Same as the _InterlockedCompareExchange_rel function, except that
  those parts of the algorithm that are marked "Atomic" are performed
  by the cmpxchg8.rel instruction.

  Syntax:

       unsigned __int64 _InterlockedCompareExchange64_rel (volatile
       unsigned int64 *Destination, unsigned __int64 Newval, unsigned
       __int64 Comparand);