
-  inline void set_first_int32_index(int value);
+  inline int first_extended_section_index();
+  inline int get_extended_section_header_offset();
 
-  inline static int OffsetAt(int number_of_int64_entries,
-                             int number_of_ptr_entries,
-                             int number_of_int32_entries) {
-    return kFirstOffset
-        + (number_of_int64_entries * kInt64Size)
-        + (number_of_ptr_entries * kPointerSize)
-        + (number_of_int32_entries * kInt32Size);
+  inline static Type next_type(Type type) {
+    DCHECK(type >= FIRST_TYPE && type < NUMBER_OF_TYPES);
+    int type_int = static_cast<int>(type);
+    return static_cast<Type>(++type_int);
   }
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ConstantPoolArray);
@@ -3317,23 +3381,6 @@ class ConstantPoolArray: public FixedArrayBase {
 //   [2 + number of descriptors * kDescriptorSize]: start of slack
 class DescriptorArray: public FixedArray {
  public:
-  // WhitenessWitness is used to prove that a descriptor array is white
-  // (unmarked), so incremental write barriers can be skipped because the
-  // marking invariant cannot be broken and slots pointing into evacuation
-  // candidates will be discovered when the object is scanned. A witness is
-  // always stack-allocated right after creating an array. By allocating a
-  // witness, incremental marking is globally disabled. The witness is then
-  // passed along wherever needed to statically prove that the array is known to
-  // be white.
-  class WhitenessWitness {
-   public:
-    inline explicit WhitenessWitness(FixedArray* array);
-    inline ~WhitenessWitness();
-
-   private:
-    IncrementalMarking* marking_;
-  };
-
   // Returns true for both shared empty_descriptor_array and for smis, which the
   // map uses to encode additional bit fields when the descriptor array is not
   // yet used.
@@ -3341,7 +3388,7 @@ class DescriptorArray: public FixedArray {
 
   // Returns the number of descriptors in the array.
   int number_of_descriptors() {
-    ASSERT(length() >= kFirstIndex || IsEmpty());
+    DCHECK(length() >= kFirstIndex || IsEmpty());
     int len = length();
     return len == 0 ? 0 : Smi::cast(get(kDescriptorLengthIndex))->value();
   }
@@ -3367,7 +3414,7 @@ class DescriptorArray: public FixedArray {
   }
 
   FixedArray* GetEnumCache() {
-    ASSERT(HasEnumCache());
+    DCHECK(HasEnumCache());
     FixedArray* bridge = FixedArray::cast(get(kEnumCacheIndex));
     return FixedArray::cast(bridge->get(kEnumCacheBridgeCacheIndex));
   }
@@ -3381,13 +3428,13 @@ class DescriptorArray: public FixedArray {
   }
 
   FixedArray* GetEnumIndicesCache() {
-    ASSERT(HasEnumIndicesCache());
+    DCHECK(HasEnumIndicesCache());
     FixedArray* bridge = FixedArray::cast(get(kEnumCacheIndex));
     return FixedArray::cast(bridge->get(kEnumCacheBridgeIndicesCacheIndex));
   }
 
   Object** GetEnumCacheSlot() {
-    ASSERT(HasEnumCache());
+    DCHECK(HasEnumCache());
     return HeapObject::RawField(reinterpret_cast<HeapObject*>(this),
                                 kEnumCacheOffset);
   }
@@ -3400,16 +3447,21 @@ class DescriptorArray: public FixedArray {
                     FixedArray* new_cache,
                     Object* new_index_cache);
 
+  bool CanHoldValue(int descriptor, Object* value);
+
   // Accessors for fetching instance descriptor at descriptor number.
   inline Name* GetKey(int descriptor_number);
   inline Object** GetKeySlot(int descriptor_number);
   inline Object* GetValue(int descriptor_number);
+  inline void SetValue(int descriptor_number, Object* value);
   inline Object** GetValueSlot(int descriptor_number);
+  static inline int GetValueOffset(int descriptor_number);
   inline Object** GetDescriptorStartSlot(int descriptor_number);
   inline Object** GetDescriptorEndSlot(int descriptor_number);
   inline PropertyDetails GetDetails(int descriptor_number);
   inline PropertyType GetType(int descriptor_number);
   inline int GetFieldIndex(int descriptor_number);
+  inline HeapType* GetFieldType(int descriptor_number);
   inline Object* GetConstant(int descriptor_number);
   inline Object* GetCallbacksObject(int descriptor_number);
   inline AccessorDescriptor* GetCallbacks(int descriptor_number);
@@ -3417,59 +3469,28 @@ class DescriptorArray: public FixedArray {
   inline Name* GetSortedKey(int descriptor_number);
   inline int GetSortedKeyIndex(int descriptor_number);
   inline void SetSortedKey(int pointer, int descriptor_number);
-  inline void InitializeRepresentations(Representation representation);
   inline void SetRepresentation(int descriptor_number,
                                 Representation representation);
 
   // Accessor for complete descriptor.
   inline void Get(int descriptor_number, Descriptor* desc);
-  inline void Set(int descriptor_number,
-                  Descriptor* desc,
-                  const WhitenessWitness&);
   inline void Set(int descriptor_number, Descriptor* desc);
+  void Replace(int descriptor_number, Descriptor* descriptor);
 
   // Append automatically sets the enumeration index. This should only be used
   // to add descriptors in bulk at the end, followed by sorting the descriptor
   // array.
-  inline void Append(Descriptor* desc, const WhitenessWitness&);
   inline void Append(Descriptor* desc);
 
-  // Transfer a complete descriptor from the src descriptor array to this
-  // descriptor array.
-  void CopyFrom(int dst_index,
-                DescriptorArray* src,
-                int src_index,
-                const WhitenessWitness&);
-  static Handle<DescriptorArray> Merge(Handle<DescriptorArray> desc,
-                                       int verbatim,
-                                       int valid,
-                                       int new_size,
-                                       int modify_index,
-                                       StoreMode store_mode,
-                                       Handle<DescriptorArray> other);
-  MUST_USE_RESULT MaybeObject* Merge(int verbatim,
-                                     int valid,
-                                     int new_size,
-                                     int modify_index,
-                                     StoreMode store_mode,
-                                     DescriptorArray* other);
-
-  bool IsMoreGeneralThan(int verbatim,
-                         int valid,
-                         int new_size,
-                         DescriptorArray* other);
-
-  MUST_USE_RESULT MaybeObject* CopyUpTo(int enumeration_index) {
-    return CopyUpToAddAttributes(enumeration_index, NONE);
-  }
+  static Handle<DescriptorArray> CopyUpTo(Handle<DescriptorArray> desc,
+                                          int enumeration_index,
+                                          int slack = 0);
 
   static Handle<DescriptorArray> CopyUpToAddAttributes(
       Handle<DescriptorArray> desc,
       int enumeration_index,
-      PropertyAttributes attributes);
-  MUST_USE_RESULT MaybeObject* CopyUpToAddAttributes(
-      int enumeration_index,
-      PropertyAttributes attributes);
+      PropertyAttributes attributes,
+      int slack = 0);
 
   // Sort the instance descriptors by the hash codes of their keys.
   void Sort();
@@ -3483,12 +3504,11 @@ class DescriptorArray: public FixedArray {
 
   // Allocates a DescriptorArray, but returns the singleton
   // empty descriptor array object if number_of_descriptors is 0.
-  MUST_USE_RESULT static MaybeObject* Allocate(Isolate* isolate,
-                                               int number_of_descriptors,
-                                               int slack = 0);
+  static Handle<DescriptorArray> Allocate(Isolate* isolate,
+                                          int number_of_descriptors,
+                                          int slack = 0);
 
-  // Casting.
-  static inline DescriptorArray* cast(Object* obj);
+  DECLARE_CAST(DescriptorArray)
 
   // Constant for denoting key was not found.
   static const int kNotFound = -1;
@@ -3518,7 +3538,7 @@ class DescriptorArray: public FixedArray {
 
 #ifdef OBJECT_PRINT
   // Print all the descriptors.
-  void PrintDescriptors(FILE* out = stdout);
+  void PrintDescriptors(OStream& os);  // NOLINT
 #endif
 
 #ifdef DEBUG
@@ -3539,6 +3559,23 @@ class DescriptorArray: public FixedArray {
   }
 
  private:
+  // WhitenessWitness is used to prove that a descriptor array is white
+  // (unmarked), so incremental write barriers can be skipped because the
+  // marking invariant cannot be broken and slots pointing into evacuation
+  // candidates will be discovered when the object is scanned. A witness is
+  // always stack-allocated right after creating an array. By allocating a
+  // witness, incremental marking is globally disabled. The witness is then
+  // passed along wherever needed to statically prove that the array is known to
+  // be white.
+  class WhitenessWitness {
+   public:
+    inline explicit WhitenessWitness(DescriptorArray* array);
+    inline ~WhitenessWitness();
+
+   private:
+    IncrementalMarking* marking_;
+  };
+
   // An entry in a DescriptorArray, represented as an (array, index) pair.
   class Entry {
    public:
@@ -3572,6 +3609,18 @@ class DescriptorArray: public FixedArray {
            kDescriptorValue;
   }
 
+  // Transfer a complete descriptor from the src descriptor array to this
+  // descriptor array.
+  void CopyFrom(int index,
+                DescriptorArray* src,
+                const WhitenessWitness&);
+
+  inline void Set(int descriptor_number,
+                  Descriptor* desc,
+                  const WhitenessWitness&);
+
+  inline void Append(Descriptor* desc, const WhitenessWitness&);
+
   // Swap first and second descriptor.
   inline void SwapSortedKeys(int first, int second);
 
@@ -3611,7 +3660,7 @@ inline int Search(T* array, Name* name, int valid_entries = 0);
 //     // Returns the hash value for object.
 //     static uint32_t HashForObject(Key key, Object* object);
 //     // Convert key to an object.
-//     static inline Object* AsObject(Heap* heap, Key key);
+//     static inline Handle<Object> AsHandle(Isolate* isolate, Key key);
 //     // The prefix size indicates number of elements in the beginning
 //     // of the backing storage.
 //     static const int kPrefixSize = ..;
@@ -3628,24 +3677,23 @@ class BaseShape {
   static const bool UsesSeed = false;
   static uint32_t Hash(Key key) { return 0; }
   static uint32_t SeededHash(Key key, uint32_t seed) {
-    ASSERT(UsesSeed);
+    DCHECK(UsesSeed);
     return Hash(key);
   }
   static uint32_t HashForObject(Key key, Object* object) { return 0; }
   static uint32_t SeededHashForObject(Key key, uint32_t seed, Object* object) {
-    ASSERT(UsesSeed);
+    DCHECK(UsesSeed);
     return HashForObject(key, object);
   }
 };
 
-template<typename Shape, typename Key>
+template<typename Derived, typename Shape, typename Key>
 class HashTable: public FixedArray {
  public:
   // Wrapper methods
   inline uint32_t Hash(Key key) {
     if (Shape::UsesSeed) {
-      return Shape::SeededHash(key,
-          GetHeap()->HashSeed());
+      return Shape::SeededHash(key, GetHeap()->HashSeed());
     } else {
       return Shape::Hash(key);
     }
@@ -3653,8 +3701,7 @@ class HashTable: public FixedArray {
 
   inline uint32_t HashForObject(Key key, Object* object) {
     if (Shape::UsesSeed) {
-      return Shape::SeededHashForObject(key,
-          GetHeap()->HashSeed(), object);
+      return Shape::SeededHashForObject(key, GetHeap()->HashSeed(), object);
     } else {
       return Shape::HashForObject(key, object);
     }
@@ -3690,9 +3737,9 @@ class HashTable: public FixedArray {
     SetNumberOfDeletedElements(NumberOfDeletedElements() + n);
   }
 
-  // Returns a new HashTable object. Might return Failure.
-  MUST_USE_RESULT static MaybeObject* Allocate(
-      Heap* heap,
+  // Returns a new HashTable object.
+  MUST_USE_RESULT static Handle<Derived> New(
+      Isolate* isolate,
       int at_least_space_for,
       MinimumCapacity capacity_option = USE_DEFAULT_MINIMUM_CAPACITY,
       PretenureFlag pretenure = NOT_TENURED);
@@ -3714,8 +3761,7 @@ class HashTable: public FixedArray {
   void IteratePrefix(ObjectVisitor* visitor);
   void IterateElements(ObjectVisitor* visitor);
 
-  // Casting.
-  static inline HashTable* cast(Object* obj);
+  DECLARE_CAST(HashTable)
 
   // Compute the probe offset (quadratic probing).
   INLINE(static uint32_t GetProbeOffset(uint32_t n)) {
@@ -3751,7 +3797,6 @@ class HashTable: public FixedArray {
   void Rehash(Key key);
 
  protected:
-  friend class ObjectHashSet;
   friend class ObjectHashTable;
 
   // Find the entry at which to insert element with the given key that
@@ -3778,15 +3823,15 @@ class HashTable: public FixedArray {
     // To scale a computed hash code to fit within the hash table, we
     // use bit-wise AND with a mask, so the capacity must be positive
     // and non-zero.
-    ASSERT(capacity > 0);
-    ASSERT(capacity <= kMaxCapacity);
+    DCHECK(capacity > 0);
+    DCHECK(capacity <= kMaxCapacity);
     set(kCapacityIndex, Smi::FromInt(capacity));
   }
 
 
   // Returns probe entry.
   static uint32_t GetProbe(uint32_t hash, uint32_t number, uint32_t size) {
-    ASSERT(IsPowerOf2(size));
+    DCHECK(IsPowerOf2(size));
     return (hash + GetProbeOffset(number)) & (size - 1);
   }
 
@@ -3799,6 +3844,17 @@ class HashTable: public FixedArray {
     return (last + number) & (size - 1);
   }
 
+  // Attempt to shrink hash table after removal of key.
+  MUST_USE_RESULT static Handle<Derived> Shrink(Handle<Derived> table, Key key);
+
+  // Ensure enough space for n additional elements.
+  MUST_USE_RESULT static Handle<Derived> EnsureCapacity(
+      Handle<Derived> table,
+      int n,
+      Key key,
+      PretenureFlag pretenure = NOT_TENURED);
+
+ private:
   // Returns _expected_ if one of entries given by the first _probe_ probes is
   // equal to  _expected_. Otherwise, returns the entry given by the probe
   // number _probe_.
@@ -3807,16 +3863,7 @@ class HashTable: public FixedArray {
   void Swap(uint32_t entry1, uint32_t entry2, WriteBarrierMode mode);
 
   // Rehashes this hash-table into the new table.
-  MUST_USE_RESULT MaybeObject* Rehash(HashTable* new_table, Key key);
-
-  // Attempt to shrink hash table after removal of key.
-  MUST_USE_RESULT MaybeObject* Shrink(Key key);
-
-  // Ensure enough space for n additional elements.
-  MUST_USE_RESULT MaybeObject* EnsureCapacity(
-      int n,
-      Key key,
-      PretenureFlag pretenure = NOT_TENURED);
+  void Rehash(Handle<Derived> new_table, Key key);
 };
 
 
@@ -3830,8 +3877,7 @@ class HashTableKey {
   // Returns the hash value for object.
   virtual uint32_t HashForObject(Object* key) = 0;
   // Returns the key object for storing into the hash table.
-  // If allocations fails a failure object is returned.
-  MUST_USE_RESULT virtual MaybeObject* AsObject(Heap* heap) = 0;
+  MUST_USE_RESULT virtual Handle<Object> AsHandle(Isolate* isolate) = 0;
   // Required.
   virtual ~HashTableKey() {}
 };
@@ -3842,16 +3888,16 @@ class StringTableShape : public BaseShape<HashTableKey*> {
   static inline bool IsMatch(HashTableKey* key, Object* value) {
     return key->IsMatch(value);
   }
+
   static inline uint32_t Hash(HashTableKey* key) {
     return key->Hash();
   }
+
   static inline uint32_t HashForObject(HashTableKey* key, Object* object) {
     return key->HashForObject(object);
   }
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      HashTableKey* key) {
-    return key->AsObject(heap);
-  }
+
+  static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
 
   static const int kPrefixSize = 0;
   static const int kEntrySize = 1;
@@ -3863,23 +3909,32 @@ class SeqOneByteString;
 //
 // No special elements in the prefix and the element size is 1
 // because only the string itself (the key) needs to be stored.
-class StringTable: public HashTable<StringTableShape, HashTableKey*> {
- public:
-  // Find string in the string table.  If it is not there yet, it is
-  // added.  The return value is the string table which might have
-  // been enlarged.  If the return value is not a failure, the string
-  // pointer *s is set to the string found.
-  MUST_USE_RESULT MaybeObject* LookupString(String* key, Object** s);
-  MUST_USE_RESULT MaybeObject* LookupKey(HashTableKey* key, Object** s);
+class StringTable: public HashTable<StringTable,
+                                    StringTableShape,
+                                    HashTableKey*> {
+ public:
+  // Find string in the string table. If it is not there yet, it is
+  // added. The return value is the string found.
+  static Handle<String> LookupString(Isolate* isolate, Handle<String> key);
+  static Handle<String> LookupKey(Isolate* isolate, HashTableKey* key);
+
+  // Tries to internalize given string and returns string handle on success
+  // or an empty handle otherwise.
+  MUST_USE_RESULT static MaybeHandle<String> InternalizeStringIfExists(
+      Isolate* isolate,
+      Handle<String> string);
 
   // Looks up a string that is equal to the given string and returns
-  // true if it is found, assigning the string to the given output
-  // parameter.
-  bool LookupStringIfExists(String* str, String** result);
-  bool LookupTwoCharsStringIfExists(uint16_t c1, uint16_t c2, String** result);
+  // string handle if it is found, or an empty handle otherwise.
+  MUST_USE_RESULT static MaybeHandle<String> LookupStringIfExists(
+      Isolate* isolate,
+      Handle<String> str);
+  MUST_USE_RESULT static MaybeHandle<String> LookupTwoCharsStringIfExists(
+      Isolate* isolate,
+      uint16_t c1,
+      uint16_t c2);
 
-  // Casting.
-  static inline StringTable* cast(Object* obj);
+  DECLARE_CAST(StringTable)
 
  private:
   template <bool seq_ascii> friend class JsonParser;
@@ -3893,6 +3948,7 @@ class MapCacheShape : public BaseShape<HashTableKey*> {
   static inline bool IsMatch(HashTableKey* key, Object* value) {
     return key->IsMatch(value);
   }
+
   static inline uint32_t Hash(HashTableKey* key) {
     return key->Hash();
   }
@@ -3901,10 +3957,7 @@ class MapCacheShape : public BaseShape<HashTableKey*> {
     return key->HashForObject(object);
   }
 
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      HashTableKey* key) {
-    return key->AsObject(heap);
-  }
+  static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
 
   static const int kPrefixSize = 0;
   static const int kEntrySize = 2;
@@ -3915,55 +3968,62 @@ class MapCacheShape : public BaseShape<HashTableKey*> {
 //
 // Maps keys that are a fixed array of unique names to a map.
 // Used for canonicalize maps for object literals.
-class MapCache: public HashTable<MapCacheShape, HashTableKey*> {
+class MapCache: public HashTable<MapCache, MapCacheShape, HashTableKey*> {
  public:
   // Find cached value for a name key, otherwise return null.
   Object* Lookup(FixedArray* key);
-  MUST_USE_RESULT MaybeObject* Put(FixedArray* key, Map* value);
-  static inline MapCache* cast(Object* obj);
+  static Handle<MapCache> Put(
+      Handle<MapCache> map_cache, Handle<FixedArray> key, Handle<Map> value);
+  DECLARE_CAST(MapCache)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(MapCache);
 };
 
 
-template <typename Shape, typename Key>
-class Dictionary: public HashTable<Shape, Key> {
- public:
-  static inline Dictionary<Shape, Key>* cast(Object* obj) {
-    return reinterpret_cast<Dictionary<Shape, Key>*>(obj);
-  }
+template <typename Derived, typename Shape, typename Key>
+class Dictionary: public HashTable<Derived, Shape, Key> {
+ protected:
+  typedef HashTable<Derived, Shape, Key> DerivedHashTable;
 
+ public:
   // Returns the value at entry.
   Object* ValueAt(int entry) {
-    return this->get(HashTable<Shape, Key>::EntryToIndex(entry) + 1);
+    return this->get(DerivedHashTable::EntryToIndex(entry) + 1);
   }
 
   // Set the value for entry.
   void ValueAtPut(int entry, Object* value) {
-    this->set(HashTable<Shape, Key>::EntryToIndex(entry) + 1, value);
+    this->set(DerivedHashTable::EntryToIndex(entry) + 1, value);
   }
 
   // Returns the property details for the property at entry.
   PropertyDetails DetailsAt(int entry) {
-    ASSERT(entry >= 0);  // Not found is -1, which is not caught by get().
+    DCHECK(entry >= 0);  // Not found is -1, which is not caught by get().
     return PropertyDetails(
-        Smi::cast(this->get(HashTable<Shape, Key>::EntryToIndex(entry) + 2)));
+        Smi::cast(this->get(DerivedHashTable::EntryToIndex(entry) + 2)));
   }
 
   // Set the details for entry.
   void DetailsAtPut(int entry, PropertyDetails value) {
-    this->set(HashTable<Shape, Key>::EntryToIndex(entry) + 2, value.AsSmi());
+    this->set(DerivedHashTable::EntryToIndex(entry) + 2, value.AsSmi());
   }
 
   // Sorting support
   void CopyValuesTo(FixedArray* elements);
 
   // Delete a property from the dictionary.
-  Object* DeleteProperty(int entry, JSObject::DeleteMode mode);
+  static Handle<Object> DeleteProperty(
+      Handle<Derived> dictionary,
+      int entry,
+      JSObject::DeleteMode mode);
 
   // Attempt to shrink the dictionary after deletion of key.
-  MUST_USE_RESULT MaybeObject* Shrink(Key key);
+  MUST_USE_RESULT static inline Handle<Derived> Shrink(
+      Handle<Derived> dictionary,
+      Key key) {
+    return DerivedHashTable::Shrink(dictionary, key);
+  }
 
   // Returns the number of elements in the dictionary filtering out properties
   // with the specified attributes.
@@ -3985,101 +4045,102 @@ class Dictionary: public HashTable<Shape, Key> {
 
   // Accessors for next enumeration index.
   void SetNextEnumerationIndex(int index) {
-    ASSERT(index != 0);
+    DCHECK(index != 0);
     this->set(kNextEnumerationIndexIndex, Smi::FromInt(index));
   }
 
   int NextEnumerationIndex() {
-    return Smi::cast(FixedArray::get(kNextEnumerationIndexIndex))->value();
+    return Smi::cast(this->get(kNextEnumerationIndexIndex))->value();
   }
 
-  // Returns a new array for dictionary usage. Might return Failure.
-  MUST_USE_RESULT static MaybeObject* Allocate(
-      Heap* heap,
+  // Creates a new dictionary.
+  MUST_USE_RESULT static Handle<Derived> New(
+      Isolate* isolate,
       int at_least_space_for,
       PretenureFlag pretenure = NOT_TENURED);
 
   // Ensure enough space for n additional elements.
-  MUST_USE_RESULT MaybeObject* EnsureCapacity(int n, Key key);
+  static Handle<Derived> EnsureCapacity(Handle<Derived> obj, int n, Key key);
 
 #ifdef OBJECT_PRINT
-  void Print(FILE* out = stdout);
+  void Print(OStream& os);  // NOLINT
 #endif
   // Returns the key (slow).
   Object* SlowReverseLookup(Object* value);
 
   // Sets the entry to (key, value) pair.
   inline void SetEntry(int entry,
-                       Object* key,
-                       Object* value);
+                       Handle<Object> key,
+                       Handle<Object> value);
   inline void SetEntry(int entry,
-                       Object* key,
-                       Object* value,
+                       Handle<Object> key,
+                       Handle<Object> value,
                        PropertyDetails details);
 
-  MUST_USE_RESULT MaybeObject* Add(Key key,
-                                   Object* value,
-                                   PropertyDetails details);
+  MUST_USE_RESULT static Handle<Derived> Add(
+      Handle<Derived> dictionary,
+      Key key,
+      Handle<Object> value,
+      PropertyDetails details);
 
  protected:
   // Generic at put operation.
-  MUST_USE_RESULT MaybeObject* AtPut(Key key, Object* value);
+  MUST_USE_RESULT static Handle<Derived> AtPut(
+      Handle<Derived> dictionary,
+      Key key,
+      Handle<Object> value);
 
   // Add entry to dictionary.
-  MUST_USE_RESULT MaybeObject* AddEntry(Key key,
-                                        Object* value,
-                                        PropertyDetails details,
-                                        uint32_t hash);
+  static void AddEntry(
+      Handle<Derived> dictionary,
+      Key key,
+      Handle<Object> value,
+      PropertyDetails details,
+      uint32_t hash);
 
   // Generate new enumeration indices to avoid enumeration index overflow.
-  MUST_USE_RESULT MaybeObject* GenerateNewEnumerationIndices();
-  static const int kMaxNumberKeyIndex =
-      HashTable<Shape, Key>::kPrefixStartIndex;
+  static void GenerateNewEnumerationIndices(Handle<Derived> dictionary);
+  static const int kMaxNumberKeyIndex = DerivedHashTable::kPrefixStartIndex;
   static const int kNextEnumerationIndexIndex = kMaxNumberKeyIndex + 1;
 };
 
 
-class NameDictionaryShape : public BaseShape<Name*> {
+class NameDictionaryShape : public BaseShape<Handle<Name> > {
  public:
-  static inline bool IsMatch(Name* key, Object* other);
-  static inline uint32_t Hash(Name* key);
-  static inline uint32_t HashForObject(Name* key, Object* object);
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      Name* key);
+  static inline bool IsMatch(Handle<Name> key, Object* other);
+  static inline uint32_t Hash(Handle<Name> key);
+  static inline uint32_t HashForObject(Handle<Name> key, Object* object);
+  static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Name> key);
   static const int kPrefixSize = 2;
   static const int kEntrySize = 3;
   static const bool kIsEnumerable = true;
 };
 
 
-class NameDictionary: public Dictionary<NameDictionaryShape, Name*> {
+class NameDictionary: public Dictionary<NameDictionary,
+                                        NameDictionaryShape,
+                                        Handle<Name> > {
+  typedef Dictionary<
+      NameDictionary, NameDictionaryShape, Handle<Name> > DerivedDictionary;
+
  public:
-  static inline NameDictionary* cast(Object* obj) {
-    ASSERT(obj->IsDictionary());
-    return reinterpret_cast<NameDictionary*>(obj);
-  }
+  DECLARE_CAST(NameDictionary)
 
   // Copies enumerable keys to preallocated fixed array.
-  FixedArray* CopyEnumKeysTo(FixedArray* storage);
-  static void DoGenerateNewEnumerationIndices(
+  void CopyEnumKeysTo(FixedArray* storage);
+  inline static void DoGenerateNewEnumerationIndices(
       Handle<NameDictionary> dictionary);
 
-  // For transforming properties of a JSObject.
-  MUST_USE_RESULT MaybeObject* TransformPropertiesToFastFor(
-      JSObject* obj,
-      int unused_property_fields);
-
   // Find entry for key, otherwise return kNotFound. Optimized version of
   // HashTable::FindEntry.
-  int FindEntry(Name* key);
+  int FindEntry(Handle<Name> key);
 };
 
 
 class NumberDictionaryShape : public BaseShape<uint32_t> {
  public:
   static inline bool IsMatch(uint32_t key, Object* other);
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      uint32_t key);
+  static inline Handle<Object> AsHandle(Isolate* isolate, uint32_t key);
   static const int kEntrySize = 3;
   static const bool kIsEnumerable = false;
 };
@@ -4107,36 +4168,31 @@ class UnseededNumberDictionaryShape : public NumberDictionaryShape {
 
 
 class SeededNumberDictionary
-    : public Dictionary<SeededNumberDictionaryShape, uint32_t> {
+    : public Dictionary<SeededNumberDictionary,
+                        SeededNumberDictionaryShape,
+                        uint32_t> {
  public:
-  static SeededNumberDictionary* cast(Object* obj) {
-    ASSERT(obj->IsDictionary());
-    return reinterpret_cast<SeededNumberDictionary*>(obj);
-  }
+  DECLARE_CAST(SeededNumberDictionary)
 
   // Type specific at put (default NONE attributes is used when adding).
-  MUST_USE_RESULT MaybeObject* AtNumberPut(uint32_t key, Object* value);
+  MUST_USE_RESULT static Handle<SeededNumberDictionary> AtNumberPut(
+      Handle<SeededNumberDictionary> dictionary,
+      uint32_t key,
+      Handle<Object> value);
   MUST_USE_RESULT static Handle<SeededNumberDictionary> AddNumberEntry(
       Handle<SeededNumberDictionary> dictionary,
       uint32_t key,
       Handle<Object> value,
       PropertyDetails details);
-  MUST_USE_RESULT MaybeObject* AddNumberEntry(uint32_t key,
-                                              Object* value,
-                                              PropertyDetails details);
 
   // Set an existing entry or add a new one if needed.
   // Return the updated dictionary.
   MUST_USE_RESULT static Handle<SeededNumberDictionary> Set(
       Handle<SeededNumberDictionary> dictionary,
-      uint32_t index,
+      uint32_t key,
       Handle<Object> value,
       PropertyDetails details);
 
-  MUST_USE_RESULT MaybeObject* Set(uint32_t key,
-                                   Object* value,
-                                   PropertyDetails details);
-
   void UpdateMaxNumberKey(uint32_t key);
 
   // If slow elements are required we will never go back to fast-case
@@ -4160,123 +4216,300 @@ class SeededNumberDictionary
 
 
 class UnseededNumberDictionary
-    : public Dictionary<UnseededNumberDictionaryShape, uint32_t> {
+    : public Dictionary<UnseededNumberDictionary,
+                        UnseededNumberDictionaryShape,
+                        uint32_t> {
  public:
-  static UnseededNumberDictionary* cast(Object* obj) {
-    ASSERT(obj->IsDictionary());
-    return reinterpret_cast<UnseededNumberDictionary*>(obj);
-  }
+  DECLARE_CAST(UnseededNumberDictionary)
 
   // Type specific at put (default NONE attributes is used when adding).
-  MUST_USE_RESULT MaybeObject* AtNumberPut(uint32_t key, Object* value);
-  MUST_USE_RESULT MaybeObject* AddNumberEntry(uint32_t key, Object* value);
+  MUST_USE_RESULT static Handle<UnseededNumberDictionary> AtNumberPut(
+      Handle<UnseededNumberDictionary> dictionary,
+      uint32_t key,
+      Handle<Object> value);
+  MUST_USE_RESULT static Handle<UnseededNumberDictionary> AddNumberEntry(
+      Handle<UnseededNumberDictionary> dictionary,
+      uint32_t key,
+      Handle<Object> value);
 
