Templatise type representation

src/types.cc

 // Copyright 2013 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 13 matching lines @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "types.h"
 #include "string-stream.h"
 
 namespace v8 {
 namespace internal {
 
-int Type::NumClasses() {
-  if (is_class()) {
+template<class Config>
+int TypeImpl<Config>::NumClasses() {
+  if (this->IsClass()) {
     return 1;
-  } else if (is_union()) {
-    Handle<Unioned> unioned = as_union();
+  } else if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     int result = 0;
     for (int i = 0; i < unioned->length(); ++i) {
-      if (union_get(unioned, i)->is_class()) ++result;
+      if (Config::union_get(unioned, i)->IsClass()) ++result;
     }
     return result;
   } else {
     return 0;
   }
 }
 
 
-int Type::NumConstants() {
-  if (is_constant()) {
+template<class Config>
+int TypeImpl<Config>::NumConstants() {
+  if (this->IsConstant()) {
     return 1;
-  } else if (is_union()) {
-    Handle<Unioned> unioned = as_union();
+  } else if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     int result = 0;
     for (int i = 0; i < unioned->length(); ++i) {
-      if (union_get(unioned, i)->is_constant()) ++result;
+      if (Config::union_get(unioned, i)->IsConstant()) ++result;
     }
     return result;
   } else {
     return 0;
   }
 }
 
 
-template<class T>
-Handle<Type> Type::Iterator<T>::get_type() {
+template<class Config> template<class T>
+typename TypeImpl<Config>::TypeHandle
+TypeImpl<Config>::Iterator<T>::get_type() {
   ASSERT(!Done());
-  return type_->is_union() ? union_get(type_->as_union(), index_) : type_;
-}
-
-template<>
-Handle<i::Map> Type::Iterator<i::Map>::Current() {
-  return get_type()->as_class();
-}
-
-template<>
-Handle<i::Object> Type::Iterator<i::Object>::Current() {
-  return get_type()->as_constant();
+  return type_->IsUnion() ? Config::union_get(type_->AsUnion(), index_) : type_;
 }
 
 
-template<>
-bool Type::Iterator<i::Map>::matches(Handle<Type> type) {
-  return type->is_class();
+// C++ cannot specialise nested templates, so we have to go through this
+// contortion with an auxiliary template to simulate it.
+template<class Config, class T>
+struct TypeImplIteratorAux {
+  static bool matches(typename TypeImpl<Config>::TypeHandle type);
+  static i::Handle<T> current(typename TypeImpl<Config>::TypeHandle type);
+};
+
+template<class Config>
+struct TypeImplIteratorAux<Config, i::Map> {
+  static bool matches(typename TypeImpl<Config>::TypeHandle type) {
+    return type->IsClass();
+  }
+  static i::Handle<i::Map> current(typename TypeImpl<Config>::TypeHandle type) {
+    return type->AsClass();
+  }
+};
+
+template<class Config>
+struct TypeImplIteratorAux<Config, i::Object> {
+  static bool matches(typename TypeImpl<Config>::TypeHandle type) {
+    return type->IsConstant();
+  }
+  static i::Handle<i::Object> current(
+      typename TypeImpl<Config>::TypeHandle type) {
+    return type->AsConstant();
+  }
+};
+
+template<class Config> template<class T>
+bool TypeImpl<Config>::Iterator<T>::matches(TypeHandle type) {
+  return TypeImplIteratorAux<Config, T>::matches(type);
 }
 
-template<>
-bool Type::Iterator<i::Object>::matches(Handle<Type> type) {
-  return type->is_constant();
+template<class Config> template<class T>
+i::Handle<T> TypeImpl<Config>::Iterator<T>::Current() {
+  return TypeImplIteratorAux<Config, T>::current(get_type());
 }
 
