Shmuel wrote >Assume that any system macro expanding to a PC or an SVC will clobber R15-R1.
Or any linkage at all (such as branch linkage by BALR, BASR, BASSM, BRASL, etc). Unless the documentation says otherwise. The default of non-preserving of regs 14-1 (and high halves 15-1 and ARs 15-1) is part of the linkage conventions. Peter Relson z/OS Core Technology Design