   // Set an existing entry or add a new one if needed.
   // Return the updated dictionary.
   MUST_USE_RESULT static Handle<UnseededNumberDictionary> Set(
       Handle<UnseededNumberDictionary> dictionary,
-      uint32_t index,
+      uint32_t key,
       Handle<Object> value);
-
-  MUST_USE_RESULT MaybeObject* Set(uint32_t key, Object* value);
 };
 
 
-template <int entrysize>
-class ObjectHashTableShape : public BaseShape<Object*> {
+class ObjectHashTableShape : public BaseShape<Handle<Object> > {
  public:
-  static inline bool IsMatch(Object* key, Object* other);
-  static inline uint32_t Hash(Object* key);
-  static inline uint32_t HashForObject(Object* key, Object* object);
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      Object* key);
+  static inline bool IsMatch(Handle<Object> key, Object* other);
+  static inline uint32_t Hash(Handle<Object> key);
+  static inline uint32_t HashForObject(Handle<Object> key, Object* object);
+  static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Object> key);
   static const int kPrefixSize = 0;
-  static const int kEntrySize = entrysize;
+  static const int kEntrySize = 2;
 };
 
 
-// ObjectHashSet holds keys that are arbitrary objects by using the identity
-// hash of the key for hashing purposes.
-class ObjectHashSet: public HashTable<ObjectHashTableShape<1>, Object*> {
+// ObjectHashTable maps keys that are arbitrary objects to object values by
+// using the identity hash of the key for hashing purposes.
+class ObjectHashTable: public HashTable<ObjectHashTable,
+                                        ObjectHashTableShape,
+                                        Handle<Object> > {
+  typedef HashTable<
+      ObjectHashTable, ObjectHashTableShape, Handle<Object> > DerivedHashTable;
  public:
-  static inline ObjectHashSet* cast(Object* obj) {
-    ASSERT(obj->IsHashTable());
-    return reinterpret_cast<ObjectHashSet*>(obj);
+  DECLARE_CAST(ObjectHashTable)
+
+  // Attempt to shrink hash table after removal of key.
+  MUST_USE_RESULT static inline Handle<ObjectHashTable> Shrink(
+      Handle<ObjectHashTable> table,
+      Handle<Object> key);
+
+  // Looks up the value associated with the given key. The hole value is
+  // returned in case the key is not present.
+  Object* Lookup(Handle<Object> key);
+
+  // Adds (or overwrites) the value associated with the given key.
+  static Handle<ObjectHashTable> Put(Handle<ObjectHashTable> table,
+                                     Handle<Object> key,
+                                     Handle<Object> value);
+
+  // Returns an ObjectHashTable (possibly |table|) where |key| has been removed.
+  static Handle<ObjectHashTable> Remove(Handle<ObjectHashTable> table,
+                                        Handle<Object> key,
+                                        bool* was_present);
+
+ private:
+  friend class MarkCompactCollector;
+
+  void AddEntry(int entry, Object* key, Object* value);
+  void RemoveEntry(int entry);
+
+  // Returns the index to the value of an entry.
+  static inline int EntryToValueIndex(int entry) {
+    return EntryToIndex(entry) + 1;
   }
+};
 
-  // Looks up whether the given key is part of this hash set.
-  bool Contains(Object* key);
 
-  static Handle<ObjectHashSet> EnsureCapacity(
-      Handle<ObjectHashSet> table,
-      int n,
-      Handle<Object> key,
-      PretenureFlag pretenure = NOT_TENURED);
+// OrderedHashTable is a HashTable with Object keys that preserves
+// insertion order. There are Map and Set interfaces (OrderedHashMap
+// and OrderedHashTable, below). It is meant to be used by JSMap/JSSet.
+//
+// Only Object* keys are supported, with Object::SameValueZero() used as the
+// equality operator and Object::GetHash() for the hash function.
+//
+// Based on the "Deterministic Hash Table" as described by Jason Orendorff at
+// https://wiki.mozilla.org/User:Jorend/Deterministic_hash_tables
+// Originally attributed to Tyler Close.
+//
+// Memory layout:
+//   [0]: bucket count
+//   [1]: element count
+//   [2]: deleted element count
+//   [3..(3 + NumberOfBuckets() - 1)]: "hash table", where each item is an
+//                            offset into the data table (see below) where the
+//                            first item in this bucket is stored.
+//   [3 + NumberOfBuckets()..length]: "data table", an array of length
+//                            Capacity() * kEntrySize, where the first entrysize
+//                            items are handled by the derived class and the
+//                            item at kChainOffset is another entry into the
+//                            data table indicating the next entry in this hash
+//                            bucket.
+//
+// When we transition the table to a new version we obsolete it and reuse parts
+// of the memory to store information how to transition an iterator to the new
+// table:
+//
+// Memory layout for obsolete table:
+//   [0]: bucket count
+//   [1]: Next newer table
+//   [2]: Number of removed holes or -1 when the table was cleared.
+//   [3..(3 + NumberOfRemovedHoles() - 1)]: The indexes of the removed holes.
+//   [3 + NumberOfRemovedHoles()..length]: Not used
+//
+template<class Derived, class Iterator, int entrysize>
+class OrderedHashTable: public FixedArray {
+ public:
+  // Returns an OrderedHashTable with a capacity of at least |capacity|.
+  static Handle<Derived> Allocate(
+      Isolate* isolate, int capacity, PretenureFlag pretenure = NOT_TENURED);
+
+  // Returns an OrderedHashTable (possibly |table|) with enough space
+  // to add at least one new element.
+  static Handle<Derived> EnsureGrowable(Handle<Derived> table);
+
+  // Returns an OrderedHashTable (possibly |table|) that's shrunken
+  // if possible.
+  static Handle<Derived> Shrink(Handle<Derived> table);
+
+  // Returns a new empty OrderedHashTable and records the clearing so that
+  // exisiting iterators can be updated.
+  static Handle<Derived> Clear(Handle<Derived> table);
+
+  // Returns an OrderedHashTable (possibly |table|) where |key| has been
+  // removed.
+  static Handle<Derived> Remove(Handle<Derived> table, Handle<Object> key,
+      bool* was_present);
+
+  // Returns kNotFound if the key isn't present.
+  int FindEntry(Handle<Object> key, int hash);
+
+  // Like the above, but doesn't require the caller to provide a hash.
+  int FindEntry(Handle<Object> key);
+
+  int NumberOfElements() {
+    return Smi::cast(get(kNumberOfElementsIndex))->value();
+  }
+
+  int NumberOfDeletedElements() {
+    return Smi::cast(get(kNumberOfDeletedElementsIndex))->value();
+  }
+
+  int UsedCapacity() { return NumberOfElements() + NumberOfDeletedElements(); }
+
+  int NumberOfBuckets() {
+    return Smi::cast(get(kNumberOfBucketsIndex))->value();
+  }
+
+  // Returns the index into the data table where the new entry
+  // should be placed. The table is assumed to have enough space
+  // for a new entry.
+  int AddEntry(int hash);
+
+  // Removes the entry, and puts the_hole in entrysize pointers
+  // (leaving the hash table chain intact).
+  void RemoveEntry(int entry);
+
+  // Returns an index into |this| for the given entry.
+  int EntryToIndex(int entry) {
+    return kHashTableStartIndex + NumberOfBuckets() + (entry * kEntrySize);
+  }
+
+  Object* KeyAt(int entry) { return get(EntryToIndex(entry)); }
+
+  bool IsObsolete() {
+    return !get(kNextTableIndex)->IsSmi();
+  }
+
+  // The next newer table. This is only valid if the table is obsolete.
+  Derived* NextTable() {
+    return Derived::cast(get(kNextTableIndex));
+  }
+
+  // When the table is obsolete we store the indexes of the removed holes.
+  int RemovedIndexAt(int index) {
+    return Smi::cast(get(kRemovedHolesIndex + index))->value();
+  }
+
+  static const int kNotFound = -1;
+  static const int kMinCapacity = 4;
+
+ private:
+  static Handle<Derived> Rehash(Handle<Derived> table, int new_capacity);
+
+  void SetNumberOfBuckets(int num) {
+    set(kNumberOfBucketsIndex, Smi::FromInt(num));
+  }
+
+  void SetNumberOfElements(int num) {
+    set(kNumberOfElementsIndex, Smi::FromInt(num));
+  }
+
+  void SetNumberOfDeletedElements(int num) {
+    set(kNumberOfDeletedElementsIndex, Smi::FromInt(num));
+  }
+
+  int Capacity() {
+    return NumberOfBuckets() * kLoadFactor;
+  }
+
+  // Returns the next entry for the given entry.
+  int ChainAt(int entry) {
+    return Smi::cast(get(EntryToIndex(entry) + kChainOffset))->value();
+  }
+
+  int HashToBucket(int hash) {
+    return hash & (NumberOfBuckets() - 1);
+  }
+
+  int HashToEntry(int hash) {
+    int bucket = HashToBucket(hash);
+    return Smi::cast(get(kHashTableStartIndex + bucket))->value();
+  }
+
+  void SetNextTable(Derived* next_table) {
+    set(kNextTableIndex, next_table);
+  }
+
+  void SetRemovedIndexAt(int index, int removed_index) {
+    return set(kRemovedHolesIndex + index, Smi::FromInt(removed_index));
+  }
 
-  // Attempt to shrink hash table after removal of key.
-  static Handle<ObjectHashSet> Shrink(Handle<ObjectHashSet> table,
-                                      Handle<Object> key);
+  static const int kNumberOfBucketsIndex = 0;
+  static const int kNumberOfElementsIndex = kNumberOfBucketsIndex + 1;
+  static const int kNumberOfDeletedElementsIndex = kNumberOfElementsIndex + 1;
+  static const int kHashTableStartIndex = kNumberOfDeletedElementsIndex + 1;
+
+  static const int kNextTableIndex = kNumberOfElementsIndex;
+  static const int kRemovedHolesIndex = kHashTableStartIndex;
 
-  // Adds the given key to this hash set.
-  static Handle<ObjectHashSet> Add(Handle<ObjectHashSet> table,
-                                   Handle<Object> key);
+  static const int kEntrySize = entrysize + 1;
+  static const int kChainOffset = entrysize;
 
-  // Removes the given key from this hash set.
-  static Handle<ObjectHashSet> Remove(Handle<ObjectHashSet> table,
-                                      Handle<Object> key);
+  static const int kLoadFactor = 2;
+  static const int kMaxCapacity =
+      (FixedArray::kMaxLength - kHashTableStartIndex)
+      / (1 + (kEntrySize * kLoadFactor));
 };
 
 
-// ObjectHashTable maps keys that are arbitrary objects to object values by
-// using the identity hash of the key for hashing purposes.
-class ObjectHashTable: public HashTable<ObjectHashTableShape<2>, Object*> {
+class JSSetIterator;
+
+
+class OrderedHashSet: public OrderedHashTable<
+    OrderedHashSet, JSSetIterator, 1> {
  public:
-  static inline ObjectHashTable* cast(Object* obj) {
-    ASSERT(obj->IsHashTable());
-    return reinterpret_cast<ObjectHashTable*>(obj);
-  }
+  DECLARE_CAST(OrderedHashSet)
 
-  static Handle<ObjectHashTable> EnsureCapacity(
-      Handle<ObjectHashTable> table,
-      int n,
-      Handle<Object> key,
-      PretenureFlag pretenure = NOT_TENURED);
+  bool Contains(Handle<Object> key);
+  static Handle<OrderedHashSet> Add(
+      Handle<OrderedHashSet> table, Handle<Object> key);
+};
 
-  // Attempt to shrink hash table after removal of key.
-  static Handle<ObjectHashTable> Shrink(Handle<ObjectHashTable> table,
-                                        Handle<Object> key);
 
-  // Looks up the value associated with the given key. The hole value is
-  // returned in case the key is not present.
-  Object* Lookup(Object* key);
+class JSMapIterator;
 
-  // Adds (or overwrites) the value associated with the given key. Mapping a
-  // key to the hole value causes removal of the whole entry.
-  static Handle<ObjectHashTable> Put(Handle<ObjectHashTable> table,
-                                     Handle<Object> key,
-                                     Handle<Object> value);
 
- private:
-  friend class MarkCompactCollector;
+class OrderedHashMap:public OrderedHashTable<
+    OrderedHashMap, JSMapIterator, 2> {
+ public:
+  DECLARE_CAST(OrderedHashMap)
 
-  void AddEntry(int entry, Object* key, Object* value);
-  void RemoveEntry(int entry);
+  Object* Lookup(Handle<Object> key);
+  static Handle<OrderedHashMap> Put(
+      Handle<OrderedHashMap> table,
+      Handle<Object> key,
+      Handle<Object> value);
 
-  // Returns the index to the value of an entry.
-  static inline int EntryToValueIndex(int entry) {
-    return EntryToIndex(entry) + 1;
+  Object* ValueAt(int entry) {
+    return get(EntryToIndex(entry) + kValueOffset);
   }
+
+ private:
+  static const int kValueOffset = 1;
 };
 
 
 template <int entrysize>
-class WeakHashTableShape : public BaseShape<Object*> {
+class WeakHashTableShape : public BaseShape<Handle<Object> > {
  public:
-  static inline bool IsMatch(Object* key, Object* other);
-  static inline uint32_t Hash(Object* key);
-  static inline uint32_t HashForObject(Object* key, Object* object);
-  MUST_USE_RESULT static inline MaybeObject* AsObject(Heap* heap,
-                                                      Object* key);
+  static inline bool IsMatch(Handle<Object> key, Object* other);
+  static inline uint32_t Hash(Handle<Object> key);
+  static inline uint32_t HashForObject(Handle<Object> key, Object* object);
+  static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Object> key);
   static const int kPrefixSize = 0;
   static const int kEntrySize = entrysize;
 };
@@ -4285,20 +4518,23 @@ class WeakHashTableShape : public BaseShape<Object*> {
 // WeakHashTable maps keys that are arbitrary objects to object values.
 // It is used for the global weak hash table that maps objects
 // embedded in optimized code to dependent code lists.
-class WeakHashTable: public HashTable<WeakHashTableShape<2>, Object*> {
+class WeakHashTable: public HashTable<WeakHashTable,
+                                      WeakHashTableShape<2>,
+                                      Handle<Object> > {
+  typedef HashTable<
+      WeakHashTable, WeakHashTableShape<2>, Handle<Object> > DerivedHashTable;
  public:
-  static inline WeakHashTable* cast(Object* obj) {
-    ASSERT(obj->IsHashTable());
-    return reinterpret_cast<WeakHashTable*>(obj);
-  }
+  DECLARE_CAST(WeakHashTable)
 
   // Looks up the value associated with the given key. The hole value is
   // returned in case the key is not present.
-  Object* Lookup(Object* key);
+  Object* Lookup(Handle<Object> key);
 
   // Adds (or overwrites) the value associated with the given key. Mapping a
   // key to the hole value causes removal of the whole entry.
-  MUST_USE_RESULT MaybeObject* Put(Object* key, Object* value);
+  MUST_USE_RESULT static Handle<WeakHashTable> Put(Handle<WeakHashTable> table,
+                                                   Handle<Object> key,
+                                                   Handle<Object> value);
 
   // This function is called when heap verification is turned on.
   void Zap(Object* value) {
@@ -4312,7 +4548,7 @@ class WeakHashTable: public HashTable<WeakHashTableShape<2>, Object*> {
  private:
   friend class MarkCompactCollector;
 
-  void AddEntry(int entry, Object* key, Object* value);
+  void AddEntry(int entry, Handle<Object> key, Handle<Object> value);
 
   // Returns the index to the value of an entry.
   static inline int EntryToValueIndex(int entry) {
@@ -4350,8 +4586,7 @@ class JSFunctionResultCache: public FixedArray {
   inline int finger_index();
   inline void set_finger_index(int finger_index);
 
-  // Casting
-  static inline JSFunctionResultCache* cast(Object* obj);
+  DECLARE_CAST(JSFunctionResultCache)
 
   DECLARE_VERIFIER(JSFunctionResultCache)
 };
@@ -4366,7 +4601,7 @@ class JSFunctionResultCache: public FixedArray {
 // routines.
 class ScopeInfo : public FixedArray {
  public:
-  static inline ScopeInfo* cast(Object* object);
+  DECLARE_CAST(ScopeInfo)
 
   // Return the type of this scope.
   ScopeType scope_type();
@@ -4374,13 +4609,11 @@ class ScopeInfo : public FixedArray {
   // Does this scope call eval?
   bool CallsEval();
 
-  // Return the language mode of this scope.
-  LanguageMode language_mode();
+  // Return the strict mode of this scope.
+  StrictMode strict_mode();
 
-  // Does this scope make a non-strict eval call?
-  bool CallsNonStrictEval() {
-    return CallsEval() && (language_mode() == CLASSIC_MODE);
-  }
+  // Does this scope make a sloppy eval call?
+  bool CallsSloppyEval() { return CallsEval() && strict_mode() == SLOPPY; }
 
   // Return the total number of locals allocated on the stack and in the
   // context. This includes the parameters that are allocated in the context.
@@ -4431,6 +4664,13 @@ class ScopeInfo : public FixedArray {
   // Return the initialization flag of the given context local.
   InitializationFlag ContextLocalInitFlag(int var);
 
+  // Return the initialization flag of the given context local.
+  MaybeAssignedFlag ContextLocalMaybeAssignedFlag(int var);
+
+  // Return true if this local was introduced by the compiler, and should not be
+  // exposed to the user in a debugger.
+  bool LocalIsSynthetic(int var);
+
   // Lookup support for serialized scope info. Returns the
   // the stack slot index for a given slot name if the slot is
   // present; otherwise returns a value < 0. The name must be an internalized
@@ -4442,9 +4682,9 @@ class ScopeInfo : public FixedArray {
   // returns a value < 0. The name must be an internalized string.
   // If the slot is present and mode != NULL, sets *mode to the corresponding
   // mode for that variable.
-  int ContextSlotIndex(String* name,
-                       VariableMode* mode,
-                       InitializationFlag* init_flag);
+  static int ContextSlotIndex(Handle<ScopeInfo> scope_info, Handle<String> name,
+                              VariableMode* mode, InitializationFlag* init_flag,
+                              MaybeAssignedFlag* maybe_assigned_flag);
 
   // Lookup support for serialized scope info. Returns the
   // parameter index for a given parameter name if the parameter is present;
@@ -4554,14 +4794,16 @@ class ScopeInfo : public FixedArray {
   // Properties of scopes.
   class ScopeTypeField:        public BitField<ScopeType,            0, 3> {};
   class CallsEvalField:        public BitField<bool,                 3, 1> {};
-  class LanguageModeField:     public BitField<LanguageMode,         4, 2> {};
-  class FunctionVariableField: public BitField<FunctionVariableInfo, 6, 2> {};
-  class FunctionVariableMode:  public BitField<VariableMode,         8, 3> {};
+  class StrictModeField:       public BitField<StrictMode,           4, 1> {};
+  class FunctionVariableField: public BitField<FunctionVariableInfo, 5, 2> {};
+  class FunctionVariableMode:  public BitField<VariableMode,         7, 3> {};
 
   // BitFields representing the encoded information for context locals in the
   // ContextLocalInfoEntries part.
   class ContextLocalMode:      public BitField<VariableMode,         0, 3> {};
   class ContextLocalInitFlag:  public BitField<InitializationFlag,   3, 1> {};
+  class ContextLocalMaybeAssignedFlag
+      : public BitField<MaybeAssignedFlag, 4, 1> {};
 };
 
 
@@ -4570,18 +4812,27 @@ class ScopeInfo : public FixedArray {
 // needs very limited number of distinct normalized maps.
 class NormalizedMapCache: public FixedArray {
  public:
-  static const int kEntries = 64;
+  static Handle<NormalizedMapCache> New(Isolate* isolate);
 
-  static Handle<Map> Get(Handle<NormalizedMapCache> cache,
-                         Handle<JSObject> object,
-                         PropertyNormalizationMode mode);
+  MUST_USE_RESULT MaybeHandle<Map> Get(Handle<Map> fast_map,
+                                       PropertyNormalizationMode mode);
+  void Set(Handle<Map> fast_map, Handle<Map> normalized_map);
 
   void Clear();
 
-  // Casting
-  static inline NormalizedMapCache* cast(Object* obj);
+  DECLARE_CAST(NormalizedMapCache)
+
+  static inline bool IsNormalizedMapCache(const Object* obj);
 
   DECLARE_VERIFIER(NormalizedMapCache)
+ private:
+  static const int kEntries = 64;
+
+  static inline int GetIndex(Handle<Map> map);
+
+  // The following declarations hide base class methods.
+  Object* get(int index);
+  void set(int index, Object* value);
 };
 
 
@@ -4606,8 +4857,8 @@ class ByteArray: public FixedArrayBase {
   // array, this function returns the number of elements a byte array should
   // have.
   static int LengthFor(int size_in_bytes) {
-    ASSERT(IsAligned(size_in_bytes, kPointerSize));
-    ASSERT(size_in_bytes >= kHeaderSize);
+    DCHECK(IsAligned(size_in_bytes, kPointerSize));
+    DCHECK(size_in_bytes >= kHeaderSize);
     return size_in_bytes - kHeaderSize;
   }
 
@@ -4617,8 +4868,7 @@ class ByteArray: public FixedArrayBase {
   // Returns a pointer to the ByteArray object for a given data start address.
   static inline ByteArray* FromDataStartAddress(Address address);
 
-  // Casting.
-  static inline ByteArray* cast(Object* obj);
+  DECLARE_CAST(ByteArray)
 
   // Dispatched behavior.
   inline int ByteArraySize() {
@@ -4645,13 +4895,15 @@ class ByteArray: public FixedArrayBase {
 class FreeSpace: public HeapObject {
  public:
   // [size]: size of the free space including the header.
-  inline int size();
+  inline int size() const;
   inline void set_size(int value);
 
+  inline int nobarrier_size() const;
+  inline void nobarrier_set_size(int value);
+
   inline int Size() { return size(); }
 
-  // Casting.
-  static inline FreeSpace* cast(Object* obj);
+  DECLARE_CAST(FreeSpace)
 
   // Dispatched behavior.
   DECLARE_PRINTER(FreeSpace)
@@ -4684,6 +4936,7 @@ class FreeSpace: public HeapObject {
 
 #define SIMD128_TYPED_ARRAY(V) \
   V(Float32x4, float32x4, FLOAT32x4, v8::internal::float32x4_value_t, 16)      \
+  V(Float64x2, float64x2, FLOAT64x2, v8::internal::float64x2_value_t, 16)      \
   V(Int32x4, int32x4, INT32x4, v8::internal::int32x4_value_t, 16)
 
 
@@ -4711,8 +4964,7 @@ class ExternalArray: public FixedArrayBase {
   // external array.
   DECL_ACCESSORS(external_pointer, void)  // Pointer to the data store.
 
-  // Casting.
-  static inline ExternalArray* cast(Object* obj);
+  DECLARE_CAST(ExternalArray)
 
   // Maximal acceptable length for an external array.
   static const int kMaxLength = 0x3fffffff;
@@ -4742,19 +4994,17 @@ class ExternalUint8ClampedArray: public ExternalArray {
 
   // Setter and getter.
   inline uint8_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalUint8ClampedArray> array,
+                                   int index);
   inline void set(int index, uint8_t value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber and
-  // undefined and clamps the converted value between 0 and 255.
-  Object* SetValue(uint32_t index, Object* value);
-
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined and clamps the converted value between 0 and 255.
   static Handle<Object> SetValue(Handle<ExternalUint8ClampedArray> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // Casting.
-  static inline ExternalUint8ClampedArray* cast(Object* obj);
+  DECLARE_CAST(ExternalUint8ClampedArray)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalUint8ClampedArray)
@@ -4769,19 +5019,16 @@ class ExternalInt8Array: public ExternalArray {
  public:
   // Setter and getter.
   inline int8_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalInt8Array> array, int index);
   inline void set(int index, int8_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalInt8Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalInt8Array* cast(Object* obj);
+  DECLARE_CAST(ExternalInt8Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalInt8Array)
@@ -4796,19 +5043,16 @@ class ExternalUint8Array: public ExternalArray {
  public:
   // Setter and getter.
   inline uint8_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalUint8Array> array, int index);
   inline void set(int index, uint8_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalUint8Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalUint8Array* cast(Object* obj);
+  DECLARE_CAST(ExternalUint8Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalUint8Array)
@@ -4823,19 +5067,16 @@ class ExternalInt16Array: public ExternalArray {
  public:
   // Setter and getter.
   inline int16_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalInt16Array> array, int index);
   inline void set(int index, int16_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalInt16Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalInt16Array* cast(Object* obj);
+  DECLARE_CAST(ExternalInt16Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalInt16Array)
@@ -4850,19 +5091,17 @@ class ExternalUint16Array: public ExternalArray {
  public:
   // Setter and getter.
   inline uint16_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalUint16Array> array,
+                                   int index);
   inline void set(int index, uint16_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalUint16Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalUint16Array* cast(Object* obj);
+  DECLARE_CAST(ExternalUint16Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalUint16Array)
@@ -4877,19 +5116,16 @@ class ExternalInt32Array: public ExternalArray {
  public:
   // Setter and getter.
   inline int32_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalInt32Array> array, int index);
   inline void set(int index, int32_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalInt32Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalInt32Array* cast(Object* obj);
+  DECLARE_CAST(ExternalInt32Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalInt32Array)
@@ -4904,19 +5140,17 @@ class ExternalUint32Array: public ExternalArray {
  public:
   // Setter and getter.
   inline uint32_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalUint32Array> array,
+                                   int index);
   inline void set(int index, uint32_t value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalUint32Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalUint32Array* cast(Object* obj);
+  DECLARE_CAST(ExternalUint32Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalUint32Array)
@@ -4931,19 +5165,17 @@ class ExternalFloat32Array: public ExternalArray {
  public:
   // Setter and getter.
   inline float get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalFloat32Array> array,
+                                   int index);
   inline void set(int index, float value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalFloat32Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalFloat32Array* cast(Object* obj);
+  DECLARE_CAST(ExternalFloat32Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalFloat32Array)
@@ -4958,19 +5190,18 @@ class ExternalFloat32x4Array: public ExternalArray {
  public:
   // Setter and getter.
   inline float32x4_value_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalFloat32x4Array> array,
+                                   int index);
   inline void set(int index, const float32x4_value_t& value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalFloat32x4Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
   // Casting.
-  static inline ExternalFloat32x4Array* cast(Object* obj);
+  DECLARE_CAST(ExternalFloat32x4Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalFloat32x4Array)
@@ -4981,22 +5212,48 @@ class ExternalFloat32x4Array: public ExternalArray {
 };
 
 
+class ExternalFloat64x2Array: public ExternalArray {
+ public:
+  // Setter and getter.
+  inline float64x2_value_t get_scalar(int index);
+  static inline Handle<Object> get(Handle<ExternalFloat64x2Array> array,
+                                   int index);
+  inline void set(int index, const float64x2_value_t& value);
+
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
+  static Handle<Object> SetValue(Handle<ExternalFloat64x2Array> array,
+                                 uint32_t index,
+                                 Handle<Object> value);
+
+  // Casting.
+  DECLARE_CAST(ExternalFloat64x2Array)
+
+  // Dispatched behavior.
+  DECLARE_PRINTER(ExternalFloat64x2Array)
+  DECLARE_VERIFIER(ExternalFloat64x2Array)
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalFloat64x2Array);
+};
+
+
 class ExternalInt32x4Array: public ExternalArray {
  public:
   // Setter and getter.
   inline int32x4_value_t get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalInt32x4Array> array,
+                                   int index);
   inline void set(int index, const int32x4_value_t& value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalInt32x4Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
 
   // Casting.
-  static inline ExternalInt32x4Array* cast(Object* obj);
+  DECLARE_CAST(ExternalInt32x4Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalInt32x4Array)
@@ -5011,19 +5268,17 @@ class ExternalFloat64Array: public ExternalArray {
  public:
   // Setter and getter.
   inline double get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<ExternalFloat64Array> array,
+                                   int index);
   inline void set(int index, double value);
 
+  // This accessor applies the correct conversion from Smi, HeapNumber
+  // and undefined.
   static Handle<Object> SetValue(Handle<ExternalFloat64Array> array,
                                  uint32_t index,
                                  Handle<Object> value);
 
-  // This accessor applies the correct conversion from Smi, HeapNumber
-  // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
-  // Casting.
-  static inline ExternalFloat64Array* cast(Object* obj);
+  DECLARE_CAST(ExternalFloat64Array)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExternalFloat64Array)
@@ -5036,14 +5291,22 @@ class ExternalFloat64Array: public ExternalArray {
 
 class FixedTypedArrayBase: public FixedArrayBase {
  public:
-  // Casting:
-  static inline FixedTypedArrayBase* cast(Object* obj);
+  DECLARE_CAST(FixedTypedArrayBase)
 
   static const int kDataOffset = kHeaderSize;
 
   inline int size();
 
+  inline int TypedArraySize(InstanceType type);
+
+  // Use with care: returns raw pointer into heap.
+  inline void* DataPtr();
+
+  inline int DataSize();
+
  private:
+  inline int DataSize(InstanceType type);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedTypedArrayBase);
 };
 
@@ -5054,8 +5317,7 @@ class FixedTypedArray: public FixedTypedArrayBase {
   typedef typename Traits::ElementType ElementType;
   static const InstanceType kInstanceType = Traits::kInstanceType;
 
-  // Casting:
-  static inline FixedTypedArray<Traits>* cast(Object* obj);
+  DECLARE_CAST(FixedTypedArray<Traits>)
 
   static inline int ElementOffset(int index) {
     return kDataOffset + index * sizeof(ElementType);
@@ -5066,13 +5328,14 @@ class FixedTypedArray: public FixedTypedArrayBase {
   }
 
   inline ElementType get_scalar(int index);
-  MUST_USE_RESULT inline MaybeObject* get(int index);
+  static inline Handle<Object> get(Handle<FixedTypedArray> array, int index);
   inline void set(int index, ElementType value);
 
+  static inline ElementType from_int(int value);
+  static inline ElementType from_double(double value);
+
   // This accessor applies the correct conversion from Smi, HeapNumber
   // and undefined.
-  MUST_USE_RESULT MaybeObject* SetValue(uint32_t index, Object* value);
-
   static Handle<Object> SetValue(Handle<FixedTypedArray<Traits> > array,
                                  uint32_t index,
                                  Handle<Object> value);
@@ -5086,12 +5349,13 @@ class FixedTypedArray: public FixedTypedArrayBase {
 
