Dave, if speed is an issue (i.e., your small routine is called many, many times), BAKR is **SLOW** even on very recent hardware. It is convenient, but normal save/restore processes beat the pants off BAKR if execution time is critical.
Considering also the traceability issue and the task cancel issue Tony references, I don't think I would go that way. I have only been in MVS/OS390/zOS shops where it is better supported since the mid-1990's, and I have yet to find any reasonable case for using BAKR/PR in any *application-level* code. HTH Peter -----Original Message----- From: IBM Mainframe Assembler List <[email protected]> On Behalf Of Tony Thigpen Sent: Friday, January 21, 2022 6:20 PM To: [email protected] Subject: Re: Saving Caller's 64-bit Regsiters Dave, I found the BAKR/PR limitation I was thinking about: From the VSE Systems Macro Ref, under STXIT: "The STXIT macro is only allowed when the linkage stack is empty. If a STXIT macro is issued in a module called with a PC or BAKR instruction (that is, the linkage stack is not empty), the calling task is canceled." Tony Thigpen Tony Thigpen wrote on 1/21/22 5:18 PM: > The definitive source is: > > Supervisor Diagnosis Reference z/VSE (for your release) Chapter 2: > Design Information > Section: z/Architecture Linkage Stack > > The z/VSE 6.1 manual has a better PDF index and the language for this > section has not changed since 4.1. > > Off the top of my head, I remember there was some conflict with > something, which I think was OCEXIT, which keeps me from using BAKR/PR. > > Tony Thigpen > > Dave Clark wrote on 1/21/22 11:17 AM: >> "IBM Mainframe Assembler List" <[email protected]> >> wrote on >> 01/21/2022 09:55:32 AM: >>> It's worse than you think. There is a save area format tag literal >>> for the save area, but it's not set by the caller. It is set by the >>> callee saying how he used the previous save area in the chain. Which >>> makes no sense. >> >> >> Hey, Tony, can the BAKR instruction be used in z/VSE? >> Meaning, is >> there a system linkage-stack on z/VSE that can be used for saving >> everything instead of using the caller's provided savearea? >> >> >> Sincerely, >> >> Dave Clark -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system.
