Inobject slack tracking is done on a per-closure basis instead of per-shared info basis.

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 4051 matching lines @@
   } else {
     set_bit_field2(bit_field2() & ~(1 << kIsExtensible));
   }
 }
 
 bool Map::is_extensible() {
   return ((1 << kIsExtensible) & bit_field2()) != 0;
 }
 
 
-void Map::set_attached_to_shared_function_info(bool value) {
-  if (value) {
-    set_bit_field2(bit_field2() | (1 << kAttachedToSharedFunctionInfo));
-  } else {
-    set_bit_field2(bit_field2() & ~(1 << kAttachedToSharedFunctionInfo));
-  }
-}
-
-bool Map::attached_to_shared_function_info() {
-  return ((1 << kAttachedToSharedFunctionInfo) & bit_field2()) != 0;
-}
-
-
 void Map::set_is_shared(bool value) {
   set_bit_field3(IsShared::update(bit_field3(), value));
 }
 
 
 bool Map::is_shared() {
   return IsShared::decode(bit_field3()); }
 
 
 void Map::set_dictionary_map(bool value) {
@@ skipping 46 matching lines @@
 void Map::set_migration_target(bool value) {
   set_bit_field3(IsMigrationTarget::update(bit_field3(), value));
 }
 
 
 bool Map::is_migration_target() {
   return IsMigrationTarget::decode(bit_field3());
 }
 
 
+void Map::set_done_inobject_slack_tracking(bool value) {
+  set_bit_field3(DoneInobjectSlackTracking::update(bit_field3(), value));
+}
+
+
+bool Map::done_inobject_slack_tracking() {
+  return DoneInobjectSlackTracking::decode(bit_field3());
+}
+
+
+void Map::set_construction_count(int value) {
+  set_bit_field3(ConstructionCount::update(bit_field3(), value));
+}
+
+
+int Map::construction_count() {
+  return ConstructionCount::decode(bit_field3());
+}
+
+
 void Map::freeze() {
   set_bit_field3(IsFrozen::update(bit_field3(), true));
 }
 
 
 bool Map::is_frozen() {
   return IsFrozen::decode(bit_field3());
 }
 
 
@@ skipping 880 matching lines @@
 ACCESSORS_TO_SMI(BreakPointInfo, source_position, kSourcePositionIndex)
 ACCESSORS_TO_SMI(BreakPointInfo, statement_position, kStatementPositionIndex)
 ACCESSORS(BreakPointInfo, break_point_objects, Object, kBreakPointObjectsIndex)
 
 ACCESSORS(SharedFunctionInfo, name, Object, kNameOffset)
 ACCESSORS(SharedFunctionInfo, optimized_code_map, Object,
                  kOptimizedCodeMapOffset)
 ACCESSORS(SharedFunctionInfo, construct_stub, Code, kConstructStubOffset)
 ACCESSORS(SharedFunctionInfo, feedback_vector, FixedArray,
           kFeedbackVectorOffset)
-ACCESSORS(SharedFunctionInfo, initial_map, Object, kInitialMapOffset)
 ACCESSORS(SharedFunctionInfo, instance_class_name, Object,
           kInstanceClassNameOffset)
 ACCESSORS(SharedFunctionInfo, function_data, Object, kFunctionDataOffset)
 ACCESSORS(SharedFunctionInfo, script, Object, kScriptOffset)
 ACCESSORS(SharedFunctionInfo, debug_info, Object, kDebugInfoOffset)
 ACCESSORS(SharedFunctionInfo, inferred_name, String, kInferredNameOffset)
 
 
 SMI_ACCESSORS(FunctionTemplateInfo, length, kLengthOffset)
 BOOL_ACCESSORS(FunctionTemplateInfo, flag, hidden_prototype,
@@ skipping 104 matching lines @@
 PSEUDO_SMI_ACCESSORS_LO(SharedFunctionInfo,
                         ast_node_count,
                         kAstNodeCountOffset)
 PSEUDO_SMI_ACCESSORS_HI(SharedFunctionInfo,
                         profiler_ticks,
                         kProfilerTicksOffset)
 
 #endif
 
 
-int SharedFunctionInfo::construction_count() {
-  return READ_BYTE_FIELD(this, kConstructionCountOffset);
-}
-
-
-void SharedFunctionInfo::set_construction_count(int value) {
-  ASSERT(0 <= value && value < 256);
-  WRITE_BYTE_FIELD(this, kConstructionCountOffset, static_cast<byte>(value));
-}
-
-
-BOOL_ACCESSORS(SharedFunctionInfo,
-               compiler_hints,
-               live_objects_may_exist,
-               kLiveObjectsMayExist)
-
-
-bool SharedFunctionInfo::IsInobjectSlackTrackingInProgress() {
-  return initial_map() != GetHeap()->undefined_value();
-}
-
-
 BOOL_GETTER(SharedFunctionInfo,
             compiler_hints,
             optimization_disabled,
             kOptimizationDisabled)
 
 
 void SharedFunctionInfo::set_optimization_disabled(bool disable) {
   set_compiler_hints(BooleanBit::set(compiler_hints(),
                                      kOptimizationDisabled,
                                      disable));
@@ skipping 30 matching lines @@
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_anonymous, kIsAnonymous)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_function, kIsFunction)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_optimize,
                kDontOptimize)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_inline, kDontInline)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_cache, kDontCache)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_flush, kDontFlush)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_generator, kIsGenerator)
 
 void SharedFunctionInfo::BeforeVisitingPointers() {
-  if (IsInobjectSlackTrackingInProgress()) DetachInitialMap();
 }
 
 
 ACCESSORS(CodeCache, default_cache, FixedArray, kDefaultCacheOffset)
 ACCESSORS(CodeCache, normal_type_cache, Object, kNormalTypeCacheOffset)
 
 ACCESSORS(PolymorphicCodeCache, cache, Object, kCacheOffset)
 
 bool Script::HasValidSource() {
   Object* src = this->source();
@@ skipping 204 matching lines @@
       Builtins::kCompileOptimizedConcurrent);
 }
 
 
 bool JSFunction::IsInOptimizationQueue() {
   return code() == GetIsolate()->builtins()->builtin(
       Builtins::kInOptimizationQueue);
 }
 
 
+bool JSFunction::IsInobjectSlackTrackingInProgress() {
+  return has_initial_map() &&
+      initial_map()->construction_count() != JSFunction::kNoSlackTracking;
+}
+
+
 Code* JSFunction::code() {
   return Code::cast(
       Code::GetObjectFromEntryAddress(FIELD_ADDR(this, kCodeEntryOffset)));
 }
 
 
 void JSFunction::set_code(Code* value) {
   ASSERT(!GetHeap()->InNewSpace(value));
   Address entry = value->entry();
   WRITE_INTPTR_FIELD(this, kCodeEntryOffset, reinterpret_cast<intptr_t>(entry));
@@ skipping 1372 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_