Inline instance object hash code into object header on 64 bit.

runtime/vm/heap.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_HEAP_H_
 #define RUNTIME_VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 15 matching lines @@
 class VirtualMemory;
 
 class Heap {
  public:
   enum Space {
     kNew,
     kOld,
     kCode,
   };
 
-  enum WeakSelector { kPeers = 0, kHashes, kObjectIds, kNumWeakSelectors };
+  enum WeakSelector {
+    kPeers = 0,
+#if !defined(HASH_IN_OBJECT_HEADER)
+    kHashes,
+#endif
+    kObjectIds,
+    kNumWeakSelectors
+  };
 
   enum ApiCallbacks { kIgnoreApiCallbacks, kInvokeApiCallbacks };
 
   enum GCReason {
     kNewSpace,
     kPromotion,
     kOldSpace,
     kFull,
     kGCAtAlloc,
     kGCTestCase,
@@ skipping 113 matching lines @@
 
   // Associate a peer with an object.  A non-existent peer is equal to NULL.
   void SetPeer(RawObject* raw_obj, void* peer) {
     SetWeakEntry(raw_obj, kPeers, reinterpret_cast<intptr_t>(peer));
   }
   void* GetPeer(RawObject* raw_obj) const {
     return reinterpret_cast<void*>(GetWeakEntry(raw_obj, kPeers));
   }
   int64_t PeerCount() const;
 
+#if !defined(HASH_IN_OBJECT_HEADER)
   // Associate an identity hashCode with an object. An non-existent hashCode
   // is equal to 0.
   void SetHash(RawObject* raw_obj, intptr_t hash) {
     SetWeakEntry(raw_obj, kHashes, hash);
   }
   intptr_t GetHash(RawObject* raw_obj) const {
     return GetWeakEntry(raw_obj, kHashes);
   }
+#endif
   int64_t HashCount() const;
 
   // Associate an id with an object (used when serializing an object).
   // A non-existant id is equal to 0.
   void SetObjectId(RawObject* raw_obj, intptr_t object_id) {
     ASSERT(Thread::Current()->IsMutatorThread());
     SetWeakEntry(raw_obj, kObjectIds, object_id);
   }
   intptr_t GetObjectId(RawObject* raw_obj) const {
     ASSERT(Thread::Current()->IsMutatorThread());
@@ skipping 199 matching lines @@
 // Note: During this scope, the code pages are non-executable.
 class WritableVMIsolateScope : StackResource {
  public:
   explicit WritableVMIsolateScope(Thread* thread);
   ~WritableVMIsolateScope();
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_HEAP_H_