 #define FIXED_TYPED_ARRAY_TRAITS(Type, type, TYPE, elementType, size)         \
   class Type##ArrayTraits {                                                   \
-    public:                                                                   \
-      typedef elementType ElementType;                                        \
-      static const InstanceType kInstanceType = FIXED_##TYPE##_ARRAY_TYPE;    \
-      static const char* Designator() { return #type " array"; }              \
-      static inline MaybeObject* ToObject(Heap* heap, elementType scalar);    \
-      static elementType defaultValue() { return elementType(); }             \
+   public:   /* NOLINT */                                                     \
+    typedef elementType ElementType;                                          \
+    static const InstanceType kInstanceType = FIXED_##TYPE##_ARRAY_TYPE;      \
+    static const char* Designator() { return #type " array"; }                \
+    static inline Handle<Object> ToHandle(Isolate* isolate,                   \
+                                          elementType scalar);                \
+    static inline elementType defaultValue();                                 \
   };                                                                          \
                                                                               \
   typedef FixedTypedArray<Type##ArrayTraits> Fixed##Type##Array;
@@ -5110,12 +5374,16 @@ TYPED_ARRAYS(FIXED_TYPED_ARRAY_TRAITS)
 class DeoptimizationInputData: public FixedArray {
  public:
   // Layout description.  Indices in the array.
-  static const int kTranslationByteArrayIndex = 0;
-  static const int kInlinedFunctionCountIndex = 1;
-  static const int kLiteralArrayIndex = 2;
-  static const int kOsrAstIdIndex = 3;
-  static const int kOsrPcOffsetIndex = 4;
-  static const int kFirstDeoptEntryIndex = 5;
+  static const int kDeoptEntryCountIndex = 0;
+  static const int kReturnAddressPatchEntryCountIndex = 1;
+  static const int kTranslationByteArrayIndex = 2;
+  static const int kInlinedFunctionCountIndex = 3;
+  static const int kLiteralArrayIndex = 4;
+  static const int kOsrAstIdIndex = 5;
+  static const int kOsrPcOffsetIndex = 6;
+  static const int kOptimizationIdIndex = 7;
+  static const int kSharedFunctionInfoIndex = 8;
+  static const int kFirstDeoptEntryIndex = 9;
 
   // Offsets of deopt entry elements relative to the start of the entry.
   static const int kAstIdRawOffset = 0;
@@ -5124,6 +5392,12 @@ class DeoptimizationInputData: public FixedArray {
   static const int kPcOffset = 3;
   static const int kDeoptEntrySize = 4;
 
+  // Offsets of return address patch entry elements relative to the start of the
+  // entry
+  static const int kReturnAddressPcOffset = 0;
+  static const int kPatchedAddressPcOffset = 1;
+  static const int kReturnAddressPatchEntrySize = 2;
+
   // Simple element accessors.
 #define DEFINE_ELEMENT_ACCESSORS(name, type)      \
   type* name() {                                  \
@@ -5138,24 +5412,41 @@ class DeoptimizationInputData: public FixedArray {
   DEFINE_ELEMENT_ACCESSORS(LiteralArray, FixedArray)
   DEFINE_ELEMENT_ACCESSORS(OsrAstId, Smi)
   DEFINE_ELEMENT_ACCESSORS(OsrPcOffset, Smi)
+  DEFINE_ELEMENT_ACCESSORS(OptimizationId, Smi)
+  DEFINE_ELEMENT_ACCESSORS(SharedFunctionInfo, Object)
 
 #undef DEFINE_ELEMENT_ACCESSORS
 
   // Accessors for elements of the ith deoptimization entry.
-#define DEFINE_ENTRY_ACCESSORS(name, type)                       \
-  type* name(int i) {                                            \
-    return type::cast(get(IndexForEntry(i) + k##name##Offset));  \
-  }                                                              \
-  void Set##name(int i, type* value) {                           \
-    set(IndexForEntry(i) + k##name##Offset, value);              \
+#define DEFINE_DEOPT_ENTRY_ACCESSORS(name, type)                \
+  type* name(int i) {                                           \
+    return type::cast(get(IndexForEntry(i) + k##name##Offset)); \
+  }                                                             \
+  void Set##name(int i, type* value) {                          \
+    set(IndexForEntry(i) + k##name##Offset, value);             \
+  }
+
+  DEFINE_DEOPT_ENTRY_ACCESSORS(AstIdRaw, Smi)
+  DEFINE_DEOPT_ENTRY_ACCESSORS(TranslationIndex, Smi)
+  DEFINE_DEOPT_ENTRY_ACCESSORS(ArgumentsStackHeight, Smi)
+  DEFINE_DEOPT_ENTRY_ACCESSORS(Pc, Smi)
+
+#undef DEFINE_DEOPT_ENTRY_ACCESSORS
+
+// Accessors for elements of the ith deoptimization entry.
+#define DEFINE_PATCH_ENTRY_ACCESSORS(name, type)                      \
+  type* name(int i) {                                                 \
+    return type::cast(                                                \
+        get(IndexForReturnAddressPatchEntry(i) + k##name##Offset));   \
+  }                                                                   \
+  void Set##name(int i, type* value) {                                \
+    set(IndexForReturnAddressPatchEntry(i) + k##name##Offset, value); \
   }
 
-  DEFINE_ENTRY_ACCESSORS(AstIdRaw, Smi)
-  DEFINE_ENTRY_ACCESSORS(TranslationIndex, Smi)
-  DEFINE_ENTRY_ACCESSORS(ArgumentsStackHeight, Smi)
-  DEFINE_ENTRY_ACCESSORS(Pc, Smi)
+  DEFINE_PATCH_ENTRY_ACCESSORS(ReturnAddressPc, Smi)
+  DEFINE_PATCH_ENTRY_ACCESSORS(PatchedAddressPc, Smi)
 
-#undef DEFINE_ENTRY_ACCESSORS
+#undef DEFINE_PATCH_ENTRY_ACCESSORS
 
   BailoutId AstId(int i) {
     return BailoutId(AstIdRaw(i)->value());
@@ -5166,28 +5457,42 @@ class DeoptimizationInputData: public FixedArray {
   }
 
   int DeoptCount() {
-    return (length() - kFirstDeoptEntryIndex) / kDeoptEntrySize;
+    return length() == 0 ? 0 : Smi::cast(get(kDeoptEntryCountIndex))->value();
+  }
+
+  int ReturnAddressPatchCount() {
+    return length() == 0
+               ? 0
+               : Smi::cast(get(kReturnAddressPatchEntryCountIndex))->value();
   }
 
   // Allocates a DeoptimizationInputData.
-  MUST_USE_RESULT static MaybeObject* Allocate(Isolate* isolate,
-                                               int deopt_entry_count,
-                                               PretenureFlag pretenure);
+  static Handle<DeoptimizationInputData> New(Isolate* isolate,
+                                             int deopt_entry_count,
+                                             int return_address_patch_count,
+                                             PretenureFlag pretenure);
 
-  // Casting.
-  static inline DeoptimizationInputData* cast(Object* obj);
+  DECLARE_CAST(DeoptimizationInputData)
 
 #ifdef ENABLE_DISASSEMBLER
-  void DeoptimizationInputDataPrint(FILE* out);
+  void DeoptimizationInputDataPrint(OStream& os);  // NOLINT
 #endif
 
  private:
+  friend class Object;  // For accessing LengthFor.
+
   static int IndexForEntry(int i) {
     return kFirstDeoptEntryIndex + (i * kDeoptEntrySize);
   }
 
-  static int LengthFor(int entry_count) {
-    return IndexForEntry(entry_count);
+  int IndexForReturnAddressPatchEntry(int i) {
+    return kFirstDeoptEntryIndex + (DeoptCount() * kDeoptEntrySize) +
+           (i * kReturnAddressPatchEntrySize);
+  }
+
+  static int LengthFor(int deopt_count, int return_address_patch_count) {
+    return kFirstDeoptEntryIndex + (deopt_count * kDeoptEntrySize) +
+           (return_address_patch_count * kReturnAddressPatchEntrySize);
   }
 };
 
@@ -5217,15 +5522,14 @@ class DeoptimizationOutputData: public FixedArray {
   }
 
   // Allocates a DeoptimizationOutputData.
-  MUST_USE_RESULT static MaybeObject* Allocate(Isolate* isolate,
-                                               int number_of_deopt_points,
-                                               PretenureFlag pretenure);
+  static Handle<DeoptimizationOutputData> New(Isolate* isolate,
+                                              int number_of_deopt_points,
+                                              PretenureFlag pretenure);
 
-  // Casting.
-  static inline DeoptimizationOutputData* cast(Object* obj);
+  DECLARE_CAST(DeoptimizationOutputData)
 
 #if defined(OBJECT_PRINT) || defined(ENABLE_DISASSEMBLER)
-  void DeoptimizationOutputDataPrint(FILE* out);
+  void DeoptimizationOutputDataPrint(OStream& os);  // NOLINT
 #endif
 };
 
@@ -5233,49 +5537,6 @@ class DeoptimizationOutputData: public FixedArray {
 // Forward declaration.
 class Cell;
 class PropertyCell;
-
-// TypeFeedbackCells is a fixed array used to hold the association between
-// cache cells and AST ids for code generated by the full compiler.
-// The format of the these objects is
-//   [i * 2]: Global property cell of ith cache cell.
-//   [i * 2 + 1]: Ast ID for ith cache cell.
-class TypeFeedbackCells: public FixedArray {
- public:
-  int CellCount() { return length() / 2; }
-  static int LengthOfFixedArray(int cell_count) { return cell_count * 2; }
-
-  // Accessors for AST ids associated with cache values.
-  inline TypeFeedbackId AstId(int index);
-  inline void SetAstId(int index, TypeFeedbackId id);
-
-  // Accessors for global property cells holding the cache values.
-  inline Cell* GetCell(int index);
-  inline void SetCell(int index, Cell* cell);
-
-  // The object that indicates an uninitialized cache.
-  static inline Handle<Object> UninitializedSentinel(Isolate* isolate);
-
-  // The object that indicates a megamorphic state.
-  static inline Handle<Object> MegamorphicSentinel(Isolate* isolate);
-
-  // The object that indicates a monomorphic state of Array with
-  // ElementsKind
-  static inline Handle<Object> MonomorphicArraySentinel(Isolate* isolate,
-      ElementsKind elements_kind);
-
-  // A raw version of the uninitialized sentinel that's safe to read during
-  // garbage collection (e.g., for patching the cache).
-  static inline Object* RawUninitializedSentinel(Heap* heap);
-
-  // Casting.
-  static inline TypeFeedbackCells* cast(Object* obj);
-
-  static const int kForInFastCaseMarker = 0;
-  static const int kForInSlowCaseMarker = 1;
-};
-
-
-// Forward declaration.
 class SafepointEntry;
 class TypeFeedbackInfo;
 
@@ -5297,6 +5558,7 @@ class Code: public HeapObject {
 #define IC_KIND_LIST(V) \
   V(LOAD_IC)            \
   V(KEYED_LOAD_IC)      \
+  V(CALL_IC)            \
   V(STORE_IC)           \
   V(KEYED_STORE_IC)     \
   V(BINARY_OP_IC)       \
@@ -5333,12 +5595,13 @@ class Code: public HeapObject {
   // Printing
   static const char* ICState2String(InlineCacheState state);
   static const char* StubType2String(StubType type);
-  static void PrintExtraICState(FILE* out, Kind kind, ExtraICState extra);
-  void Disassemble(const char* name, FILE* out = stdout);
+  static void PrintExtraICState(OStream& os,  // NOLINT
+                                Kind kind, ExtraICState extra);
+  void Disassemble(const char* name, OStream& os);  // NOLINT
 #endif  // ENABLE_DISASSEMBLER
 
   // [instruction_size]: Size of the native instructions
-  inline int instruction_size();
+  inline int instruction_size() const;
   inline void set_instruction_size(int value);
 
   // [relocation_info]: Code relocation information
@@ -5355,14 +5618,13 @@ class Code: public HeapObject {
   // [raw_type_feedback_info]: This field stores various things, depending on
   // the kind of the code object.
   //   FUNCTION           => type feedback information.
-  //   STUB               => various things, e.g. a SMI
-  //   OPTIMIZED_FUNCTION => the next_code_link for optimized code list.
+  //   STUB and ICs       => major/minor key as Smi.
   DECL_ACCESSORS(raw_type_feedback_info, Object)
   inline Object* type_feedback_info();
   inline void set_type_feedback_info(
       Object* value, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-  inline int stub_info();
-  inline void set_stub_info(int info);
+  inline uint32_t stub_key();
+  inline void set_stub_key(uint32_t key);
 
   // [next_code_link]: Link for lists of optimized or deoptimized code.
   // Note that storage for this field is overlapped with typefeedback_info.
@@ -5376,11 +5638,11 @@ class Code: public HeapObject {
   // [ic_age]: Inline caching age: the value of the Heap::global_ic_age
   // at the moment when this object was created.
   inline void set_ic_age(int count);
-  inline int ic_age();
+  inline int ic_age() const;
 
   // [prologue_offset]: Offset of the function prologue, used for aging
   // FUNCTIONs and OPTIMIZED_FUNCTIONs.
-  inline int prologue_offset();
+  inline int prologue_offset() const;
   inline void set_prologue_offset(int offset);
 
   // Unchecked accessors to be used during GC.
@@ -5394,24 +5656,10 @@ class Code: public HeapObject {
 
   // [flags]: Access to specific code flags.
   inline Kind kind();
-  inline Kind handler_kind() {
-    return static_cast<Kind>(arguments_count());
-  }
   inline InlineCacheState ic_state();  // Only valid for IC stubs.
   inline ExtraICState extra_ic_state();  // Only valid for IC stubs.
 
-  inline ExtraICState extended_extra_ic_state();  // Only valid for
-                                                  // non-call IC stubs.
-  static bool needs_extended_extra_ic_state(Kind kind) {
-    // TODO(danno): This is a bit of a hack right now since there are still
-    // clients of this API that pass "extra" values in for argc. These clients
-    // should be retrofitted to used ExtendedExtraICState.
-    return kind == COMPARE_NIL_IC || kind == TO_BOOLEAN_IC ||
-           kind == BINARY_OP_IC;
-  }
-
   inline StubType type();  // Only valid for monomorphic IC stubs.
-  inline int arguments_count();  // Only valid for call IC stubs.
 
   // Testers for IC stub kinds.
   inline bool is_inline_cache_stub();
@@ -5421,25 +5669,42 @@ class Code: public HeapObject {
   inline bool is_keyed_load_stub() { return kind() == KEYED_LOAD_IC; }
   inline bool is_store_stub() { return kind() == STORE_IC; }
   inline bool is_keyed_store_stub() { return kind() == KEYED_STORE_IC; }
+  inline bool is_call_stub() { return kind() == CALL_IC; }
   inline bool is_binary_op_stub() { return kind() == BINARY_OP_IC; }
   inline bool is_compare_ic_stub() { return kind() == COMPARE_IC; }
   inline bool is_compare_nil_ic_stub() { return kind() == COMPARE_NIL_IC; }
   inline bool is_to_boolean_ic_stub() { return kind() == TO_BOOLEAN_IC; }
   inline bool is_keyed_stub();
+  inline bool is_optimized_code() { return kind() == OPTIMIZED_FUNCTION; }
+  inline bool is_weak_stub();
+  inline void mark_as_weak_stub();
+  inline bool is_invalidated_weak_stub();
+  inline void mark_as_invalidated_weak_stub();
+
+  inline bool CanBeWeakStub() {
+    Kind k = kind();
+    return (k == LOAD_IC || k == STORE_IC || k == KEYED_LOAD_IC ||
+            k == KEYED_STORE_IC || k == COMPARE_NIL_IC) &&
+           ic_state() == MONOMORPHIC;
+  }
+
+  inline bool IsCodeStubOrIC();
 
   inline void set_raw_kind_specific_flags1(int value);
   inline void set_raw_kind_specific_flags2(int value);
 
-  // [major_key]: For kind STUB or BINARY_OP_IC, the major key.
-  inline int major_key();
-  inline void set_major_key(int value);
-  inline bool has_major_key();
-
-  // For kind STUB or ICs, tells whether or not a code object was generated by
-  // the optimizing compiler (but it may not be an optimized function).
-  bool is_crankshafted();
+  // [is_crankshafted]: For kind STUB or ICs, tells whether or not a code
+  // object was generated by either the hydrogen or the TurboFan optimizing
+  // compiler (but it may not be an optimized function).
+  inline bool is_crankshafted();
+  inline bool is_hydrogen_stub();  // Crankshafted, but not a function.
   inline void set_is_crankshafted(bool value);
 
+  // [is_turbofanned]: For kind STUB or OPTIMIZED_FUNCTION, tells whether the
+  // code object was generated by the TurboFan optimizing compiler.
+  inline bool is_turbofanned();
+  inline void set_is_turbofanned(bool value);
+
   // [optimizable]: For FUNCTION kind, tells if it is optimizable.
   inline bool optimizable();
   inline void set_optimizable(bool value);
@@ -5471,12 +5736,16 @@ class Code: public HeapObject {
   inline int profiler_ticks();
   inline void set_profiler_ticks(int ticks);
 
+  // [builtin_index]: For BUILTIN kind, tells which builtin index it has.
+  inline int builtin_index();
+  inline void set_builtin_index(int id);
+
   // [stack_slots]: For kind OPTIMIZED_FUNCTION, the number of stack slots
   // reserved in the code prologue.
   inline unsigned stack_slots();
   inline void set_stack_slots(unsigned slots);
 
-  // [safepoint_table_start]: For kind OPTIMIZED_CODE, the offset in
+  // [safepoint_table_start]: For kind OPTIMIZED_FUNCTION, the offset in
   // the instruction stream where the safepoint table starts.
   inline unsigned safepoint_table_offset();
   inline void set_safepoint_table_offset(unsigned offset);
@@ -5487,7 +5756,6 @@ class Code: public HeapObject {
   inline void set_back_edge_table_offset(unsigned offset);
 
   inline bool back_edges_patched_for_osr();
-  inline void set_back_edges_patched_for_osr(bool value);
 
   // [to_boolean_foo]: For kind TO_BOOLEAN_IC tells what state the stub is in.
   inline byte to_boolean_state();
@@ -5512,7 +5780,6 @@ class Code: public HeapObject {
 
   // Find an object in a stub with a specified map
   Object* FindNthObject(int n, Map* match_map);
-  void ReplaceNthObject(int n, Map* match_map, Object* replace_with);
 
   // Find the first allocation site in an IC stub.
   AllocationSite* FindFirstAllocationSite();
@@ -5520,8 +5787,6 @@ class Code: public HeapObject {
   // Find the first map in an IC stub.
   Map* FindFirstMap();
   void FindAllMaps(MapHandleList* maps);
-  void FindAllTypes(TypeHandleList* types);
-  void ReplaceFirstMap(Map* replace);
 
   // Find the first handler in an IC stub.
   Code* FindFirstHandler();
@@ -5530,10 +5795,18 @@ class Code: public HeapObject {
   // enough handlers can be found.
   bool FindHandlers(CodeHandleList* code_list, int length = -1);
 
+  // Find the handler for |map|.
+  MaybeHandle<Code> FindHandlerForMap(Map* map);
+
   // Find the first name in an IC stub.
   Name* FindFirstName();
 
-  void ReplaceNthCell(int n, Cell* replace_with);
+  class FindAndReplacePattern;
+  // For each (map-to-find, object-to-replace) pair in the pattern, this
+  // function replaces the corresponding placeholder in the code with the
+  // object-to-replace. The function assumes that pairs in the pattern come in
+  // the same order as the placeholders in the code.
+  void FindAndReplace(const FindAndReplacePattern& pattern);
 
   // The entire code object including its header is copied verbatim to the
   // snapshot so that it can be written in one, fast, memcpy during
@@ -5546,29 +5819,26 @@ class Code: public HeapObject {
 
   // Flags operations.
   static inline Flags ComputeFlags(
-      Kind kind,
-      InlineCacheState ic_state = UNINITIALIZED,
-      ExtraICState extra_ic_state = kNoExtraICState,
-      StubType type = NORMAL,
-      int argc = -1,
-      InlineCacheHolderFlag holder = OWN_MAP);
+      Kind kind, InlineCacheState ic_state = UNINITIALIZED,
+      ExtraICState extra_ic_state = kNoExtraICState, StubType type = NORMAL,
+      CacheHolderFlag holder = kCacheOnReceiver);
 
   static inline Flags ComputeMonomorphicFlags(
-      Kind kind,
-      ExtraICState extra_ic_state = kNoExtraICState,
-      InlineCacheHolderFlag holder = OWN_MAP,
-      StubType type = NORMAL,
-      int argc = -1);
+      Kind kind, ExtraICState extra_ic_state = kNoExtraICState,
+      CacheHolderFlag holder = kCacheOnReceiver, StubType type = NORMAL);
+
+  static inline Flags ComputeHandlerFlags(
+      Kind handler_kind, StubType type = NORMAL,
+      CacheHolderFlag holder = kCacheOnReceiver);
 
   static inline InlineCacheState ExtractICStateFromFlags(Flags flags);
   static inline StubType ExtractTypeFromFlags(Flags flags);
+  static inline CacheHolderFlag ExtractCacheHolderFromFlags(Flags flags);
   static inline Kind ExtractKindFromFlags(Flags flags);
-  static inline InlineCacheHolderFlag ExtractCacheHolderFromFlags(Flags flags);
   static inline ExtraICState ExtractExtraICStateFromFlags(Flags flags);
-  static inline ExtraICState ExtractExtendedExtraICStateFromFlags(Flags flags);
-  static inline int ExtractArgumentsCountFromFlags(Flags flags);
 
   static inline Flags RemoveTypeFromFlags(Flags flags);
+  static inline Flags RemoveTypeAndHolderFromFlags(Flags flags);
 
   // Convert a target address into a code object.
   static inline Code* GetCodeFromTargetAddress(Address address);
@@ -5603,7 +5873,7 @@ class Code: public HeapObject {
 
   // Returns the object size for a given body (used for allocation).
   static int SizeFor(int body_size) {
-    ASSERT_SIZE_TAG_ALIGNED(body_size);
+    DCHECK_SIZE_TAG_ALIGNED(body_size);
     return RoundUp(kHeaderSize + body_size, kCodeAlignment);
   }
 
@@ -5611,7 +5881,7 @@ class Code: public HeapObject {
   // the layout of the code object into account.
   int ExecutableSize() {
     // Check that the assumptions about the layout of the code object holds.
-    ASSERT_EQ(static_cast<int>(instruction_start() - address()),
+    DCHECK_EQ(static_cast<int>(instruction_start() - address()),
               Code::kHeaderSize);
     return instruction_size() + Code::kHeaderSize;
   }
@@ -5620,8 +5890,7 @@ class Code: public HeapObject {
   int SourcePosition(Address pc);
   int SourceStatementPosition(Address pc);
 
-  // Casting.
-  static inline Code* cast(Object* obj);
+  DECLARE_CAST(Code)
 
   // Dispatched behavior.
   int CodeSize() { return SizeFor(body_size()); }
@@ -5636,8 +5905,6 @@ class Code: public HeapObject {
   void ClearInlineCaches();
   void ClearInlineCaches(Kind kind);
 
-  void ClearTypeFeedbackCells(Heap* heap);
-
   BailoutId TranslatePcOffsetToAstId(uint32_t pc_offset);
   uint32_t TranslateAstIdToPcOffset(BailoutId ast_id);
 
@@ -5663,7 +5930,7 @@ class Code: public HeapObject {
   static void MakeCodeAgeSequenceYoung(byte* sequence, Isolate* isolate);
   static void MarkCodeAsExecuted(byte* sequence, Isolate* isolate);
   void MakeOlder(MarkingParity);
-  static bool IsYoungSequence(byte* sequence);
+  static bool IsYoungSequence(Isolate* isolate, byte* sequence);
   bool IsOld();
   Age GetAge();
   // Gets the raw code age, including psuedo code-age values such as
@@ -5680,7 +5947,18 @@ class Code: public HeapObject {
   void VerifyEmbeddedObjectsDependency();
 #endif
 
-  static bool IsWeakEmbeddedObject(Kind kind, Object* object);
+  inline bool CanContainWeakObjects() {
+    return is_optimized_code() || is_weak_stub();
+  }
+
+  inline bool IsWeakObject(Object* object) {
+    return (is_optimized_code() && !is_turbofanned() &&
+            IsWeakObjectInOptimizedCode(object)) ||
+           (is_weak_stub() && IsWeakObjectInIC(object));
+  }
+
+  static inline bool IsWeakObjectInOptimizedCode(Object* object);
+  static inline bool IsWeakObjectInIC(Object* object);
 
   // Max loop nesting marker used to postpose OSR. We don't take loop
   // nesting that is deeper than 5 levels into account.
@@ -5692,10 +5970,11 @@ class Code: public HeapObject {
   static const int kHandlerTableOffset = kRelocationInfoOffset + kPointerSize;
   static const int kDeoptimizationDataOffset =
       kHandlerTableOffset + kPointerSize;
+  // For FUNCTION kind, we store the type feedback info here.
   static const int kTypeFeedbackInfoOffset =
       kDeoptimizationDataOffset + kPointerSize;
-  static const int kNextCodeLinkOffset = kTypeFeedbackInfoOffset;  // Shared.
-  static const int kGCMetadataOffset = kTypeFeedbackInfoOffset + kPointerSize;
+  static const int kNextCodeLinkOffset = kTypeFeedbackInfoOffset + kPointerSize;
+  static const int kGCMetadataOffset = kNextCodeLinkOffset + kPointerSize;
   static const int kICAgeOffset =
       kGCMetadataOffset + kPointerSize;
   static const int kFlagsOffset = kICAgeOffset + kIntSize;
@@ -5722,42 +6001,40 @@ class Code: public HeapObject {
   class FullCodeFlagsHasDebugBreakSlotsField: public BitField<bool, 1, 1> {};
   class FullCodeFlagsIsCompiledOptimizable: public BitField<bool, 2, 1> {};
 
-  static const int kAllowOSRAtLoopNestingLevelOffset = kFullCodeFlags + 1;
-  static const int kProfilerTicksOffset = kAllowOSRAtLoopNestingLevelOffset + 1;
+  static const int kProfilerTicksOffset = kFullCodeFlags + 1;
 
   // Flags layout.  BitField<type, shift, size>.
-  class ICStateField: public BitField<InlineCacheState, 0, 3> {};
-  class TypeField: public BitField<StubType, 3, 1> {};
-  class CacheHolderField: public BitField<InlineCacheHolderFlag, 5, 1> {};
-  class KindField: public BitField<Kind, 6, 4> {};
-  // TODO(bmeurer): Bit 10 is available for free use. :-)
-  class ExtraICStateField: public BitField<ExtraICState, 11, 6> {};
-  class ExtendedExtraICStateField: public BitField<ExtraICState, 11,
+  class ICStateField : public BitField<InlineCacheState, 0, 4> {};
+  class TypeField : public BitField<StubType, 4, 1> {};
+  class CacheHolderField : public BitField<CacheHolderFlag, 5, 2> {};
+  class KindField : public BitField<Kind, 7, 4> {};
+  class ExtraICStateField: public BitField<ExtraICState, 11,
       PlatformSmiTagging::kSmiValueSize - 11 + 1> {};  // NOLINT
-  STATIC_ASSERT(ExtraICStateField::kShift == ExtendedExtraICStateField::kShift);
 
   // KindSpecificFlags1 layout (STUB and OPTIMIZED_FUNCTION)
   static const int kStackSlotsFirstBit = 0;
   static const int kStackSlotsBitCount = 24;
-  static const int kHasFunctionCacheFirstBit =
+  static const int kHasFunctionCacheBit =
       kStackSlotsFirstBit + kStackSlotsBitCount;
-  static const int kHasFunctionCacheBitCount = 1;
-  static const int kMarkedForDeoptimizationFirstBit =
-      kStackSlotsFirstBit + kStackSlotsBitCount + 1;
-  static const int kMarkedForDeoptimizationBitCount = 1;
+  static const int kMarkedForDeoptimizationBit = kHasFunctionCacheBit + 1;
+  static const int kWeakStubBit = kMarkedForDeoptimizationBit + 1;
+  static const int kInvalidatedWeakStubBit = kWeakStubBit + 1;
+  static const int kIsTurbofannedBit = kInvalidatedWeakStubBit + 1;
 
   STATIC_ASSERT(kStackSlotsFirstBit + kStackSlotsBitCount <= 32);
-  STATIC_ASSERT(kHasFunctionCacheFirstBit + kHasFunctionCacheBitCount <= 32);
-  STATIC_ASSERT(kMarkedForDeoptimizationFirstBit +
-                kMarkedForDeoptimizationBitCount <= 32);
+  STATIC_ASSERT(kIsTurbofannedBit + 1 <= 32);
 
   class StackSlotsField: public BitField<int,
       kStackSlotsFirstBit, kStackSlotsBitCount> {};  // NOLINT
-  class HasFunctionCacheField: public BitField<bool,
-      kHasFunctionCacheFirstBit, kHasFunctionCacheBitCount> {};  // NOLINT
-  class MarkedForDeoptimizationField: public BitField<bool,
-      kMarkedForDeoptimizationFirstBit,
-      kMarkedForDeoptimizationBitCount> {};  // NOLINT
+  class HasFunctionCacheField : public BitField<bool, kHasFunctionCacheBit, 1> {
+  };  // NOLINT
+  class MarkedForDeoptimizationField
+      : public BitField<bool, kMarkedForDeoptimizationBit, 1> {};   // NOLINT
+  class WeakStubField : public BitField<bool, kWeakStubBit, 1> {};  // NOLINT
+  class InvalidatedWeakStubField
+      : public BitField<bool, kInvalidatedWeakStubBit, 1> {};  // NOLINT
+  class IsTurbofannedField : public BitField<bool, kIsTurbofannedBit, 1> {
+  };  // NOLINT
 
   // KindSpecificFlags2 layout (ALL)
   static const int kIsCrankshaftedBit = 0;
@@ -5765,42 +6042,26 @@ class Code: public HeapObject {
       kIsCrankshaftedBit, 1> {};  // NOLINT
 
   // KindSpecificFlags2 layout (STUB and OPTIMIZED_FUNCTION)
-  static const int kStubMajorKeyFirstBit = kIsCrankshaftedBit + 1;
-  static const int kSafepointTableOffsetFirstBit =
-      kStubMajorKeyFirstBit + kStubMajorKeyBits;
+  static const int kSafepointTableOffsetFirstBit = kIsCrankshaftedBit + 1;
   static const int kSafepointTableOffsetBitCount = 24;
 
-  STATIC_ASSERT(kStubMajorKeyFirstBit + kStubMajorKeyBits <= 32);
   STATIC_ASSERT(kSafepointTableOffsetFirstBit +
                 kSafepointTableOffsetBitCount <= 32);
-  STATIC_ASSERT(1 + kStubMajorKeyBits +
-                kSafepointTableOffsetBitCount <= 32);
+  STATIC_ASSERT(1 + kSafepointTableOffsetBitCount <= 32);
 
   class SafepointTableOffsetField: public BitField<int,
       kSafepointTableOffsetFirstBit,
       kSafepointTableOffsetBitCount> {};  // NOLINT
-  class StubMajorKeyField: public BitField<int,
-      kStubMajorKeyFirstBit, kStubMajorKeyBits> {};  // NOLINT
 
