Today i try write variant function std::call_once on Qt, but i can't write fast version because QAtomicInt doesn't have FAST atomic methods like:

std::atomic<T>::load(std::memory_order_relaxed);
std::atomic<T>::load(std::memory_order_consume);
std::atomic<T>::load(std::memory_order_acquire);
std::atomic<T>::load(std::memory_order_seq_cst);

std::atomic<T>::store(value, std::memory_order_release);
std::atomic<T>::store(value, std::memory_order_relaxed);
std::atomic<T>::store(value, std::memory_order_seq_cst);

Instead it i used FetchAndStoreAcquire (Load) and FetchAndStoreRelease (Store). My algorithm 15 sec on 1 billion operations, std::call_once - 9 sec.

And why QAtomicInt doesn't have atomic operators like "operator=" and "operator int() const"?