Excellent idea! Could be a superb mechanism for setting up instruction-tracing or debugging software (see program TRACE390 in CBT file 391, for example) without the overhead of ESTAE or the (currently unsupported under z/OS) TRAP exits.
But perhaps not directly from any general register (think extreme EREG that reloads ALL registers from the last stack entry, including the one you used to execute the EREG, or LMG 0,15,...). Perhaps a dedicated (set of?) "instruction register(s)"? That would be cool. Would need at least RR type instructions to load them from GR's. Just dreaming . . . Peter -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of John McKown Sent: Thursday, May 11, 2017 2:39 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Performance of Decimal Floating Point Instruction On Thu, May 11, 2017 at 1:28 PM, Charles Mills <charl...@mcn.org> wrote: > Absent EX how do you do a variable length PACK or MVO or ... > I said that I didn't _like_ EX. Not that I didn't _use_ it. I'd prefer to "synthesize" an instruction into a 64 bit GPR and then "EX" the contents of the GPR. That would allow me to do more than just modify the value in second byte of the instruction. I understand why EX exists (just as you have pointed out) and why it does what it does. But a more generalized facility would be, to me, "nicer". But, in reality (which stinks in some ways), I understand that IBM won't create a new instruction "because John thinks it would be nice". [grin] > Surely not with an MVI into the instruction stream ... > > Charles > > -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system.
