Can I infer from this that XR/XGR, all else being equal, is to be preferred (slightly) over LHI/LGHI? If so, why might that be? I would have thought the one that doesn't touch the CC would be "more efficient" than the one that does. Or am I misreading your statement?
-----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of Peter Relson Sent: Monday, April 04, 2016 8:49 PM To: [email protected] Subject: Re: Microprocessor Optimization Primer Relaying info on recommendation for clearing a reg -- if you're doing a 32-bit GR clear and don't care about the CC or would prefer the CC to be cleared, use XR -- if you're doing a 64-bit GR clear and don't care about the CC or would prefer the CC to be cleared, use XGR. -- if you're doing a 32-bit GR clear and cannot destroy the CC, use LHI. -- if you're doing a 64-bit GR clear and cannot destroy the CC, use LGHI. Peter Relson z/OS Core Technology Design The information contained in this electronic communication and any document attached hereto or transmitted herewith is confidential and intended for the exclusive use of the individual or entity named above. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any examination, use, dissemination, distribution or copying of this communication or any part thereof is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail and destroy this communication. Thank you.
