Use Unique<Object> in HConstant and remove UniqueValueId.

src/unique.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
@@ skipping 36 matching lines @@
 // Creating a Unique<T> requires first dereferencing the handle to obtain
 // the address of the object, which is used as the hashcode and the basis for
 // comparison. The object can be moved later by the GC, but comparison
 // and hashing use the old address of the object, without dereferencing it.
 //
 // Careful! Comparison of two Uniques is only correct if both were created
 // in the same "era" of GC or if at least one is a non-movable object.
 template <typename T>
 class Unique V8_FINAL {
  public:
-  // TODO(titzer): make private and introduce a factory.
+  // TODO(titzer): make private and introduce a uniqueness scope.
   explicit Unique(Handle<T> handle) {
     if (handle.is_null()) {
       raw_address_ = NULL;
     } else {
       // This is a best-effort check to prevent comparing Unique<T>'s created
       // in different GC eras; we require heap allocation to be disallowed at
       // creation time.
       // NOTE: we currently consider maps to be non-movable, so no special
       // assurance is required for creating a Unique<Map>.
       // TODO(titzer): other immortable immovable objects are also fine.
@@ skipping 36 matching lines @@
   inline intptr_t Hashcode() const {
     ASSERT(IsInitialized());
     return reinterpret_cast<intptr_t>(raw_address_);
   }
 
   inline bool IsNull() const {
     ASSERT(IsInitialized());
     return raw_address_ == NULL;
   }
 
-  // Extract the handle from this Unique in order to dereference it.
-  // WARNING: Only do this if you have access to the heap.

[Toon Verwaest, 2013/09/24 09:17:54]

Any reason you removed this comment?

+  inline bool IsKnownGlobal(void* global) const {
+    ASSERT(IsInitialized());
+    return raw_address_ == reinterpret_cast<Address>(global);
+  }
+
   inline Handle<T> handle() const {
     return handle_;
   }
 
   inline bool IsInitialized() const {
     return raw_address_ != NULL || handle_.is_null();
   }
 
   // TODO(titzer): this is a hack to migrate to Unique<T> incrementally.
   static Unique<T> CreateUninitialized(Handle<T> handle) {
-    return Unique<T>(static_cast<Address>(NULL), handle);
+    return Unique<T>(reinterpret_cast<Address>(NULL), handle);
+  }
+
+  static Unique<T> CreateImmovable(Handle<T> handle) {
+    return Unique<T>(reinterpret_cast<Address>(*handle), handle);
   }
 
   friend class UniqueSet<T>;  // Uses internal details for speed.
   template <class U>
   friend class Unique;  // For comparing raw_address values.
 
  private:
   Address raw_address_;
   Handle<T> handle_;
 };
@@ skipping 27 matching lines @@
 
   // Compare this set against another set. O(|this|).
   bool Equals(UniqueSet<T>* that) const {
     if (that->size_ != this->size_) return false;
     for (int i = 0; i < this->size_; i++) {
       if (this->array_[i] != that->array_[i]) return false;
     }
     return true;
   }
 
+  // Check whether this set contains the given element. O(|this|)
+  // TODO(titzer): use binary search for large sets to make this O(log|this|)
   template <typename U>
   bool Contains(Unique<U> elem) const {
-    // TODO(titzer): use binary search for larger sets.
     for (int i = 0; i < size_; i++) {
       if (this->array_[i] == elem) return true;
     }
     return false;
   }
 
   // Check if this set is a subset of the given set. O(|this| + |that|).
   bool IsSubset(UniqueSet<T>* that) const {
     if (that->size_ < this->size_) return false;
     int j = 0;
@@ skipping 109 matching lines @@
       capacity_ = new_capacity;
       array_ = new_array;
     }
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_UNIQUE_H_