John, (I was brief yesterday because I was AFK) - now I am back
>> I need to follow that up with another instruction to set the AR2 to primary mode unless I am certain that AR2 has not been "messed with". yea- but why would you do that? If you are without a base, it is likely code- right? Instructions can only execute in the primary address space. So you sample will likely be (I extended the names) LARL R2,SOME_LABEL_IN_CODE_SECTION LAE R2,0(R2,0) SET AR2 TO ZERO in CASE THE CALLEE IS TOO DUMB​ This is a sample for passing some parm. When you do it yourself (like moving a constant to the dataspace) you need a zero in some AR >> I guess that I really want LARLE to set AR2 as well a GPR2. Not - not realy- There is no need for it. You need an AR with zero in it if your intent is to move some constants from non AR based stuff to a dataspace (while in AR mode) 14 and 15 come in handy (they are very transient and are extrem likely to have a zero) -- Martin Pi_cap_CPU - all you ever need around MWLC/SCRT/CMT in z/VSE more at http://www.picapcpu.de
