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

src/objects.cc

 // Copyright 2013 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.
 
 #include "v8.h"
 
 #include "accessors.h"
 #include "allocation-site-scopes.h"
 #include "api.h"
 #include "arguments.h"
@@ skipping 10188 matching lines @@
     JSObject::OptimizeAsPrototype(Handle<JSObject>::cast(value));
   }
 
   // Now some logic for the maps of the objects that are created by using this
   // function as a constructor.
   if (function->has_initial_map()) {
     // If the function has allocated the initial map replace it with a
     // copy containing the new prototype.  Also complete any in-object
     // slack tracking that is in progress at this point because it is
     // still tracking the old copy.
-    if (function->shared()->IsInobjectSlackTrackingInProgress()) {
-      function->shared()->CompleteInobjectSlackTracking();
+    if (function->IsInobjectSlackTrackingInProgress()) {
+      function->CompleteInobjectSlackTracking();
     }
     Handle<Map> new_map = Map::Copy(handle(function->initial_map()));
     new_map->set_prototype(*value);
 
     // If the function is used as the global Array function, cache the
     // initial map (and transitioned versions) in the native context.
     Context* native_context = function->context()->native_context();
     Object* array_function = native_context->get(Context::ARRAY_FUNCTION_INDEX);
     if (array_function->IsJSFunction() &&
         *function == JSFunction::cast(array_function)) {
@@ skipping 88 matching lines @@
   if (function->has_instance_prototype()) {
     prototype = handle(function->instance_prototype(), isolate);
   } else {
     prototype = isolate->factory()->NewFunctionPrototype(function);
   }
   map->set_inobject_properties(in_object_properties);
   map->set_unused_property_fields(in_object_properties);
   map->set_prototype(*prototype);
   ASSERT(map->has_fast_object_elements());
 
-  if (!function->shared()->is_generator()) {
-    function->shared()->StartInobjectSlackTracking(*map);
-  }
-
   // Finally link initial map and constructor function.
   function->set_initial_map(*map);
   map->set_constructor(*function);
+
+  if (!function->shared()->is_generator()) {
+    function->StartInobjectSlackTracking();
+  }
 }
 
 
 void JSFunction::SetInstanceClassName(String* name) {
   shared()->set_instance_class_name(name);
 }
 
 
 void JSFunction::PrintName(FILE* out) {
   SmartArrayPointer<char> name = shared()->DebugName()->ToCString();
@@ skipping 366 matching lines @@
   ASSERT(!id.IsNone());
   Code* unoptimized = code();
   DeoptimizationOutputData* data =
       DeoptimizationOutputData::cast(unoptimized->deoptimization_data());
   unsigned ignore = Deoptimizer::GetOutputInfo(data, id, this);
   USE(ignore);
   return true;  // Return true if there was no ASSERT.
 }
 
 
-void SharedFunctionInfo::StartInobjectSlackTracking(Map* map) {
-  ASSERT(!IsInobjectSlackTrackingInProgress());
+void JSFunction::StartInobjectSlackTracking() {
+  ASSERT(has_initial_map() && !IsInobjectSlackTrackingInProgress());
 
   if (!FLAG_clever_optimizations) return;
+  Map* map = initial_map();
 
   // Only initiate the tracking the first time.
-  if (live_objects_may_exist()) return;
-  set_live_objects_may_exist(true);
+  if (map->done_inobject_slack_tracking()) return;
+  map->set_done_inobject_slack_tracking(true);
 
   // No tracking during the snapshot construction phase.
   Isolate* isolate = GetIsolate();
   if (Serializer::enabled(isolate)) return;
 
   if (map->unused_property_fields() == 0) return;
 
-  // Nonzero counter is a leftover from the previous attempt interrupted
-  // by GC, keep it.
-  if (construction_count() == 0) {
-    set_construction_count(kGenerousAllocationCount);
-  }
-  set_initial_map(map);
-  Builtins* builtins = isolate->builtins();
-  ASSERT_EQ(builtins->builtin(Builtins::kJSConstructStubGeneric),
-            construct_stub());
-  set_construct_stub(builtins->builtin(Builtins::kJSConstructStubCountdown));
+  map->set_construction_count(kGenerousAllocationCount);
 }
 
