[vm] Implement more efficient CAS in simarm/simarm64 modes

runtime/vm/atomic_simulator.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.
-
-#ifndef RUNTIME_VM_ATOMIC_SIMULATOR_H_
-#define RUNTIME_VM_ATOMIC_SIMULATOR_H_
-
-#if !defined RUNTIME_VM_ATOMIC_H_
-#error Do not include atomic_simulator.h directly. Use atomic.h instead.
-#endif
-
-namespace dart {
-
-#if defined(USING_SIMULATOR_ATOMICS)
-// Forward atomic operations to the simulator if the simulator is active.
-inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
-                                                  uword old_value,
-                                                  uword new_value) {
-  return Simulator::CompareExchange(ptr, old_value, new_value);
-}
-
-inline uint32_t AtomicOperations::CompareAndSwapUint32(uint32_t* ptr,
-                                                       uint32_t old_value,
-                                                       uint32_t new_value) {
-  return Simulator::CompareExchangeUint32(ptr, old_value, new_value);
-}
-#endif  // defined(USING_SIMULATOR_ATOMICS)
-
-}  // namespace dart
-
-#endif  // RUNTIME_VM_ATOMIC_SIMULATOR_H_