Use distinct maps for oddballs with special handling in the type system.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2739 matching lines @@
 bool Heap::CreateInitialMaps() {
   Object* obj;
   { MaybeObject* maybe_obj = AllocatePartialMap(MAP_TYPE, Map::kSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   // Map::cast cannot be used due to uninitialized map field.
   Map* new_meta_map = reinterpret_cast<Map*>(obj);
   set_meta_map(new_meta_map);
   new_meta_map->set_map(new_meta_map);
 
-  { MaybeObject* maybe_obj =
-        AllocatePartialMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
-    if (!maybe_obj->ToObject(&obj)) return false;
+  { // Partial map allocation
+#define ALLOCATE_PARTIAL_MAP(instance_type, size, field_name)                  \
+    { Map* map;                                                                \
+      if (!AllocatePartialMap((instance_type), (size))->To(&map)) return false;\
+      set_##field_name##_map(map);                                             \
+    }
+
+    ALLOCATE_PARTIAL_MAP(FIXED_ARRAY_TYPE, kVariableSizeSentinel, fixed_array);
+    ALLOCATE_PARTIAL_MAP(ODDBALL_TYPE, Oddball::kSize, undefined);
+    ALLOCATE_PARTIAL_MAP(ODDBALL_TYPE, Oddball::kSize, null);
+    ALLOCATE_PARTIAL_MAP(CONSTANT_POOL_ARRAY_TYPE, kVariableSizeSentinel,
+                         constant_pool_array);
+
+#undef ALLOCATE_PARTIAL_MAP
   }
-  set_fixed_array_map(Map::cast(obj));
-
-  { MaybeObject* maybe_obj = AllocatePartialMap(ODDBALL_TYPE, Oddball::kSize);
-    if (!maybe_obj->ToObject(&obj)) return false;
-  }
-  set_oddball_map(Map::cast(obj));
-
-  { MaybeObject* maybe_obj =
-        AllocatePartialMap(CONSTANT_POOL_ARRAY_TYPE, kVariableSizeSentinel);
-    if (!maybe_obj->ToObject(&obj)) return false;
-  }
-  set_constant_pool_array_map(Map::cast(obj));
 
   // Allocate the empty array.
   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_empty_fixed_array(FixedArray::cast(obj));
 
-  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
+  { MaybeObject* maybe_obj = Allocate(null_map(), OLD_POINTER_SPACE);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_null_value(Oddball::cast(obj));
   Oddball::cast(obj)->set_kind(Oddball::kNull);
 
-  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
+  { MaybeObject* maybe_obj = Allocate(undefined_map(), OLD_POINTER_SPACE);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_undefined_value(Oddball::cast(obj));
   Oddball::cast(obj)->set_kind(Oddball::kUndefined);
   ASSERT(!InNewSpace(undefined_value()));
 
   // Allocate the empty descriptor array.
   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
     if (!maybe_obj->ToObject(&obj)) return false;
   }
@@ skipping 10 matching lines @@
   meta_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
   meta_map()->init_back_pointer(undefined_value());
   meta_map()->set_instance_descriptors(empty_descriptor_array());
 
   fixed_array_map()->set_code_cache(empty_fixed_array());
   fixed_array_map()->set_dependent_code(
       DependentCode::cast(empty_fixed_array()));
   fixed_array_map()->init_back_pointer(undefined_value());
   fixed_array_map()->set_instance_descriptors(empty_descriptor_array());
 
-  oddball_map()->set_code_cache(empty_fixed_array());
-  oddball_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
-  oddball_map()->init_back_pointer(undefined_value());
-  oddball_map()->set_instance_descriptors(empty_descriptor_array());
+  undefined_map()->set_code_cache(empty_fixed_array());
+  undefined_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
+  undefined_map()->init_back_pointer(undefined_value());
+  undefined_map()->set_instance_descriptors(empty_descriptor_array());
+
+  null_map()->set_code_cache(empty_fixed_array());
+  null_map()->set_dependent_code(DependentCode::cast(empty_fixed_array()));
+  null_map()->init_back_pointer(undefined_value());
+  null_map()->set_instance_descriptors(empty_descriptor_array());
 
   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_back_pointer(undefined_value());
   constant_pool_array_map()->set_instance_descriptors(empty_descriptor_array());
 
   // Fix prototype object for existing maps.
   meta_map()->set_prototype(null_value());
   meta_map()->set_constructor(null_value());
 
   fixed_array_map()->set_prototype(null_value());
   fixed_array_map()->set_constructor(null_value());
 
-  oddball_map()->set_prototype(null_value());
-  oddball_map()->set_constructor(null_value());
+  undefined_map()->set_prototype(null_value());
+  undefined_map()->set_constructor(null_value());
+
+  null_map()->set_prototype(null_value());
+  null_map()->set_constructor(null_value());
 
   constant_pool_array_map()->set_prototype(null_value());
   constant_pool_array_map()->set_constructor(null_value());
 