   // KindSpecificFlags2 layout (FUNCTION)
   class BackEdgeTableOffsetField: public BitField<int,
-      kIsCrankshaftedBit + 1, 29> {};  // NOLINT
-  class BackEdgesPatchedForOSRField: public BitField<bool,
-      kIsCrankshaftedBit + 1 + 29, 1> {};  // NOLINT
-
-  // Signed field cannot be encoded using the BitField class.
-  static const int kArgumentsCountShift = 17;
-  static const int kArgumentsCountMask = ~((1 << kArgumentsCountShift) - 1);
-  static const int kArgumentsBits =
-      PlatformSmiTagging::kSmiValueSize - Code::kArgumentsCountShift + 1;
-  static const int kMaxArguments = (1 << kArgumentsBits) - 1;
+      kIsCrankshaftedBit + 1, 27> {};  // NOLINT
+  class AllowOSRAtLoopNestingLevelField: public BitField<int,
+      kIsCrankshaftedBit + 1 + 27, 4> {};  // NOLINT
+  STATIC_ASSERT(AllowOSRAtLoopNestingLevelField::kMax >= kMaxLoopNestingMarker);
 
-  // ICs can use either argument count or ExtendedExtraIC, since their storage
-  // overlaps.
-  STATIC_ASSERT(ExtraICStateField::kShift +
-                ExtraICStateField::kSize + kArgumentsBits ==
-                ExtendedExtraICStateField::kShift +
-                ExtendedExtraICStateField::kSize);
+  static const int kArgumentsBits = 16;
+  static const int kMaxArguments = (1 << kArgumentsBits) - 1;
 
   // This constant should be encodable in an ARM instruction.
   static const int kFlagsNotUsedInLookup =
@@ -5808,6 +6069,7 @@ class Code: public HeapObject {
 
  private:
   friend class RelocIterator;
+  friend class Deoptimizer;  // For FindCodeAgeSequence.
 
   void ClearInlineCaches(Kind* kind);
 
@@ -5815,7 +6077,7 @@ class Code: public HeapObject {
   byte* FindCodeAgeSequence();
   static void GetCodeAgeAndParity(Code* code, Age* age,
                                   MarkingParity* parity);
-  static void GetCodeAgeAndParity(byte* sequence, Age* age,
+  static void GetCodeAgeAndParity(Isolate* isolate, byte* sequence, Age* age,
                                   MarkingParity* parity);
   static Code* GetCodeAgeStub(Isolate* isolate, Age age, MarkingParity parity);
 
@@ -5852,9 +6114,14 @@ class CompilationInfo;
 class DependentCode: public FixedArray {
  public:
   enum DependencyGroup {
+    // Group of IC stubs that weakly embed this map and depend on being
+    // invalidated when the map is garbage collected. Dependent IC stubs form
+    // a linked list. This group stores only the head of the list. This means
+    // that the number_of_entries(kWeakICGroup) is 0 or 1.
+    kWeakICGroup,
     // Group of code that weakly embed this map and depend on being
     // deoptimized when the map is garbage collected.
-    kWeaklyEmbeddedGroup,
+    kWeakCodeGroup,
     // Group of code that embed a transition to this map, and depend on being
     // deoptimized when the transition is replaced by a new version.
     kTransitionGroup,
@@ -5869,6 +6136,12 @@ class DependentCode: public FixedArray {
     // Group of code that depends on global property values in property cells
     // not being changed.
     kPropertyCellChangedGroup,
+    // Group of code that omit run-time type checks for the field(s) introduced
+    // by this map.
+    kFieldTypeGroup,
+    // Group of code that omit run-time type checks for initial maps of
+    // constructors.
+    kInitialMapChangedGroup,
     // Group of code that depends on tenuring information in AllocationSites
     // not being changed.
     kAllocationSiteTenuringChangedGroup,
@@ -5905,6 +6178,7 @@ class DependentCode: public FixedArray {
 
   bool MarkCodeForDeoptimization(Isolate* isolate,
                                  DependentCode::DependencyGroup group);
+  void AddToDependentICList(Handle<Code> stub);
 
   // The following low-level accessors should only be used by this class
   // and the mark compact collector.
@@ -5918,7 +6192,7 @@ class DependentCode: public FixedArray {
   inline Object* object_at(int i);
   inline void clear_at(int i);
   inline void copy(int from, int to);
-  static inline DependentCode* cast(Object* object);
+  DECLARE_CAST(DependentCode)
 
   static DependentCode* ForObject(Handle<HeapObject> object,
                                   DependencyGroup group);
@@ -5977,15 +6251,19 @@ class Map: public HeapObject {
   class NumberOfOwnDescriptorsBits: public BitField<int,
       kDescriptorIndexBitCount, kDescriptorIndexBitCount> {};  // NOLINT
   STATIC_ASSERT(kDescriptorIndexBitCount + kDescriptorIndexBitCount == 20);
-  class IsShared:                   public BitField<bool, 20,  1> {};
-  class FunctionWithPrototype:      public BitField<bool, 21,  1> {};
-  class DictionaryMap:              public BitField<bool, 22,  1> {};
-  class OwnsDescriptors:            public BitField<bool, 23,  1> {};
-  class HasInstanceCallHandler:     public BitField<bool, 24,  1> {};
-  class Deprecated:                 public BitField<bool, 25,  1> {};
-  class IsFrozen:                   public BitField<bool, 26,  1> {};
-  class IsUnstable:                 public BitField<bool, 27,  1> {};
-  class IsMigrationTarget:          public BitField<bool, 28,  1> {};
+  class DictionaryMap : public BitField<bool, 20, 1> {};
+  class OwnsDescriptors : public BitField<bool, 21, 1> {};
+  class HasInstanceCallHandler : public BitField<bool, 22, 1> {};
+  class Deprecated : public BitField<bool, 23, 1> {};
+  class IsFrozen : public BitField<bool, 24, 1> {};
+  class IsUnstable : public BitField<bool, 25, 1> {};
+  class IsMigrationTarget : public BitField<bool, 26, 1> {};
+  class DoneInobjectSlackTracking : public BitField<bool, 27, 1> {};
+  // Bit 28 is free.
+
+  // Keep this bit field at the very end for better code in
+  // Builtins::kJSConstructStubGeneric stub.
+  class ConstructionCount:          public BitField<int, 29, 3> {};
 
   // Tells whether the object in the prototype property will be used
   // for instances created from this function.  If the prototype
@@ -6054,18 +6332,18 @@ class Map: public HeapObject {
 
   inline void set_is_extensible(bool value);
   inline bool is_extensible();
+  inline void set_is_prototype_map(bool value);
+  inline bool is_prototype_map();
 
   inline void set_elements_kind(ElementsKind elements_kind) {
-    ASSERT(elements_kind < kElementsKindCount);
-    ASSERT(kElementsKindCount <= (1 << kElementsKindBitCount));
-    set_bit_field2((bit_field2() & ~kElementsKindMask) |
-        (elements_kind << kElementsKindShift));
-    ASSERT(this->elements_kind() == elements_kind);
+    DCHECK(elements_kind < kElementsKindCount);
+    DCHECK(kElementsKindCount <= (1 << Map::ElementsKindBits::kSize));
+    set_bit_field2(Map::ElementsKindBits::update(bit_field2(), elements_kind));
+    DCHECK(this->elements_kind() == elements_kind);
   }
 
   inline ElementsKind elements_kind() {
-    return static_cast<ElementsKind>(
-        (bit_field2() & kElementsKindMask) >> kElementsKindShift);
+    return Map::ElementsKindBits::decode(bit_field2());
   }
 
   // Tells whether the instance has fast elements that are only Smis.
@@ -6090,8 +6368,8 @@ class Map: public HeapObject {
     return IsFastElementsKind(elements_kind());
   }
 
-  inline bool has_non_strict_arguments_elements() {
-    return elements_kind() == NON_STRICT_ARGUMENTS_ELEMENTS;
+  inline bool has_sloppy_arguments_elements() {
+    return elements_kind() == SLOPPY_ARGUMENTS_ELEMENTS;
   }
 
   inline bool has_external_array_elements() {
@@ -6108,7 +6386,7 @@ class Map: public HeapObject {
 
   inline bool has_slow_elements_kind() {
     return elements_kind() == DICTIONARY_ELEMENTS
-        || elements_kind() == NON_STRICT_ARGUMENTS_ELEMENTS;
+        || elements_kind() == SLOPPY_ARGUMENTS_ELEMENTS;
   }
 
   static bool IsValidElementsTransition(ElementsKind from_kind,
@@ -6118,48 +6396,49 @@ class Map: public HeapObject {
   // map with DICTIONARY_ELEMENTS was found in the prototype chain.
   bool DictionaryElementsInPrototypeChainOnly();
 
-  inline bool HasTransitionArray();
+  inline bool HasTransitionArray() const;
   inline bool HasElementsTransition();
   inline Map* elements_transition_map();
-  MUST_USE_RESULT inline MaybeObject* set_elements_transition_map(
-      Map* transitioned_map);
-  inline void SetTransition(int transition_index, Map* target);
-  inline Map* GetTransition(int transition_index);
 
-  static Handle<TransitionArray> AddTransition(Handle<Map> map,
-                                               Handle<Name> key,
-                                               Handle<Map> target,
-                                               SimpleTransitionFlag flag);
+  inline Map* GetTransition(int transition_index);
+  inline int SearchTransition(Name* name);
+  inline FixedArrayBase* GetInitialElements();
 
-  MUST_USE_RESULT inline MaybeObject* AddTransition(Name* key,
-                                                    Map* target,
-                                                    SimpleTransitionFlag flag);
   DECL_ACCESSORS(transitions, TransitionArray)
-  inline void ClearTransitions(Heap* heap,
-                               WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
 
-  void DeprecateTransitionTree();
-  void DeprecateTarget(Name* key, DescriptorArray* new_descriptors);
+  static inline Handle<String> ExpectedTransitionKey(Handle<Map> map);
+  static inline Handle<Map> ExpectedTransitionTarget(Handle<Map> map);
+
+  // Try to follow an existing transition to a field with attributes NONE. The
+  // return value indicates whether the transition was successful.
+  static inline Handle<Map> FindTransitionToField(Handle<Map> map,
+                                                  Handle<Name> key);
 
   Map* FindRootMap();
-  Map* FindUpdatedMap(int verbatim, int length, DescriptorArray* descriptors);
-  Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);
+  Map* FindFieldOwner(int descriptor);
 
   inline int GetInObjectPropertyOffset(int index);
 
   int NumberOfFields();
 
-  bool InstancesNeedRewriting(Map* target,
-                              int target_number_of_fields,
-                              int target_inobject,
-                              int target_unused);
-  static Handle<Map> GeneralizeAllFieldRepresentations(
-      Handle<Map> map,
-      Representation new_representation);
+  // TODO(ishell): candidate with JSObject::MigrateToMap().
+  bool InstancesNeedRewriting(Map* target, int target_number_of_fields,
+                              int target_inobject, int target_unused,
+                              int* old_number_of_fields);
+  // TODO(ishell): moveit!
+  static Handle<Map> GeneralizeAllFieldRepresentations(Handle<Map> map);
+  MUST_USE_RESULT static Handle<HeapType> GeneralizeFieldType(
+      Handle<HeapType> type1,
+      Handle<HeapType> type2,
+      Isolate* isolate);
+  static void GeneralizeFieldType(Handle<Map> map,
+                                  int modify_index,
+                                  Handle<HeapType> new_field_type);
   static Handle<Map> GeneralizeRepresentation(
       Handle<Map> map,
       int modify_index,
       Representation new_representation,
+      Handle<HeapType> new_field_type,
       StoreMode store_mode);
   static Handle<Map> CopyGeneralizeAllRepresentations(
       Handle<Map> map,
@@ -6167,32 +6446,22 @@ class Map: public HeapObject {
       StoreMode store_mode,
       PropertyAttributes attributes,
       const char* reason);
+  static Handle<Map> CopyGeneralizeAllRepresentations(
+      Handle<Map> map,
+      int modify_index,
+      StoreMode store_mode,
+      const char* reason);
 
-  void PrintGeneralization(FILE* file,
-                           const char* reason,
-                           int modify_index,
-                           int split,
-                           int descriptors,
-                           bool constant_to_field,
-                           Representation old_representation,
-                           Representation new_representation);
+  static Handle<Map> PrepareForDataProperty(Handle<Map> old_map,
+                                            int descriptor_number,
+                                            Handle<Object> value);
+
+  static Handle<Map> Normalize(Handle<Map> map, PropertyNormalizationMode mode);
 
   // Returns the constructor name (the name (possibly, inferred name) of the
   // function that was used to instantiate the object).
   String* constructor_name();
 
-  // Tells whether the map is attached to SharedFunctionInfo
-  // (for inobject slack tracking).
-  inline void set_attached_to_shared_function_info(bool value);
-
-  inline bool attached_to_shared_function_info();
-
-  // Tells whether the map is shared between objects that may have different
-  // behavior. If true, the map should never be modified, instead a clone
-  // should be created and modified.
-  inline void set_is_shared(bool value);
-  inline bool is_shared();
-
   // Tells whether the map is used for JSObjects in dictionary mode (ie
   // normalized objects, ie objects for which HasFastProperties returns false).
   // A map can never be used for both dictionary mode and fast mode JSObjects.
@@ -6221,7 +6490,7 @@ class Map: public HeapObject {
   // [stub cache]: contains stubs compiled for this map.
   DECL_ACCESSORS(code_cache, Object)
 
-  // [dependent code]: list of optimized codes that have this map embedded.
+  // [dependent code]: list of optimized codes that weakly embed this map.
   DECL_ACCESSORS(dependent_code, DependentCode)
 
   // [back pointer]: points back to the parent map from which a transition
@@ -6242,13 +6511,8 @@ class Map: public HeapObject {
   //    2 + 2 * i: prototype
   //    3 + 2 * i: target map
   inline FixedArray* GetPrototypeTransitions();
-  MUST_USE_RESULT inline MaybeObject* SetPrototypeTransitions(
-      FixedArray* prototype_transitions);
   inline bool HasPrototypeTransitions();
 
-  inline HeapObject* UncheckedPrototypeTransitions();
-  inline TransitionArray* unchecked_transition_array();
-
   static const int kProtoTransitionHeaderSize = 1;
   static const int kProtoTransitionNumberOfEntriesOffset = 0;
   static const int kProtoTransitionElementsPerEntry = 2;
@@ -6264,7 +6528,7 @@ class Map: public HeapObject {
 
   inline void SetNumberOfProtoTransitions(int value) {
     FixedArray* cache = GetPrototypeTransitions();
-    ASSERT(cache->length() != 0);
+    DCHECK(cache->length() != 0);
     cache->set(kProtoTransitionNumberOfEntriesOffset, Smi::FromInt(value));
   }
 
@@ -6288,7 +6552,7 @@ class Map: public HeapObject {
 
   int LastAdded() {
     int number_of_own_descriptors = NumberOfOwnDescriptors();
-    ASSERT(number_of_own_descriptors > 0);
+    DCHECK(number_of_own_descriptors > 0);
     return number_of_own_descriptors - 1;
   }
 
@@ -6297,7 +6561,7 @@ class Map: public HeapObject {
   }
 
   void SetNumberOfOwnDescriptors(int number) {
-    ASSERT(number <= instance_descriptors()->number_of_descriptors());
+    DCHECK(number <= instance_descriptors()->number_of_descriptors());
     set_bit_field3(NumberOfOwnDescriptorsBits::update(bit_field3(), number));
   }
 
@@ -6309,15 +6573,15 @@ class Map: public HeapObject {
 
   void SetEnumLength(int length) {
     if (length != kInvalidEnumCacheSentinel) {
-      ASSERT(length >= 0);
-      ASSERT(length == 0 || instance_descriptors()->HasEnumCache());
-      ASSERT(length <= NumberOfOwnDescriptors());
+      DCHECK(length >= 0);
+      DCHECK(length == 0 || instance_descriptors()->HasEnumCache());
+      DCHECK(length <= NumberOfOwnDescriptors());
     }
     set_bit_field3(EnumLengthBits::update(bit_field3(), length));
   }
 
   inline bool owns_descriptors();
-  inline void set_owns_descriptors(bool is_shared);
+  inline void set_owns_descriptors(bool owns_descriptors);
   inline bool has_instance_call_handler();
   inline void set_has_instance_call_handler();
   inline void freeze();
@@ -6326,6 +6590,10 @@ class Map: public HeapObject {
   inline bool is_stable();
   inline void set_migration_target(bool value);
   inline bool is_migration_target();
+  inline void set_done_inobject_slack_tracking(bool value);
+  inline bool done_inobject_slack_tracking();
+  inline void set_construction_count(int value);
+  inline int construction_count();
   inline void deprecate();
   inline bool is_deprecated();
   inline bool CanBeDeprecated();
@@ -6334,57 +6602,67 @@ class Map: public HeapObject {
   // is found by re-transitioning from the root of the transition tree using the
   // descriptor array of the map. Returns NULL if no updated map is found.
   // This method also applies any pending migrations along the prototype chain.
-  static Handle<Map> CurrentMapForDeprecated(Handle<Map> map);
+  static MaybeHandle<Map> TryUpdate(Handle<Map> map) V8_WARN_UNUSED_RESULT;
   // Same as above, but does not touch the prototype chain.
-  static Handle<Map> CurrentMapForDeprecatedInternal(Handle<Map> map);
+  static MaybeHandle<Map> TryUpdateInternal(Handle<Map> map)
+      V8_WARN_UNUSED_RESULT;
+
+  // Returns a non-deprecated version of the input. This method may deprecate
+  // existing maps along the way if encodings conflict. Not for use while
+  // gathering type feedback. Use TryUpdate in those cases instead.
+  static Handle<Map> Update(Handle<Map> map);
 
-  static Handle<Map> RawCopy(Handle<Map> map, int instance_size);
-  MUST_USE_RESULT MaybeObject* RawCopy(int instance_size);
-  MUST_USE_RESULT MaybeObject* CopyWithPreallocatedFieldDescriptors();
   static Handle<Map> CopyDropDescriptors(Handle<Map> map);
-  MUST_USE_RESULT MaybeObject* CopyDropDescriptors();
-  static Handle<Map> CopyReplaceDescriptors(Handle<Map> map,
-                                            Handle<DescriptorArray> descriptors,
-                                            TransitionFlag flag,
-                                            Handle<Name> name);
-  MUST_USE_RESULT MaybeObject* CopyReplaceDescriptors(
-      DescriptorArray* descriptors,
-      TransitionFlag flag,
-      Name* name = NULL,
-      SimpleTransitionFlag simple_flag = FULL_TRANSITION);
-  static Handle<Map> CopyInstallDescriptors(
+  static Handle<Map> CopyInsertDescriptor(Handle<Map> map,
+                                          Descriptor* descriptor,
+                                          TransitionFlag flag);
+
+  MUST_USE_RESULT static MaybeHandle<Map> CopyWithField(
       Handle<Map> map,
-      int new_descriptor,
-      Handle<DescriptorArray> descriptors);
-  MUST_USE_RESULT MaybeObject* ShareDescriptor(DescriptorArray* descriptors,
-                                               Descriptor* descriptor);
-  MUST_USE_RESULT MaybeObject* CopyAddDescriptor(Descriptor* descriptor,
-                                                 TransitionFlag flag);
-  MUST_USE_RESULT MaybeObject* CopyInsertDescriptor(Descriptor* descriptor,
-                                                    TransitionFlag flag);
-  MUST_USE_RESULT MaybeObject* CopyReplaceDescriptor(
-      DescriptorArray* descriptors,
-      Descriptor* descriptor,
-      int index,
+      Handle<Name> name,
+      Handle<HeapType> type,
+      PropertyAttributes attributes,
+      Representation representation,
+      TransitionFlag flag);
+
+  MUST_USE_RESULT static MaybeHandle<Map> CopyWithConstant(
+      Handle<Map> map,
+      Handle<Name> name,
+      Handle<Object> constant,
+      PropertyAttributes attributes,
       TransitionFlag flag);
-  MUST_USE_RESULT MaybeObject* AsElementsKind(ElementsKind kind);
 
-  MUST_USE_RESULT MaybeObject* CopyAsElementsKind(ElementsKind kind,
-                                                  TransitionFlag flag);
+  // Returns a new map with all transitions dropped from the given map and
+  // the ElementsKind set.
+  static Handle<Map> TransitionElementsTo(Handle<Map> map,
+                                          ElementsKind to_kind);
+
+  static Handle<Map> AsElementsKind(Handle<Map> map, ElementsKind kind);
+
+  static Handle<Map> CopyAsElementsKind(Handle<Map> map,
+                                        ElementsKind kind,
+                                        TransitionFlag flag);
 
   static Handle<Map> CopyForObserved(Handle<Map> map);
 
-  static Handle<Map> CopyNormalized(Handle<Map> map,
-                                    PropertyNormalizationMode mode,
-                                    NormalizedMapSharingMode sharing);
+  static Handle<Map> CopyForFreeze(Handle<Map> map);
+  // Maximal number of fast properties. Used to restrict the number of map
+  // transitions to avoid an explosion in the number of maps for objects used as
+  // dictionaries.
+  inline bool TooManyFastProperties(StoreFromKeyed store_mode);
+  static Handle<Map> TransitionToDataProperty(Handle<Map> map,
+                                              Handle<Name> name,
+                                              Handle<Object> value,
+                                              PropertyAttributes attributes,
+                                              StoreFromKeyed store_mode);
 
-  inline void AppendDescriptor(Descriptor* desc,
-                               const DescriptorArray::WhitenessWitness&);
+  inline void AppendDescriptor(Descriptor* desc);
 
   // Returns a copy of the map, with all transitions dropped from the
   // instance descriptors.
   static Handle<Map> Copy(Handle<Map> map);
-  MUST_USE_RESULT MaybeObject* Copy();
+  static Handle<Map> Create(Handle<JSFunction> constructor,
+                            int extra_inobject_properties);
 
   // Returns the next free property index (only valid for FAST MODE).
   int NextFreePropertyIndex();
@@ -6401,11 +6679,7 @@ class Map: public HeapObject {
         inobject_properties();
   }
 
-  // Casting.
-  static inline Map* cast(Object* obj);
-
-  // Locate an accessor in the instance descriptor.
-  AccessorDescriptor* FindAccessor(Name* name);
+  DECLARE_CAST(Map)
 
   // Code cache operations.
 
@@ -6416,7 +6690,6 @@ class Map: public HeapObject {
   static void UpdateCodeCache(Handle<Map> map,
                               Handle<Name> name,
                               Handle<Code> code);
-  MUST_USE_RESULT MaybeObject* UpdateCodeCache(Name* name, Code* code);
 
   // Extend the descriptor array of the map with the list of descriptors.
   // In case of duplicates, the latest descriptor is used.
@@ -6441,15 +6714,7 @@ class Map: public HeapObject {
   void ClearNonLiveTransitions(Heap* heap);
 
   // Computes a hash value for this map, to be used in HashTables and such.
-  int Hash();
-
-  bool EquivalentToForTransition(Map* other);
-
-  // Compares this map to another to see if they describe equivalent objects.
-  // If |mode| is set to CLEAR_INOBJECT_PROPERTIES, |other| is treated as if
-  // it had exactly zero inobject properties.
-  // The "shared" flags of both this map and |other| are ignored.
-  bool EquivalentToForNormalization(Map* other, PropertyNormalizationMode mode);
+  int Hash();
 
   // Returns the map that this map transitions to if its elements_kind
   // is changed to |elements_kind|, or NULL if no such map is cached yet.
@@ -6461,16 +6726,6 @@ class Map: public HeapObject {
   // elements_kind that's found in |candidates|, or null handle if no match is
   // found at all.
   Handle<Map> FindTransitionedMap(MapHandleList* candidates);
-  Map* FindTransitionedMap(MapList* candidates);
-
-  // Zaps the contents of backing data structures. Note that the
-  // heap verifier (i.e. VerifyMarkingVisitor) relies on zapping of objects
-  // holding weak references when incremental marking is used, because it also
-  // iterates over objects that are otherwise unreachable.
-  // In general we only want to call these functions in release mode when
-  // heap verification is turned on.
-  void ZapPrototypeTransitions();
-  void ZapTransitions();
 
   bool CanTransition() {
     // Only JSObject and subtypes have map transitions and back pointers.
@@ -6481,6 +6736,10 @@ class Map: public HeapObject {
   bool IsJSObjectMap() {
     return instance_type() >= FIRST_JS_OBJECT_TYPE;
   }
+  bool IsJSProxyMap() {
+    InstanceType type = instance_type();
+    return FIRST_JS_PROXY_TYPE <= type && type <= LAST_JS_PROXY_TYPE;
+  }
   bool IsJSGlobalProxyMap() {
     return instance_type() == JS_GLOBAL_PROXY_TYPE;
   }
@@ -6492,18 +6751,17 @@ class Map: public HeapObject {
     return type == JS_GLOBAL_OBJECT_TYPE || type == JS_BUILTINS_OBJECT_TYPE;
   }
 
-  // Fires when the layout of an object with a leaf map changes.
-  // This includes adding transitions to the leaf map or changing
-  // the descriptor array.
-  inline void NotifyLeafMapLayoutChange();
-
   inline bool CanOmitMapChecks();
 
-  void AddDependentCompilationInfo(DependentCode::DependencyGroup group,
-                                   CompilationInfo* info);
+  static void AddDependentCompilationInfo(Handle<Map> map,
+                                          DependentCode::DependencyGroup group,
+                                          CompilationInfo* info);
 
-  void AddDependentCode(DependentCode::DependencyGroup group,
-                        Handle<Code> code);
+  static void AddDependentCode(Handle<Map> map,
+                               DependentCode::DependencyGroup group,
+                               Handle<Code> code);
+  static void AddDependentIC(Handle<Map> map,
+                             Handle<Code> stub);
 
   bool IsMapInArrayPrototypeChain();
 
@@ -6512,7 +6770,7 @@ class Map: public HeapObject {
   DECLARE_VERIFIER(Map)
 
 #ifdef VERIFY_HEAP
-  void SharedMapVerify();
+  void DictionaryMapVerify();
   void VerifyOmittedMapChecks();
 #endif
 
@@ -6531,18 +6789,16 @@ class Map: public HeapObject {
   // transitions are in the form of a map where the keys are prototype objects
   // and the values are the maps the are transitioned to.
   static const int kMaxCachedPrototypeTransitions = 256;
-  static Handle<Map> GetPrototypeTransition(Handle<Map> map,
-                                            Handle<Object> prototype);
-  static Handle<Map> PutPrototypeTransition(Handle<Map> map,
-                                            Handle<Object> prototype,
-                                            Handle<Map> target_map);
+  static Handle<Map> TransitionToPrototype(Handle<Map> map,
+                                           Handle<Object> prototype);
 
   static const int kMaxPreAllocatedPropertyFields = 255;
 
   // Layout description.
   static const int kInstanceSizesOffset = HeapObject::kHeaderSize;
   static const int kInstanceAttributesOffset = kInstanceSizesOffset + kIntSize;
-  static const int kPrototypeOffset = kInstanceAttributesOffset + kIntSize;
+  static const int kBitField3Offset = kInstanceAttributesOffset + kIntSize;
+  static const int kPrototypeOffset = kBitField3Offset + kPointerSize;
   static const int kConstructorOffset = kPrototypeOffset + kPointerSize;
   // Storage for the transition array is overloaded to directly contain a back
   // pointer if unused. When the map has transitions, the back pointer is
@@ -6554,13 +6810,12 @@ class Map: public HeapObject {
       kTransitionsOrBackPointerOffset + kPointerSize;
   static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
   static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;
-  static const int kBitField3Offset = kDependentCodeOffset + kPointerSize;
-  static const int kSize = kBitField3Offset + kPointerSize;
+  static const int kSize = kDependentCodeOffset + kPointerSize;
 
   // Layout of pointer fields. Heap iteration code relies on them
   // being continuously allocated.
   static const int kPointerFieldsBeginOffset = Map::kPrototypeOffset;
-  static const int kPointerFieldsEndOffset = kBitField3Offset + kPointerSize;
+  static const int kPointerFieldsEndOffset = kSize;
 
   // Byte offsets within kInstanceSizesOffset.
   static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;
@@ -6574,52 +6829,144 @@ class Map: public HeapObject {
   static const int kVisitorIdOffset = kInstanceSizesOffset + kVisitorIdByte;
 
   // Byte offsets within kInstanceAttributesOffset attributes.
+#if V8_TARGET_LITTLE_ENDIAN
+  // Order instance type and bit field together such that they can be loaded
+  // together as a 16-bit word with instance type in the lower 8 bits regardless
+  // of endianess. Also provide endian-independent offset to that 16-bit word.
   static const int kInstanceTypeOffset = kInstanceAttributesOffset + 0;
-  static const int kUnusedPropertyFieldsOffset = kInstanceAttributesOffset + 1;
-  static const int kBitFieldOffset = kInstanceAttributesOffset + 2;
-  static const int kBitField2Offset = kInstanceAttributesOffset + 3;
+  static const int kBitFieldOffset = kInstanceAttributesOffset + 1;
+#else
+  static const int kBitFieldOffset = kInstanceAttributesOffset + 0;
+  static const int kInstanceTypeOffset = kInstanceAttributesOffset + 1;
+#endif
+  static const int kInstanceTypeAndBitFieldOffset =
+      kInstanceAttributesOffset + 0;
+  static const int kBitField2Offset = kInstanceAttributesOffset + 2;
+  static const int kUnusedPropertyFieldsOffset = kInstanceAttributesOffset + 3;
 
-  STATIC_CHECK(kInstanceTypeOffset == Internals::kMapInstanceTypeOffset);
+  STATIC_ASSERT(kInstanceTypeAndBitFieldOffset ==
+                Internals::kMapInstanceTypeAndBitFieldOffset);
 
   // Bit positions for bit field.
-  static const int kUnused = 0;  // To be used for marking recently used maps.
-  static const int kHasNonInstancePrototype = 1;
-  static const int kIsHiddenPrototype = 2;
-  static const int kHasNamedInterceptor = 3;
-  static const int kHasIndexedInterceptor = 4;
-  static const int kIsUndetectable = 5;
-  static const int kIsObserved = 6;
-  static const int kIsAccessCheckNeeded = 7;
+  static const int kHasNonInstancePrototype = 0;
+  static const int kIsHiddenPrototype = 1;
+  static const int kHasNamedInterceptor = 2;
+  static const int kHasIndexedInterceptor = 3;
+  static const int kIsUndetectable = 4;
+  static const int kIsObserved = 5;
+  static const int kIsAccessCheckNeeded = 6;
+  class FunctionWithPrototype: public BitField<bool, 7,  1> {};
 
