Function atomic_cxchg 

pub unsafe fn atomic_cxchg<T: Copy, const ORD_SUCC: AtomicOrdering, const ORD_FAIL: AtomicOrdering>(
    dst: *mut T,
    old: T,
    src: T,
) -> (T, bool)

🔬This is a nightly-only experimental API. (core_intrinsics)

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Stores a value if the current value is the same as the old value. T must be an integer or pointer type.

The stabilized version of this intrinsic is available on the atomic types via the compare_exchange method. For example, AtomicBool::compare_exchange.