That's a great point, Tony. I know I've written many things with a LTR/BNP/BCTR sequence; this removes one instruction, as well as being less obscure/idiomatic for the youngsters!
-----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Tony Harminc Sent: Thursday, July 10, 2025 3:12 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Food for thought. On Thu, 10 Jul 2025 at 12:39, Mark Hammack < 00001b4f3fed68ca-dmarc-requ...@listserv.uga.edu> wrote: [...] > > Really, the same question can be asked about: > > BCTR Rx,0 vs. > AHI Rx,-1 I've been using the AHI for this for many years now because by far the most frequent reason I want to subtract 1 from a register is to use it immediately in an EX of an MVC or TR or the like. And in this case it's very good to have that condition code, because you can with one BM/JM instruction following the AHI avoid the case where your MVC or whatever runs with a length of 256 because some earlier code didn't anticipate the original content of Rx being 0. This is a common cause of overlays, in my experience. Tony H.