   // Bit positions for bit field 2
   static const int kIsExtensible = 0;
   static const int kStringWrapperSafeForDefaultValueOf = 1;
-  static const int kAttachedToSharedFunctionInfo = 2;
-  // No bits can be used after kElementsKindFirstBit, they are all reserved for
-  // storing ElementKind.
-  static const int kElementsKindShift = 3;
-  static const int kElementsKindBitCount = 5;
+  class IsPrototypeMapBits : public BitField<bool, 2, 1> {};
+  class ElementsKindBits: public BitField<ElementsKind, 3, 5> {};
 
   // Derived values from bit field 2
-  static const int kElementsKindMask = (-1 << kElementsKindShift) &
-      ((1 << (kElementsKindShift + kElementsKindBitCount)) - 1);
   static const int8_t kMaximumBitField2FastElementValue = static_cast<int8_t>(
-      (FAST_ELEMENTS + 1) << Map::kElementsKindShift) - 1;
+      (FAST_ELEMENTS + 1) << Map::ElementsKindBits::kShift) - 1;
   static const int8_t kMaximumBitField2FastSmiElementValue =
       static_cast<int8_t>((FAST_SMI_ELEMENTS + 1) <<
-                          Map::kElementsKindShift) - 1;
+                          Map::ElementsKindBits::kShift) - 1;
   static const int8_t kMaximumBitField2FastHoleyElementValue =
       static_cast<int8_t>((FAST_HOLEY_ELEMENTS + 1) <<
-                          Map::kElementsKindShift) - 1;
+                          Map::ElementsKindBits::kShift) - 1;
   static const int8_t kMaximumBitField2FastHoleySmiElementValue =
       static_cast<int8_t>((FAST_HOLEY_SMI_ELEMENTS + 1) <<
-                          Map::kElementsKindShift) - 1;
+                          Map::ElementsKindBits::kShift) - 1;
 
   typedef FixedBodyDescriptor<kPointerFieldsBeginOffset,
                               kPointerFieldsEndOffset,
                               kSize> BodyDescriptor;
 
+  // Compares this map to another to see if they describe equivalent objects.
+  // If |mode| is set to CLEAR_INOBJECT_PROPERTIES, |other| is treated as if
+  // it had exactly zero inobject properties.
+  // The "shared" flags of both this map and |other| are ignored.
+  bool EquivalentToForNormalization(Map* other, PropertyNormalizationMode mode);
+
  private:
+  static void ConnectElementsTransition(Handle<Map> parent, Handle<Map> child);
+  static void ConnectTransition(Handle<Map> parent, Handle<Map> child,
+                                Handle<Name> name, SimpleTransitionFlag flag);
+
+  bool EquivalentToForTransition(Map* other);
+  static Handle<Map> RawCopy(Handle<Map> map, int instance_size);
+  static Handle<Map> ShareDescriptor(Handle<Map> map,
+                                     Handle<DescriptorArray> descriptors,
+                                     Descriptor* descriptor);
+  static Handle<Map> CopyInstallDescriptors(
+      Handle<Map> map,
+      int new_descriptor,
+      Handle<DescriptorArray> descriptors);
+  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,
+      SimpleTransitionFlag simple_flag = FULL_TRANSITION);
+  static Handle<Map> CopyReplaceDescriptor(Handle<Map> map,
+                                           Handle<DescriptorArray> descriptors,
+                                           Descriptor* descriptor,
+                                           int index,
+                                           TransitionFlag flag);
+
+  static Handle<Map> CopyNormalized(Handle<Map> map,
+                                    PropertyNormalizationMode mode);
+
+  // Fires when the layout of an object with a leaf map changes.
+  // This includes adding transitions to the leaf map or changing
+  // the descriptor array.
+  inline void NotifyLeafMapLayoutChange();
+
+  static Handle<Map> TransitionElementsToSlow(Handle<Map> object,
+                                              ElementsKind to_kind);
+
+  // Zaps the contents of backing data structures. Note that the
+  // heap verifier (i.e. VerifyMarkingVisitor) relies on zapping of objects
+  // holding weak references when incremental marking is used, because it also
+  // iterates over objects that are otherwise unreachable.
+  // In general we only want to call these functions in release mode when
+  // heap verification is turned on.
+  void ZapPrototypeTransitions();
+  void ZapTransitions();
+
+  void DeprecateTransitionTree();
+  void DeprecateTarget(Name* key, DescriptorArray* new_descriptors);
+
+  Map* FindLastMatchMap(int verbatim, int length, DescriptorArray* descriptors);
+
+  void UpdateFieldType(int descriptor_number, Handle<Name> name,
+                       Handle<HeapType> new_type);
+
+  void PrintGeneralization(FILE* file,
+                           const char* reason,
+                           int modify_index,
+                           int split,
+                           int descriptors,
+                           bool constant_to_field,
+                           Representation old_representation,
+                           Representation new_representation,
+                           HeapType* old_field_type,
+                           HeapType* new_field_type);
+
+  static inline void SetPrototypeTransitions(
+      Handle<Map> map,
+      Handle<FixedArray> prototype_transitions);
+
+  static Handle<Map> GetPrototypeTransition(Handle<Map> map,
+                                            Handle<Object> prototype);
+  static Handle<Map> PutPrototypeTransition(Handle<Map> map,
+                                            Handle<Object> prototype,
+                                            Handle<Map> target_map);
+
+  static const int kFastPropertiesSoftLimit = 12;
+  static const int kMaxFastProperties = 128;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(Map);
 };
 
@@ -6630,7 +6977,7 @@ class Map: public HeapObject {
 class Struct: public HeapObject {
  public:
   inline void InitializeBody(int object_size);
-  static inline Struct* cast(Object* that);
+  DECLARE_CAST(Struct)
 };
 
 
@@ -6640,7 +6987,7 @@ class Box : public Struct {
   // [value]: the boxed contents.
   DECL_ACCESSORS(value, Object)
 
-  static inline Box* cast(Object* obj);
+  DECLARE_CAST(Box)
 
   // Dispatched behavior.
   DECLARE_PRINTER(Box)
@@ -6692,9 +7039,6 @@ class Script: public Struct {
   // extracted.
   DECL_ACCESSORS(column_offset, Smi)
 
-  // [data]: additional data associated with this script.
-  DECL_ACCESSORS(data, Object)
-
   // [context_data]: context data for the context this script was compiled in.
   DECL_ACCESSORS(context_data, Object)
 
@@ -6718,6 +7062,12 @@ class Script: public Struct {
   // [flags]: Holds an exciting bitfield.
   DECL_ACCESSORS(flags, Smi)
 
+  // [source_url]: sourceURL from magic comment
+  DECL_ACCESSORS(source_url, Object)
+
+  // [source_url]: sourceMappingURL magic comment
+  DECL_ACCESSORS(source_mapping_url, Object)
+
   // [compilation_type]: how the the script was compiled. Encoded in the
   // 'flags' field.
   inline CompilationType compilation_type();
@@ -6734,12 +7084,29 @@ class Script: public Struct {
   // the 'flags' field.
   DECL_BOOLEAN_ACCESSORS(is_shared_cross_origin)
 
-  static inline Script* cast(Object* obj);
+  DECLARE_CAST(Script)
 
   // If script source is an external string, check that the underlying
   // resource is accessible. Otherwise, always return true.
   inline bool HasValidSource();
 
+  // Convert code position into column number.
+  static int GetColumnNumber(Handle<Script> script, int code_pos);
+
+  // Convert code position into (zero-based) line number.
+  // The non-handlified version does not allocate, but may be much slower.
+  static int GetLineNumber(Handle<Script> script, int code_pos);
+  int GetLineNumber(int code_pos);
+
+  static Handle<Object> GetNameOrSourceURL(Handle<Script> script);
+
+  // Init line_ends array with code positions of line ends inside script source.
+  static void InitLineEnds(Handle<Script> script);
+
+  // Get the JS object wrapping the given script; create it if none exists.
+  static Handle<JSObject> GetWrapper(Handle<Script> script);
+  void ClearWrapperCache();
+
   // Dispatched behavior.
   DECLARE_PRINTER(Script)
   DECLARE_VERIFIER(Script)
@@ -6748,8 +7115,7 @@ class Script: public Struct {
   static const int kNameOffset = kSourceOffset + kPointerSize;
   static const int kLineOffsetOffset = kNameOffset + kPointerSize;
   static const int kColumnOffsetOffset = kLineOffsetOffset + kPointerSize;
-  static const int kDataOffset = kColumnOffsetOffset + kPointerSize;
-  static const int kContextOffset = kDataOffset + kPointerSize;
+  static const int kContextOffset = kColumnOffsetOffset + kPointerSize;
   static const int kWrapperOffset = kContextOffset + kPointerSize;
   static const int kTypeOffset = kWrapperOffset + kPointerSize;
   static const int kLineEndsOffset = kTypeOffset + kPointerSize;
@@ -6759,9 +7125,13 @@ class Script: public Struct {
       kEvalFromSharedOffset + kPointerSize;
   static const int kFlagsOffset =
       kEvalFrominstructionsOffsetOffset + kPointerSize;
-  static const int kSize = kFlagsOffset + kPointerSize;
+  static const int kSourceUrlOffset = kFlagsOffset + kPointerSize;
+  static const int kSourceMappingUrlOffset = kSourceUrlOffset + kPointerSize;
+  static const int kSize = kSourceMappingUrlOffset + kPointerSize;
 
  private:
+  int GetLineNumberWithArray(int code_pos);
+
   // Bit positions in the flags field.
   static const int kCompilationTypeBit = 0;
   static const int kCompilationStateBit = 1;
@@ -6781,8 +7151,11 @@ class Script: public Struct {
 // Installation of ids for the selected builtin functions is handled
 // by the bootstrapper.
 #define FUNCTIONS_WITH_ID_LIST(V)                   \
+  V(Array.prototype, indexOf, ArrayIndexOf)         \
+  V(Array.prototype, lastIndexOf, ArrayLastIndexOf) \
   V(Array.prototype, push, ArrayPush)               \
   V(Array.prototype, pop, ArrayPop)                 \
+  V(Array.prototype, shift, ArrayShift)             \
   V(Function.prototype, apply, FunctionApply)       \
   V(String.prototype, charCodeAt, StringCharCodeAt) \
   V(String.prototype, charAt, StringCharAt)         \
@@ -6797,27 +7170,38 @@ class Script: public Struct {
   V(Math, pow, MathPow)                             \
   V(Math, max, MathMax)                             \
   V(Math, min, MathMin)                             \
-  V(Math, imul, MathImul)
+  V(Math, imul, MathImul)                           \
+  V(Math, clz32, MathClz32)                         \
+  V(Math, fround, MathFround)
 
 #define SIMD_NULLARY_OPERATIONS(V)                                             \
   V(SIMD.float32x4, zero, Float32x4Zero, Float32x4)                            \
+  V(SIMD.float64x2, zero, Float64x2Zero, Float64x2)                            \
   V(SIMD.int32x4, zero, Int32x4Zero, Int32x4)
 
 #define SIMD_UNARY_OPERATIONS(V)                                               \
+  V(SIMD, float32x4, Float32x4Coercion, Float32x4, Float32x4)                  \
+  V(SIMD, float64x2, Float64x2Coercion, Float64x2, Float64x2)                  \
+  V(SIMD, int32x4, Int32x4Coercion, Int32x4, Int32x4)                          \
   V(SIMD.float32x4, abs, Float32x4Abs, Float32x4, Float32x4)                   \
-  V(SIMD.float32x4, bitsToInt32x4, Float32x4BitsToInt32x4, Int32x4, Float32x4) \
+  V(SIMD.float32x4, fromInt32x4, Int32x4ToFloat32x4, Float32x4, Int32x4)       \
+  V(SIMD.float32x4, fromInt32x4Bits, Int32x4BitsToFloat32x4, Float32x4,        \
+    Int32x4)                                                                   \
   V(SIMD.float32x4, neg, Float32x4Neg, Float32x4, Float32x4)                   \
   V(SIMD.float32x4, reciprocal, Float32x4Reciprocal, Float32x4, Float32x4)     \
   V(SIMD.float32x4, reciprocalSqrt, Float32x4ReciprocalSqrt,                   \
     Float32x4, Float32x4)                                                      \
   V(SIMD.float32x4, splat, Float32x4Splat, Float32x4, Double)                  \
   V(SIMD.float32x4, sqrt, Float32x4Sqrt, Float32x4, Float32x4)                 \
-  V(SIMD.float32x4, toInt32x4, Float32x4ToInt32x4, Int32x4, Float32x4)         \
-  V(SIMD.int32x4, bitsToFloat32x4, Int32x4BitsToFloat32x4, Float32x4, Int32x4) \
+  V(SIMD.float64x2, abs, Float64x2Abs, Float64x2, Float64x2)                   \
+  V(SIMD.float64x2, neg, Float64x2Neg, Float64x2, Float64x2)                   \
+  V(SIMD.float64x2, sqrt, Float64x2Sqrt, Float64x2, Float64x2)                 \
+  V(SIMD.int32x4, fromFloat32x4, Float32x4ToInt32x4, Int32x4, Float32x4)       \
+  V(SIMD.int32x4, fromFloat32x4Bits, Float32x4BitsToInt32x4, Int32x4,          \
+    Float32x4)                                                                 \
   V(SIMD.int32x4, neg, Int32x4Neg, Int32x4, Int32x4)                           \
   V(SIMD.int32x4, not, Int32x4Not, Int32x4, Int32x4)                           \
-  V(SIMD.int32x4, splat, Int32x4Splat, Int32x4, Integer32)                     \
-  V(SIMD.int32x4, toFloat32x4, Int32x4ToFloat32x4, Float32x4, Int32x4)
+  V(SIMD.int32x4, splat, Int32x4Splat, Int32x4, Integer32)
 
 // Do not need to install them in InstallExperimentalSIMDBuiltinFunctionIds.
 #define SIMD_UNARY_OPERATIONS_FOR_PROPERTY_ACCESS(V)                           \
@@ -6827,6 +7211,10 @@ class Script: public Struct {
   V(SIMD.float32x4.prototype, y, Float32x4GetY, Double, Float32x4)             \
   V(SIMD.float32x4.prototype, z, Float32x4GetZ, Double, Float32x4)             \
   V(SIMD.float32x4.prototype, w, Float32x4GetW, Double, Float32x4)             \
+  V(SIMD.float64x2.prototype, signMask, Float64x2GetSignMask, Integer32,       \
+    Float64x2)                                                                 \
+  V(SIMD.float64x2.prototype, x, Float64x2GetX, Double, Float64x2)             \
+  V(SIMD.float64x2.prototype, y, Float64x2GetY, Double, Float64x2)             \
   V(SIMD.int32x4.prototype, signMask, Int32x4GetSignMask, Integer32, Int32x4)  \
   V(SIMD.int32x4.prototype, x, Int32x4GetX, Integer32, Int32x4)                \
   V(SIMD.int32x4.prototype, y, Int32x4GetY, Integer32, Int32x4)                \
@@ -6862,6 +7250,16 @@ class Script: public Struct {
   V(SIMD.float32x4, withY, Float32x4WithY, Float32x4, Float32x4, Double)       \
   V(SIMD.float32x4, withZ, Float32x4WithZ, Float32x4, Float32x4, Double)       \
   V(SIMD.float32x4, withW, Float32x4WithW, Float32x4, Float32x4, Double)       \
+  V(SIMD.float64x2, add, Float64x2Add, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, div, Float64x2Div, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, max, Float64x2Max, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, min, Float64x2Min, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, mul, Float64x2Mul, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, sub, Float64x2Sub, Float64x2, Float64x2, Float64x2)        \
+  V(SIMD.float64x2, scale, Float64x2Scale, Float64x2, Float64x2, Double)       \
+  V(SIMD.float64x2, withX, Float64x2WithX, Float64x2, Float64x2, Double)       \
+  V(SIMD.float64x2, withY, Float64x2WithY, Float64x2, Float64x2, Double)       \
+  V(SIMD, float64x2, Float64x2Constructor, Float64x2, Double, Double)          \
   V(SIMD.int32x4, add, Int32x4Add, Int32x4, Int32x4, Int32x4)                  \
   V(SIMD.int32x4, and, Int32x4And, Int32x4, Int32x4, Int32x4)                  \
   V(SIMD.int32x4, mul, Int32x4Mul, Int32x4, Int32x4, Int32x4)                  \
@@ -6890,8 +7288,11 @@ class Script: public Struct {
     Float32x4)                                                                 \
   V(SIMD.float32x4, shuffleMix, Float32x4ShuffleMix, Float32x4, Float32x4,     \
     Float32x4, Integer32)                                                      \
-  V(SIMD.int32x4, select, Int32x4Select, Float32x4, Int32x4, Float32x4,        \
-    Float32x4)
+  V(SIMD.float32x4, select, Float32x4Select, Float32x4, Int32x4, Float32x4,    \
+    Float32x4)                                                                 \
+  V(SIMD.float64x2, clamp, Float64x2Clamp, Float64x2, Float64x2, Float64x2,    \
+    Float64x2)                                                                 \
+  V(SIMD.int32x4, select, Int32x4Select, Int32x4, Int32x4, Int32x4, Int32x4)
 
 #define SIMD_QUARTERNARY_OPERATIONS(V)                                         \
   V(SIMD, float32x4, Float32x4Constructor, Float32x4, Double, Double, Double,  \
@@ -6903,6 +7304,8 @@ class Script: public Struct {
 #define SIMD_ARRAY_OPERATIONS(V)                                               \
   V(Float32x4Array.prototype, getAt, Float32x4ArrayGetAt)                      \
   V(Float32x4Array.prototype, setAt, Float32x4ArraySetAt)                      \
+  V(Float64x2Array.prototype, getAt, Float64x2ArrayGetAt)                      \
+  V(Float64x2Array.prototype, setAt, Float64x2ArraySetAt)                      \
   V(Int32x4Array.prototype, getAt, Int32x4ArrayGetAt)                          \
   V(Int32x4Array.prototype, setAt, Int32x4ArraySetAt)
 
@@ -6979,14 +7382,12 @@ class SharedFunctionInfo: public HeapObject {
   // Removed a specific optimized code object from the optimized code map.
   void EvictFromOptimizedCodeMap(Code* optimized_code, const char* reason);
 
+  void ClearTypeFeedbackInfo();
+
   // Trims the optimized code map after entries have been removed.
   void TrimOptimizedCodeMap(int shrink_by);
 
   // Add a new entry to the optimized code map.
-  MUST_USE_RESULT MaybeObject* AddToOptimizedCodeMap(Context* native_context,
-                                                     Code* code,
-                                                     FixedArray* literals,
-                                                     BailoutId osr_ast_id);
   static void AddToOptimizedCodeMap(Handle<SharedFunctionInfo> shared,
                                     Handle<Context> native_context,
                                     Handle<Code> code,
@@ -7001,13 +7402,6 @@ class SharedFunctionInfo: public HeapObject {
   static const int kLiteralsOffset = 2;
   static const int kOsrAstIdOffset = 3;
   static const int kEntryLength = 4;
-  static const int kFirstContextSlot = FixedArray::kHeaderSize +
-      (kEntriesStart + kContextOffset) * kPointerSize;
-  static const int kFirstCodeSlot = FixedArray::kHeaderSize +
-      (kEntriesStart + kCachedCodeOffset) * kPointerSize;
-  static const int kFirstOsrAstIdSlot = FixedArray::kHeaderSize +
-      (kEntriesStart + kOsrAstIdOffset) * kPointerSize;
-  static const int kSecondEntryIndex = kEntryLength + kEntriesStart;
   static const int kInitialLength = kEntriesStart + kEntryLength;
 
   // [scope_info]: Scope info.
@@ -7021,11 +7415,11 @@ class SharedFunctionInfo: public HeapObject {
 
   // [length]: The function length - usually the number of declared parameters.
   // Use up to 2^30 parameters.
-  inline int length();
+  inline int length() const;
   inline void set_length(int value);
 
   // [formal parameter count]: The declared number of parameters.
-  inline int formal_parameter_count();
+  inline int formal_parameter_count() const;
   inline void set_formal_parameter_count(int value);
 
   // Set the formal parameter count so the function code will be
@@ -7033,104 +7427,14 @@ class SharedFunctionInfo: public HeapObject {
   inline void DontAdaptArguments();
 
   // [expected_nof_properties]: Expected number of properties for the function.
-  inline int expected_nof_properties();
+  inline int expected_nof_properties() const;
   inline void set_expected_nof_properties(int value);
 
-  // Inobject slack tracking is the way to reclaim unused inobject space.
-  //
-  // The instance size is initially determined by adding some slack to
-  // expected_nof_properties (to allow for a few extra properties added
-  // after the constructor). There is no guarantee that the extra space
-  // will not be wasted.
-  //
-  // Here is the algorithm to reclaim the unused inobject space:
-  // - Detect the first constructor call for this SharedFunctionInfo.
-  //   When it happens enter the "in progress" state: remember the
-  //   constructor's initial_map and install a special construct stub that
-  //   counts constructor calls.
-  // - While the tracking is in progress create objects filled with
-  //   one_pointer_filler_map instead of undefined_value. This way they can be
-  //   resized quickly and safely.
-  // - Once enough (kGenerousAllocationCount) objects have been created
-  //   compute the 'slack' (traverse the map transition tree starting from the
-  //   initial_map and find the lowest value of unused_property_fields).
-  // - Traverse the transition tree again and decrease the instance size
-  //   of every map. Existing objects will resize automatically (they are
-  //   filled with one_pointer_filler_map). All further allocations will
-  //   use the adjusted instance size.
-  // - Decrease expected_nof_properties so that an allocations made from
-  //   another context will use the adjusted instance size too.
-  // - Exit "in progress" state by clearing the reference to the initial_map
-  //   and setting the regular construct stub (generic or inline).
-  //
-  //  The above is the main event sequence. Some special cases are possible
-  //  while the tracking is in progress:
-  //
-  // - GC occurs.
-  //   Check if the initial_map is referenced by any live objects (except this
-  //   SharedFunctionInfo). If it is, continue tracking as usual.
-  //   If it is not, clear the reference and reset the tracking state. The
-  //   tracking will be initiated again on the next constructor call.
-  //
-  // - The constructor is called from another context.
-  //   Immediately complete the tracking, perform all the necessary changes
-  //   to maps. This is  necessary because there is no efficient way to track
-  //   multiple initial_maps.
-  //   Proceed to create an object in the current context (with the adjusted
-  //   size).
-  //
-  // - A different constructor function sharing the same SharedFunctionInfo is
-  //   called in the same context. This could be another closure in the same
-  //   context, or the first function could have been disposed.
-  //   This is handled the same way as the previous case.
-  //
-  //  Important: inobject slack tracking is not attempted during the snapshot
-  //  creation.
-
-  static const int kGenerousAllocationCount = 8;
-
-  // [construction_count]: Counter for constructor calls made during
-  // the tracking phase.
-  inline int construction_count();
-  inline void set_construction_count(int value);
-
-  // [initial_map]: initial map of the first function called as a constructor.
-  // Saved for the duration of the tracking phase.
-  // This is a weak link (GC resets it to undefined_value if no other live
-  // object reference this map).
-  DECL_ACCESSORS(initial_map, Object)
-
-  // True if the initial_map is not undefined and the countdown stub is
-  // installed.
-  inline bool IsInobjectSlackTrackingInProgress();
-
-  // Starts the tracking.
-  // Stores the initial map and installs the countdown stub.
-  // IsInobjectSlackTrackingInProgress is normally true after this call,
-  // except when tracking have not been started (e.g. the map has no unused
-  // properties or the snapshot is being built).
-  void StartInobjectSlackTracking(Map* map);
-
-  // Completes the tracking.
-  // IsInobjectSlackTrackingInProgress is false after this call.
-  void CompleteInobjectSlackTracking();
-
-  // Invoked before pointers in SharedFunctionInfo are being marked.
-  // Also clears the optimized code map.
-  inline void BeforeVisitingPointers();
-
-  // Clears the initial_map before the GC marking phase to ensure the reference
-  // is weak. IsInobjectSlackTrackingInProgress is false after this call.
-  void DetachInitialMap();
-
-  // Restores the link to the initial map after the GC marking phase.
-  // IsInobjectSlackTrackingInProgress is true after this call.
-  void AttachInitialMap(Map* map);
-
-  // False if there are definitely no live objects created from this function.
-  // True if live objects _may_ exist (existence not guaranteed).
-  // May go back from true to false after GC.
-  DECL_BOOLEAN_ACCESSORS(live_objects_may_exist)
+  // [feedback_vector] - accumulates ast node feedback from full-codegen and
+  // (increasingly) from crankshafted code where sufficient feedback isn't
+  // available. Currently the field is duplicated in
+  // TypeFeedbackInfo::feedback_vector, but the allocation is done here.
+  DECL_ACCESSORS(feedback_vector, FixedArray)
 
   // [instance class name]: class name for instances.
   DECL_ACCESSORS(instance_class_name, Object)
@@ -7152,7 +7456,7 @@ class SharedFunctionInfo: public HeapObject {
   DECL_ACCESSORS(script, Object)
 
   // [num_literals]: Number of literals used by this function.
-  inline int num_literals();
+  inline int num_literals() const;
   inline void set_num_literals(int value);
 
   // [start_position_and_type]: Field used to store both the source code
@@ -7160,7 +7464,7 @@ class SharedFunctionInfo: public HeapObject {
   // and whether or not the function is a toplevel function. The two
   // least significants bit indicates whether the function is an
   // expression and the rest contains the source code position.
-  inline int start_position_and_type();
+  inline int start_position_and_type() const;
   inline void set_start_position_and_type(int value);
 
   // [debug info]: Debug information.
@@ -7177,15 +7481,15 @@ class SharedFunctionInfo: public HeapObject {
   String* DebugName();
 
   // Position of the 'function' token in the script source.
-  inline int function_token_position();
+  inline int function_token_position() const;
   inline void set_function_token_position(int function_token_position);
 
   // Position of this function in the script source.
-  inline int start_position();
+  inline int start_position() const;
   inline void set_start_position(int start_position);
 
   // End position of this function in the script source.
-  inline int end_position();
+  inline int end_position() const;
   inline void set_end_position(int end_position);
 
   // Is this function a function expression in the source code.
@@ -7196,13 +7500,14 @@ class SharedFunctionInfo: public HeapObject {
 
   // Bit field containing various information collected by the compiler to
   // drive optimization.
-  inline int compiler_hints();
+  inline int compiler_hints() const;
   inline void set_compiler_hints(int value);
 
-  inline int ast_node_count();
+  inline int ast_node_count() const;
   inline void set_ast_node_count(int count);
 
-  inline int profiler_ticks();
+  inline int profiler_ticks() const;
+  inline void set_profiler_ticks(int ticks);
 
   // Inline cache age is used to infer whether the function survived a context
   // disposal or not. In the former case we reset the opt_count.
@@ -7226,20 +7531,9 @@ class SharedFunctionInfo: public HeapObject {
   // spending time attempting to optimize it again.
   DECL_BOOLEAN_ACCESSORS(optimization_disabled)
 
-  // Indicates the language mode of the function's code as defined by the
-  // current harmony drafts for the next ES language standard. Possible
-  // values are:
-  // 1. CLASSIC_MODE - Unrestricted syntax and semantics, same as in ES5.
-  // 2. STRICT_MODE - Restricted syntax and semantics, same as in ES5.
-  // 3. EXTENDED_MODE - Only available under the harmony flag, not part of ES5.
-  inline LanguageMode language_mode();
-  inline void set_language_mode(LanguageMode language_mode);
-
-  // Indicates whether the language mode of this function is CLASSIC_MODE.
-  inline bool is_classic_mode();
-
-  // Indicates whether the language mode of this function is EXTENDED_MODE.
-  inline bool is_extended_mode();
+  // Indicates the language mode.
+  inline StrictMode strict_mode();
+  inline void set_strict_mode(StrictMode strict_mode);
 
   // False if the function definitely does not allocate an arguments object.
   DECL_BOOLEAN_ACCESSORS(uses_arguments)
@@ -7273,12 +7567,6 @@ class SharedFunctionInfo: public HeapObject {
   // Is this a function or top-level/eval code.
   DECL_BOOLEAN_ACCESSORS(is_function)
 
-  // Indicates that the function cannot be optimized.
-  DECL_BOOLEAN_ACCESSORS(dont_optimize)
-
-  // Indicates that the function cannot be inlined.
-  DECL_BOOLEAN_ACCESSORS(dont_inline)
-
   // Indicates that code for this function cannot be cached.
   DECL_BOOLEAN_ACCESSORS(dont_cache)
 
@@ -7288,6 +7576,9 @@ class SharedFunctionInfo: public HeapObject {
   // Indicates that this function is a generator.
   DECL_BOOLEAN_ACCESSORS(is_generator)
 
+  // Indicates that this function is an arrow function.
+  DECL_BOOLEAN_ACCESSORS(is_arrow)
+
   // Indicates whether or not the code in the shared function support
   // deoptimization.
   inline bool has_deoptimization_support();
@@ -7301,13 +7592,13 @@ class SharedFunctionInfo: public HeapObject {
 
   inline BailoutReason DisableOptimizationReason();
 
-  // Lookup the bailout ID and ASSERT that it exists in the non-optimized
+  // Lookup the bailout ID and DCHECK that it exists in the non-optimized
   // code, returns whether it asserted (i.e., always true if assertions are
   // disabled).
   bool VerifyBailoutId(BailoutId id);
 
   // [source code]: Source code for the function.
-  bool HasSourceCode();
+  bool HasSourceCode() const;
   Handle<Object> GetSourceCode();
 
   // Number of times the function was optimized.
@@ -7328,11 +7619,11 @@ class SharedFunctionInfo: public HeapObject {
 
   // Stores deopt_count, opt_reenable_tries and ic_age as bit-fields.
   inline void set_counters(int value);
-  inline int counters();
+  inline int counters() const;
 
   // Stores opt_count and bailout_reason as bit-fields.
   inline void set_opt_count_and_bailout_reason(int value);
-  inline int opt_count_and_bailout_reason();
+  inline int opt_count_and_bailout_reason() const;
 
   void set_bailout_reason(BailoutReason reason) {
     set_opt_count_and_bailout_reason(
@@ -7340,11 +7631,6 @@ class SharedFunctionInfo: public HeapObject {
                                                reason));
   }
 
-  void set_dont_optimize_reason(BailoutReason reason) {
-    set_bailout_reason(reason);
-    set_dont_optimize(reason != kNoReason);
-  }
-
   // Check whether or not this function is inlineable.
   bool IsInlineable();
 