 
-template<class T>
-void Type::Iterator<T>::Advance() {
+template<class Config> template<class T>
+void TypeImpl<Config>::Iterator<T>::Advance() {
   ++index_;
-  if (type_->is_union()) {
-    Handle<Unioned> unioned = type_->as_union();
+  if (type_->IsUnion()) {
+    UnionedHandle unioned = type_->AsUnion();
     for (; index_ < unioned->length(); ++index_) {
-      if (matches(union_get(unioned, index_))) return;
+      if (matches(Config::union_get(unioned, index_))) return;
     }
   } else if (index_ == 0 && matches(type_)) {
     return;
   }
   index_ = -1;
 }
 
-template class Type::Iterator<i::Map>;
-template class Type::Iterator<i::Object>;
-
 
 // Get the smallest bitset subsuming this type.
-int Type::LubBitset() {
-  if (this->is_bitset()) {
-    return this->as_bitset();
-  } else if (this->is_union()) {
-    Handle<Unioned> unioned = this->as_union();
+template<class Config>
+int TypeImpl<Config>::LubBitset() {
+  if (this->IsBitset()) {
+    return this->AsBitset();
+  } else if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     int bitset = kNone;
     for (int i = 0; i < unioned->length(); ++i) {
-      bitset |= union_get(unioned, i)->LubBitset();
+      bitset |= Config::union_get(unioned, i)->LubBitset();
     }
     return bitset;
-  } else if (this->is_class()) {
-    return LubBitset(*this->as_class());
+  } else if (this->IsClass()) {
+    return LubBitset(*this->AsClass());
   } else {
-    return LubBitset(*this->as_constant());
+    return LubBitset(*this->AsConstant());
   }
 }
 
 
-int Type::LubBitset(i::Object* value) {
+template<class Config>
+int TypeImpl<Config>::LubBitset(i::Object* value) {
   if (value->IsSmi()) return kSmi;
   i::Map* map = i::HeapObject::cast(value)->map();
   if (map->instance_type() == HEAP_NUMBER_TYPE) {
     int32_t i;
     uint32_t u;
     if (value->ToInt32(&i)) return Smi::IsValid(i) ? kSmi : kOtherSigned32;
     if (value->ToUint32(&u)) return kUnsigned32;
     return kDouble;
   }
   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?
     UNREACHABLE();
   }
-  return Type::LubBitset(map);
+  return LubBitset(map);
 }
 
 
-int Type::LubBitset(i::Map* map) {
+template<class Config>
+int TypeImpl<Config>::LubBitset(i::Map* map) {
   switch (map->instance_type()) {
     case STRING_TYPE:
     case ASCII_STRING_TYPE:
     case CONS_STRING_TYPE:
     case CONS_ASCII_STRING_TYPE:
     case SLICED_STRING_TYPE:
     case SLICED_ASCII_STRING_TYPE:
     case EXTERNAL_STRING_TYPE:
     case EXTERNAL_ASCII_STRING_TYPE:
     case EXTERNAL_STRING_WITH_ONE_BYTE_DATA_TYPE:
@@ skipping 61 matching lines @@
     case FIXED_ARRAY_TYPE:
       return kInternal;
     default:
       UNREACHABLE();
       return kNone;
   }
 }
 
 
 // Get the largest bitset subsumed by this type.
-int Type::GlbBitset() {
-  if (this->is_bitset()) {
-    return this->as_bitset();
-  } else if (this->is_union()) {
+template<class Config>
+int TypeImpl<Config>::GlbBitset() {
+  if (this->IsBitset()) {
+    return this->AsBitset();
+  } else if (this->IsUnion()) {
     // All but the first are non-bitsets and thus would yield kNone anyway.
-    return union_get(this->as_union(), 0)->GlbBitset();
+    return Config::union_get(this->AsUnion(), 0)->GlbBitset();
   } else {
     return kNone;
   }
 }
 
