C++: Difference between calling memcpy and __builtin_memcpy

[Florian Weimer <fweimer@xxxxxxxxxx>]

For the C++ compilers version which recognize memcpy, is there a
difference between calling memcpy via your own extern "C" declaration,
and calling __builtin_memcpy?

What about calling memcpy through a function which has a "memcpy" asm alias?

Thanks,
Florian