If you are running "sometimes" on older hardware I think you have a greater risk from unsupported z/OS than from unsupported instructions.
I'm not sure, but I think that IILF came along no later than the zEC12. Any machine older than the zEC12 only supports z/OS V2R2 and below. V2R2 went out of service almost four years ago. If you are running a current z/OS it won't run on older hardware. I also think you are at greater risk of encountering unsupported instructions in optimized COBOL 6 code than in hand-built assembler. And I would never, ever embed data in the instruction stream. Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Jon Perryman Sent: Sunday, April 14, 2024 11:09 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Complex immediate fields > On current hardware there is an IILF (LFI) instruction, and I would like to >> use it instead of the XR/ICM sequence. Before using any modern instructions, ask yourself if they are worth the risk. Does your disaster recovery site guarantee this as a minimum machine level. Maybe your employer has older machines available in case of capacity problems. How about company acquisition. You need to consider the impact. >Back in he Assembler XF era I would code something like > LA R0,L'DEST > LA R1,DEST > XR R15,R15 > ICM R15,8,=C' ' > MVCL R0,R14 Why use LFI when better alternatives for ICM =C' ' have been around forever. J bydata data dc A(X'40000000',0,L'dest) bydata LM R15,R1,data Since the J instruction only updates the PSW, I'm guessing it will replace the update PSW in the previous instruction thus making this a single instruction on current hardware but still compatible with older hardware. Alternatively, there is the NILH instruction which has existed for a couple decades.
