"and bits 0-31 remain unchanged" does not mean set to zero.
-- 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 6:47 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: GETMAIN LOC=32 On Thu, 2 Feb 2023 23:37:16 +0000, Seymour J Metz <sme...@gmu.edu> wrote: >The semantics of LA are that it doesn't clear the top half in AM64. LOAD ADDRESS LA R±,D²(X²,B²) [RX] In the 24-bit addressing mode, the address is placed in bit positions 40-63, bits 32-39 are set to zeros, and bits 0-31 remain unchanged.. In the 31-bit addressing mode, the address is placed in bit positions 33-63, bit 32 is set to zero, and bits 0-31 remain unchanged. In the 64-bit addressing mode, the address is placed in bit positions 0-63. Ergo, LA R3,0 in AM64 will set the entire 64 bits of R3 to 0. Which is all I need. And a S/370 instruction. > Even if you clear the top halves yourself, there are still coding > issues for 31-bit addresses in AM64. Fix the coding issues so that they are AM32/64-clean? Also they aren't really 31-bit addresses. If an "L" instruction is used to load an address, it is a 32-bit address, which will suddenly be visible when running in AM64 (or a restored 360/67 running as AM32). BFN. Paul. >-- >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 6:24 PM >To: IBM-MAIN@LISTSERV.UA.EDU >Subject: Re: GETMAIN LOC=32 > >On Thu, 2 Feb 2023 23:22:00 +0000, Seymour J Metz <sme...@gmu.edu> wrote: > >>> And given that the high 32 bits are required to be 0, by convention, >> >>Where do you see that? > >That was my first message in the last 24 hours. > >Do an LA on program entry, for all undefined registers. > >Maybe I should have said "proposed convention". I'm happy >to switch semantics to whatever is less confusing. > >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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
