Are there hidden 64bit atomic instructions on A11 GPU?

I need to perform atomic-max operation on 64bit integers.

I know no types other than

int

,

uint

and

bool

have official support for atomic operations, but given that you can perform (officially unsupported) 64bit integer math in Metal on iOS, I guess there might be undocumented AIR assembly instructions for 64bit atomic operations (I tried the obvious ones, but without any success — Xcode outputs "

Compiler failed with XPC_ERROR_CONNECTION_INTERRUPTED

").

How can I list all supported AIR assembly operations?