You mean like LOAD ON CONDITION and STORE ON CONDITION? They were added in the 9th edition of the POPS.
Robert Ngan CSC Financial Services Group From: "McKown, John" <[email protected]> To: [email protected] Date: 2012/11/26 15:39 Subject: Stupid? though on a new "execute" instruction. Sent by: IBM Mainframe Assembler List <[email protected]> It's the holiday season. So be nice. There currently exist 2 execute variants. The old base+displacement and the new relative. Now that we have 64 bit registers, why not have an RR instruction where the first register the modifying value but the second register contains the actual instruction to be executed. I have no idea how the hardware actually works internally, so perhaps this would be a huge kludge. But, then, at present the EX instruction must copy the referenced instruction "somewhere" and modify it "somehow". So why couldn't it copy from a register as well as from the D-cache? Or, maybe, how about an EX which works like EXRL but the relative instruction is "hard coded" to be the next instruction in line? The problem, of course, is that this new EX would then need to "skip over" the just executed instruction. And I don't know how to handle "interruptible" instructions. But EX can do it, so I guess the same way. Yes, I realize these are likely not of much importance. It's just that there's nothing going on and for the rest of the year we are in "don't do anything" mode so that month-end, quarter-end, and year-end processing will be smooth. OK, since I have you here anyway. What about a real weirdie? An instruction which says whether or not to execute the next instruction, based on the condition code? That would enable every instruction to be a conditional instruction. Perhaps EXNC (Execute Next Conditional). What comes to mind? Perhaps: SLR R2,R2 LTR R1,R1 EXNC NZ L R2,0(,R1) LTR R2,R2 JZ BADADDR Which would load the contents of R2 with the address contained in R1 unless it was zero. Or maybe (combining both of the above) L R1,LEN LENGTH OF FIELD AHI R1,-1 DECREMENT FOR EX EXNZ EXRI R1 EX NEXT INSTRUCTION MVC RECEIVE(0),FROM Returning you now to your regularly scheduled, useful, email. -- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * [email protected] * www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets(r) is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company(r), Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM
