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

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index b8110920b22de919ee7968ec22e7461d45c8e6d4..670860004cafc10150fd33acc1f9b051392dc506 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -72,7 +72,7 @@ namespace internal {
   V(Map, fixed_cow_array_map, FixedCOWArrayMap)                                \
   V(Map, fixed_double_array_map, FixedDoubleArrayMap)                          \
   V(Map, constant_pool_array_map, ConstantPoolArrayMap)                        \
-  V(Object, no_interceptor_result_sentinel, NoInterceptorResultSentinel)       \
+  V(Oddball, no_interceptor_result_sentinel, NoInterceptorResultSentinel)      \
   V(Map, hash_table_map, HashTableMap)                                         \
   V(FixedArray, empty_fixed_array, EmptyFixedArray)                            \
   V(ByteArray, empty_byte_array, EmptyByteArray)                               \
@@ -89,7 +89,7 @@ namespace internal {
   V(FixedArray, single_character_string_cache, SingleCharacterStringCache)     \
   V(FixedArray, string_split_cache, StringSplitCache)                          \
   V(FixedArray, regexp_multiple_cache, RegExpMultipleCache)                    \
-  V(Object, termination_exception, TerminationException)                       \
+  V(Oddball, termination_exception, TerminationException)                      \
   V(Smi, hash_seed, HashSeed)                                                  \
   V(Map, symbol_map, SymbolMap)                                                \
   V(Map, string_map, StringMap)                                                \
@@ -179,6 +179,11 @@ namespace internal {
   V(Map, block_context_map, BlockContextMap)                                   \
   V(Map, module_context_map, ModuleContextMap)                                 \
   V(Map, global_context_map, GlobalContextMap)                                 \
+  V(Map, undefined_map, UndefinedMap)                                          \
+  V(Map, the_hole_map, TheHoleMap)                                             \
+  V(Map, null_map, NullMap)                                                    \
+  V(Map, boolean_map, BooleanMap)                                              \
+  V(Map, uninitialized_map, UninitializedMap)                                  \
   V(Map, oddball_map, OddballMap)                                              \

[rossberg, 2014/04/07 09:04:03]

Can't we have distinct maps for the other oddballs as well and get rid of this
entirely?

[Benedikt Meurer, 2014/04/07 09:30:19]

Done.

   V(Map, message_object_map, JSMessageObjectMap)                               \
   V(Map, foreign_map, ForeignMap)                                              \
@@ -266,7 +271,11 @@ namespace internal {
   V(block_context_map)                    \
   V(module_context_map)                   \
   V(global_context_map)                   \
-  V(oddball_map)                          \
+  V(undefined_map)                        \
+  V(the_hole_map)                         \
+  V(null_map)                             \
+  V(boolean_map)                          \
+  V(uninitialized_map)                    \
   V(message_object_map)                   \
   V(foreign_map)                          \
   V(neander_map)
@@ -2213,7 +2222,8 @@ class Heap {
 
   void CreateFixedStubs();
 
-  MUST_USE_RESULT MaybeObject* CreateOddball(const char* to_string,
+  MUST_USE_RESULT MaybeObject* CreateOddball(Map* map,
+                                             const char* to_string,
                                              Object* to_number,
                                              byte kind);