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

src/types.cc

Index: src/types.cc
diff --git a/src/types.cc b/src/types.cc
index 98592cf5c242d3e3c7739a94c8ded31dd2a60288..4c3cee753be12faa4a5d9dd61d2e009ba2694f11 100644
--- a/src/types.cc
+++ b/src/types.cc
@@ -140,14 +140,6 @@ int TypeImpl<Config>::LubBitset(i::Object* value) {
         value->ToInt32(&i) ? (Smi::IsValid(i) ? kSignedSmall : kOtherSigned32) :
         value->ToUint32(&u) ? kUnsigned32 : kFloat);
   }
-  if (map->instance_type() == ODDBALL_TYPE) {
-    if (value->IsUndefined()) return kUndefined;
-    if (value->IsNull()) return kNull;
-    if (value->IsBoolean()) return kBoolean;
-    if (value->IsTheHole()) return kAny;  // TODO(rossberg): kNone?
-    if (value->IsUninitialized()) return kNone;
-    UNREACHABLE();
-  }
   return LubBitset(map);
 }
 
@@ -178,8 +170,16 @@ int TypeImpl<Config>::LubBitset(i::Map* map) {
       return kString;
     case SYMBOL_TYPE:
       return kSymbol;
-    case ODDBALL_TYPE:
+    case ODDBALL_TYPE: {
+      Heap* heap = map->GetHeap();
+      if (map == heap->undefined_map()) return kUndefined;
+      if (map == heap->the_hole_map()) return kAny;  // TODO(rossberg): kNone?
+      if (map == heap->null_map()) return kNull;
+      if (map == heap->boolean_map()) return kBoolean;
+      if (map == heap->uninitialized_map()) return kNone;
+      ASSERT(map == heap->oddball_map());
       return kOddball;

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

I think you could now return kInternal here and eliminate the Oddball type.

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

Done.

+    }
     case HEAP_NUMBER_TYPE:
       return kFloat & kTaggedPtr;
     case JS_VALUE_TYPE:
@@ -251,8 +251,7 @@ template<class Config>
 typename TypeImpl<Config>::TypeHandle TypeImpl<Config>::NowOf(
     i::Object* value, Region* region) {
   if (value->IsSmi() ||
-      i::HeapObject::cast(value)->map()->instance_type() == HEAP_NUMBER_TYPE ||
-      i::HeapObject::cast(value)->map()->instance_type() == ODDBALL_TYPE) {
+      i::HeapObject::cast(value)->map()->instance_type() == HEAP_NUMBER_TYPE) {
     return Of(value, region);
   }
   return Class(i::handle(i::HeapObject::cast(value)->map()), region);