BTW, note that Duff's device leads to an irreducible flow graph. In one compiler I know of, that led to really bad code (it gave up on putting variables in regi

BTW, note that Duff's device leads to an irreducible flow graph. In one compiler I know of, that led to really bad code (it gave up on putting variables in registers); in others, I think that the changes to make the flow graph reducible undoes the jump into the middle of the loop.