New unified type representation

src/types.h

+// 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// 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.
+
+#ifndef V8_TYPES_H_
+#define V8_TYPES_H_
+
+#include "v8.h"
+
+#include "objects.h"
+
+namespace v8 {
+namespace internal {
+
+class Type : public Object {

[Sven Panne, 2013/06/05 08:02:41]

Although I hate comments in general, a comment describing the cunning Type
representation might be appropriate here.

[rossberg, 2013/06/05 09:44:24]

Done.

+ public:
+  static Type* None() { return from_bitset(kNone); }
+  static Type* Any() { return from_bitset(kAny); }
+
+  static Type* Oddball() { return from_bitset(kOddball); }
+  static Type* Boolean() { return from_bitset(kBoolean); }
+  static Type* Null() { return from_bitset(kNull); }
+  static Type* Undefined() { return from_bitset(kUndefined); }
+
+  static Type* Number() { return from_bitset(kNumber); }
+  static Type* Smi() { return from_bitset(kSmi); }
+  static Type* Double() { return from_bitset(kDouble); }
+
+  static Type* Name() { return from_bitset(kName); }
+  static Type* UniqueName() { return from_bitset(kUniqueName); }
+  static Type* String() { return from_bitset(kString); }
+  static Type* InternalizedString() { return from_bitset(kInternalizedString); }
+  static Type* Symbol() { return from_bitset(kSymbol); }
+
+  static Type* Receiver() { return from_bitset(kReceiver); }
+  static Type* Object() { return from_bitset(kObject); }
+  static Type* Array() { return from_bitset(kArray); }
+  static Type* Function() { return from_bitset(kFunction); }
+  static Type* Proxy() { return from_bitset(kProxy); }
+
+  static Type* Class(Handle<Map> map) { return from_handle(map); }
+  static Type* Constant(Handle<HeapObject> value) {
+    ASSERT(!value->IsMap() && !value->IsFixedArray());
+    return from_handle(value);
+  }
+
+  static Type* Union(Handle<Type> type1, Handle<Type> type2);
+  static Type* Optional(Handle<Type> type);  // type \/ Undefined
+
+  bool Is(Handle<Type> that);
+  bool Maybe(Handle<Type> that);
+
+  // TODO(rossberg): method to iterate unions?
+
+ private:
+  // A union is a fixed array containing types. Invariants:
+  // - its length is at least 2
+  // - at most one field is a bitset, and it must go into index 0
+  // - no field is a union
+  typedef FixedArray Unioned;
+
+  enum {
+    kNull = 1<<0,
+    kUndefined = 1<<1,
+    kBoolean = 1<<2,
+    kSmi = 1<<3,
+    kDouble = 1<<4,
+    kSymbol = 1<<5,
+    kInternalizedString = 1<<6,
+    kOtherString = 1<<7,
+    kArray = 1<<8,
+    kFunction = 1<<9,
+    kOtherObject = 1<<10,
+    kProxy = 1<<11,
+
+    kOddball = kBoolean | kNull | kUndefined,
+    kNumber = kSmi | kDouble,
+    kString = kInternalizedString | kOtherString,
+    kUniqueName = kSymbol | kInternalizedString,
+    kName = kSymbol | kString,
+    kObject = kArray | kFunction | kOtherObject,
+    kReceiver = kObject | kProxy,
+    kAny = kOddball | kNumber | kName | kReceiver,
+    kNone = 0
+  };
+
+  bool is_bitset() { return this->IsSmi(); }
+  bool is_class() { return this->IsMap(); }
+  bool is_constant() { return !(is_bitset() || is_class() || is_union()); }
+  bool is_union() { return this->IsFixedArray(); }
+
+  int as_bitset() { return Smi::cast(this)->value(); }
+  Handle<Map> as_class() { return Handle<Map>::cast(handle()); }
+  Handle<HeapObject> as_constant() { return Handle<HeapObject>::cast(handle());}

[Sven Panne, 2013/06/05 08:02:41]

Cheater! ;-)

[rossberg, 2013/06/05 09:44:24]

No more, wanted to add an assertion anyway. :)

+  Handle<Unioned> as_union() { return Handle<Unioned>::cast(handle()); }
+
+  Handle<Type> handle() { return handle_via(this); }
+  Handle<Type> handle_via(Type* type) {
+    ASSERT(type->IsHeapObject());

[Sven Panne, 2013/06/05 08:02:41]

No need for this ASSERT, HeapObject::cast already does the same.

[rossberg, 2013/06/05 09:44:24]

Yeah, but I wanted to make it very explicit.

+    return v8::internal::handle(this, HeapObject::cast(type)->GetIsolate());
+  }
+
+  static Type* from_bitset(int bitset) {
+    return static_cast<Type*>(Object::cast(Smi::FromInt(bitset)));
+  }
+  static Type* from_handle(Handle<HeapObject> handle) {
+    return static_cast<Type*>(Object::cast(*handle));
+  }
+
+  static Handle<Type> union_get(Handle<Unioned> unioned, int i) {
+    Type* type = static_cast<Type*>(unioned->get(i));
+    ASSERT(!type->is_union());
+    return type->handle_via(from_handle(unioned));
+  }
+
+  int LubBitset();
+  int GlbBitset();
+  bool InUnion(Handle<Unioned> unioned, int current_size);
+  int ExtendUnion(Handle<Unioned> unioned, int current_size);
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_TYPES_H_