CVTBSM2 was added long ago for a different reason entirely -- it had to do with transitioning from AMODE 24 back to AMODE 31. As Tom M pointed out, it can be used for the same purpose as CVTBSM0F, of course using register 2 rather than 15 to hold the 8-byte value. If anyone truly wants to use CVTBSM2, they're welcome to (but you might let me know so that I'd know to change the field to be PI).
It is less effective for debuggers if you use CVTBSM2 (or your own stub) rather than CVTBSM0F because the RTM system trace entry for "retry" special-cases a retry address of CVTBSM0F and puts the 8-byte value from SDWAG6415 into the trace entry as the retry address. Peter Relson z/OS Core Technology Design