 
 // Most precise _current_ type of a value (usually its class).
-Type* Type::OfCurrently(Handle<i::Object> value) {
-  if (value->IsSmi()) return Smi();
+template<class Config>
+typename TypeImpl<Config>::TypeHandle TypeImpl<Config>::OfCurrently(
+    i::Handle<i::Object> value, Region* region) {
+  if (value->IsSmi()) return Smi(region);
   i::Map* map = i::HeapObject::cast(*value)->map();
   if (map->instance_type() == HEAP_NUMBER_TYPE ||
       map->instance_type() == ODDBALL_TYPE) {
-    return Type::Of(value);
+    return Of(value, region);
   }
-  return Class(i::handle(map));
+  return Class(i::handle(map), region);
 }
 
 
 // Check this <= that.
-bool Type::SlowIs(Type* that) {
+template<class Config>
+bool TypeImpl<Config>::SlowIs(TypeImpl* that) {
   // Fast path for bitsets.
-  if (this->is_none()) return true;
-  if (that->is_bitset()) {
-    return (this->LubBitset() | that->as_bitset()) == that->as_bitset();
+  if (this->IsNone()) return true;
+  if (that->IsBitset()) {
+    return (this->LubBitset() | that->AsBitset()) == that->AsBitset();
   }
 
-  if (that->is_class()) {
-    return this->is_class() && *this->as_class() == *that->as_class();
+  if (that->IsClass()) {
+    return this->IsClass() && *this->AsClass() == *that->AsClass();
   }
-  if (that->is_constant()) {
-    return this->is_constant() && *this->as_constant() == *that->as_constant();
+  if (that->IsConstant()) {
+    return this->IsConstant() && *this->AsConstant() == *that->AsConstant();
   }
 
   // (T1 \/ ... \/ Tn) <= T  <=>  (T1 <= T) /\ ... /\ (Tn <= T)
-  if (this->is_union()) {
-    Handle<Unioned> unioned = this->as_union();
+  if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> this_i = union_get(unioned, i);
+      TypeHandle this_i = Config::union_get(unioned, i);
       if (!this_i->Is(that)) return false;
     }
     return true;
   }
 
   // T <= (T1 \/ ... \/ Tn)  <=>  (T <= T1) \/ ... \/ (T <= Tn)
   // (iff T is not a union)
-  ASSERT(!this->is_union());
-  if (that->is_union()) {
-    Handle<Unioned> unioned = that->as_union();
+  ASSERT(!this->IsUnion());
+  if (that->IsUnion()) {
+    UnionedHandle unioned = that->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> that_i = union_get(unioned, i);
+      TypeHandle that_i = Config::union_get(unioned, i);
       if (this->Is(that_i)) return true;
-      if (this->is_bitset()) break;  // Fast fail, no other field is a bitset.
+      if (this->IsBitset()) break;  // Fast fail, only first field is a bitset.
     }
     return false;
   }
 
   return false;
 }
 
 
-bool Type::IsCurrently(Type* that) {
+template<class Config>
+bool TypeImpl<Config>::IsCurrently(TypeImpl* that) {
   return this->Is(that) ||
-      (this->is_constant() && that->is_class() &&
-       this->as_constant()->IsHeapObject() &&
-       i::HeapObject::cast(*this->as_constant())->map() == *that->as_class());
+      (this->IsConstant() && that->IsClass() &&
+       this->AsConstant()->IsHeapObject() &&
+       i::HeapObject::cast(*this->AsConstant())->map() == *that->AsClass());
 }
 
 
 // Check this overlaps that.
-bool Type::Maybe(Type* that) {
+template<class Config>
+bool TypeImpl<Config>::Maybe(TypeImpl* that) {
   // Fast path for bitsets.
-  if (this->is_bitset()) {
-    return (this->as_bitset() & that->LubBitset()) != 0;
+  if (this->IsBitset()) {
+    return (this->AsBitset() & that->LubBitset()) != 0;
   }
-  if (that->is_bitset()) {
-    return (this->LubBitset() & that->as_bitset()) != 0;
+  if (that->IsBitset()) {
+    return (this->LubBitset() & that->AsBitset()) != 0;
   }
 
