Initial SIMDBC interpreter.

runtime/vm/atomic_macos.h

Index: runtime/vm/atomic_macos.h
diff --git a/runtime/vm/atomic_macos.h b/runtime/vm/atomic_macos.h
index ae5da3ada6ac43fe71462114cadb2de31e955225..479ca30b35394bc25c799efacbf1293377297839 100644
--- a/runtime/vm/atomic_macos.h
+++ b/runtime/vm/atomic_macos.h
@@ -41,7 +41,7 @@ inline void AtomicOperations::DecrementBy(intptr_t* p, intptr_t value) {
 }
 
 
-#if !defined(USING_SIMULATOR)
+#if !defined(USING_SIMULATOR_ATOMICS)
 inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
                                                   uword old_value,
                                                   uword new_value) {
@@ -54,7 +54,7 @@ inline uint32_t AtomicOperations::CompareAndSwapUint32(uint32_t* ptr,
                                                        uint32_t new_value) {
   return __sync_val_compare_and_swap(ptr, old_value, new_value);
 }
-#endif  // !defined(USING_SIMULATOR)
+#endif  // !defined(USING_SIMULATOR_ATOMICS)
 
 }  // namespace dart