Function std::intrinsics::atomic_cxchg_relaxed

pub unsafe extern "rust-intrinsic" fn atomic_cxchg_relaxed<T>(dst: *mut T,                                                              old: T,                                                              src: T)                                                              -> (T, bool)

Stores a value if the current value is the same as the old value. The stabilized version of this intrinsic is available on the std::sync::atomic types via the compare_exchange method by passing Ordering::Relaxed as both the success and failure parameters. For example, AtomicBool::compare_exchange.