Even ignoring the usual optimizations like using SIMD and loop unrolling to find parallelism when doing memcpy, the compiler actually has techniques for spotting certain loop idioms so it can actually replace the loop with a memcpy library call if it deems it profitable (e.g. tell it it's likely to have N>bigNumber and it'll go for a library)
There are additional optimizations like using C's printf without any extra arguments, the compiler will replace that with a call to puts, which doesn't have the formatting code. You can see this in Compiler Explorer.
