The latest Enterprise COBOL compiler still generates them, along with a lot of other "anachronisms" related to enforcing the ancient COBOL standards from 1985.
But this discussion has not touched on another crucial piece of any decision to use or not use "newer" (FSVO "new") instructions -- Do they save CPU time or use more of it? Ease of programming development is only one measure necessary to that decision; actual CPU usage is (IMHO) the more important one, especially in this day and age of bursting-at-the-seams CPU loads. In the last 5 years, each time on nearly-new z hardware, I have more than once analyzed business-critical batch application program suites for CPU "hot spots" with tools like Strobe or Tritune to find that an MVCL or a CLCL was at the heart of a large CPU "hot spot". In every case I saw, replacing that "xxCL" with a simpler "xxC" loop actually sped up the programs by a statistically measurable amount. Counterintuitive perhaps, but true. Laugh all you want, but when CPU cycles are at a premium, one does what is necessary to survive and meet all SLA's. If IBM guaranteed that newer, extended instructions would always use less CPU time than loops of their non-extended predecessors, that would be a sound reason to move forward. Sadly, they do not make any such promises, and the reality is frequently the opposite -- "newer" equals "more expensive in CPU time". Mr. Gilmore's description of the unexpected bonus he found from using the "new(er)" CKSUM instruction to speed his computation is the exception to the rule, in my experience. I do understand that the time is coming (has come?) when all such hand optimizations will likely be less than useful or even obsolete exercises. I see the complex optimizations produced from the Metal C compiler to avoid delays in the CPU pipeline, and I know that there is no way that any reasonable level of expertise in hand coding can compete with that complex process. Peter -----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of David Stokes Sent: Tuesday, April 16, 2013 8:45 AM To: [email protected] Subject: AW: TRTE and new instructions Does anyone still use CLCL and MVCL? CLCLE and MVCLE have been around for, like, well over ten years. -----Ursprüngliche Nachricht----- Von: IBM Mainframe Assembler List [mailto:[email protected]] Im Auftrag von John Gilmore Gesendet: Dienstag, 16. April 2013 14:14 An: [email protected] Betreff: Re: TRTE and new instructions <Snipped> CLCL and MVCL are now old enough so that I seldom now hear them deprecated in this way, but arguments that CLC and MVC used iteratively were good enough were still very common ten years ago. <snipped> John Gilmore, Ashland, MA 01721 - USA -- 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.
