1) It's useless to reason about the performance of generated assembly unless you use -O{1,2,3}. Another commenter says that they're surprised std::move isn't inlined; that's because -O{1,2,3} isn't passed.

2) If you care that much about performance, you can avoid all copies by returning by reference in this case.

3) The author seems to misunderstand std::move — in this case, std::move can only pessimize performance and never optimize because the move constructor of std::array is the exact same as the copy constructor.

For example, move constructors help performance for std::vector because the move constructor will copy the backing buffer's pointer instead of copying the entire backing buffer itself.

Since std::array<T> is a thin wrapper around T[], the entire array is stored on the stack, and there is no possible optimization that a move could make — stack values must be copied (or otherwise initialized) in move constructors. In fact, since std::array is an aggregate type, there isn't even a user-defined move constructor (or copy constructor)! https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-...