Comment by slaymaker1907

And memcpy is kind of special to C/C++ compilers. Sure, it exists as a function, but it will often have special purpose code generated for that particular location.

It’s obvious why you want to inline memcpy, but the specialization is more interesting. For example, I’ve seen the compiler optimize a memcpy with a static number of bytes and then use SIMD registers to do the copying with no loop at all. It can even be smart enough to take advantage of memory alignment for this.