Ah, yes you can do that, but its not interrupt-safe so you have to be careful
if driving several pins from the same port (especially via libraries).
Or is there an atomic read-modify-write for this? Been a while since I played
with the Due, my impression was the set and clear registers are there specifically
to allow single-instruction update without having to worry about interrupts using the
same port. Effectively the read-modify-write is done implicitly at the lowest level
in hardware.