   // (T1 \/ ... \/ Tn) overlaps T <=> (T1 overlaps T) \/ ... \/ (Tn overlaps T)
-  if (this->is_union()) {
-    Handle<Unioned> unioned = this->as_union();
+  if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> this_i = union_get(unioned, i);
+      TypeHandle this_i = Config::union_get(unioned, i);
       if (this_i->Maybe(that)) return true;
     }
     return false;
   }
 
   // T overlaps (T1 \/ ... \/ Tn) <=> (T overlaps T1) \/ ... \/ (T overlaps Tn)
-  if (that->is_union()) {
-    Handle<Unioned> unioned = that->as_union();
+  if (that->IsUnion()) {
+    UnionedHandle unioned = that->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> that_i = union_get(unioned, i);
+      TypeHandle that_i = Config::union_get(unioned, i);
       if (this->Maybe(that_i)) return true;
     }
     return false;
   }
 
-  ASSERT(!that->is_union());
-  if (this->is_class()) {
-    return that->is_class() && *this->as_class() == *that->as_class();
+  ASSERT(!this->IsUnion() && !that->IsUnion());
+  if (this->IsClass()) {
+    return that->IsClass() && *this->AsClass() == *that->AsClass();
   }
-  if (this->is_constant()) {
-    return that->is_constant() && *this->as_constant() == *that->as_constant();
+  if (this->IsConstant()) {
+    return that->IsConstant() && *this->AsConstant() == *that->AsConstant();
   }
 
   return false;
 }
 
 
-bool Type::InUnion(Handle<Unioned> unioned, int current_size) {
-  ASSERT(!this->is_union());
+template<class Config>
+bool TypeImpl<Config>::InUnion(UnionedHandle unioned, int current_size) {
+  ASSERT(!this->IsUnion());
   for (int i = 0; i < current_size; ++i) {
-    Handle<Type> type = union_get(unioned, i);
+    TypeHandle type = Config::union_get(unioned, i);
     if (this->Is(type)) return true;
   }
   return false;
 }
 
 
 // Get non-bitsets from this which are not subsumed by union, store at unioned,
 // starting at index. Returns updated index.
-int Type::ExtendUnion(Handle<Unioned> result, int current_size) {
+template<class Config>
+int TypeImpl<Config>::ExtendUnion(UnionedHandle result, int current_size) {
   int old_size = current_size;
-  if (this->is_class() || this->is_constant()) {
+  if (this->IsClass() || this->IsConstant()) {
     if (!this->InUnion(result, old_size)) result->set(current_size++, this);
-  } else if (this->is_union()) {
-    Handle<Unioned> unioned = this->as_union();
+  } else if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> type = union_get(unioned, i);
-      ASSERT(i == 0 || !(type->is_bitset() || type->Is(union_get(unioned, 0))));
-      if (type->is_bitset()) continue;
-      if (!type->InUnion(result, old_size)) result->set(current_size++, *type);
+      TypeHandle type = Config::union_get(unioned, i);
+      ASSERT(i == 0 ||
+             !(type->IsBitset() || type->Is(Config::union_get(unioned, 0))));
+      if (!type->IsBitset() && !type->InUnion(result, old_size)) {
+        result->set(current_size++, *type);
+      }
     }
   }
   return current_size;
 }
 
 
 // Union is O(1) on simple bit unions, but O(n*m) on structured unions.
 // TODO(rossberg): Should we use object sets somehow? Is it worth it?
-Type* Type::Union(Handle<Type> type1, Handle<Type> type2) {
+template<class Config>
+typename TypeImpl<Config>::TypeHandle TypeImpl<Config>::Union(
+    TypeHandle type1, TypeHandle type2, Region* region) {
   // Fast case: bit sets.
-  if (type1->is_bitset() && type2->is_bitset()) {
-    return from_bitset(type1->as_bitset() | type2->as_bitset());
+  if (type1->IsBitset() && type2->IsBitset()) {
+    return Config::from_bitset(type1->AsBitset() | type2->AsBitset(), region);
   }
 
