John Ehrman had an MVC2 macro using this concept. Uses the length of OP2
On February 26, 2024 3:44:17 PM GMT+02:00, Seymour J Metz <sme...@gmu.edu> wrote: >Why? What are you trying to solve by wrappng the MVC in a macro? > > MVC 0(2),0 > ORG *-4 > DC S(&OP1) > DC S(&OP2) > >but, again, why? > >-- >Shmuel (Seymour J.) Metz >http://mason.gmu.edu/~smetz3 >עַם יִשְׂרָאֵל חַי >נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר > >________________________________________ >From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> on behalf >of David Eisenberg <deisenbe...@optonline.net> >Sent: Monday, February 26, 2024 8:22 AM >To: ASSEMBLER-LIST@LISTSERV.UGA.EDU >Subject: Macro parameters: parsing a relocatable address > >I’m seeking some guidance if anyone is able to help. I’d like to write a macro >like this: > >&NAME MYCLC &FIELD1,&FIELD2 > >in which both &FIELD1 and &FIELD2 are relocatable addresses. It’s &FIELD1 that >is of particular interest to me. &FIELD1 might be expressed as a hard-coded >displacement and base register, or a relocatable symbol… or it could be an >absolute symbol equivalent to a displacement, followed by a base register… >etc. I.e., it could be any valid relocatable address syntax. What &FIELD1 will >*not* have is an *explicit length.* The macro parameters will specify valid >relocatable addresses, and nothing more. > >My question: I’d like the MYCLC macro to generate a CLC instruction in which >the two parameters are compared to each other for a constant length of 2. So >far, the only ways I can think of to do this are: > >1. Parse &FIELD1 to figure out how the relocatable address is expressed, and >insert an explicit length of 2 to generate a valid CLC first operand. I would >do it that way, but (unless I'm missing something) it seems quite complex to >code. >2. Generate this DC statement: DC X’D501’,S(&FIELD1,&FIELD2) . This seems to >work, but it’s a bit unattractive in a PRINT GEN (and it looks a bit odd in >the assembly listing, because the assembler doesn't treat it like a machine >instruction in the object code on the left side of the listing). > >I’m wondering if anyone can suggest a reasonable way to code option 1 above. >Can the macro assembler give me any help in parsing &FIELD1 so that I can >transform that parameter to insert an explicit length, regardless of how >&FIELD1 is expressed? Or is there some other approach that I haven’t >considered at all? Or should I just go with option 2 above? > >Please note that I don’t want the macro to generate more than one machine >instruction. One way or another, I just want the macro to generate a CLC for a >length of 2. (And I really do want the CLC located in the macro as opposed to >open code, because the macro does some analysis on the comparands prior to >generating the CLC.) > >Any advice would be appreciated... thank you! > >David
