Revert of Revert of Simplify and compact transitions storage

src/heap/heap.cc

 // Copyright 2012 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 "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 2459 matching lines @@
   map->set_instance_type(instance_type);
   map->set_prototype(null_value(), SKIP_WRITE_BARRIER);
   map->set_constructor_or_backpointer(null_value(), SKIP_WRITE_BARRIER);
   map->set_instance_size(instance_size);
   map->set_inobject_properties(0);
   map->set_pre_allocated_property_fields(0);
   map->set_code_cache(empty_fixed_array(), SKIP_WRITE_BARRIER);
   map->set_dependent_code(DependentCode::cast(empty_fixed_array()),
                           SKIP_WRITE_BARRIER);
   map->set_weak_cell_cache(Smi::FromInt(0));
-  map->init_transitions(undefined_value());
+  map->set_raw_transitions(Smi::FromInt(0));
   map->set_unused_property_fields(0);
   map->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     map->set_layout_descriptor(LayoutDescriptor::FastPointerLayout());
   }
   // Must be called only after |instance_type|, |instance_size| and
   // |layout_descriptor| are set.
   map->set_visitor_id(StaticVisitorBase::GetVisitorId(map));
   map->set_bit_field(0);
   map->set_bit_field2(1 << Map::kIsExtensible);
@@ skipping 113 matching lines @@
   // Allocate the constant pool array.
   {
     AllocationResult allocation = AllocateEmptyConstantPoolArray();
     if (!allocation.To(&obj)) return false;
   }
   set_empty_constant_pool_array(ConstantPoolArray::cast(obj));
 
   // Fix the instance_descriptors for the existing maps.
   meta_map()->set_code_cache(empty_fixed_array());
   meta_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
-  meta_map()->init_transitions(undefined_value());
+  meta_map()->set_raw_transitions(Smi::FromInt(0));
   meta_map()->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     meta_map()->set_layout_descriptor(LayoutDescriptor::FastPointerLayout());
   }
 
   fixed_array_map()->set_code_cache(empty_fixed_array());
   fixed_array_map()->set_dependent_code(
       DependentCode::cast(empty_fixed_array()));
-  fixed_array_map()->init_transitions(undefined_value());
+  fixed_array_map()->set_raw_transitions(Smi::FromInt(0));
   fixed_array_map()->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     fixed_array_map()->set_layout_descriptor(
         LayoutDescriptor::FastPointerLayout());
   }
 
   undefined_map()->set_code_cache(empty_fixed_array());
   undefined_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
-  undefined_map()->init_transitions(undefined_value());
+  undefined_map()->set_raw_transitions(Smi::FromInt(0));
   undefined_map()->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     undefined_map()->set_layout_descriptor(
         LayoutDescriptor::FastPointerLayout());
   }
 
   null_map()->set_code_cache(empty_fixed_array());
   null_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
-  null_map()->init_transitions(undefined_value());
+  null_map()->set_raw_transitions(Smi::FromInt(0));
   null_map()->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     null_map()->set_layout_descriptor(LayoutDescriptor::FastPointerLayout());
   }
 
   constant_pool_array_map()->set_code_cache(empty_fixed_array());
   constant_pool_array_map()->set_dependent_code(
       DependentCode::cast(empty_fixed_array()));
-  constant_pool_array_map()->init_transitions(undefined_value());
+  constant_pool_array_map()->set_raw_transitions(Smi::FromInt(0));
   constant_pool_array_map()->set_instance_descriptors(empty_descriptor_array());
   if (FLAG_unbox_double_fields) {
     constant_pool_array_map()->set_layout_descriptor(
         LayoutDescriptor::FastPointerLayout());
   }
 
   // Fix prototype object for existing maps.
   meta_map()->set_prototype(null_value());
   meta_map()->set_constructor_or_backpointer(null_value());
 
@@ skipping 3884 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal