Sure. And given that the high 32 bits are required to be 0, by convention, which is why I mentioned the use of LA on each undefined register on entry, the computation is:
0 + 0 = 0 Just what the doctor ordered. BFN. Paul. On Thu, 2 Feb 2023 23:10:47 +0000, Seymour J Metz <sme...@gmu.edu> wrote: >"The address computa- tion follows the rules for address arithmetic." > >In AM64 that means that the base and index are 64 bits. > > >-- >Shmuel (Seymour J.) Metz >http://mason.gmu.edu/~smetz3 > >________________________________________ >From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of >Paul Edwards [mutazi...@gmail.com] >Sent: Thursday, February 2, 2023 5:59 PM >To: IBM-MAIN@LISTSERV.UA.EDU >Subject: Re: GETMAIN LOC=32 > >On Thu, 2 Feb 2023 14:45:31 -0800, Ed Jaffe <edja...@phoenixsoftware.com> >wrote: > >>On 2/2/2023 2:36 PM, Paul Edwards wrote: >>> But on top of that, I was looking for a z/OS change to >>> guarantee the high halves were zero. And the new >>> information is that I don't need that guarantee. I can >>> make my S/370 applications "more-properly-written" >>> by taking clear of clearing the high halves themselves, >>> without being dependent on z/OS. >> >>We take exactly the opposite approach because we have been "burned." >> >>We set Traps(IeaInitArSrb,IeaInitRegsTask) in DIAGxx to ensure the >>operating system puts garbage in the ARs and the high halves. >> >>That way we won't accidentally develop code that depends on these >>registers being pre-initialized to zero. > >Ok, that sounds like a good idea, and again, LA (a S/370 >instruction) should cope with clearing that garbage, so that >a "properly-written" (or maybe "appropriately-written") S/370 >program can protect itself while running in AM64. > >BFN. Paul. > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, >send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, >send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
