Can non-atomic-load be reordered after atomic-acquire-load?

Question

As known in since C++11 there are 6 memory orders, and in documentation written about std::memory_order_acquire:

• http://en.cppreference.com/w/cpp/

Answer 1

Just to answer your headline question: yes, any loads (whether atomic or non-atomic) can be re-ordered after an atomic load. Similarly any stores can be re-ordered before an atomic store.

However, an atomic store is not necessarily allowed to be re-ordered after an atomic load or vice verse (atomic load re-ordered before atomic store).

See Herb Sutter's talk around 44:00.