   // Fast case: top or bottom types.
-  if (type1->SameValue(Type::Any())) return *type1;
-  if (type2->SameValue(Type::Any())) return *type2;
-  if (type1->SameValue(Type::None())) return *type2;
-  if (type2->SameValue(Type::None())) return *type1;
+  if (type1->IsAny()) return type1;
+  if (type2->IsAny()) return type2;
+  if (type1->IsNone()) return type2;
+  if (type2->IsNone()) return type1;
 
   // Semi-fast case: Unioned objects are neither involved nor produced.
-  if (!(type1->is_union() || type2->is_union())) {
-    if (type1->Is(type2)) return *type2;
-    if (type2->Is(type1)) return *type1;
+  if (!(type1->IsUnion() || type2->IsUnion())) {
+    if (type1->Is(type2)) return type2;
+    if (type2->Is(type1)) return type1;
   }
 
   // Slow case: may need to produce a Unioned object.
-  Isolate* isolate = NULL;
-  int size = type1->is_bitset() || type2->is_bitset() ? 1 : 0;
-  if (!type1->is_bitset()) {
-    isolate = i::HeapObject::cast(*type1)->GetIsolate();
-    size += (type1->is_union() ? type1->as_union()->length() : 1);
+  int size = type1->IsBitset() || type2->IsBitset() ? 1 : 0;
+  if (!type1->IsBitset()) {
+    size += (type1->IsUnion() ? type1->AsUnion()->length() : 1);
   }
-  if (!type2->is_bitset()) {
-    isolate = i::HeapObject::cast(*type2)->GetIsolate();
-    size += (type2->is_union() ? type2->as_union()->length() : 1);
+  if (!type2->IsBitset()) {
+    size += (type2->IsUnion() ? type2->AsUnion()->length() : 1);
   }
-  ASSERT(isolate != NULL);
   ASSERT(size >= 2);
-  Handle<Unioned> unioned = isolate->factory()->NewFixedArray(size);
+  UnionedHandle unioned = Config::union_create(size, region);
   size = 0;
 
   int bitset = type1->GlbBitset() | type2->GlbBitset();
-  if (bitset != kNone) unioned->set(size++, from_bitset(bitset));
+  if (bitset != kNone) unioned->set(size++, Config::from_bitset(bitset));
   size = type1->ExtendUnion(unioned, size);
   size = type2->ExtendUnion(unioned, size);
 
   if (size == 1) {
-    return *union_get(unioned, 0);
+    return Config::union_get(unioned, 0);
   } else if (size == unioned->length()) {
-    return from_handle(unioned);
+    return Config::from_union(unioned);
   }
 
   // There was an overlap. Copy to smaller union.
-  Handle<Unioned> result = isolate->factory()->NewFixedArray(size);
+  UnionedHandle result = Config::union_create(size, region);
   for (int i = 0; i < size; ++i) result->set(i, unioned->get(i));
-  return from_handle(result);
+  return Config::from_union(result);
 }
 
 
 // Get non-bitsets from this which are also in that, store at unioned,
 // starting at index. Returns updated index.
-int Type::ExtendIntersection(
-    Handle<Unioned> result, Handle<Type> that, int current_size) {
+template<class Config>
+int TypeImpl<Config>::ExtendIntersection(
+    UnionedHandle result, TypeHandle that, int current_size) {
   int old_size = current_size;
-  if (this->is_class() || this->is_constant()) {
+  if (this->IsClass() || this->IsConstant()) {
     if (this->Is(that) && !this->InUnion(result, old_size))
       result->set(current_size++, this);
-  } else if (this->is_union()) {
-    Handle<Unioned> unioned = this->as_union();
+  } else if (this->IsUnion()) {
+    UnionedHandle unioned = this->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> type = union_get(unioned, i);
-      ASSERT(i == 0 || !(type->is_bitset() || type->Is(union_get(unioned, 0))));
-      if (type->is_bitset()) continue;
-      if (type->Is(that) && !type->InUnion(result, old_size))
+      TypeHandle type = Config::union_get(unioned, i);
+      ASSERT(i == 0 ||
+             !(type->IsBitset() || type->Is(Config::union_get(unioned, 0))));
+      if (!type->IsBitset() && type->Is(that) &&
+          !type->InUnion(result, old_size)) {
         result->set(current_size++, *type);
+      }
     }
   }
   return current_size;
 }
 
