Concurrent sweep on x64.

runtime/vm/assembler_x64.h

 // Copyright (c) 2013, 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 VM_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 735 matching lines @@
 
   void StoreIntoObjectNoBarrier(Register object,
                                 const Address& dest,
                                 Register value);
 
   void DoubleNegate(XmmRegister d);
   void FloatNegate(XmmRegister f);
 
   void DoubleAbs(XmmRegister reg);
 
-  void LockCmpxchgl(const Address& address, Register reg) {
+  void LockCmpxchgq(const Address& address, Register reg) {
     lock();
-    cmpxchgl(address, reg);
+    cmpxchgq(address, reg);
   }
 
   void PushRegisters(intptr_t cpu_register_set, intptr_t xmm_register_set);
   void PopRegisters(intptr_t cpu_register_set, intptr_t xmm_register_set);
 
   void EnterFrame(intptr_t frame_space);
   void LeaveFrame();
   void ReserveAlignedFrameSpace(intptr_t frame_space);
 
   // Create a frame for calling into runtime that preserves all volatile
@@ skipping 387 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_