Adapt Danno's Track Allocation Info idea to fast literals. When allocating a literal array,

src/objects.h

 // 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
@@ skipping 273 matching lines @@
                                                                                \
   V(ACCESSOR_INFO_TYPE)                                                        \
   V(ACCESSOR_PAIR_TYPE)                                                        \
   V(ACCESS_CHECK_INFO_TYPE)                                                    \
   V(INTERCEPTOR_INFO_TYPE)                                                     \
   V(CALL_HANDLER_INFO_TYPE)                                                    \
   V(FUNCTION_TEMPLATE_INFO_TYPE)                                               \
   V(OBJECT_TEMPLATE_INFO_TYPE)                                                 \
   V(SIGNATURE_INFO_TYPE)                                                       \
   V(TYPE_SWITCH_INFO_TYPE)                                                     \
+  V(ALLOCATION_SITE_INFO_TYPE)                                                 \
   V(SCRIPT_TYPE)                                                               \
   V(CODE_CACHE_TYPE)                                                           \
   V(POLYMORPHIC_CODE_CACHE_TYPE)                                               \
   V(TYPE_FEEDBACK_INFO_TYPE)                                                   \
   V(ALIASED_ARGUMENTS_ENTRY_TYPE)                                              \
                                                                                \
   V(FIXED_ARRAY_TYPE)                                                          \
   V(FIXED_DOUBLE_ARRAY_TYPE)                                                   \
   V(SHARED_FUNCTION_INFO_TYPE)                                                 \
                                                                                \
@@ skipping 133 matching lines @@
   V(ACCESSOR_INFO, AccessorInfo, accessor_info)                                \
   V(ACCESSOR_PAIR, AccessorPair, accessor_pair)                                \
   V(ACCESS_CHECK_INFO, AccessCheckInfo, access_check_info)                     \
   V(INTERCEPTOR_INFO, InterceptorInfo, interceptor_info)                       \
   V(CALL_HANDLER_INFO, CallHandlerInfo, call_handler_info)                     \
   V(FUNCTION_TEMPLATE_INFO, FunctionTemplateInfo, function_template_info)      \
   V(OBJECT_TEMPLATE_INFO, ObjectTemplateInfo, object_template_info)            \
   V(SIGNATURE_INFO, SignatureInfo, signature_info)                             \
   V(TYPE_SWITCH_INFO, TypeSwitchInfo, type_switch_info)                        \
   V(SCRIPT, Script, script)                                                    \
+  V(ALLOCATION_SITE_INFO, AllocationSiteInfo, allocation_site_info)            \
   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(DEBUG_INFO, DebugInfo, debug_info)                                         \
   V(BREAK_POINT_INFO, BreakPointInfo, break_point_info)
 #else
@@ skipping 142 matching lines @@
   // Structs.
   ACCESSOR_INFO_TYPE,
   ACCESSOR_PAIR_TYPE,
   ACCESS_CHECK_INFO_TYPE,
   INTERCEPTOR_INFO_TYPE,
   CALL_HANDLER_INFO_TYPE,
   FUNCTION_TEMPLATE_INFO_TYPE,
   OBJECT_TEMPLATE_INFO_TYPE,
   SIGNATURE_INFO_TYPE,
   TYPE_SWITCH_INFO_TYPE,
+  ALLOCATION_SITE_INFO_TYPE,
   SCRIPT_TYPE,
   CODE_CACHE_TYPE,
   POLYMORPHIC_CODE_CACHE_TYPE,
   TYPE_FEEDBACK_INFO_TYPE,
   ALIASED_ARGUMENTS_ENTRY_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,
@@ skipping 1386 matching lines @@
   inline MUST_USE_RESULT MaybeObject* GetElementsTransitionMap(
       Isolate* isolate,
       ElementsKind elements_kind);
   MUST_USE_RESULT MaybeObject* GetElementsTransitionMapSlow(
       ElementsKind elements_kind);
 
   static Handle<Object> TransitionElementsKind(Handle<JSObject> object,
                                                ElementsKind to_kind);
 
   MUST_USE_RESULT MaybeObject* TransitionElementsKind(ElementsKind to_kind);
+  MUST_USE_RESULT MaybeObject* PossiblyTransitionBoilerplate(
+      ElementsKind to_kind);
 
   // Replaces an existing transition with a transition to a map with a FIELD.
   MUST_USE_RESULT MaybeObject* ConvertTransitionToMapTransition(
       int transition_index,
       String* name,
       Object* new_value,
       PropertyAttributes attributes);
 
   // Converts a descriptor of any other type to a real field, backed by the
   // properties array.
@@ skipping 4865 matching lines @@
   class ICsWithTypeInfoCountField: public BitField<int, 0,
       kSmiValueSize - kTypeChangeChecksumBits> {};  // NOLINT
   class InlinedTypeChangeChecksum: public BitField<int,
       kSmiValueSize - kTypeChangeChecksumBits,
       kTypeChangeChecksumBits> {};  // NOLINT
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TypeFeedbackInfo);
 };
 
 
+class AllocationSiteInfo: public Struct {
+ public:
+  DECL_ACCESSORS(payload, Object)
+
+  static inline AllocationSiteInfo* cast(Object* obj);
+
+#ifdef OBJECT_PRINT
+  inline void AllocationSiteInfoPrint() {
+    AllocationSiteInfoPrint(stdout);
+  }
+  void AllocationSiteInfoPrint(FILE* out);

[danno, 2013/01/04 08:50:55]

Maybe use some variant of DECLARE_PRINTER?

[mvstanton, 2013/01/04 12:07:52]

Done.

+#endif
+#ifdef DEBUG
+  void AllocationSiteInfoVerify();

[danno, 2013/01/04 08:50:55]

Use DECLARE_VERIFIER instead of explicitly declaring the Verifier yourself.

[mvstanton, 2013/01/04 12:07:52]

Done.

+#endif
+
+  // Returns NULL if no AllocationSiteInfo is available for object.
+  static AllocationSiteInfo* FindAfterJSObject(JSObject* object);
+
+  static const int kPayloadOffset = HeapObject::kHeaderSize;
+  static const int kSize = kPayloadOffset + kPointerSize;
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(AllocationSiteInfo);
+};
+
+
 // Representation of a slow alias as part of a non-strict arguments objects.
 // For fast aliases (if HasNonStrictArgumentsElements()):
 // - the parameter map contains an index into the context
 // - all attributes of the element have default values
 // For slow aliases (if HasDictionaryArgumentsElements()):
 // - the parameter map contains no fast alias mapping (i.e. the hole)
 // - this struct (in the slow backing store) contains an index into the context
 // - all attributes are available as part if the property details
 class AliasedArgumentsEntry: public Struct {
  public:
@@ skipping 1975 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_