Hi Michael, You may want to check out the IBM Z optimization primers if you're super serious about this. Here's a link, and I believe there's a z15 version as well in 2020... https://community.ibm.com/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=d1cdb394-0159-464c-92a3-3f74f8c545c4
I did a little very rough benchmarking a few years ago on a z13 and found that all of the instructions you mentioned performed comparably. I suspect the same is true today. HTH, Mike -----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of Schmitt, Michael Sent: Wednesday, March 10, 2021 6:26 PM To: [email protected] Subject: Add 1, Subtract 1 Caution! This message was sent from outside your organization. I was taught long ago to add 1 to a register using LA r#,1(,r#) and to subtract 1 using BCTR r#,0. Is the fastest way now to use AHI r#,1 and AHI r#,-1?