   { // Map allocation
 #define ALLOCATE_MAP(instance_type, size, field_name)                          \
     { Map* map;                                                                \
       if (!AllocateMap((instance_type), size)->To(&map)) return false;         \
       set_##field_name##_map(map);                                             \
     }
 
 #define ALLOCATE_VARSIZE_MAP(instance_type, field_name)                        \
     ALLOCATE_MAP(instance_type, kVariableSizeSentinel, field_name)
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, fixed_cow_array)
     ASSERT(fixed_array_map() != fixed_cow_array_map());
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, scope_info)
     ALLOCATE_MAP(HEAP_NUMBER_TYPE, HeapNumber::kSize, heap_number)
     ALLOCATE_MAP(SYMBOL_TYPE, Symbol::kSize, symbol)
     ALLOCATE_MAP(FOREIGN_TYPE, Foreign::kSize, foreign)
 
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, the_hole);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, boolean);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, uninitialized);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, arguments_marker);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, no_interceptor_result_sentinel);
+    ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, termination_exception);
+
     for (unsigned i = 0; i < ARRAY_SIZE(string_type_table); i++) {
       const StringTypeTable& entry = string_type_table[i];
       { MaybeObject* maybe_obj = AllocateMap(entry.type, entry.size);
         if (!maybe_obj->ToObject(&obj)) return false;
       }
       roots_[entry.index] = Map::cast(obj);
     }
 
     ALLOCATE_VARSIZE_MAP(STRING_TYPE, undetectable_string)
     undetectable_string_map()->set_is_undetectable();
@@ skipping 163 matching lines @@
   if (!maybe_result->To(&site)) return maybe_result;
   site->Initialize();
 
   // Link the site
   site->set_weak_next(allocation_sites_list());
   set_allocation_sites_list(site);
   return site;
 }
 
 
-MaybeObject* Heap::CreateOddball(const char* to_string,
+MaybeObject* Heap::CreateOddball(Map* map,
+                                 const char* to_string,
                                  Object* to_number,
                                  byte kind) {
   Object* result;
-  { MaybeObject* maybe_result = Allocate(oddball_map(), OLD_POINTER_SPACE);
+  { MaybeObject* maybe_result = Allocate(map, OLD_POINTER_SPACE);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   return Oddball::cast(result)->Initialize(this, to_string, to_number, kind);
 }
 
 
 bool Heap::CreateApiObjects() {
   Object* obj;
 
   { MaybeObject* maybe_obj = AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
@@ skipping 104 matching lines @@
                                       Oddball::kUndefined);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
 
   // Initialize the null_value.
   { MaybeObject* maybe_obj = null_value()->Initialize(
       this, "null", Smi::FromInt(0), Oddball::kNull);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
 
-  { MaybeObject* maybe_obj = CreateOddball("true",
+  { MaybeObject* maybe_obj = CreateOddball(boolean_map(),
+                                           "true",
                                            Smi::FromInt(1),
                                            Oddball::kTrue);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_true_value(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("false",
+  { MaybeObject* maybe_obj = CreateOddball(boolean_map(),
+                                           "false",
                                            Smi::FromInt(0),
                                            Oddball::kFalse);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_false_value(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("hole",
+  { MaybeObject* maybe_obj = CreateOddball(the_hole_map(),
+                                           "hole",
                                            Smi::FromInt(-1),
                                            Oddball::kTheHole);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_the_hole_value(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("uninitialized",
+  { MaybeObject* maybe_obj = CreateOddball(uninitialized_map(),
+                                           "uninitialized",
                                            Smi::FromInt(-1),
                                            Oddball::kUninitialized);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_uninitialized_value(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("arguments_marker",
+  { MaybeObject* maybe_obj = CreateOddball(arguments_marker_map(),
+                                           "arguments_marker",
                                            Smi::FromInt(-4),
                                            Oddball::kArgumentMarker);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_arguments_marker(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("no_interceptor_result_sentinel",
+  { MaybeObject* maybe_obj = CreateOddball(no_interceptor_result_sentinel_map(),
+                                           "no_interceptor_result_sentinel",
                                            Smi::FromInt(-2),
                                            Oddball::kOther);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
-  set_no_interceptor_result_sentinel(obj);
+  set_no_interceptor_result_sentinel(Oddball::cast(obj));
 
-  { MaybeObject* maybe_obj = CreateOddball("termination_exception",
+  { MaybeObject* maybe_obj = CreateOddball(termination_exception_map(),
+                                           "termination_exception",
                                            Smi::FromInt(-3),
                                            Oddball::kOther);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
-  set_termination_exception(obj);
+  set_termination_exception(Oddball::cast(obj));
 
   for (unsigned i = 0; i < ARRAY_SIZE(constant_string_table); i++) {
     { MaybeObject* maybe_obj =
           InternalizeUtf8String(constant_string_table[i].contents);
       if (!maybe_obj->ToObject(&obj)) return false;
     }
     roots_[constant_string_table[i].index] = String::cast(obj);
   }
 
   // Allocate the hidden string which is used to identify the hidden properties
@@ skipping 4633 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
 
   OS::MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   OS::MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal