You could certainly do a normal STM R14,R12,12(R13); 4(R13) is normally the back point for 24-bit linkage.
The 72-byte SA only has 15 words left at offset 12; that's not enough for that STGM, so you need to test first. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [ASSEMBLER-LIST@LISTSERV.UGA.EDU] on behalf of Mark Hammack [mark.hamm...@gmail.com] Sent: Tuesday, November 30, 2021 12:43 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Base-less macros Couldn't do a "normal" STM R14,R12,4(R13) since that would overlay the area to be checked. STGM 14,12,8(13) would probably work in most cases. Either the first 72 bytes will be rewritten with the STM or the data is already stored. The only issue I see is possibly debugging, trying to decipher the RSA chain to figure out what routine was called prior to the current routine (had to do that a couple of times). *Mark* On Tue, Nov 30, 2021 at 10:13 AM Charles Mills <charl...@mcn.org> wrote: > > the caller must provide a large enough area to allow for the 144 byte > > Does that not make the problem go away? Simply automatically always save > the low order halves of the registers, and if the subroutine will be > altering the high halves, save those also. Done. The *caller* has no say in > the save area format. > > Charles > > > -----Original Message----- > From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] > On Behalf Of Mark Hammack > Sent: Tuesday, November 30, 2021 7:54 AM > To: ASSEMBLER-LIST@LISTSERV.UGA.EDU > Subject: Re: Base-less macros > > In our case, the caller doesn't "know" whether the called subroutine is > base 31 or base 64. So it is up to the called subroutine to "figure out" > whether the caller used a 72 byte save area or a 144 byte save area. > Parameters to the macro set addressing mode, RSA size, etc. This allows > for a 31 bit module to call a 64 bit subroutine and vice versa. That's > what I really mean by "switches between". The one caveat is that the > caller must provide a large enough area to allow for the 144 byte area. > > Since some subroutines accept arguments in R0 and/or R1 (and unfortunately > assume other registers are pre-loaded) those can't be touched before being > saved. Likewise, if the routine is called from another 64 bit subroutine, > the high halves of registers are (potentially) in use. However, since > (currently) all of our programs run below the bar, using the high half of > R14 may be an option. I need to look into using a FPR or AR but the 4 byte > literal pool works for now. Storing R14 in 8(R13) is not a bad idea > either. >