 
 // Intersection is O(1) on simple bit unions, but O(n*m) on structured unions.
 // TODO(rossberg): Should we use object sets somehow? Is it worth it?
-Type* Type::Intersect(Handle<Type> type1, Handle<Type> type2) {
+template<class Config>
+typename TypeImpl<Config>::TypeHandle TypeImpl<Config>::Intersect(
+    TypeHandle type1, TypeHandle type2, Region* region) {
   // Fast case: bit sets.
-  if (type1->is_bitset() && type2->is_bitset()) {
-    return from_bitset(type1->as_bitset() & type2->as_bitset());
+  if (type1->IsBitset() && type2->IsBitset()) {
+    return Config::from_bitset(type1->AsBitset() & type2->AsBitset(), region);
   }
 
   // Fast case: top or bottom types.
-  if (type1->SameValue(Type::None())) return *type1;
-  if (type2->SameValue(Type::None())) return *type2;
-  if (type1->SameValue(Type::Any())) return *type2;
-  if (type2->SameValue(Type::Any())) return *type1;
+  if (type1->IsNone()) return type1;
+  if (type2->IsNone()) return type2;
+  if (type1->IsAny()) return type2;
+  if (type2->IsAny()) return type1;
 
   // Semi-fast case: Unioned objects are neither involved nor produced.
-  if (!(type1->is_union() || type2->is_union())) {
-    if (type1->Is(type2)) return *type1;
-    if (type2->Is(type1)) return *type2;
+  if (!(type1->IsUnion() || type2->IsUnion())) {
+    if (type1->Is(type2)) return type1;
+    if (type2->Is(type1)) return type2;
   }
 
   // Slow case: may need to produce a Unioned object.
-  Isolate* isolate = NULL;
   int size = 0;
-  if (!type1->is_bitset()) {
-    isolate = i::HeapObject::cast(*type1)->GetIsolate();
-    size = (type1->is_union() ? type1->as_union()->length() : 2);
+  if (!type1->IsBitset()) {
+    size = (type1->IsUnion() ? type1->AsUnion()->length() : 2);
   }
-  if (!type2->is_bitset()) {
-    isolate = i::HeapObject::cast(*type2)->GetIsolate();
-    int size2 = (type2->is_union() ? type2->as_union()->length() : 2);
+  if (!type2->IsBitset()) {
+    int size2 = (type2->IsUnion() ? type2->AsUnion()->length() : 2);
     size = (size == 0 ? size2 : Min(size, size2));
   }
-  ASSERT(isolate != NULL);
   ASSERT(size >= 2);
-  Handle<Unioned> unioned = isolate->factory()->NewFixedArray(size);
+  UnionedHandle unioned = Config::union_create(size, region);
   size = 0;
 
   int bitset = type1->GlbBitset() & type2->GlbBitset();
-  if (bitset != kNone) unioned->set(size++, from_bitset(bitset));
+  if (bitset != kNone) unioned->set(size++, Config::from_bitset(bitset));
   size = type1->ExtendIntersection(unioned, type2, size);
   size = type2->ExtendIntersection(unioned, type1, size);
 
   if (size == 0) {
-    return None();
+    return None(region);
   } else if (size == 1) {
-    return *union_get(unioned, 0);
+    return Config::union_get(unioned, 0);
   } else if (size == unioned->length()) {
-    return from_handle(unioned);
+    return Config::from_union(unioned);
   }
 
