/* Performs an atomic compare exchange operation on the 16-bit unsigned integer specified by Value. If Value is equal to CompareValue, then Value is set to ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue, then Value is returned. The compare exchange operation must be performed using MP safe mechanisms. */
UINT16 EFIAPI InternalSyncCompareExchange16(IN OUT volatile UINT16 *Value, IN UINT16 CompareValue, IN UINT16 ExchangeValue)
/* Performs an atomic compare exchange operation on the 16-bit unsigned integer specified by Value. If Value is equal to CompareValue, then Value is set to ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue, then Value is returned. The compare exchange operation must be performed using MP safe mechanisms. */
UINT16 EFIAPI InternalSyncCompareExchange16(IN OUT volatile UINT16 *Value, IN UINT16 CompareValue, IN UINT16 ExchangeValue)
{
  __asm__ __volatile__ (
    "lock                 \n\t"
    "cmpxchgw    %2, %1   \n\t"
    : "+a" (CompareValue),
      "+m" (*Value)
    : "q"  (ExchangeValue)
    : "memory",
      "cc"
  );
  return CompareValue;
}