Relaying info on recommendation for clearing a reg -- if you're doing a 32-bit GR clear and don't care about the CC or would prefer the CC to be cleared, use XR -- if you're doing a 64-bit GR clear and don't care about the CC or would prefer the CC to be cleared, use XGR. -- if you're doing a 32-bit GR clear and cannot destroy the CC, use LHI. -- if you're doing a 64-bit GR clear and cannot destroy the CC, use LGHI.
Peter Relson z/OS Core Technology Design
