On 4 April 2011 11:23, Paul Gilmartin <paulgboul...@aim.com> wrote: > On Apr 4, 2011, at 09:09, Tony Harminc wrote: > >> On 4 April 2011 08:01, Joe Owens <joe_ow...@standardlife.com> 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.
I'm sure you're right, but I'm not getting the point. Tony H.