 
-// Called from GC, hence reinterpret_cast and unchecked accessors.
-void SharedFunctionInfo::DetachInitialMap() {
-  Map* map = reinterpret_cast<Map*>(initial_map());
-
-  // Make the map remember to restore the link if it survives the GC.
-  map->set_bit_field2(
-      map->bit_field2() | (1 << Map::kAttachedToSharedFunctionInfo));
-
-  // Undo state changes made by StartInobjectTracking (except the
-  // construction_count). This way if the initial map does not survive the GC
-  // then StartInobjectTracking will be called again the next time the
-  // constructor is called. The countdown will continue and (possibly after
-  // several more GCs) CompleteInobjectSlackTracking will eventually be called.
-  Heap* heap = map->GetHeap();
-  set_initial_map(heap->undefined_value());
-  Builtins* builtins = heap->isolate()->builtins();
-  ASSERT_EQ(builtins->builtin(Builtins::kJSConstructStubCountdown),
-            *RawField(this, kConstructStubOffset));
-  set_construct_stub(builtins->builtin(Builtins::kJSConstructStubGeneric));
-  // It is safe to clear the flag: it will be set again if the map is live.
-  set_live_objects_may_exist(false);
-}
-
-
-// Called from GC, hence reinterpret_cast and unchecked accessors.
-void SharedFunctionInfo::AttachInitialMap(Map* map) {
-  map->set_bit_field2(
-      map->bit_field2() & ~(1 << Map::kAttachedToSharedFunctionInfo));
-
-  // Resume inobject slack tracking.
-  set_initial_map(map);
-  Builtins* builtins = map->GetHeap()->isolate()->builtins();
-  ASSERT_EQ(builtins->builtin(Builtins::kJSConstructStubGeneric),
-            *RawField(this, kConstructStubOffset));
-  set_construct_stub(builtins->builtin(Builtins::kJSConstructStubCountdown));
-  // The map survived the gc, so there may be objects referencing it.
-  set_live_objects_may_exist(true);
-}
-
-
 void SharedFunctionInfo::ResetForNewContext(int new_ic_age) {
   code()->ClearInlineCaches();
   // If we clear ICs, we need to clear the type feedback vector too, since
   // CallICs are synced with a feedback vector slot.
   ClearTypeFeedbackInfo();
   set_ic_age(new_ic_age);
   if (code()->kind() == Code::FUNCTION) {
     code()->set_profiler_ticks(0);
     if (optimization_disabled() &&
         opt_count() >= FLAG_max_opt_count) {
@@ skipping 19 matching lines @@
   int slack = *reinterpret_cast<int*>(data);
   map->set_inobject_properties(map->inobject_properties() - slack);
   map->set_unused_property_fields(map->unused_property_fields() - slack);
   map->set_instance_size(map->instance_size() - slack * kPointerSize);
 
   // Visitor id might depend on the instance size, recalculate it.
   map->set_visitor_id(StaticVisitorBase::GetVisitorId(map));
 }
 
 
-void SharedFunctionInfo::CompleteInobjectSlackTracking() {
-  ASSERT(live_objects_may_exist() && IsInobjectSlackTrackingInProgress());
-  Map* map = Map::cast(initial_map());
+void JSFunction::CompleteInobjectSlackTracking() {
+  ASSERT(has_initial_map());
+  Map* map = initial_map();
 
-  Heap* heap = map->GetHeap();
-  set_initial_map(heap->undefined_value());
-  Builtins* builtins = heap->isolate()->builtins();
-  ASSERT_EQ(builtins->builtin(Builtins::kJSConstructStubCountdown),
-            construct_stub());
-  set_construct_stub(builtins->builtin(Builtins::kJSConstructStubGeneric));
+  ASSERT(map->done_inobject_slack_tracking());
+  map->set_construction_count(kNoSlackTracking);
 
   int slack = map->unused_property_fields();
   map->TraverseTransitionTree(&GetMinInobjectSlack, &slack);
   if (slack != 0) {
     // Resize the initial map and all maps in its transition tree.
     map->TraverseTransitionTree(&ShrinkInstanceSize, &slack);
-
-    // Give the correct expected_nof_properties to initial maps created later.
-    ASSERT(expected_nof_properties() >= slack);
-    set_expected_nof_properties(expected_nof_properties() - slack);
   }
 }
 
 
 int SharedFunctionInfo::SearchOptimizedCodeMap(Context* native_context,
                                                BailoutId osr_ast_id) {
   DisallowHeapAllocation no_gc;
   ASSERT(native_context->IsNativeContext());
   if (!FLAG_cache_optimized_code) return -1;
   Object* value = optimized_code_map();
@@ skipping 6425 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal