> On Dec 1, 2016, at 4:55 PM, Jiho Choi via swift-dev <swift-dev@swift.org> > wrote: > > Thanks for the explanation. > One last question is why non-atomic ARC operations still use atomic load and > store. Wouldn't regular memory operations be enough?
According to the C++ memory model, all operations on an atomic<T> must be atomic. It is undefined behavior to cast a pointer to the atomic into a T* and perform normal loads and stores. "Relaxed" loads and stores however imply no ordering with other threads, so compile down to plain nonatomic CPU instructions. -Joe _______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
