Revert "[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_