Removed unnecessary generalization of all fields in Map::GeneralizeRepresentation() (introduced in …

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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 2241 matching lines @@
   deprecate();
   dependent_code()->DeoptimizeDependentCodeGroup(
       GetIsolate(), DependentCode::kTransitionGroup);
   NotifyLeafMapLayoutChange();
 }
 
 
 // Invalidates a transition target at |key|, and installs |new_descriptors| over
 // the current instance_descriptors to ensure proper sharing of descriptor
 // arrays.
-void Map::DeprecateTarget(Name* key, DescriptorArray* new_descriptors,
+// Returns true if the transition target at given key was deprecated.
+bool Map::DeprecateTarget(Name* key, DescriptorArray* new_descriptors,
                           LayoutDescriptor* new_layout_descriptor) {
+  bool transition_target_deprecated = false;
   if (HasTransitionArray()) {
     TransitionArray* transitions = this->transitions();
     int transition = transitions->Search(key);
     if (transition != TransitionArray::kNotFound) {
       transitions->GetTarget(transition)->DeprecateTransitionTree();
+      transition_target_deprecated = true;
     }
   }
 
   // Don't overwrite the empty descriptor array.
-  if (NumberOfOwnDescriptors() == 0) return;
+  if (NumberOfOwnDescriptors() == 0) return transition_target_deprecated;
 
   DescriptorArray* to_replace = instance_descriptors();
   Map* current = this;
   GetHeap()->incremental_marking()->RecordWrites(to_replace);
   while (current->instance_descriptors() == to_replace) {
     current->SetEnumLength(kInvalidEnumCacheSentinel);
     current->UpdateDescriptors(new_descriptors, new_layout_descriptor);
     Object* next = current->GetBackPointer();
     if (next->IsUndefined()) break;
     current = Map::cast(next);
   }
 
   set_owns_descriptors(false);
+  return transition_target_deprecated;
 }
 
 
 Map* Map::FindRootMap() {
   Map* result = this;
   while (true) {
     Object* back = result->GetBackPointer();
     if (back->IsUndefined()) return result;
     result = Map::cast(back);
   }
@@ skipping 427 matching lines @@
   DCHECK(store_mode != FORCE_FIELD ||
          new_descriptors->GetDetails(modify_index).type() == FIELD);
 
   Handle<Map> split_map(root_map->FindLastMatchMap(
           root_nof, old_nof, *new_descriptors), isolate);
   int split_nof = split_map->NumberOfOwnDescriptors();
   DCHECK_NE(old_nof, split_nof);
 
   Handle<LayoutDescriptor> new_layout_descriptor =
       LayoutDescriptor::New(split_map, new_descriptors, old_nof);
-  split_map->DeprecateTarget(old_descriptors->GetKey(split_nof),
-                             *new_descriptors, *new_layout_descriptor);
+  bool transition_target_deprecated =
+      split_map->DeprecateTarget(old_descriptors->GetKey(split_nof),
+                                 *new_descriptors, *new_layout_descriptor);
+
+  // 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 && !split_map->CanHaveMoreTransitions()) {
+    return CopyGeneralizeAllRepresentations(old_map, modify_index, store_mode,
+                                            "GenAll_CantHaveMoreTransitions");
+  }
 
   if (FLAG_trace_generalization) {
     PropertyDetails old_details = old_descriptors->GetDetails(modify_index);
     PropertyDetails new_details = new_descriptors->GetDetails(modify_index);
     Handle<HeapType> old_field_type = (old_details.type() == FIELD)
         ? handle(old_descriptors->GetFieldType(modify_index), isolate)
         : HeapType::Constant(handle(old_descriptors->GetValue(modify_index),
                                     isolate), isolate);
     Handle<HeapType> new_field_type = (new_details.type() == FIELD)
         ? handle(new_descriptors->GetFieldType(modify_index), isolate)
         : HeapType::Constant(handle(new_descriptors->GetValue(modify_index),
                                     isolate), isolate);
     old_map->PrintGeneralization(
         stdout, "", modify_index, split_nof, old_nof,
         old_details.type() == CONSTANT && store_mode == FORCE_FIELD,
         old_details.representation(), new_details.representation(),
         *old_field_type, *new_field_type);
   }
 
   // Add missing transitions.
   Handle<Map> new_map = split_map;
   for (int i = split_nof; i < old_nof; ++i) {
-    if (!new_map->CanHaveMoreTransitions()) {
-      return CopyGeneralizeAllRepresentations(old_map, modify_index, store_mode,
-                                              "can't have more transitions");
-    }
     new_map = CopyInstallDescriptors(new_map, i, new_descriptors,
                                      new_layout_descriptor);
   }
   new_map->set_owns_descriptors(true);
   return new_map;
 }
 
 
 // Generalize the representation of all FIELD descriptors.
 Handle<Map> Map::GeneralizeAllFieldRepresentations(
@@ skipping 14043 matching lines @@
   Handle<DependentCode> codes =
       DependentCode::Insert(handle(cell->dependent_code(), info->isolate()),
                             DependentCode::kPropertyCellChangedGroup,
                             info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal