Robert Ngan wrote: <snip> Vector registers (VRs) 8 - 15, bytes 0 - 7, and the entirety of VRs 16 - 23 are unchanged. 16-23 only! Not 16-31. Is this correct? </snip>
Yes it is correct (and you didn't even ask about VRs 0-7). As with the FPRs, some of the vector regs are considered "volatile" and need not be preserved if used. A program might be able to take advantage of that, if using the regs when not calling anything. Only the part about regs 8-15 bytes 0-7 is related to the fact that the VR storage overlaps the FPR storage. Peter Relson z/OS Core Technology Design
