Why is memcpy slower than a reinterpret_cast when parsing binary data?

Question

TLDR: I forgot to enable compiler optimizations. With the optimizations enabled the performance is (nearly) identical.

Original post

When r

Answer 1

memcpy cannot copy to a register, it does a memory-to-memory copy. The reinterpret_cast in get_int_v1 can change the type of pointer held in a register, and that doesn't even require a register-to-register copy.