There are entirely new pass manager classes for 3.4 (and presumably going forward). It's conceptually similar, but with many subtle changes and different method names and call sequences, and they haven't finished the docs for it (the Kaleidescope sample app hasn't been updated for the new API). I needed to get OSL at least building against 3.4+ right away, but intend to go back and make it work with the new native APIs when I have more time. At some point (3.5? or later?) the legacy versions will probably disappear, so sooner or later I definitely have to make it work. I may do it quite soon, but it will take a lot less effort on my part if I wait until after they finish the docs.