   // There were dropped cases. Copy to smaller union.
-  Handle<Unioned> result = isolate->factory()->NewFixedArray(size);
+  UnionedHandle result = Config::union_create(size, region);
   for (int i = 0; i < size; ++i) result->set(i, unioned->get(i));
-  return from_handle(result);
+  return Config::from_union(result);
 }
 
 
-Type* Type::Optional(Handle<Type> type) {
-  return type->is_bitset()
-      ? from_bitset(type->as_bitset() | kUndefined)
-      : Union(type, Undefined()->handle_via_isolate_of(*type));
-}
-
-
+// TODO(rossberg): this does not belong here.
 Representation Representation::FromType(Handle<Type> type) {
   if (type->Is(Type::None())) return Representation::None();
   if (type->Is(Type::Smi())) return Representation::Smi();
   if (type->Is(Type::Signed32())) return Representation::Integer32();
   if (type->Is(Type::Number())) return Representation::Double();
   return Representation::Tagged();
 }
 
 
 #ifdef OBJECT_PRINT
-void Type::TypePrint() {
+template<class Config>
+void TypeImpl<Config>::TypePrint() {
   TypePrint(stdout);
   PrintF(stdout, "\n");
   Flush(stdout);
 }
 
 
-const char* Type::bitset_name(int bitset) {
+template<class Config>
+const char* TypeImpl<Config>::bitset_name(int bitset) {
   switch (bitset) {
     #define PRINT_COMPOSED_TYPE(type, value) case k##type: return #type;
     BITSET_TYPE_LIST(PRINT_COMPOSED_TYPE)
     #undef PRINT_COMPOSED_TYPE
     default:
       return NULL;
   }
 }
 
 
-void Type::TypePrint(FILE* out) {
-  if (is_bitset()) {
-    int bitset = as_bitset();
+template<class Config>
+void TypeImpl<Config>::TypePrint(FILE* out) {
+  if (this->IsBitset()) {
+    int bitset = this->AsBitset();
     const char* name = bitset_name(bitset);
     if (name != NULL) {
       PrintF(out, "%s", name);
     } else {
       bool is_first = true;
       PrintF(out, "(");
       for (int mask = 1; mask != 0; mask = mask << 1) {
         if ((bitset & mask) != 0) {
           if (!is_first) PrintF(out, " | ");
           is_first = false;
           PrintF(out, "%s", bitset_name(mask));
         }
       }
       PrintF(out, ")");
     }
-  } else if (is_constant()) {
-    PrintF(out, "Constant(%p : ", static_cast<void*>(*as_constant()));
-    from_bitset(LubBitset())->TypePrint(out);
+  } else if (this->IsConstant()) {
+    PrintF(out, "Constant(%p : ", static_cast<void*>(*this->AsConstant()));
+    Config::from_bitset(this->LubBitset())->TypePrint(out);
     PrintF(")");
-  } else if (is_class()) {
-    PrintF(out, "Class(%p < ", static_cast<void*>(*as_class()));
-    from_bitset(LubBitset())->TypePrint(out);
+  } else if (this->IsClass()) {
+    PrintF(out, "Class(%p < ", static_cast<void*>(*this->AsClass()));
+    Config::from_bitset(this->LubBitset())->TypePrint(out);
     PrintF(")");
-  } else if (is_union()) {
+  } else if (this->IsUnion()) {
     PrintF(out, "(");
-    Handle<Unioned> unioned = as_union();
+    UnionedHandle unioned = this->AsUnion();
     for (int i = 0; i < unioned->length(); ++i) {
-      Handle<Type> type_i = union_get(unioned, i);
+      TypeHandle type_i = Config::union_get(unioned, i);
       if (i > 0) PrintF(out, " | ");
       type_i->TypePrint(out);
     }
     PrintF(out, ")");
   }
 }
 #endif
 
 
+template class TypeImpl<HeapTypeConfig>;
+template class TypeImpl<HeapTypeConfig>::Iterator<i::Map>;
+template class TypeImpl<HeapTypeConfig>::Iterator<i::Object>;
+
+
 } }  // namespace v8::internal