Enable concurrent sweep on MIPS and ARM64.

runtime/vm/simulator_arm64.h

 // Copyright (c) 2014, 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.
 
 // Declares a Simulator for ARM64 instructions if we are not generating a native
 // ARM64 binary. This Simulator allows us to run and debug ARM64 code generation
 // on regular desktop machines.
 // Dart calls into generated code by "calling" the InvokeDartCode stub,
 // which will start execution in the Simulator or forwards to the real entry
 // on a ARM64 HW platform.
@@ skipping 190 matching lines @@
   static Mutex* exclusive_access_lock_;
   static const int kNumAddressTags = 16;
   static struct AddressTag {
     Thread* thread;
     uword addr;
   } exclusive_access_state_[kNumAddressTags];
   static int next_address_tag_;
 
   // Synchronization primitives support.
   void ClearExclusive();
-  intptr_t ReadExclusiveW(uword addr, Instr* instr);
-  intptr_t WriteExclusiveW(uword addr, intptr_t value, Instr* instr);
+  intptr_t ReadExclusiveX(uword addr, Instr* instr);
+  intptr_t WriteExclusiveX(uword addr, intptr_t value, Instr* instr);
 
   // Set access to given address to 'exclusive state' for current thread.
   static void SetExclusiveAccess(uword addr);
 
   // Returns true if the current thread has exclusive access to given address,
   // returns false otherwise. In either case, set access to given address to
   // 'open state' for all threads.
   // If given addr is NULL, set access to 'open state' for current
   // thread (CLREX).
   static bool HasExclusiveAccessAndOpen(uword addr);
@@ skipping 49 matching lines @@
   }
 
   friend class SimulatorDebugger;
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // VM_SIMULATOR_ARM64_H_