@@ -7358,15 +7644,12 @@ class SharedFunctionInfo: public HeapObject {
   int CalculateInObjectProperties();
 
   // Dispatched behavior.
-  // Set max_length to -1 for unlimited length.
-  void SourceCodePrint(StringStream* accumulator, int max_length);
   DECLARE_PRINTER(SharedFunctionInfo)
   DECLARE_VERIFIER(SharedFunctionInfo)
 
   void ResetForNewContext(int new_ic_age);
 
-  // Casting.
-  static inline SharedFunctionInfo* cast(Object* obj);
+  DECLARE_CAST(SharedFunctionInfo)
 
   // Constants.
   static const int kDontAdaptArgumentsSentinel = -1;
@@ -7385,16 +7668,12 @@ class SharedFunctionInfo: public HeapObject {
   static const int kScriptOffset = kFunctionDataOffset + kPointerSize;
   static const int kDebugInfoOffset = kScriptOffset + kPointerSize;
   static const int kInferredNameOffset = kDebugInfoOffset + kPointerSize;
-  static const int kInitialMapOffset =
+  static const int kFeedbackVectorOffset =
       kInferredNameOffset + kPointerSize;
-  // ast_node_count is a Smi field. It could be grouped with another Smi field
-  // into a PSEUDO_SMI_ACCESSORS pair (on x64), if one becomes available.
-  static const int kAstNodeCountOffset =
-      kInitialMapOffset + kPointerSize;
 #if V8_HOST_ARCH_32_BIT
   // Smi fields.
   static const int kLengthOffset =
-      kAstNodeCountOffset + kPointerSize;
+      kFeedbackVectorOffset + kPointerSize;
   static const int kFormalParameterCountOffset = kLengthOffset + kPointerSize;
   static const int kExpectedNofPropertiesOffset =
       kFormalParameterCountOffset + kPointerSize;
@@ -7412,9 +7691,13 @@ class SharedFunctionInfo: public HeapObject {
       kCompilerHintsOffset + kPointerSize;
   static const int kCountersOffset =
       kOptCountAndBailoutReasonOffset + kPointerSize;
+  static const int kAstNodeCountOffset =
+      kCountersOffset + kPointerSize;
+  static const int kProfilerTicksOffset =
+      kAstNodeCountOffset + kPointerSize;
 
   // Total size.
-  static const int kSize = kCountersOffset + kPointerSize;
+  static const int kSize = kProfilerTicksOffset + kPointerSize;
 #else
   // The only reason to use smi fields instead of int fields
   // is to allow iteration without maps decoding during
@@ -7426,7 +7709,7 @@ class SharedFunctionInfo: public HeapObject {
   // word is not set and thus this word cannot be treated as pointer
   // to HeapObject during old space traversal.
   static const int kLengthOffset =
-      kAstNodeCountOffset + kPointerSize;
+      kFeedbackVectorOffset + kPointerSize;
   static const int kFormalParameterCountOffset =
       kLengthOffset + kIntSize;
 
@@ -7447,30 +7730,23 @@ class SharedFunctionInfo: public HeapObject {
 
   static const int kOptCountAndBailoutReasonOffset =
       kCompilerHintsOffset + kIntSize;
-
   static const int kCountersOffset =
       kOptCountAndBailoutReasonOffset + kIntSize;
 
-  // Total size.
-  static const int kSize = kCountersOffset + kIntSize;
+  static const int kAstNodeCountOffset =
+      kCountersOffset + kIntSize;
+  static const int kProfilerTicksOffset =
+      kAstNodeCountOffset + kIntSize;
 
-#endif
+  // Total size.
+  static const int kSize = kProfilerTicksOffset + kIntSize;
 
-  // The construction counter for inobject slack tracking is stored in the
-  // most significant byte of compiler_hints which is otherwise unused.
-  // Its offset depends on the endian-ness of the architecture.
-#if __BYTE_ORDER == __LITTLE_ENDIAN
-  static const int kConstructionCountOffset = kCompilerHintsOffset + 3;
-#elif __BYTE_ORDER == __BIG_ENDIAN
-  static const int kConstructionCountOffset = kCompilerHintsOffset + 0;
-#else
-#error Unknown byte ordering
 #endif
 
   static const int kAlignedSize = POINTER_SIZE_ALIGN(kSize);
 
   typedef FixedBodyDescriptor<kNameOffset,
-                              kInitialMapOffset + kPointerSize,
+                              kFeedbackVectorOffset + kPointerSize,
                               kSize> BodyDescriptor;
 
   // Bit positions in start_position_and_type.
@@ -7485,10 +7761,8 @@ class SharedFunctionInfo: public HeapObject {
   enum CompilerHints {
     kAllowLazyCompilation,
     kAllowLazyCompilationWithoutContext,
-    kLiveObjectsMayExist,
     kOptimizationDisabled,
     kStrictModeFunction,
-    kExtendedModeFunction,
     kUsesArguments,
     kHasDuplicateParameters,
     kNative,
@@ -7497,11 +7771,10 @@ class SharedFunctionInfo: public HeapObject {
     kIsAnonymous,
     kNameShouldPrintAsAnonymous,
     kIsFunction,
-    kDontOptimize,
-    kDontInline,
     kDontCache,
     kDontFlush,
     kIsGenerator,
+    kIsArrow,
     kCompilerHintsCount  // Pseudo entry
   };
 
@@ -7533,26 +7806,18 @@ class SharedFunctionInfo: public HeapObject {
   static const int kStrictModeBitWithinByte =
       (kStrictModeFunction + kCompilerHintsSmiTagSize) % kBitsPerByte;
 
-  static const int kExtendedModeBitWithinByte =
-      (kExtendedModeFunction + kCompilerHintsSmiTagSize) % kBitsPerByte;
-
   static const int kNativeBitWithinByte =
       (kNative + kCompilerHintsSmiTagSize) % kBitsPerByte;
 
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if defined(V8_TARGET_LITTLE_ENDIAN)
   static const int kStrictModeByteOffset = kCompilerHintsOffset +
       (kStrictModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte;
-  static const int kExtendedModeByteOffset = kCompilerHintsOffset +
-      (kExtendedModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte;
   static const int kNativeByteOffset = kCompilerHintsOffset +
       (kNative + kCompilerHintsSmiTagSize) / kBitsPerByte;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif defined(V8_TARGET_BIG_ENDIAN)
   static const int kStrictModeByteOffset = kCompilerHintsOffset +
       (kCompilerHintsSize - 1) -
       ((kStrictModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte);
-  static const int kExtendedModeByteOffset = kCompilerHintsOffset +
-      (kCompilerHintsSize - 1) -
-      ((kExtendedModeFunction + kCompilerHintsSmiTagSize) / kBitsPerByte);
   static const int kNativeByteOffset = kCompilerHintsOffset +
       (kCompilerHintsSize - 1) -
       ((kNative + kCompilerHintsSmiTagSize) / kBitsPerByte);
@@ -7565,6 +7830,18 @@ class SharedFunctionInfo: public HeapObject {
 };
 
 
+// Printing support.
+struct SourceCodeOf {
+  explicit SourceCodeOf(SharedFunctionInfo* v, int max = -1)
+      : value(v), max_length(max) {}
+  const SharedFunctionInfo* value;
+  int max_length;
+};
+
+
+OStream& operator<<(OStream& os, const SourceCodeOf& v);
+
+
 class JSGeneratorObject: public JSObject {
  public:
   // [function]: The function corresponding to this generator object.
@@ -7581,19 +7858,21 @@ class JSGeneratorObject: public JSObject {
   // A positive offset indicates a suspended generator.  The special
   // kGeneratorExecuting and kGeneratorClosed values indicate that a generator
   // cannot be resumed.
-  inline int continuation();
+  inline int continuation() const;
   inline void set_continuation(int continuation);
+  inline bool is_closed();
+  inline bool is_executing();
+  inline bool is_suspended();
 
   // [operand_stack]: Saved operand stack.
   DECL_ACCESSORS(operand_stack, FixedArray)
 
   // [stack_handler_index]: Index of first stack handler in operand_stack, or -1
   // if the captured activation had no stack handler.
-  inline int stack_handler_index();
+  inline int stack_handler_index() const;
   inline void set_stack_handler_index(int stack_handler_index);
 
-  // Casting.
-  static inline JSGeneratorObject* cast(Object* obj);
+  DECLARE_CAST(JSGeneratorObject)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSGeneratorObject)
@@ -7617,7 +7896,7 @@ class JSGeneratorObject: public JSObject {
   enum ResumeMode { NEXT, THROW };
 
   // Yielding from a generator returns an object with the following inobject
-  // properties.  See Context::generator_result_map() for the map.
+  // properties.  See Context::iterator_result_map() for the map.
   static const int kResultValuePropertyIndex = 0;
   static const int kResultDonePropertyIndex = 1;
   static const int kResultPropertyCount = 2;
@@ -7641,8 +7920,7 @@ class JSModule: public JSObject {
   // [scope_info]: Scope info.
   DECL_ACCESSORS(scope_info, ScopeInfo)
 
-  // Casting.
-  static inline JSModule* cast(Object* obj);
+  DECLARE_CAST(JSModule)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSModule)
@@ -7671,6 +7949,7 @@ class JSFunction: public JSObject {
   // [context]: The context for this function.
   inline Context* context();
   inline void set_context(Object* context);
+  inline JSObject* global_proxy();
 
   // [code]: The generated code object for this function.  Executed
   // when the function is invoked, e.g. foo() or new foo(). See
@@ -7684,6 +7963,12 @@ class JSFunction: public JSObject {
   // Tells whether this function is builtin.
   inline bool IsBuiltin();
 
+  // Tells whether this function is defined in a native script.
+  inline bool IsFromNativeScript();
+
+  // Tells whether this function is defined in an extension script.
+  inline bool IsFromExtensionScript();
+
   // Tells whether or not the function needs arguments adaption.
   inline bool NeedsArgumentsAdaption();
 
@@ -7699,9 +7984,6 @@ class JSFunction: public JSObject {
   void MarkForConcurrentOptimization();
   void MarkInOptimizationQueue();
 
-  static bool CompileOptimized(Handle<JSFunction> function,
-                               ClearExceptionFlag flag);
-
   // Tells whether or not the function is already marked for lazy
   // recompilation.
   inline bool IsMarkedForOptimization();
@@ -7710,6 +7992,54 @@ class JSFunction: public JSObject {
   // Tells whether or not the function is on the concurrent recompilation queue.
   inline bool IsInOptimizationQueue();
 
+  // Inobject slack tracking is the way to reclaim unused inobject space.
+  //
+  // The instance size is initially determined by adding some slack to
+  // expected_nof_properties (to allow for a few extra properties added
+  // after the constructor). There is no guarantee that the extra space
+  // will not be wasted.
+  //
+  // Here is the algorithm to reclaim the unused inobject space:
+  // - Detect the first constructor call for this JSFunction.
+  //   When it happens enter the "in progress" state: initialize construction
+  //   counter in the initial_map and set the |done_inobject_slack_tracking|
+  //   flag.
+  // - While the tracking is in progress create objects filled with
+  //   one_pointer_filler_map instead of undefined_value. This way they can be
+  //   resized quickly and safely.
+  // - Once enough (kGenerousAllocationCount) objects have been created
+  //   compute the 'slack' (traverse the map transition tree starting from the
+  //   initial_map and find the lowest value of unused_property_fields).
+  // - Traverse the transition tree again and decrease the instance size
+  //   of every map. Existing objects will resize automatically (they are
+  //   filled with one_pointer_filler_map). All further allocations will
+  //   use the adjusted instance size.
+  // - SharedFunctionInfo's expected_nof_properties left unmodified since
+  //   allocations made using different closures could actually create different
+  //   kind of objects (see prototype inheritance pattern).
+  //
+  //  Important: inobject slack tracking is not attempted during the snapshot
+  //  creation.
+
+  static const int kGenerousAllocationCount = Map::ConstructionCount::kMax;
+  static const int kFinishSlackTracking     = 1;
+  static const int kNoSlackTracking         = 0;
+
+  // True if the initial_map is set and the object constructions countdown
+  // counter is not zero.
+  inline bool IsInobjectSlackTrackingInProgress();
+
+  // Starts the tracking.
+  // Initializes object constructions countdown counter in the initial map.
+  // IsInobjectSlackTrackingInProgress is normally true after this call,
+  // except when tracking have not been started (e.g. the map has no unused
+  // properties or the snapshot is being built).
+  void StartInobjectSlackTracking();
+
+  // Completes the tracking.
+  // IsInobjectSlackTrackingInProgress is false after this call.
+  void CompleteInobjectSlackTracking();
+
   // [literals_or_bindings]: Fixed array holding either
   // the materialized literals or the bindings of a bound function.
   //
@@ -7734,7 +8064,8 @@ class JSFunction: public JSObject {
 
   // The initial map for an object created by this constructor.
   inline Map* initial_map();
-  inline void set_initial_map(Map* value);
+  static void SetInitialMap(Handle<JSFunction> function, Handle<Map> map,
+                            Handle<Object> prototype);
   inline bool has_initial_map();
   static void EnsureHasInitialMap(Handle<JSFunction> function);
 
@@ -7753,7 +8084,7 @@ class JSFunction: public JSObject {
 
   // After prototype is removed, it will not be created when accessed, and
   // [[Construct]] from this function will not be allowed.
-  void RemovePrototype();
+  bool RemovePrototype();
   inline bool should_have_prototype();
 
   // Accessor for this function's initial map's [[class]]
@@ -7779,8 +8110,7 @@ class JSFunction: public JSObject {
   // Prints the name of the function using PrintF.
   void PrintName(FILE* out = stdout);
 
-  // Casting.
-  static inline JSFunction* cast(Object* obj);
+  DECLARE_CAST(JSFunction)
 
   // Iterates the objects, including code objects indirectly referenced
   // through pointers to the first instruction in the code object.
@@ -7840,10 +8170,12 @@ class JSGlobalProxy : public JSObject {
   // It is null value if this object is not used by any context.
   DECL_ACCESSORS(native_context, Object)
 
-  // Casting.
-  static inline JSGlobalProxy* cast(Object* obj);
+  // [hash]: The hash code property (undefined if not initialized yet).
+  DECL_ACCESSORS(hash, Object)
 
-  inline bool IsDetachedFrom(GlobalObject* global);
+  DECLARE_CAST(JSGlobalProxy)
+
+  inline bool IsDetachedFrom(GlobalObject* global) const;
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSGlobalProxy)
@@ -7851,7 +8183,8 @@ class JSGlobalProxy : public JSObject {
 
   // Layout description.
   static const int kNativeContextOffset = JSObject::kHeaderSize;
-  static const int kSize = kNativeContextOffset + kPointerSize;
+  static const int kHashOffset = kNativeContextOffset + kPointerSize;
+  static const int kSize = kHashOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSGlobalProxy);
@@ -7874,30 +8207,20 @@ class GlobalObject: public JSObject {
   // [global context]: the most recent (i.e. innermost) global context.
   DECL_ACCESSORS(global_context, Context)
 
-  // [global receiver]: the global receiver object of the context
-  DECL_ACCESSORS(global_receiver, JSObject)
+  // [global proxy]: the global proxy object of the context
+  DECL_ACCESSORS(global_proxy, JSObject)
 
   // Retrieve the property cell used to store a property.
   PropertyCell* GetPropertyCell(LookupResult* result);
 
-  // This is like GetProperty, but is used when you know the lookup won't fail
-  // by throwing an exception.  This is for the debug and builtins global
-  // objects, where it is known which properties can be expected to be present
-  // on the object.
-  Object* GetPropertyNoExceptionThrown(Name* key) {
-    Object* answer = GetProperty(key)->ToObjectUnchecked();
-    return answer;
-  }
-
-  // Casting.
-  static inline GlobalObject* cast(Object* obj);
+  DECLARE_CAST(GlobalObject)
 
   // Layout description.
   static const int kBuiltinsOffset = JSObject::kHeaderSize;
   static const int kNativeContextOffset = kBuiltinsOffset + kPointerSize;
   static const int kGlobalContextOffset = kNativeContextOffset + kPointerSize;
-  static const int kGlobalReceiverOffset = kGlobalContextOffset + kPointerSize;
-  static const int kHeaderSize = kGlobalReceiverOffset + kPointerSize;
+  static const int kGlobalProxyOffset = kGlobalContextOffset + kPointerSize;
+  static const int kHeaderSize = kGlobalProxyOffset + kPointerSize;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(GlobalObject);
@@ -7907,8 +8230,7 @@ class GlobalObject: public JSObject {
 // JavaScript global object.
 class JSGlobalObject: public GlobalObject {
  public:
-  // Casting.
-  static inline JSGlobalObject* cast(Object* obj);
+  DECLARE_CAST(JSGlobalObject)
 
   // Ensure that the global object has a cell for the given property name.
   static Handle<PropertyCell> EnsurePropertyCell(Handle<JSGlobalObject> global,
@@ -7940,8 +8262,7 @@ class JSBuiltinsObject: public GlobalObject {
   inline Code* javascript_builtin_code(Builtins::JavaScript id);
   inline void set_javascript_builtin_code(Builtins::JavaScript id, Code* value);
 
-  // Casting.
-  static inline JSBuiltinsObject* cast(Object* obj);
+  DECLARE_CAST(JSBuiltinsObject)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSBuiltinsObject)
@@ -7970,15 +8291,13 @@ class JSBuiltinsObject: public GlobalObject {
 };
 
 
-// Representation for JS Wrapper objects, String, Number, Float32x4, Int32x4,
-// Boolean, etc.
+// Representation for JS Wrapper objects, String, Number, Boolean, etc.
 class JSValue: public JSObject {
  public:
   // [value]: the object being wrapped.
   DECL_ACCESSORS(value, Object)
 
-  // Casting.
-  static inline JSValue* cast(Object* obj);
+  DECLARE_CAST(JSValue)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSValue)
@@ -8016,11 +8335,10 @@ class JSDate: public JSObject {
   // [sec]: caches seconds. Either undefined, smi, or NaN.
   DECL_ACCESSORS(sec, Object)
   // [cache stamp]: sample of the date cache stamp at the
-  // moment when local fields were cached.
+  // moment when chached fields were cached.
   DECL_ACCESSORS(cache_stamp, Object)
 
-  // Casting.
-  static inline JSDate* cast(Object* obj);
+  DECLARE_CAST(JSDate)
 
   // Returns the date field with the specified index.
   // See FieldIndex for the list of date fields.
@@ -8080,7 +8398,7 @@ class JSDate: public JSObject {
   Object* GetUTCField(FieldIndex index, double value, DateCache* date_cache);
 
   // Computes and caches the cacheable fields of the date.
-  inline void SetLocalFields(int64_t local_time_ms, DateCache* date_cache);
+  inline void SetCachedFields(int64_t local_time_ms, DateCache* date_cache);
 
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSDate);
@@ -8104,22 +8422,18 @@ class JSMessageObject: public JSObject {
   // [script]: the script from which the error message originated.
   DECL_ACCESSORS(script, Object)
 
-  // [stack_trace]: the stack trace for this error message.
-  DECL_ACCESSORS(stack_trace, Object)
-
   // [stack_frames]: an array of stack frames for this error object.
   DECL_ACCESSORS(stack_frames, Object)
 
   // [start_position]: the start position in the script for the error message.
-  inline int start_position();
+  inline int start_position() const;
   inline void set_start_position(int value);
 
   // [end_position]: the end position in the script for the error message.
-  inline int end_position();
+  inline int end_position() const;
   inline void set_end_position(int value);
 
-  // Casting.
-  static inline JSMessageObject* cast(Object* obj);
+  DECLARE_CAST(JSMessageObject)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSMessageObject)
@@ -8129,8 +8443,7 @@ class JSMessageObject: public JSObject {
   static const int kTypeOffset = JSObject::kHeaderSize;
   static const int kArgumentsOffset = kTypeOffset + kPointerSize;
   static const int kScriptOffset = kArgumentsOffset + kPointerSize;
-  static const int kStackTraceOffset = kScriptOffset + kPointerSize;
-  static const int kStackFramesOffset = kStackTraceOffset + kPointerSize;
+  static const int kStackFramesOffset = kScriptOffset + kPointerSize;
   static const int kStartPositionOffset = kStackFramesOffset + kPointerSize;
   static const int kEndPositionOffset = kStartPositionOffset + kPointerSize;
   static const int kSize = kEndPositionOffset + kPointerSize;
@@ -8204,7 +8517,7 @@ class JSRegExp: public JSObject {
     }
   }
 
-  static inline JSRegExp* cast(Object* obj);
+  DECLARE_CAST(JSRegExp)
 
   // Dispatched behavior.
   DECLARE_VERIFIER(JSRegExp)
@@ -8294,41 +8607,35 @@ class CompilationCacheShape : public BaseShape<HashTableKey*> {
     return key->HashForObject(object);
   }
 
-  MUST_USE_RESULT static MaybeObject* AsObject(Heap* heap,
-                                               HashTableKey* key) {
-    return key->AsObject(heap);
-  }
+  static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
 
   static const int kPrefixSize = 0;
   static const int kEntrySize = 2;
 };
 
 
-class CompilationCacheTable: public HashTable<CompilationCacheShape,
+class CompilationCacheTable: public HashTable<CompilationCacheTable,
+                                              CompilationCacheShape,
                                               HashTableKey*> {
  public:
   // Find cached value for a string key, otherwise return null.
-  Object* Lookup(String* src, Context* context);
-  Object* LookupEval(String* src,
-                     Context* context,
-                     LanguageMode language_mode,
-                     int scope_position);
-  Object* LookupRegExp(String* source, JSRegExp::Flags flags);
-  MUST_USE_RESULT MaybeObject* Put(String* src,
-                                   Context* context,
-                                   Object* value);
-  MUST_USE_RESULT MaybeObject* PutEval(String* src,
-                                       Context* context,
-                                       SharedFunctionInfo* value,
-                                       int scope_position);
-  MUST_USE_RESULT MaybeObject* PutRegExp(String* src,
-                                         JSRegExp::Flags flags,
-                                         FixedArray* value);
-
-  // Remove given value from cache.
+  Handle<Object> Lookup(Handle<String> src, Handle<Context> context);
+  Handle<Object> LookupEval(Handle<String> src, Handle<Context> context,
+                     StrictMode strict_mode, int scope_position);
+  Handle<Object> LookupRegExp(Handle<String> source, JSRegExp::Flags flags);
+  static Handle<CompilationCacheTable> Put(
+      Handle<CompilationCacheTable> cache, Handle<String> src,
+      Handle<Context> context, Handle<Object> value);
+  static Handle<CompilationCacheTable> PutEval(
+      Handle<CompilationCacheTable> cache, Handle<String> src,
+      Handle<Context> context, Handle<SharedFunctionInfo> value,
+      int scope_position);
+  static Handle<CompilationCacheTable> PutRegExp(
+      Handle<CompilationCacheTable> cache, Handle<String> src,
+      JSRegExp::Flags flags, Handle<FixedArray> value);
   void Remove(Object* value);
 
-  static inline CompilationCacheTable* cast(Object* obj);
+  DECLARE_CAST(CompilationCacheTable)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheTable);
@@ -8341,7 +8648,8 @@ class CodeCache: public Struct {
   DECL_ACCESSORS(normal_type_cache, Object)
 
   // Add the code object to the cache.
-  MUST_USE_RESULT MaybeObject* Update(Name* name, Code* code);
+  static void Update(
+      Handle<CodeCache> cache, Handle<Name> name, Handle<Code> code);
 
   // Lookup code object in the cache. Returns code object if found and undefined
   // if not.
@@ -8356,7 +8664,7 @@ class CodeCache: public Struct {
   // Remove an object from the cache with the provided internal index.
   void RemoveByIndex(Object* name, Code* code, int index);
 
-  static inline CodeCache* cast(Object* obj);
+  DECLARE_CAST(CodeCache)
 
   // Dispatched behavior.
   DECLARE_PRINTER(CodeCache)
@@ -8368,8 +8676,10 @@ class CodeCache: public Struct {
   static const int kSize = kNormalTypeCacheOffset + kPointerSize;
 
  private:
-  MUST_USE_RESULT MaybeObject* UpdateDefaultCache(Name* name, Code* code);
-  MUST_USE_RESULT MaybeObject* UpdateNormalTypeCache(Name* name, Code* code);
+  static void UpdateDefaultCache(
+      Handle<CodeCache> code_cache, Handle<Name> name, Handle<Code> code);
+  static void UpdateNormalTypeCache(
+      Handle<CodeCache> code_cache, Handle<Name> name, Handle<Code> code);
   Object* LookupDefaultCache(Name* name, Code::Flags flags);
   Object* LookupNormalTypeCache(Name* name, Code::Flags flags);
 
@@ -8397,26 +8707,27 @@ class CodeCacheHashTableShape : public BaseShape<HashTableKey*> {
     return key->HashForObject(object);
   }
 
-  MUST_USE_RESULT static MaybeObject* AsObject(Heap* heap,
-                                               HashTableKey* key) {
-    return key->AsObject(heap);
-  }
+  static inline Handle<Object> AsHandle(Isolate* isolate, HashTableKey* key);
 
   static const int kPrefixSize = 0;
   static const int kEntrySize = 2;
 };
 
 
-class CodeCacheHashTable: public HashTable<CodeCacheHashTableShape,
+class CodeCacheHashTable: public HashTable<CodeCacheHashTable,
+                                           CodeCacheHashTableShape,
                                            HashTableKey*> {
  public:
   Object* Lookup(Name* name, Code::Flags flags);
-  MUST_USE_RESULT MaybeObject* Put(Name* name, Code* code);
+  static Handle<CodeCacheHashTable> Put(
+      Handle<CodeCacheHashTable> table,
+      Handle<Name> name,
+      Handle<Code> code);
 
   int GetIndex(Name* name, Code::Flags flags);
   void RemoveByIndex(int index);
 
-  static inline CodeCacheHashTable* cast(Object* obj);
+  DECLARE_CAST(CodeCacheHashTable)
 
   // Initial size of the fixed array backing the hash table.
   static const int kInitialSize = 64;
@@ -8435,14 +8746,11 @@ class PolymorphicCodeCache: public Struct {
                      Code::Flags flags,
                      Handle<Code> code);
 
-  MUST_USE_RESULT MaybeObject* Update(MapHandleList* maps,
-                                      Code::Flags flags,
-                                      Code* code);
 
   // Returns an undefined value if the entry is not found.
   Handle<Object> Lookup(MapHandleList* maps, Code::Flags flags);
 
-  static inline PolymorphicCodeCache* cast(Object* obj);
+  DECLARE_CAST(PolymorphicCodeCache)
 
   // Dispatched behavior.
   DECLARE_PRINTER(PolymorphicCodeCache)
@@ -8457,15 +8765,19 @@ class PolymorphicCodeCache: public Struct {
 
 
 class PolymorphicCodeCacheHashTable
-    : public HashTable<CodeCacheHashTableShape, HashTableKey*> {
+    : public HashTable<PolymorphicCodeCacheHashTable,
+                       CodeCacheHashTableShape,
+                       HashTableKey*> {
  public:
   Object* Lookup(MapHandleList* maps, int code_kind);
 
-  MUST_USE_RESULT MaybeObject* Put(MapHandleList* maps,
-                                   int code_kind,
-                                   Code* code);
+  static Handle<PolymorphicCodeCacheHashTable> Put(
+      Handle<PolymorphicCodeCacheHashTable> hash_table,
+      MapHandleList* maps,
+      int code_kind,
+      Handle<Code> code);
 
-  static inline PolymorphicCodeCacheHashTable* cast(Object* obj);
+  DECLARE_CAST(PolymorphicCodeCacheHashTable)
 
   static const int kInitialSize = 64;
  private:
@@ -8479,7 +8791,10 @@ class TypeFeedbackInfo: public Struct {
   inline void set_ic_total_count(int count);
 
   inline int ic_with_type_info_count();
-  inline void change_ic_with_type_info_count(int count);
+  inline void change_ic_with_type_info_count(int delta);
+
+  inline int ic_generic_count();
+  inline void change_ic_generic_count(int delta);
 
   inline void initialize_storage();
 
@@ -8489,9 +8804,8 @@ class TypeFeedbackInfo: public Struct {
   inline void set_inlined_type_change_checksum(int checksum);
   inline bool matches_inlined_type_change_checksum(int checksum);
 
-  DECL_ACCESSORS(type_feedback_cells, TypeFeedbackCells)
 
-  static inline TypeFeedbackInfo* cast(Object* obj);
+  DECLARE_CAST(TypeFeedbackInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(TypeFeedbackInfo)
@@ -8499,8 +8813,24 @@ class TypeFeedbackInfo: public Struct {
 
   static const int kStorage1Offset = HeapObject::kHeaderSize;
   static const int kStorage2Offset = kStorage1Offset + kPointerSize;
-  static const int kTypeFeedbackCellsOffset = kStorage2Offset + kPointerSize;
-  static const int kSize = kTypeFeedbackCellsOffset + kPointerSize;
+  static const int kStorage3Offset = kStorage2Offset + kPointerSize;
+  static const int kSize = kStorage3Offset + kPointerSize;
+
+  // TODO(mvstanton): move these sentinel declarations to shared function info.
+  // The object that indicates an uninitialized cache.
+  static inline Handle<Object> UninitializedSentinel(Isolate* isolate);
+
+  // The object that indicates a megamorphic state.
+  static inline Handle<Object> MegamorphicSentinel(Isolate* isolate);
+
+  // The object that indicates a monomorphic state of Array with
+  // ElementsKind
+  static inline Handle<Object> MonomorphicArraySentinel(Isolate* isolate,
+      ElementsKind elements_kind);
+
+  // A raw version of the uninitialized sentinel that's safe to read during
+  // garbage collection (e.g., for patching the cache).
+  static inline Object* RawUninitializedSentinel(Heap* heap);
 
  private:
   static const int kTypeChangeChecksumBits = 7;
@@ -8537,11 +8867,14 @@ class AllocationSite: public Struct {
   enum PretenureDecision {
     kUndecided = 0,
     kDontTenure = 1,
-    kTenure = 2,
-    kZombie = 3,
+    kMaybeTenure = 2,
+    kTenure = 3,
+    kZombie = 4,
     kLastPretenureDecisionValue = kZombie
   };
 
+  const char* PretenureDecisionName(PretenureDecision decision);
+
   DECL_ACCESSORS(transition_info, Object)
   // nested_site threads a list of sites that represent nested literals
   // walked in a particular order. So [[1, 2], 1, 2] will have one
@@ -8563,8 +8896,9 @@ class AllocationSite: public Struct {
   class DoNotInlineBit:         public BitField<bool,         29,  1> {};
 
