Initial SIMDBC interpreter.

runtime/vm/atomic_simulator.h

Index: runtime/vm/atomic_simulator.h
diff --git a/runtime/vm/atomic_simulator.h b/runtime/vm/atomic_simulator.h
index 2b52a227c1f774430a9aaacd6cf4a1922844f589..78e7f88eb015061f2c3598e76056d85f10e7040e 100644
--- a/runtime/vm/atomic_simulator.h
+++ b/runtime/vm/atomic_simulator.h
@@ -11,7 +11,7 @@
 
 namespace dart {
 
-#if defined(USING_SIMULATOR)
+#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,
@@ -25,7 +25,7 @@ inline uint32_t AtomicOperations::CompareAndSwapUint32(uint32_t* ptr,
                                                        uint32_t new_value) {
   return Simulator::CompareExchangeUint32(ptr, old_value, new_value);
 }
-#endif  // defined(USING_SIMULATOR)
+#endif  // defined(USING_SIMULATOR_ATOMICS)
 
 }  // namespace dart