Not that BAKR is a "new 64 bit instruction" (neither "new" nor "64 bit"), but POp does tell you what you need to do to use the instruction by describing exactly how the instruction behaves. How you do what you need to do is your choice.
You made an unfounded assumption related to how PR works. You don't "have" to do a BSM prior to the BAKR. And, in fact, in some cases it would be wrong to do so (the typical example is if your interface is invoked via BASSM). If you want the PR paired with a BAKR to return in AMODE 31 then the address saved must indicate AMODE 31. How you accomplish that is up to you. Peter Relson z/OS Core Technology Design
