+# Use compiler atomic builtins, when disabled use our legacy uatomic implementation.
+# Disabled by default
+AE_FEATURE_DEFAULT_DISABLE
+AE_FEATURE([compiler-atomic-builtins], [Enable the use of compiler atomic builtins.])
+
+# emit legacy memory barriers
+# Enable by default
+AE_FEATURE_DEFAULT_ENABLE
+AE_FEATURE([legacy-mb], [Disable legacy memory barriers.])
+