Function std::intrinsics::atomic_xsub_acqrel

pub unsafe extern "rust-intrinsic" fn atomic_xsub_acqrel<T>(    dst: *mut T,     src: T) -> T where    T: Copy, 

Subtract from the current value, returning the previous value.

The stabilized version of this intrinsic is available on the atomic types via the fetch_sub method by passing Ordering::AcqRel as the order. For example, AtomicIsize::fetch_sub.