Much of the Mill is not new; we don't bother filing those parts. Much that is not new is very good, and was abandoned for reasons unrelated to the actual merits. The first compiler I ever wrote was for the Burroughs B6500, which in 1970 had better security than any current commercial architecture. That compiler is still in use.

Security in architecture is the history of a race to the bottom, driven by newbie customers not knowing there was such a thing and the economics of chip-making. We may hope that there are fewer newbies now. That leaves economics. To a large extent the Mill has been an effort to make old ideas economically viable to today's customers.