[runtime] Speed up allocating instances in the runtime by having a quick-check for inobject slack t…

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 581ac0eaa054989339eec9070ca2fd555aece0b7..54c557f795c62e21ac72bf68d17e9814683159e9 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9326,8 +9326,6 @@ Handle<Map> Map::RawCopy(Handle<Map> map, int instance_size) {
   if (!map->is_dictionary_map()) {
     new_bit_field3 = IsUnstable::update(new_bit_field3, false);
   }
-  new_bit_field3 =
-      ConstructionCounter::update(new_bit_field3, kNoSlackTracking);
   result->set_bit_field3(new_bit_field3);
   return result;
 }
@@ -9414,6 +9412,7 @@ Handle<Map> Map::CopyNormalized(Handle<Map> map,
 
   result->set_dictionary_map(true);
   result->set_migration_target(false);
+  result->set_construction_counter(kNoSlackTracking);
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) result->DictionaryMapVerify();
@@ -12729,6 +12728,7 @@ static void ShrinkInstanceSize(Map* map, void* data) {
   map->SetInObjectProperties(map->GetInObjectProperties() - slack);
   map->set_unused_property_fields(map->unused_property_fields() - slack);
   map->set_instance_size(map->instance_size() - slack * kPointerSize);
+  map->set_construction_counter(Map::kNoSlackTracking);
 
   // Visitor id might depend on the instance size, recalculate it.
   map->set_visitor_id(Heap::GetStaticVisitorIdForMap(map));
@@ -12739,8 +12739,6 @@ void Map::CompleteInobjectSlackTracking() {
   // Has to be an initial map.
   DCHECK(GetBackPointer()->IsUndefined());
 
-  set_construction_counter(kNoSlackTracking);
-
   int slack = unused_property_fields();
   TransitionArray::TraverseTransitionTree(this, &GetMinInobjectSlack, &slack);
   if (slack != 0) {
@@ -13332,6 +13330,7 @@ MaybeHandle<Map> JSFunction::GetDerivedMap(Isolate* isolate,
 
       JSFunction::SetInitialMap(function, map, prototype);
       map->SetConstructor(*constructor);
+      map->set_construction_counter(Map::kNoSlackTracking);
       map->StartInobjectSlackTracking();
       return map;
     }