   // Bitfields for pretenure_data
-  class MementoFoundCountBits:  public BitField<int,          0, 28> {};
-  class PretenureDecisionBits:  public BitField<PretenureDecision, 28, 2> {};
+  class MementoFoundCountBits:  public BitField<int,               0, 26> {};
+  class PretenureDecisionBits:  public BitField<PretenureDecision, 26, 3> {};
+  class DeoptDependentCodeBit:  public BitField<bool,              29, 1> {};
   STATIC_ASSERT(PretenureDecisionBits::kMax >= kLastPretenureDecisionValue);
 
   // Increments the mementos found counter and returns true when the first
@@ -8589,6 +8923,18 @@ class AllocationSite: public Struct {
         SKIP_WRITE_BARRIER);
   }
 
+  bool deopt_dependent_code() {
+    int value = pretenure_data()->value();
+    return DeoptDependentCodeBit::decode(value);
+  }
+
+  void set_deopt_dependent_code(bool deopt) {
+    int value = pretenure_data()->value();
+    set_pretenure_data(
+        Smi::FromInt(DeoptDependentCodeBit::update(value, deopt)),
+        SKIP_WRITE_BARRIER);
+  }
+
   int memento_found_count() {
     int value = pretenure_data()->value();
     return MementoFoundCountBits::decode(value);
@@ -8612,12 +8958,20 @@ class AllocationSite: public Struct {
     return pretenure_decision() == kZombie;
   }
 
+  bool IsMaybeTenure() {
+    return pretenure_decision() == kMaybeTenure;
+  }
+
   inline void MarkZombie();
 
-  inline bool DigestPretenuringFeedback();
+  inline bool MakePretenureDecision(PretenureDecision current_decision,
+                                    double ratio,
+                                    bool maximum_size_scavenge);
+
+  inline bool DigestPretenuringFeedback(bool maximum_size_scavenge);
 
   ElementsKind GetElementsKind() {
-    ASSERT(!SitePointsToLiteral());
+    DCHECK(!SitePointsToLiteral());
     int value = Smi::cast(transition_info())->value();
     return ElementsKindBits::decode(value);
   }
@@ -8646,7 +9000,8 @@ class AllocationSite: public Struct {
     return transition_info()->IsJSArray() || transition_info()->IsJSObject();
   }
 
-  MaybeObject* DigestTransitionFeedback(ElementsKind to_kind);
+  static void DigestTransitionFeedback(Handle<AllocationSite> site,
+                                       ElementsKind to_kind);
 
   enum Reason {
     TENURING,
@@ -8660,7 +9015,7 @@ class AllocationSite: public Struct {
   DECLARE_PRINTER(AllocationSite)
   DECLARE_VERIFIER(AllocationSite)
 
-  static inline AllocationSite* cast(Object* obj);
+  DECLARE_CAST(AllocationSite)
   static inline AllocationSiteMode GetMode(
       ElementsKind boilerplate_elements_kind);
   static inline AllocationSiteMode GetMode(ElementsKind from, ElementsKind to);
@@ -8708,22 +9063,22 @@ class AllocationMemento: public Struct {
         !AllocationSite::cast(allocation_site())->IsZombie();
   }
   AllocationSite* GetAllocationSite() {
-    ASSERT(IsValid());
+    DCHECK(IsValid());
     return AllocationSite::cast(allocation_site());
   }
 
   DECLARE_PRINTER(AllocationMemento)
   DECLARE_VERIFIER(AllocationMemento)
 
-  static inline AllocationMemento* cast(Object* obj);
+  DECLARE_CAST(AllocationMemento)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(AllocationMemento);
 };
 
 
-// Representation of a slow alias as part of a non-strict arguments objects.
-// For fast aliases (if HasNonStrictArgumentsElements()):
+// Representation of a slow alias as part of a sloppy arguments objects.
+// For fast aliases (if HasSloppyArgumentsElements()):
 // - the parameter map contains an index into the context
 // - all attributes of the element have default values
 // For slow aliases (if HasDictionaryArgumentsElements()):
@@ -8732,10 +9087,10 @@ class AllocationMemento: public Struct {
 // - all attributes are available as part if the property details
 class AliasedArgumentsEntry: public Struct {
  public:
-  inline int aliased_context_slot();
+  inline int aliased_context_slot() const;
   inline void set_aliased_context_slot(int count);
 
-  static inline AliasedArgumentsEntry* cast(Object* obj);
+  DECLARE_CAST(AliasedArgumentsEntry)
 
   // Dispatched behavior.
   DECLARE_PRINTER(AliasedArgumentsEntry)
@@ -8807,6 +9162,19 @@ class StringHasher {
 };
 
 
+class IteratingStringHasher : public StringHasher {
+ public:
+  static inline uint32_t Hash(String* string, uint32_t seed);
+  inline void VisitOneByteString(const uint8_t* chars, int length);
+  inline void VisitTwoByteString(const uint16_t* chars, int length);
+
+ private:
+  inline IteratingStringHasher(int len, uint32_t seed)
+      : StringHasher(len, seed) {}
+  DISALLOW_COPY_AND_ASSIGN(IteratingStringHasher);
+};
+
+
 // The characteristics of a string are stored in its map.  Retrieving these
 // few bits of information is moderately expensive, involving two memory
 // loads where the second is dependent on the first.  To improve efficiency
@@ -8820,7 +9188,7 @@ class StringHasher {
 // concrete performance benefit at that particular point in the code.
 class StringShape BASE_EMBEDDED {
  public:
-  inline explicit StringShape(String* s);
+  inline explicit StringShape(const String* s);
   inline explicit StringShape(Map* s);
   inline explicit StringShape(InstanceType t);
   inline bool IsSequential();
@@ -8872,14 +9240,12 @@ class Name: public HeapObject {
 
   // Equality operations.
   inline bool Equals(Name* other);
+  inline static bool Equals(Handle<Name> one, Handle<Name> two);
 
   // Conversion.
   inline bool AsArrayIndex(uint32_t* index);
 
-  // Casting.
-  static inline Name* cast(Object* obj);
-
-  bool IsCacheable(Isolate* isolate);
+  DECLARE_CAST(Name)
 
   DECLARE_PRINTER(Name)
 
@@ -8913,23 +9279,22 @@ class Name: public HeapObject {
   static const int kArrayIndexLengthBits =
       kBitsPerInt - kArrayIndexValueBits - kNofHashBitFields;
 
-  STATIC_CHECK((kArrayIndexLengthBits > 0));
-
-  static const int kArrayIndexHashLengthShift =
-      kArrayIndexValueBits + kNofHashBitFields;
+  STATIC_ASSERT((kArrayIndexLengthBits > 0));
 
-  static const int kArrayIndexHashMask = (1 << kArrayIndexHashLengthShift) - 1;
-
-  static const int kArrayIndexValueMask =
-      ((1 << kArrayIndexValueBits) - 1) << kHashShift;
+  class ArrayIndexValueBits : public BitField<unsigned int, kNofHashBitFields,
+      kArrayIndexValueBits> {};  // NOLINT
+  class ArrayIndexLengthBits : public BitField<unsigned int,
+      kNofHashBitFields + kArrayIndexValueBits,
+      kArrayIndexLengthBits> {};  // NOLINT
 
   // Check that kMaxCachedArrayIndexLength + 1 is a power of two so we
   // could use a mask to test if the length of string is less than or equal to
   // kMaxCachedArrayIndexLength.
-  STATIC_CHECK(IS_POWER_OF_TWO(kMaxCachedArrayIndexLength + 1));
+  STATIC_ASSERT(IS_POWER_OF_TWO(kMaxCachedArrayIndexLength + 1));
 
-  static const int kContainsCachedArrayIndexMask =
-      (~kMaxCachedArrayIndexLength << kArrayIndexHashLengthShift) |
+  static const unsigned int kContainsCachedArrayIndexMask =
+      (~static_cast<unsigned>(kMaxCachedArrayIndexLength)
+       << ArrayIndexLengthBits::kShift) |
       kIsNotArrayIndexMask;
 
   // Value of empty hash field indicating that the hash is not computed.
@@ -8955,8 +9320,7 @@ class Symbol: public Name {
   // [is_private]: whether this is a private symbol.
   DECL_BOOLEAN_ACCESSORS(is_private)
 
-  // Casting.
-  static inline Symbol* cast(Object* obj);
+  DECLARE_CAST(Symbol)
 
   // Dispatched behavior.
   DECLARE_PRINTER(Symbol)
@@ -8990,6 +9354,34 @@ class String: public Name {
  public:
   enum Encoding { ONE_BYTE_ENCODING, TWO_BYTE_ENCODING };
 
+  // Array index strings this short can keep their index in the hash field.
+  static const int kMaxCachedArrayIndexLength = 7;
+
+  // For strings which are array indexes the hash value has the string length
+  // mixed into the hash, mainly to avoid a hash value of zero which would be
+  // the case for the string '0'. 24 bits are used for the array index value.
+  static const int kArrayIndexValueBits = 24;
+  static const int kArrayIndexLengthBits =
+      kBitsPerInt - kArrayIndexValueBits - kNofHashBitFields;
+
+  STATIC_ASSERT((kArrayIndexLengthBits > 0));
+
+  class ArrayIndexValueBits : public BitField<unsigned int, kNofHashBitFields,
+      kArrayIndexValueBits> {};  // NOLINT
+  class ArrayIndexLengthBits : public BitField<unsigned int,
+      kNofHashBitFields + kArrayIndexValueBits,
+      kArrayIndexLengthBits> {};  // NOLINT
+
+  // Check that kMaxCachedArrayIndexLength + 1 is a power of two so we
+  // could use a mask to test if the length of string is less than or equal to
+  // kMaxCachedArrayIndexLength.
+  STATIC_ASSERT(IS_POWER_OF_TWO(kMaxCachedArrayIndexLength + 1));
+
+  static const unsigned int kContainsCachedArrayIndexMask =
+      (~static_cast<unsigned>(kMaxCachedArrayIndexLength)
+       << ArrayIndexLengthBits::kShift) |
+      kIsNotArrayIndexMask;
+
   // Representation of the flat content of a String.
   // A non-flat string doesn't have flat content.
   // A flat string has content that's encoded as a sequence of either
@@ -9007,44 +9399,58 @@ class String: public Name {
     // Return the one byte content of the string. Only use if IsAscii() returns
     // true.
     Vector<const uint8_t> ToOneByteVector() {
-      ASSERT_EQ(ASCII, state_);
-      return buffer_;
+      DCHECK_EQ(ASCII, state_);
+      return Vector<const uint8_t>(onebyte_start, length_);
     }
     // Return the two-byte content of the string. Only use if IsTwoByte()
     // returns true.
     Vector<const uc16> ToUC16Vector() {
-      ASSERT_EQ(TWO_BYTE, state_);
-      return Vector<const uc16>::cast(buffer_);
+      DCHECK_EQ(TWO_BYTE, state_);
+      return Vector<const uc16>(twobyte_start, length_);
+    }
+
+    uc16 Get(int i) {
+      DCHECK(i < length_);
+      DCHECK(state_ != NON_FLAT);
+      if (state_ == ASCII) return onebyte_start[i];
+      return twobyte_start[i];
     }
 
    private:
     enum State { NON_FLAT, ASCII, TWO_BYTE };
 
     // Constructors only used by String::GetFlatContent().
-    explicit FlatContent(Vector<const uint8_t> chars)
-        : buffer_(chars),
-          state_(ASCII) { }
-    explicit FlatContent(Vector<const uc16> chars)
-        : buffer_(Vector<const byte>::cast(chars)),
-          state_(TWO_BYTE) { }
-    FlatContent() : buffer_(), state_(NON_FLAT) { }
-
-    Vector<const uint8_t> buffer_;
+    explicit FlatContent(const uint8_t* start, int length)
+        : onebyte_start(start), length_(length), state_(ASCII) { }
+    explicit FlatContent(const uc16* start, int length)
+        : twobyte_start(start), length_(length), state_(TWO_BYTE) { }
+    FlatContent() : onebyte_start(NULL), length_(0), state_(NON_FLAT) { }
+
+    union {
+      const uint8_t* onebyte_start;
+      const uc16* twobyte_start;
+    };
+    int length_;
     State state_;
 
     friend class String;
   };
 
   // Get and set the length of the string.
-  inline int length();
+  inline int length() const;
   inline void set_length(int value);
 
+  // Get and set the length of the string using acquire loads and release
+  // stores.
+  inline int synchronized_length() const;
+  inline void synchronized_set_length(int value);
+
   // Returns whether this string has only ASCII chars, i.e. all of them can
   // be ASCII encoded.  This might be the case even if the string is
   // two-byte.  Such strings may appear when the embedder prefers
   // two-byte external representations even for ASCII data.
-  inline bool IsOneByteRepresentation();
-  inline bool IsTwoByteRepresentation();
+  inline bool IsOneByteRepresentation() const;
+  inline bool IsTwoByteRepresentation() const;
 
   // Cons and slices have an encoding flag that may not represent the actual
   // encoding of the underlying string.  This is taken into account here.
@@ -9062,7 +9468,7 @@ class String: public Name {
   // to this method are not efficient unless the string is flat.
   INLINE(uint16_t Get(int index));
 
-  // Try to flatten the string.  Checks first inline to see if it is
+  // Flattens the string.  Checks first inline to see if it is
   // necessary.  Does nothing if the string is not a cons string.
   // Flattening allocates a sequential string with the same data as
   // the given string and mutates the cons string to a degenerate
@@ -9074,15 +9480,9 @@ class String: public Name {
   //
   // Degenerate cons strings are handled specially by the garbage
   // collector (see IsShortcutCandidate).
-  //
-  // Use FlattenString from Handles.cc to flatten even in case an
-  // allocation failure happens.
-  inline MaybeObject* TryFlatten(PretenureFlag pretenure = NOT_TENURED);
 
-  // Convenience function.  Has exactly the same behavior as
-  // TryFlatten(), except in the case of failure returns the original
-  // string.
-  inline String* TryFlattenGetString(PretenureFlag pretenure = NOT_TENURED);
+  static inline Handle<String> Flatten(Handle<String> string,
+                                       PretenureFlag pretenure = NOT_TENURED);
 
   // Tries to return the content of a flat string as a structure holding either
   // a flat vector of char or of uc16.
@@ -9101,6 +9501,7 @@ class String: public Name {
 
   // String equality operations.
   inline bool Equals(String* other);
+  inline static bool Equals(Handle<String> one, Handle<String> two);
   bool IsUtf8EqualTo(Vector<const char> str, bool allow_prefix_match = false);
   bool IsOneByteEqualTo(Vector<const uint8_t> str);
   bool IsTwoByteEqualTo(Vector<const uc16> str);
@@ -9141,8 +9542,7 @@ class String: public Name {
   // Conversion.
   inline bool AsArrayIndex(uint32_t* index);
 
-  // Casting.
-  static inline String* cast(Object* obj);
+  DECLARE_CAST(String)
 
   void PrintOn(FILE* out);
 
@@ -9151,6 +9551,7 @@ class String: public Name {
 
   // Dispatched behavior.
   void StringShortPrint(StringStream* accumulator);
+  void PrintUC16(OStream& os, int start = 0, int end = -1);  // NOLINT
 #ifdef OBJECT_PRINT
   char* ToAsciiArray();
 #endif
@@ -9166,18 +9567,19 @@ class String: public Name {
   // Maximum number of characters to consider when trying to convert a string
   // value into an array index.
   static const int kMaxArrayIndexSize = 10;
-  STATIC_CHECK(kMaxArrayIndexSize < (1 << kArrayIndexLengthBits));
+  STATIC_ASSERT(kMaxArrayIndexSize < (1 << kArrayIndexLengthBits));
 
   // Max char codes.
   static const int32_t kMaxOneByteCharCode = unibrow::Latin1::kMaxChar;
   static const uint32_t kMaxOneByteCharCodeU = unibrow::Latin1::kMaxChar;
   static const int kMaxUtf16CodeUnit = 0xffff;
+  static const uint32_t kMaxUtf16CodeUnitU = kMaxUtf16CodeUnit;
 
   // Value of hash field containing computed hash equal to zero.
   static const int kEmptyStringHash = kIsNotArrayIndexMask;
 
   // Maximal string length.
-  static const int kMaxLength = (1 << (32 - 2)) - 1;
+  static const int kMaxLength = (1 << 28) - 16;
 
   // Max length for computing hash. For strings longer than this limit the
   // string length is used as the hash value.
@@ -9203,7 +9605,7 @@ class String: public Name {
     const char* start = chars;
     const char* limit = chars + length;
 #ifdef V8_HOST_CAN_READ_UNALIGNED
-    ASSERT(unibrow::Utf8::kMaxOneByteChar == 0x7F);
+    DCHECK(unibrow::Utf8::kMaxOneByteChar == 0x7F);
     const uintptr_t non_ascii_mask = kUintptrAllBitsSet / 0xFF * 0x80;
     while (chars + sizeof(uintptr_t) <= limit) {
       if (*reinterpret_cast<const uintptr_t*>(chars) & non_ascii_mask) {
@@ -9244,42 +9646,32 @@ class String: public Name {
     return NonOneByteStart(chars, length) >= length;
   }
 
-  // TODO(dcarney): Replace all instances of this with VisitFlat.
-  template<class Visitor, class ConsOp>
-  static inline void Visit(String* string,
-                           unsigned offset,
-                           Visitor& visitor,
-                           ConsOp& cons_op,
-                           int32_t type,
-                           unsigned length);
-
   template<class Visitor>
   static inline ConsString* VisitFlat(Visitor* visitor,
                                       String* string,
-                                      int offset,
-                                      int length,
-                                      int32_t type);
+                                      int offset = 0);
 
-  template<class Visitor>
-  static inline ConsString* VisitFlat(Visitor* visitor,
-                                      String* string,
-                                      int offset = 0) {
-    int32_t type = string->map()->instance_type();
-    return VisitFlat(visitor, string, offset, string->length(), type);
-  }
+  static Handle<FixedArray> CalculateLineEnds(Handle<String> string,
+                                              bool include_ending_line);
+
+  // Use the hash field to forward to the canonical internalized string
+  // when deserializing an internalized string.
+  inline void SetForwardedInternalizedString(String* string);
+  inline String* GetForwardedInternalizedString();
 
  private:
   friend class Name;
+  friend class StringTableInsertionKey;
 
-  // Try to flatten the top level ConsString that is hiding behind this
-  // string.  This is a no-op unless the string is a ConsString.  Flatten
-  // mutates the ConsString and might return a failure.
-  MUST_USE_RESULT MaybeObject* SlowTryFlatten(PretenureFlag pretenure);
+  static Handle<String> SlowFlatten(Handle<ConsString> cons,
+                                    PretenureFlag tenure);
 
   // 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);
 
+  static bool SlowEquals(Handle<String> one, Handle<String> two);
+
   // Slow case of AsArrayIndex.
   bool SlowAsArrayIndex(uint32_t* index);
 
@@ -9293,8 +9685,7 @@ class String: public Name {
 // The SeqString abstract class captures sequential string values.
 class SeqString: public String {
  public:
-  // Casting.
-  static inline SeqString* cast(Object* obj);
+  DECLARE_CAST(SeqString)
 
   // Layout description.
   static const int kHeaderSize = String::kSize;
@@ -9324,8 +9715,7 @@ class SeqOneByteString: public SeqString {
 
   inline uint8_t* GetChars();
 
-  // Casting
-  static inline SeqOneByteString* cast(Object* obj);
+  DECLARE_CAST(SeqOneByteString)
 
   // Garbage collection support.  This method is called by the
   // garbage collector to compute the actual size of an AsciiString
@@ -9339,9 +9729,7 @@ class SeqOneByteString: public SeqString {
 
   // Maximal memory usage for a single sequential ASCII string.
   static const int kMaxSize = 512 * MB - 1;
-  // Maximal length of a single sequential ASCII string.
-  // Q.v. String::kMaxLength which is the maximal size of concatenated strings.
-  static const int kMaxLength = (kMaxSize - kHeaderSize);
+  STATIC_ASSERT((kMaxSize - kHeaderSize) >= String::kMaxLength);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(SeqOneByteString);
@@ -9366,8 +9754,7 @@ class SeqTwoByteString: public SeqString {
   // For regexp code.
   const uint16_t* SeqTwoByteStringGetData(unsigned start);
 
-  // Casting
-  static inline SeqTwoByteString* cast(Object* obj);
+  DECLARE_CAST(SeqTwoByteString)
 
   // Garbage collection support.  This method is called by the
   // garbage collector to compute the actual size of a TwoByteString
@@ -9381,9 +9768,8 @@ class SeqTwoByteString: public SeqString {
 
   // Maximal memory usage for a single sequential two-byte string.
   static const int kMaxSize = 512 * MB - 1;
-  // Maximal length of a single sequential two-byte string.
-  // Q.v. String::kMaxLength which is the maximal size of concatenated strings.
-  static const int kMaxLength = (kMaxSize - kHeaderSize) / sizeof(uint16_t);
+  STATIC_ASSERT(static_cast<int>((kMaxSize - kHeaderSize)/sizeof(uint16_t)) >=
+               String::kMaxLength);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(SeqTwoByteString);
@@ -9419,8 +9805,7 @@ class ConsString: public String {
   // Dispatched behavior.
   uint16_t ConsStringGet(int index);
 
-  // Casting.
-  static inline ConsString* cast(Object* obj);
+  DECLARE_CAST(ConsString)
 
   // Layout description.
   static const int kFirstOffset = POINTER_SIZE_ALIGN(String::kSize);
@@ -9457,14 +9842,13 @@ class SlicedString: public String {
   inline String* parent();
   inline void set_parent(String* parent,
                          WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-  inline int offset();
+  inline int offset() const;
   inline void set_offset(int offset);
 
   // Dispatched behavior.
   uint16_t SlicedStringGet(int index);
 
-  // Casting.
-  static inline SlicedString* cast(Object* obj);
+  DECLARE_CAST(SlicedString)
 
   // Layout description.
   static const int kParentOffset = POINTER_SIZE_ALIGN(String::kSize);
@@ -9496,8 +9880,7 @@ class SlicedString: public String {
 // API.  Therefore, ExternalStrings should not be used internally.
 class ExternalString: public String {
  public:
-  // Casting
-  static inline ExternalString* cast(Object* obj);
+  DECLARE_CAST(ExternalString)
 
   // Layout description.
   static const int kResourceOffset = POINTER_SIZE_ALIGN(String::kSize);
@@ -9511,7 +9894,7 @@ class ExternalString: public String {
   // Return whether external string is short (data pointer is not cached).
   inline bool is_short();
 
-  STATIC_CHECK(kResourceOffset == Internals::kStringResourceOffset);
+  STATIC_ASSERT(kResourceOffset == Internals::kStringResourceOffset);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalString);
@@ -9541,8 +9924,7 @@ class ExternalAsciiString: public ExternalString {
   // Dispatched behavior.
   inline uint16_t ExternalAsciiStringGet(int index);
 
-  // Casting.
-  static inline ExternalAsciiString* cast(Object* obj);
+  DECLARE_CAST(ExternalAsciiString)
 
   // Garbage collection support.
   inline void ExternalAsciiStringIterateBody(ObjectVisitor* v);
@@ -9581,8 +9963,7 @@ class ExternalTwoByteString: public ExternalString {
   // For regexp code.
   inline const uint16_t* ExternalTwoByteStringGetData(unsigned start);
 
-  // Casting.
-  static inline ExternalTwoByteString* cast(Object* obj);
+  DECLARE_CAST(ExternalTwoByteString)
 
   // Garbage collection support.
   inline void ExternalTwoByteStringIterateBody(ObjectVisitor* v);
@@ -9652,57 +10033,64 @@ class ConsStringNullOp {
 // This maintains an off-stack representation of the stack frames required
 // to traverse a ConsString, allowing an entirely iterative and restartable
 // traversal of the entire string
-// Note: this class is not GC-safe.
 class ConsStringIteratorOp {
  public:
   inline ConsStringIteratorOp() {}
-  String* Operate(String* string,
-                  unsigned* offset_out,
-                  int32_t* type_out,
-                  unsigned* length_out);
-  inline String* ContinueOperation(int32_t* type_out, unsigned* length_out);
-  inline void Reset();
-  inline bool HasMore();
+  inline explicit ConsStringIteratorOp(ConsString* cons_string,
+                                       int offset = 0) {
+    Reset(cons_string, offset);
+  }
+  inline void Reset(ConsString* cons_string, int offset = 0) {
+    depth_ = 0;
+    // Next will always return NULL.
+    if (cons_string == NULL) return;
+    Initialize(cons_string, offset);
+  }
+  // Returns NULL when complete.
+  inline String* Next(int* offset_out) {
+    *offset_out = 0;
+    if (depth_ == 0) return NULL;
+    return Continue(offset_out);
+  }
 
  private:
-  // TODO(dcarney): Templatize this out for different stack sizes.
-  static const unsigned kStackSize = 32;
+  static const int kStackSize = 32;
   // Use a mask instead of doing modulo operations for stack wrapping.
-  static const unsigned kDepthMask = kStackSize-1;
+  static const int kDepthMask = kStackSize-1;
   STATIC_ASSERT(IS_POWER_OF_TWO(kStackSize));
-  static inline unsigned OffsetForDepth(unsigned depth);
+  static inline int OffsetForDepth(int depth);
 
   inline void PushLeft(ConsString* string);
   inline void PushRight(ConsString* string);
   inline void AdjustMaximumDepth();
   inline void Pop();
-  String* NextLeaf(bool* blew_stack, int32_t* type_out, unsigned* length_out);
-  String* Search(unsigned* offset_out,
-                 int32_t* type_out,
-                 unsigned* length_out);
+  inline bool StackBlown() { return maximum_depth_ - depth_ == kStackSize; }
+  void Initialize(ConsString* cons_string, int offset);
+  String* Continue(int* offset_out);
+  String* NextLeaf(bool* blew_stack);
+  String* Search(int* offset_out);
 
-  unsigned depth_;
-  unsigned maximum_depth_;
   // Stack must always contain only frames for which right traversal
   // has not yet been performed.
   ConsString* frames_[kStackSize];
-  unsigned consumed_;
   ConsString* root_;
+  int depth_;
+  int maximum_depth_;
+  int consumed_;
   DISALLOW_COPY_AND_ASSIGN(ConsStringIteratorOp);
 };
 
 
-// Note: this class is not GC-safe.
 class StringCharacterStream {
  public:
   inline StringCharacterStream(String* string,
                                ConsStringIteratorOp* op,
-                               unsigned offset = 0);
+                               int offset = 0);
   inline uint16_t GetNext();
   inline bool HasMore();
-  inline void Reset(String* string, unsigned offset = 0);
-  inline void VisitOneByteString(const uint8_t* chars, unsigned length);
-  inline void VisitTwoByteString(const uint16_t* chars, unsigned length);
+  inline void Reset(String* string, int offset = 0);
+  inline void VisitOneByteString(const uint8_t* chars, int length);
+  inline void VisitTwoByteString(const uint16_t* chars, int length);
 
  private:
   bool is_one_byte_;
@@ -9738,20 +10126,20 @@ class Oddball: public HeapObject {
   // [to_number]: Cached to_number computed at startup.
   DECL_ACCESSORS(to_number, Object)
 
-  inline byte kind();
+  inline byte kind() const;
   inline void set_kind(byte kind);
 
-  // Casting.
-  static inline Oddball* cast(Object* obj);
+  DECLARE_CAST(Oddball)
 
   // Dispatched behavior.
   DECLARE_VERIFIER(Oddball)
 
   // Initialize the fields.
-  MUST_USE_RESULT MaybeObject* Initialize(Heap* heap,
-                                          const char* to_string,
-                                          Object* to_number,
-                                          byte kind);
+  static void Initialize(Isolate* isolate,
+                         Handle<Oddball> oddball,
+                         const char* to_string,
+                         Handle<Object> to_number,
+                         byte kind);
 
   // Layout description.
   static const int kToStringOffset = HeapObject::kHeaderSize;
@@ -9768,14 +10156,15 @@ class Oddball: public HeapObject {
   static const byte kUndefined = 5;
   static const byte kUninitialized = 6;
   static const byte kOther = 7;
+  static const byte kException = 8;
 
   typedef FixedBodyDescriptor<kToStringOffset,
                               kToNumberOffset + kPointerSize,
                               kSize> BodyDescriptor;
 
-  STATIC_CHECK(kKindOffset == Internals::kOddballKindOffset);
-  STATIC_CHECK(kNull == Internals::kNullOddballKind);
-  STATIC_CHECK(kUndefined == Internals::kUndefinedOddballKind);
+  STATIC_ASSERT(kKindOffset == Internals::kOddballKindOffset);
+  STATIC_ASSERT(kNull == Internals::kNullOddballKind);
+  STATIC_ASSERT(kUndefined == Internals::kUndefinedOddballKind);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Oddball);
@@ -9787,12 +10176,11 @@ class Cell: public HeapObject {
   // [value]: value of the global property.
   DECL_ACCESSORS(value, Object)
 
-  // Casting.
-  static inline Cell* cast(Object* obj);
+  DECLARE_CAST(Cell)
 
   static inline Cell* FromValueAddress(Address value) {
     Object* result = FromAddress(value - kValueOffset);
-    ASSERT(result->IsCell() || result->IsPropertyCell());
+    DCHECK(result->IsCell() || result->IsPropertyCell());
     return static_cast<Cell*>(result);
   }
 
@@ -9839,12 +10227,10 @@ class PropertyCell: public Cell {
   static Handle<HeapType> UpdatedType(Handle<PropertyCell> cell,
                                       Handle<Object> value);
 
-  void AddDependentCompilationInfo(CompilationInfo* info);
-
-  void AddDependentCode(Handle<Code> code);
+  static void AddDependentCompilationInfo(Handle<PropertyCell> cell,
+                                          CompilationInfo* info);
 
-  // Casting.
-  static inline PropertyCell* cast(Object* obj);
+  DECLARE_CAST(PropertyCell)
 
   inline Address TypeAddress() {
     return address() + kTypeOffset;
@@ -9881,35 +10267,37 @@ class JSProxy: public JSReceiver {
   // [hash]: The hash code property (undefined if not initialized yet).
   DECL_ACCESSORS(hash, Object)
 
-  // Casting.
-  static inline JSProxy* cast(Object* obj);
+  DECLARE_CAST(JSProxy)
 
-  MUST_USE_RESULT MaybeObject* GetPropertyWithHandler(
-      Object* receiver,
-      Name* name);
-  MUST_USE_RESULT MaybeObject* GetElementWithHandler(
-      Object* receiver,
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithHandler(
+      Handle<JSProxy> proxy,
+      Handle<Object> receiver,
+      Handle<Name> name);
+  MUST_USE_RESULT static inline MaybeHandle<Object> GetElementWithHandler(
+      Handle<JSProxy> proxy,
+      Handle<Object> receiver,
       uint32_t index);
 
