On Apr 4, 2011, at 09:09, Tony Harminc wrote: > On 4 April 2011 08:01, Joe Owens <[email protected]> wrote: > >> One question occurs - must I now use extended save areas, as I am doing >> something to the top halves of the GPRs, or will the system take care of >> that for me? (There are no amode 64 progs on the calling chain). > > Perhaps it's obvious, but... You don't need to do anything if you are > merely using the 64-bit GPRs for calculation, i.e. the system will not > munge the high halves just because there is an interrupt and you lose > control, no matter what addressing mode you are in and what save area > scheme, if any, you use. You need to worry only if you want to call a > routine (your subroutine or a system service) and have a 64-bit value > in a GPR that you want preserved. It's almost certainly easier just to > make sure such values are safely stored before you make the call than > it is to update the save area scheme. > The called routine may have no control over what its caller does or does not do.
-- gil
