Map::ReconfigureProperty() should mark map as unstable when it returns a different map.

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 <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 2547 matching lines @@
     if (modify_index >= 0) {
       PropertyDetails details = target_descriptors->GetDetails(modify_index);
       DCHECK_EQ(new_kind, details.kind());
       DCHECK_EQ(new_attributes, details.attributes());
       DCHECK(new_representation.fits_into(details.representation()));
       DCHECK(details.location() != kField ||
              new_field_type->NowIs(
                  target_descriptors->GetFieldType(modify_index)));
     }
 #endif
+    if (*target_map != *old_map) {
+      old_map->NotifyLeafMapLayoutChange();
+    }
     return target_map;
   }
 
   // Find the last compatible target map in the transition tree.
   for (int i = target_nof; i < old_nof; ++i) {
     PropertyDetails old_details = old_descriptors->GetDetails(i);
     PropertyKind next_kind;
     PropertyAttributes next_attributes;
     if (modify_index == i) {
       next_kind = new_kind;
@@ skipping 233 matching lines @@
     split_attributes = new_attributes;
   } else {
     PropertyDetails split_prop_details = old_descriptors->GetDetails(split_nof);
     split_kind = split_prop_details.kind();
     split_attributes = split_prop_details.attributes();
   }
   bool transition_target_deprecated = split_map->DeprecateTarget(
       split_kind, old_descriptors->GetKey(split_nof), split_attributes,
       *new_descriptors, *new_layout_descriptor);
 
-  if (from_kind != to_kind) {
-    // There was an elements kind change in the middle of transition tree and
-    // we reconstructed the tree so that all elements kind transitions are
-    // done at the beginning, therefore the |old_map| is no longer stable.
-    old_map->NotifyLeafMapLayoutChange();
-  }
-
   // If |transition_target_deprecated| is true then the transition array
   // already contains entry for given descriptor. This means that the transition
   // could be inserted regardless of whether transitions array is full or not.
   if (!transition_target_deprecated &&
       !TransitionArray::CanHaveMoreTransitions(split_map)) {
     return CopyGeneralizeAllRepresentations(old_map, modify_index, store_mode,
                                             new_kind, new_attributes,
                                             "GenAll_CantHaveMoreTransitions");
   }
 
+  old_map->NotifyLeafMapLayoutChange();
+
   if (FLAG_trace_generalization && modify_index >= 0) {
     PropertyDetails old_details = old_descriptors->GetDetails(modify_index);
     PropertyDetails new_details = new_descriptors->GetDetails(modify_index);
     Handle<HeapType> old_field_type =
         (old_details.type() == DATA)
             ? handle(old_descriptors->GetFieldType(modify_index), isolate)
             : HeapType::Constant(
                   handle(old_descriptors->GetValue(modify_index), isolate),
                   isolate);
     Handle<HeapType> new_field_type =
@@ skipping 13794 matching lines @@
                                             Handle<Object> new_value) {
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 }  // namespace internal
 }  // namespace v8