Ensure we can reliably check the cell for validity of global property

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 6fd95030c538d2d5618eb680b1c0a8752b535e75..02b55c84897ce8b7c24404a297779a487adf20c9 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -523,6 +523,38 @@ MaybeHandle<Object> JSObject::SetPropertyWithFailedAccessCheck(
 }
 
 
+static void ReplaceExistingPropertyCell(Handle<GlobalObject> global, int entry,
+                                        Handle<Object> value) {
+  Isolate* isolate = global->GetIsolate();
+  Handle<PropertyCell> cell(
+      PropertyCell::cast(global->property_dictionary()->ValueAt(entry)));
+
+  Handle<PropertyCell> new_cell = isolate->factory()->NewPropertyCell(value);
+  global->property_dictionary()->ValueAtPut(entry, *new_cell);
+
+  Handle<Object> hole = isolate->factory()->the_hole_value();
+  if (*hole == cell->value()) {
+    PropertyCell::SetValueInferType(cell,
+                                    isolate->factory()->undefined_value());
+  } else {
+    PropertyCell::SetValueInferType(cell, hole);
+  }
+}
+
+
+void GlobalObject::InvalidatePropertyCell(Handle<GlobalObject> global,
+                                          Handle<Name> name) {
+  DCHECK(!global->HasFastProperties());
+  int entry = global->property_dictionary()->FindEntry(name);
+  if (entry != NameDictionary::kNotFound) {
+    PropertyCell* cell =
+        PropertyCell::cast(global->property_dictionary()->ValueAt(entry));
+    Handle<Object> value(cell->value(), global->GetIsolate());
+    ReplaceExistingPropertyCell(global, entry, value);
+  }
+}
+
+
 void JSObject::SetNormalizedProperty(Handle<JSObject> object,
                                      Handle<Name> name,
                                      Handle<Object> value,
@@ -565,7 +597,12 @@ void JSObject::SetNormalizedProperty(Handle<JSObject> object,
   if (object->IsGlobalObject()) {
     Handle<PropertyCell> cell(
         PropertyCell::cast(property_dictionary->ValueAt(entry)));
-    PropertyCell::SetValueInferType(cell, value);
+    if (details.type() != property_dictionary->DetailsAt(entry).type()) {
+      ReplaceExistingPropertyCell(Handle<GlobalObject>::cast(object), entry,
+                                  value);
+    } else {
+      PropertyCell::SetValueInferType(cell, value);
+    }
     // Please note we have to update the property details.
     property_dictionary->DetailsAtPut(entry, details);
   } else {
@@ -1776,14 +1813,13 @@ void JSObject::AddSlowProperty(Handle<JSObject> object,
     // In case name is an orphaned property reuse the cell.
     int entry = dict->FindEntry(name);
     if (entry != NameDictionary::kNotFound) {
-      Handle<PropertyCell> cell(PropertyCell::cast(dict->ValueAt(entry)));
-      PropertyCell::SetValueInferType(cell, value);
+      ReplaceExistingPropertyCell(Handle<GlobalObject>::cast(object), entry,
+                                  value);
       // Assign an enumeration index to the property and update
       // SetNextEnumerationIndex.
       int index = dict->NextEnumerationIndex();
       PropertyDetails details(attributes, DATA, index);
-      dict->SetNextEnumerationIndex(index + 1);
-      dict->SetEntry(entry, name, cell, details);
+      dict->DetailsAtPut(entry, details);
       return;
     }
     value = isolate->factory()->NewPropertyCell(value);
@@ -5312,9 +5348,8 @@ void JSObject::DeleteNormalizedProperty(Handle<JSObject> object,
   if (object->IsGlobalObject()) {
     PropertyDetails details = dictionary->DetailsAt(entry);
     DCHECK(details.IsConfigurable());
-    Handle<PropertyCell> cell(PropertyCell::cast(dictionary->ValueAt(entry)));
-    Handle<Object> value = isolate->factory()->the_hole_value();
-    PropertyCell::SetValueInferType(cell, value);
+    ReplaceExistingPropertyCell(Handle<GlobalObject>::cast(object), entry,
+                                isolate->factory()->the_hole_value());
     dictionary->DetailsAtPut(entry, details.AsDeleted());
     return;
   }
@@ -7432,12 +7467,7 @@ Handle<Map> Map::TransitionToAccessorProperty(Handle<Map> map,
   Isolate* isolate = name->GetIsolate();
 
   // Dictionary maps can always have additional data properties.
-  if (map->is_dictionary_map()) {
-    // For global objects, property cells are inlined. We need to change the
-    // map.
-    if (map->IsGlobalObjectMap()) return Copy(map, "GlobalAccessor");
-    return map;
-  }
+  if (map->is_dictionary_map()) return map;
 
   // Migrate to the newest map before transitioning to the new property.
   map = Update(map);
@@ -15311,32 +15341,6 @@ Handle<Object> ExternalFloat64Array::SetValue(
 }
 
 
-void GlobalObject::InvalidatePropertyCell(Handle<GlobalObject> global,
-                                          Handle<Name> name) {
-  DCHECK(!global->HasFastProperties());
-  Isolate* isolate = global->GetIsolate();
-  int entry = global->property_dictionary()->FindEntry(name);
-  if (entry != NameDictionary::kNotFound) {
-    Handle<PropertyCell> cell(
-        PropertyCell::cast(global->property_dictionary()->ValueAt(entry)));
-
-    Handle<Object> value(cell->value(), isolate);
-    Handle<PropertyCell> new_cell = isolate->factory()->NewPropertyCell(value);
-    global->property_dictionary()->ValueAtPut(entry, *new_cell);
-
-    Handle<Object> hole = isolate->factory()->the_hole_value();
-    if (*hole != *value) {
-      PropertyCell::SetValueInferType(cell, hole);
-    } else {
-      // If property value was the hole, set it to any other value,
-      // to ensure that LoadNonexistent ICs execute a miss.
-      Handle<Object> undefined = isolate->factory()->undefined_value();
-      PropertyCell::SetValueInferType(cell, undefined);
-    }
-  }
-}
-
-
 Handle<PropertyCell> GlobalObject::EnsurePropertyCell(
     Handle<GlobalObject> global, Handle<Name> name) {
   DCHECK(!global->HasFastProperties());