   // If the handler defines an accessor property with a setter, invoke it.
   // If it defines an accessor property without a setter, or a data property
   // that is read-only, throw. In all these cases set '*done' to true,
   // otherwise set it to false.
-  static Handle<Object> SetPropertyViaPrototypesWithHandler(
-      Handle<JSProxy> proxy,
-      Handle<JSReceiver> receiver,
-      Handle<Name> name,
-      Handle<Object> value,
-      PropertyAttributes attributes,
-      StrictModeFlag strict_mode,
-      bool* done);
-
-  MUST_USE_RESULT PropertyAttributes GetPropertyAttributeWithHandler(
-      JSReceiver* receiver,
-      Name* name);
-  MUST_USE_RESULT PropertyAttributes GetElementAttributeWithHandler(
-      JSReceiver* receiver,
-      uint32_t index);
+  MUST_USE_RESULT
+  static MaybeHandle<Object> SetPropertyViaPrototypesWithHandler(
+      Handle<JSProxy> proxy, Handle<Object> receiver, Handle<Name> name,
+      Handle<Object> value, StrictMode strict_mode, bool* done);
+
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetPropertyAttributesWithHandler(Handle<JSProxy> proxy,
+                                       Handle<Object> receiver,
+                                       Handle<Name> name);
+  MUST_USE_RESULT static Maybe<PropertyAttributes>
+      GetElementAttributeWithHandler(Handle<JSProxy> proxy,
+                                     Handle<JSReceiver> receiver,
+                                     uint32_t index);
+  MUST_USE_RESULT static MaybeHandle<Object> SetPropertyWithHandler(
+      Handle<JSProxy> proxy, Handle<Object> receiver, Handle<Name> name,
+      Handle<Object> value, StrictMode strict_mode);
 
   // Turn the proxy into an (empty) JSObject.
   static void Fix(Handle<JSProxy> proxy);
@@ -9919,10 +10307,12 @@ class JSProxy: public JSReceiver {
 
   // Invoke a trap by name. If the trap does not exist on this's handler,
   // but derived_trap is non-NULL, invoke that instead.  May cause GC.
-  Handle<Object> CallTrap(const char* name,
-                          Handle<Object> derived_trap,
-                          int argc,
-                          Handle<Object> args[]);
+  MUST_USE_RESULT static MaybeHandle<Object> CallTrap(
+      Handle<JSProxy> proxy,
+      const char* name,
+      Handle<Object> derived_trap,
+      int argc,
+      Handle<Object> args[]);
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSProxy)
@@ -9938,7 +10328,7 @@ class JSProxy: public JSReceiver {
   static const int kHeaderSize = kPaddingOffset;
   static const int kPaddingSize = kSize - kPaddingOffset;
 
-  STATIC_CHECK(kPaddingSize >= 0);
+  STATIC_ASSERT(kPaddingSize >= 0);
 
   typedef FixedBodyDescriptor<kHandlerOffset,
                               kPaddingOffset,
@@ -9947,31 +10337,30 @@ class JSProxy: public JSReceiver {
  private:
   friend class JSReceiver;
 
-  static Handle<Object> SetPropertyWithHandler(Handle<JSProxy> proxy,
-                                               Handle<JSReceiver> receiver,
-                                               Handle<Name> name,
-                                               Handle<Object> value,
-                                               PropertyAttributes attributes,
-                                               StrictModeFlag strict_mode);
-  static Handle<Object> SetElementWithHandler(Handle<JSProxy> proxy,
-                                              Handle<JSReceiver> receiver,
-                                              uint32_t index,
-                                              Handle<Object> value,
-                                              StrictModeFlag strict_mode);
+  MUST_USE_RESULT static inline MaybeHandle<Object> SetElementWithHandler(
+      Handle<JSProxy> proxy,
+      Handle<JSReceiver> receiver,
+      uint32_t index,
+      Handle<Object> value,
+      StrictMode strict_mode);
 
-  static bool HasPropertyWithHandler(Handle<JSProxy> proxy, Handle<Name> name);
-  static bool HasElementWithHandler(Handle<JSProxy> proxy, uint32_t index);
+  MUST_USE_RESULT static Maybe<bool> HasPropertyWithHandler(
+      Handle<JSProxy> proxy, Handle<Name> name);
+  MUST_USE_RESULT static inline Maybe<bool> HasElementWithHandler(
+      Handle<JSProxy> proxy, uint32_t index);
 
-  static Handle<Object> DeletePropertyWithHandler(Handle<JSProxy> proxy,
-                                                  Handle<Name> name,
-                                                  DeleteMode mode);
-  static Handle<Object> DeleteElementWithHandler(Handle<JSProxy> proxy,
-                                                 uint32_t index,
-                                                 DeleteMode mode);
+  MUST_USE_RESULT static MaybeHandle<Object> DeletePropertyWithHandler(
+      Handle<JSProxy> proxy,
+      Handle<Name> name,
+      DeleteMode mode);
+  MUST_USE_RESULT static MaybeHandle<Object> DeleteElementWithHandler(
+      Handle<JSProxy> proxy,
+      uint32_t index,
+      DeleteMode mode);
 
   MUST_USE_RESULT Object* GetIdentityHash();
 
-  static Handle<Object> GetOrCreateIdentityHash(Handle<JSProxy> proxy);
+  static Handle<Smi> GetOrCreateIdentityHash(Handle<JSProxy> proxy);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSProxy);
 };
@@ -9985,8 +10374,7 @@ class JSFunctionProxy: public JSProxy {
   // [construct_trap]: The construct trap.
   DECL_ACCESSORS(construct_trap, Object)
 
-  // Casting.
-  static inline JSFunctionProxy* cast(Object* obj);
+  DECLARE_CAST(JSFunctionProxy)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSFunctionProxy)
@@ -9999,7 +10387,7 @@ class JSFunctionProxy: public JSProxy {
   static const int kSize = JSFunction::kSize;
   static const int kPaddingSize = kSize - kPaddingOffset;
 
-  STATIC_CHECK(kPaddingSize >= 0);
+  STATIC_ASSERT(kPaddingSize >= 0);
 
   typedef FixedBodyDescriptor<kHandlerOffset,
                               kConstructTrapOffset + kPointerSize,
@@ -10010,45 +10398,150 @@ class JSFunctionProxy: public JSProxy {
 };
 
 
-// The JSSet describes EcmaScript Harmony sets
-class JSSet: public JSObject {
+class JSCollection : public JSObject {
  public:
-  // [set]: the backing hash set containing keys.
+  // [table]: the backing hash table
   DECL_ACCESSORS(table, Object)
 
-  // Casting.
-  static inline JSSet* cast(Object* obj);
+  static const int kTableOffset = JSObject::kHeaderSize;
+  static const int kSize = kTableOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSCollection);
+};
+
+
+// The JSSet describes EcmaScript Harmony sets
+class JSSet : public JSCollection {
+ public:
+  DECLARE_CAST(JSSet)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSSet)
   DECLARE_VERIFIER(JSSet)
 
-  static const int kTableOffset = JSObject::kHeaderSize;
-  static const int kSize = kTableOffset + kPointerSize;
-
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSSet);
 };
 
 
 // The JSMap describes EcmaScript Harmony maps
-class JSMap: public JSObject {
+class JSMap : public JSCollection {
  public:
-  // [table]: the backing hash table mapping keys to values.
-  DECL_ACCESSORS(table, Object)
-
-  // Casting.
-  static inline JSMap* cast(Object* obj);
+  DECLARE_CAST(JSMap)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSMap)
   DECLARE_VERIFIER(JSMap)
 
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSMap);
+};
+
+
+// OrderedHashTableIterator is an iterator that iterates over the keys and
+// values of an OrderedHashTable.
+//
+// The iterator has a reference to the underlying OrderedHashTable data,
+// [table], as well as the current [index] the iterator is at.
+//
+// When the OrderedHashTable is rehashed it adds a reference from the old table
+// to the new table as well as storing enough data about the changes so that the
+// iterator [index] can be adjusted accordingly.
+//
+// When the [Next] result from the iterator is requested, the iterator checks if
+// there is a newer table that it needs to transition to.
+template<class Derived, class TableType>
+class OrderedHashTableIterator: public JSObject {
+ public:
+  // [table]: the backing hash table mapping keys to values.
+  DECL_ACCESSORS(table, Object)
+
+  // [index]: The index into the data table.
+  DECL_ACCESSORS(index, Smi)
+
+  // [kind]: The kind of iteration this is. One of the [Kind] enum values.
+  DECL_ACCESSORS(kind, Smi)
+
+#ifdef OBJECT_PRINT
+  void OrderedHashTableIteratorPrint(OStream& os);  // NOLINT
+#endif
+
   static const int kTableOffset = JSObject::kHeaderSize;
-  static const int kSize = kTableOffset + kPointerSize;
+  static const int kIndexOffset = kTableOffset + kPointerSize;
+  static const int kKindOffset = kIndexOffset + kPointerSize;
+  static const int kSize = kKindOffset + kPointerSize;
+
+  enum Kind {
+    kKindKeys = 1,
+    kKindValues = 2,
+    kKindEntries = 3
+  };
+
+  // Whether the iterator has more elements. This needs to be called before
+  // calling |CurrentKey| and/or |CurrentValue|.
+  bool HasMore();
+
+  // Move the index forward one.
+  void MoveNext() {
+    set_index(Smi::FromInt(Smi::cast(index())->value() + 1));
+  }
+
+  // Populates the array with the next key and value and then moves the iterator
+  // forward.
+  // This returns the |kind| or 0 if the iterator is already at the end.
+  Smi* Next(JSArray* value_array);
+
+  // Returns the current key of the iterator. This should only be called when
+  // |HasMore| returns true.
+  inline Object* CurrentKey();
 
  private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(JSMap);
+  // Transitions the iterator to the non obsolete backing store. This is a NOP
+  // if the [table] is not obsolete.
+  void Transition();
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(OrderedHashTableIterator);
+};
+
+
+class JSSetIterator: public OrderedHashTableIterator<JSSetIterator,
+                                                     OrderedHashSet> {
+ public:
+  // Dispatched behavior.
+  DECLARE_PRINTER(JSSetIterator)
+  DECLARE_VERIFIER(JSSetIterator)
+
+  DECLARE_CAST(JSSetIterator)
+
+  // Called by |Next| to populate the array. This allows the subclasses to
+  // populate the array differently.
+  inline void PopulateValueArray(FixedArray* array);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSSetIterator);
+};
+
+
+class JSMapIterator: public OrderedHashTableIterator<JSMapIterator,
+                                                     OrderedHashMap> {
+ public:
+  // Dispatched behavior.
+  DECLARE_PRINTER(JSMapIterator)
+  DECLARE_VERIFIER(JSMapIterator)
+
+  DECLARE_CAST(JSMapIterator)
+
+  // Called by |Next| to populate the array. This allows the subclasses to
+  // populate the array differently.
+  inline void PopulateValueArray(FixedArray* array);
+
+ private:
+  // Returns the current value of the iterator. This should only be called when
+  // |HasMore| returns true.
+  inline Object* CurrentValue();
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSMapIterator);
 };
 
 
@@ -10073,8 +10566,7 @@ class JSWeakCollection: public JSObject {
 // The JSWeakMap describes EcmaScript Harmony weak maps
 class JSWeakMap: public JSWeakCollection {
  public:
-  // Casting.
-  static inline JSWeakMap* cast(Object* obj);
+  DECLARE_CAST(JSWeakMap)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSWeakMap)
@@ -10088,8 +10580,7 @@ class JSWeakMap: public JSWeakCollection {
 // The JSWeakSet describes EcmaScript Harmony weak sets
 class JSWeakSet: public JSWeakCollection {
  public:
-  // Casting.
-  static inline JSWeakSet* cast(Object* obj);
+  DECLARE_CAST(JSWeakSet)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSWeakSet)
@@ -10123,8 +10614,7 @@ class JSArrayBuffer: public JSObject {
   // [weak_first_array]: weak linked list of views.
   DECL_ACCESSORS(weak_first_view, Object)
 
-  // Casting.
-  static inline JSArrayBuffer* cast(Object* obj);
+  DECLARE_CAST(JSArrayBuffer)
 
   // Neutering. Only neuters the buffer, not associated typed arrays.
   void Neuter();
@@ -10166,8 +10656,7 @@ class JSArrayBufferView: public JSObject {
   // [weak_next]: linked list of typed arrays over the same array buffer.
   DECL_ACCESSORS(weak_next, Object)
 
-  // Casting.
-  static inline JSArrayBufferView* cast(Object* obj);
+  DECLARE_CAST(JSArrayBufferView)
 
   DECLARE_VERIFIER(JSArrayBufferView)
 
@@ -10193,12 +10682,13 @@ class JSTypedArray: public JSArrayBufferView {
   // Neutering. Only neuters this typed array.
   void Neuter();
 
-  // Casting.
-  static inline JSTypedArray* cast(Object* obj);
+  DECLARE_CAST(JSTypedArray)
 
   ExternalArrayType type();
   size_t element_size();
 
+  Handle<JSArrayBuffer> GetBuffer();
+
   // Dispatched behavior.
   DECLARE_PRINTER(JSTypedArray)
   DECLARE_VERIFIER(JSTypedArray)
@@ -10210,6 +10700,9 @@ class JSTypedArray: public JSArrayBufferView {
       kSize + v8::ArrayBufferView::kInternalFieldCount * kPointerSize;
 
  private:
+  static Handle<JSArrayBuffer> MaterializeArrayBuffer(
+      Handle<JSTypedArray> typed_array);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSTypedArray);
 };
 
@@ -10219,8 +10712,7 @@ class JSDataView: public JSArrayBufferView {
   // Only neuters this DataView
   void Neuter();
 
-  // Casting.
-  static inline JSDataView* cast(Object* obj);
+  DECLARE_CAST(JSDataView)
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSDataView)
@@ -10236,6 +10728,115 @@ class JSDataView: public JSArrayBufferView {
 };
 
 
+class Float32x4: public JSObject {
+ public:
+  typedef float32x4_value_t value_t;
+  static const int kValueSize = kFloat32x4Size;
+  static const InstanceType kInstanceType = FLOAT32x4_TYPE;
+  static inline const char* Name();
+  static inline int kRuntimeAllocatorId();
+
+  // [value]: the FixedFloat32x4Array with length 1.
+  DECL_ACCESSORS(value, Object)
+
+  // Casting.
+  DECLARE_CAST(Float32x4)
+
+  // Dispatched behavior.
+  void Float32x4Print(OStream& os);
+  DECLARE_VERIFIER(Float32x4)
+
+  // Helpers.
+  static const int kLanes = 4;
+  inline float getAt(int index);
+  inline float x() { return getAt(0); }
+  inline float y() { return getAt(1); }
+  inline float z() { return getAt(2); }
+  inline float w() { return getAt(3); }
+  inline float32x4_value_t get();
+  inline void set(float32x4_value_t f32x4);
+
+  // Layout description.
+  static const int kValueOffset = JSObject::kHeaderSize;
+  static const int kSize = kValueOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Float32x4);
+};
+
+
+class Float64x2: public JSObject {
+ public:
+  typedef float64x2_value_t value_t;
+  static const int kValueSize = kFloat64x2Size;
+  static const InstanceType kInstanceType = FLOAT64x2_TYPE;
+  static inline const char* Name();
+  static inline int kRuntimeAllocatorId();
+
+  // [value]: the FixedFloat64x2Array with length 1.
+  DECL_ACCESSORS(value, Object)
+
+  // Casting.
+  DECLARE_CAST(Float64x2)
+
+  // Dispatched behavior.
+  void Float64x2Print(OStream& os);
+  DECLARE_VERIFIER(Float64x2)
+
+  // Helpers.
+  static const int kLanes = 2;
+  inline double getAt(int index);
+  inline double x() { return getAt(0); }
+  inline double y() { return getAt(1); }
+  inline float64x2_value_t get();
+  inline void set(float64x2_value_t f64x2);
+
+  // Layout description.
+  static const int kValueOffset = JSObject::kHeaderSize;
+  static const int kSize = kValueOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Float64x2);
+};
+
+
+class Int32x4: public JSObject {
+ public:
+  typedef int32x4_value_t value_t;
+  static const int kValueSize = kInt32x4Size;
+  static const InstanceType kInstanceType = INT32x4_TYPE;
+  static inline const char* Name();
+  static inline int kRuntimeAllocatorId();
+
+  // [value]: the FixedInt32x4Array with length 1.
+  DECL_ACCESSORS(value, Object)
+
+  // Casting.
+  DECLARE_CAST(Int32x4)
+
+  // Dispatched behavior.
+  void Int32x4Print(OStream& os);
+  DECLARE_VERIFIER(Int32x4)
+
+  // Helpers.
+  static const int kLanes = 4;
+  inline int32_t getAt(int32_t index);
+  inline int32_t x() { return getAt(0); }
+  inline int32_t y() { return getAt(1); }
+  inline int32_t z() { return getAt(2); }
+  inline int32_t w() { return getAt(3); }
+  inline int32x4_value_t get();
+  inline void set(int32x4_value_t i32x4);
+
+  // Layout description.
+  static const int kValueOffset = JSObject::kHeaderSize;
+  static const int kSize = kValueOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Int32x4);
+};
+
+
 // Foreign describes objects pointing from JavaScript to C structures.
 // Since they cannot contain references to JS HeapObjects they can be
 // placed in old_data_space.
@@ -10245,8 +10846,7 @@ class Foreign: public HeapObject {
   inline Address foreign_address();
   inline void set_foreign_address(Address value);
 
-  // Casting.
-  static inline Foreign* cast(Object* obj);
+  DECLARE_CAST(Foreign)
 
   // Dispatched behavior.
   inline void ForeignIterateBody(ObjectVisitor* v);
@@ -10263,7 +10863,7 @@ class Foreign: public HeapObject {
   static const int kForeignAddressOffset = HeapObject::kHeaderSize;
   static const int kSize = kForeignAddressOffset + kPointerSize;
 
-  STATIC_CHECK(kForeignAddressOffset == Internals::kForeignAddressOffset);
+  STATIC_ASSERT(kForeignAddressOffset == Internals::kForeignAddressOffset);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Foreign);
@@ -10288,28 +10888,37 @@ class JSArray: public JSObject {
                                            uint32_t index,
                                            Handle<Object> value);
 
-  MUST_USE_RESULT MaybeObject* JSArrayUpdateLengthFromIndex(uint32_t index,
-                                                            Object* value);
+  static bool IsReadOnlyLengthDescriptor(Handle<Map> jsarray_map);
+  static bool WouldChangeReadOnlyLength(Handle<JSArray> array, uint32_t index);
+  static MaybeHandle<Object> ReadOnlyLengthError(Handle<JSArray> array);
 
   // Initialize the array with the given capacity. The function may
   // fail due to out-of-memory situations, but only if the requested
   // capacity is non-zero.
-  MUST_USE_RESULT MaybeObject* Initialize(int capacity, int length = 0);
+  static void Initialize(Handle<JSArray> array, int capacity, int length = 0);
 
   // Initializes the array to a certain length.
   inline bool AllowsSetElementsLength();
   // Can cause GC.
-  MUST_USE_RESULT MaybeObject* SetElementsLength(Object* length);
+  MUST_USE_RESULT static MaybeHandle<Object> SetElementsLength(
+      Handle<JSArray> array,
+      Handle<Object> length);
 
   // Set the content of the array to the content of storage.
-  MUST_USE_RESULT inline MaybeObject* SetContent(FixedArrayBase* storage);
+  static inline void SetContent(Handle<JSArray> array,
+                                Handle<FixedArrayBase> storage);
 
-  // Casting.
-  static inline JSArray* cast(Object* obj);
+  DECLARE_CAST(JSArray)
 
-  // Uses handles.  Ensures that the fixed array backing the JSArray has at
+  // Ensures that the fixed array backing the JSArray has at
   // least the stated size.
-  inline void EnsureSize(int minimum_size_of_backing_fixed_array);
+  static inline void EnsureSize(Handle<JSArray> array,
+                                int minimum_size_of_backing_fixed_array);
+
+  // Expand the fixed array backing of a fast-case JSArray to at least
+  // the requested size.
+  static void Expand(Handle<JSArray> array,
+                     int minimum_size_of_backing_fixed_array);
 
   // Dispatched behavior.
   DECLARE_PRINTER(JSArray)
@@ -10323,10 +10932,6 @@ class JSArray: public JSObject {
   static const int kSize = kLengthOffset + kPointerSize;
 
  private:
-  // Expand the fixed array backing of a fast-case JSArray to at least
-  // the requested size.
-  void Expand(int minimum_size_of_backing_fixed_array);
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSArray);
 };
 
@@ -10367,16 +10972,16 @@ class AccessorInfo: public Struct {
   inline bool all_can_write();
   inline void set_all_can_write(bool value);
 
-  inline bool prohibits_overwriting();
-  inline void set_prohibits_overwriting(bool value);
-
   inline PropertyAttributes property_attributes();
   inline void set_property_attributes(PropertyAttributes attributes);
 
   // Checks whether the given receiver is compatible with this accessor.
+  static bool IsCompatibleReceiverType(Isolate* isolate,
+                                       Handle<AccessorInfo> info,
+                                       Handle<HeapType> type);
   inline bool IsCompatibleReceiver(Object* receiver);
 
-  static inline AccessorInfo* cast(Object* obj);
+  DECLARE_CAST(AccessorInfo)
 
   // Dispatched behavior.
   DECLARE_VERIFIER(AccessorInfo)
@@ -10393,11 +10998,13 @@ class AccessorInfo: public Struct {
   static const int kSize = kExpectedReceiverTypeOffset + kPointerSize;
 
  private:
+  inline bool HasExpectedReceiverType() {
+    return expected_receiver_type()->IsFunctionTemplateInfo();
+  }
   // Bit positions in flag.
   static const int kAllCanReadBit = 0;
   static const int kAllCanWriteBit = 1;
-  static const int kProhibitsOverwritingBit = 2;
-  class AttributesField: public BitField<PropertyAttributes, 3, 3> {};
+  class AttributesField: public BitField<PropertyAttributes, 2, 3> {};
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AccessorInfo);
 };
@@ -10475,7 +11082,7 @@ class DeclaredAccessorDescriptor: public Struct {
  public:
   DECL_ACCESSORS(serialized_data, ByteArray)
 
-  static inline DeclaredAccessorDescriptor* cast(Object* obj);
+  DECLARE_CAST(DeclaredAccessorDescriptor)
 
   static Handle<DeclaredAccessorDescriptor> Create(
       Isolate* isolate,
@@ -10498,7 +11105,7 @@ class DeclaredAccessorInfo: public AccessorInfo {
  public:
   DECL_ACCESSORS(descriptor, DeclaredAccessorDescriptor)
 
-  static inline DeclaredAccessorInfo* cast(Object* obj);
+  DECLARE_CAST(DeclaredAccessorInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(DeclaredAccessorInfo)
@@ -10519,7 +11126,7 @@ class DeclaredAccessorInfo: public AccessorInfo {
 // the request is ignored.
 //
 // If the accessor in the prototype has the READ_ONLY property attribute, then
-// a new value is added to the local object when the property is set.
+// a new value is added to the derived object when the property is set.
 // This shadows the accessor in the prototype.
 class ExecutableAccessorInfo: public AccessorInfo {
  public:
@@ -10527,7 +11134,7 @@ class ExecutableAccessorInfo: public AccessorInfo {
   DECL_ACCESSORS(setter, Object)
   DECL_ACCESSORS(data, Object)
 
-  static inline ExecutableAccessorInfo* cast(Object* obj);
+  DECLARE_CAST(ExecutableAccessorInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ExecutableAccessorInfo)
@@ -10538,6 +11145,8 @@ class ExecutableAccessorInfo: public AccessorInfo {
   static const int kDataOffset = kSetterOffset + kPointerSize;
   static const int kSize = kDataOffset + kPointerSize;
 
+  inline void clear_setter();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExecutableAccessorInfo);
 };
@@ -10549,20 +11158,12 @@ class ExecutableAccessorInfo: public AccessorInfo {
 //   * undefined: considered an accessor by the spec, too, strangely enough
 //   * the hole: an accessor which has not been set
 //   * a pointer to a map: a transition used to ensure map sharing
-// access_flags provides the ability to override access checks on access check
-// failure.
 class AccessorPair: public Struct {
  public:
   DECL_ACCESSORS(getter, Object)
   DECL_ACCESSORS(setter, Object)
-  DECL_ACCESSORS(access_flags, Smi)
-
-  inline void set_access_flags(v8::AccessControl access_control);
-  inline bool all_can_read();
-  inline bool all_can_write();
-  inline bool prohibits_overwriting();
 
-  static inline AccessorPair* cast(Object* obj);
+  DECLARE_CAST(AccessorPair)
 
   static Handle<AccessorPair> Copy(Handle<AccessorPair> pair);
 
@@ -10597,14 +11198,9 @@ class AccessorPair: public Struct {
 
   static const int kGetterOffset = HeapObject::kHeaderSize;
   static const int kSetterOffset = kGetterOffset + kPointerSize;
-  static const int kAccessFlagsOffset = kSetterOffset + kPointerSize;
-  static const int kSize = kAccessFlagsOffset + kPointerSize;
+  static const int kSize = kSetterOffset + kPointerSize;
 
  private:
-  static const int kAllCanReadBit = 0;
-  static const int kAllCanWriteBit = 1;
-  static const int kProhibitsOverwritingBit = 2;
-
   // Strangely enough, in addition to functions and harmony proxies, the spec
   // requires us to consider undefined as a kind of accessor, too:
   //    var obj = {};
@@ -10624,7 +11220,7 @@ class AccessCheckInfo: public Struct {
   DECL_ACCESSORS(indexed_callback, Object)
   DECL_ACCESSORS(data, Object)
 
-  static inline AccessCheckInfo* cast(Object* obj);
+  DECLARE_CAST(AccessCheckInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(AccessCheckInfo)
@@ -10649,7 +11245,7 @@ class InterceptorInfo: public Struct {
   DECL_ACCESSORS(enumerator, Object)
   DECL_ACCESSORS(data, Object)
 
-  static inline InterceptorInfo* cast(Object* obj);
+  DECLARE_CAST(InterceptorInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(InterceptorInfo)
@@ -10673,7 +11269,7 @@ class CallHandlerInfo: public Struct {
   DECL_ACCESSORS(callback, Object)
   DECL_ACCESSORS(data, Object)
 
-  static inline CallHandlerInfo* cast(Object* obj);
+  DECLARE_CAST(CallHandlerInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(CallHandlerInfo)
@@ -10722,7 +11318,7 @@ class FunctionTemplateInfo: public TemplateInfo {
   DECL_ACCESSORS(access_check_info, Object)
   DECL_ACCESSORS(flag, Smi)
 
-  inline int length();
+  inline int length() const;
   inline void set_length(int value);
 
   // Following properties use flag bits.
@@ -10735,7 +11331,7 @@ class FunctionTemplateInfo: public TemplateInfo {
   DECL_BOOLEAN_ACCESSORS(remove_prototype)
   DECL_BOOLEAN_ACCESSORS(do_not_cache)
 
-  static inline FunctionTemplateInfo* cast(Object* obj);
+  DECLARE_CAST(FunctionTemplateInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(FunctionTemplateInfo)
@@ -10784,7 +11380,7 @@ class ObjectTemplateInfo: public TemplateInfo {
   DECL_ACCESSORS(constructor, Object)
   DECL_ACCESSORS(internal_field_count, Object)
 
-  static inline ObjectTemplateInfo* cast(Object* obj);
+  DECLARE_CAST(ObjectTemplateInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(ObjectTemplateInfo)
@@ -10802,7 +11398,7 @@ class SignatureInfo: public Struct {
   DECL_ACCESSORS(receiver, Object)
   DECL_ACCESSORS(args, Object)
 
-  static inline SignatureInfo* cast(Object* obj);
+  DECLARE_CAST(SignatureInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(SignatureInfo)
@@ -10821,7 +11417,7 @@ class TypeSwitchInfo: public Struct {
  public:
   DECL_ACCESSORS(types, Object)
 
-  static inline TypeSwitchInfo* cast(Object* obj);
+  DECLARE_CAST(TypeSwitchInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(TypeSwitchInfo)
@@ -10832,7 +11428,6 @@ class TypeSwitchInfo: public Struct {
 };
 
 
-#ifdef ENABLE_DEBUGGER_SUPPORT
 // The DebugInfo class holds additional information for a function being
 // debugged.
 class DebugInfo: public Struct {
@@ -10867,7 +11462,7 @@ class DebugInfo: public Struct {
   // Get the number of break points for this function.
   int GetBreakPointCount();
 
-  static inline DebugInfo* cast(Object* obj);
+  DECLARE_CAST(DebugInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(DebugInfo)
@@ -10882,6 +11477,8 @@ class DebugInfo: public Struct {
       kActiveBreakPointsCountIndex + kPointerSize;
   static const int kSize = kBreakPointsStateIndex + kPointerSize;
 
+  static const int kEstimatedNofBreakPointsInFunction = 16;
+
  private:
   static const int kNoBreakPointInfo = -1;
 
@@ -10919,7 +11516,7 @@ class BreakPointInfo: public Struct {
   // Get the number of break points for this code position.
   int GetBreakPointCount();
 
-  static inline BreakPointInfo* cast(Object* obj);
+  DECLARE_CAST(BreakPointInfo)
 
   // Dispatched behavior.
   DECLARE_PRINTER(BreakPointInfo)
@@ -10936,17 +11533,18 @@ class BreakPointInfo: public Struct {
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(BreakPointInfo);
 };
-#endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 #undef DECL_BOOLEAN_ACCESSORS
 #undef DECL_ACCESSORS
+#undef DECLARE_CAST
 #undef DECLARE_VERIFIER
 
 #define VISITOR_SYNCHRONIZATION_TAGS_LIST(V)                            \
   V(kStringTable, "string_table", "(Internalized strings)")             \
   V(kExternalStringsTable, "external_strings_table", "(External strings)") \
   V(kStrongRootList, "strong_root_list", "(Strong roots)")              \
+  V(kSmiRootList, "smi_root_list", "(Smi roots)")                       \
   V(kInternalizedString, "internalized_string", "(Internal string)")    \
   V(kBootstrapper, "bootstrapper", "(Bootstrapper)")                    \
   V(kTop, "top", "(Isolate)")                                           \
@@ -10986,6 +11584,9 @@ class ObjectVisitor BASE_EMBEDDED {
   // Handy shorthand for visiting a single pointer.
   virtual void VisitPointer(Object** p) { VisitPointers(p, p + 1); }
 
+  // Visit weak next_code_link in Code object.
+  virtual void VisitNextCodeLink(Object** p) { VisitPointers(p, p + 1); }
+
   // To allow lazy clearing of inline caches the visitor has
   // a rich interface for iterating over Code objects..