Reduce field type tracking to a single stable map per field.

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 2308 matching lines @@
   DataDescriptor d(name, instance_descriptors()->GetFieldIndex(descriptor),
                    new_type, details.attributes(), new_representation);
   instance_descriptors()->Replace(descriptor, &d);
 }
 
 
 // static
 Handle<HeapType> Map::GeneralizeFieldType(Handle<HeapType> type1,
                                           Handle<HeapType> type2,
                                           Isolate* isolate) {
-  static const int kMaxClassesPerFieldType = 5;
   if (type1->NowIs(type2)) return type2;
   if (type2->NowIs(type1)) return type1;
-  if (type1->NowStable() && type2->NowStable()) {
-    Handle<HeapType> type = HeapType::Union(type1, type2, isolate);
-    if (type->NumClasses() <= kMaxClassesPerFieldType) {
-      DCHECK(type->NowStable());
-      DCHECK(type1->NowIs(type));
-      DCHECK(type2->NowIs(type));
-      return type;
-    }
-  }
   return HeapType::Any(isolate);
 }
 
 
 // static
 void Map::GeneralizeFieldType(Handle<Map> map, int modify_index,
                               Representation new_representation,
                               Handle<HeapType> new_field_type) {
   Isolate* isolate = map->GetIsolate();
 
@@ skipping 14856 matching lines @@
                                                CompilationInfo* info) {
   Handle<DependentCode> codes = DependentCode::InsertCompilationInfo(
       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