Ref: Your note of Sun, 1 Dec 2019 21:51:39 -0000 > Hi there, > > APAR PH00902 has this neat get-out clause... > <snip> > > The presence of a mnemonic in the above lists does not necessarily mean that > the corresponding instruction is available to use. The list may include > mnemonics reserved for possible future use, so that if the corresponding > instructions are made available before the next major hardware level this > will not result in any new potential clashes with library macros. > > Melvyn Maltz.
Yes, for z15 this applies specifically to SORTL. The architects can invent ingenious enhancements but cannot confirm from theory alone whether a new instruction provides sufficient practical benefit to be worth making available and supporting as a standard instruction unless a software product implements code to exploit it, at least on an experimental basis, and then measures the results and decides whether it is worth exploiting in the software. I assume that did not happen in time for z15 GA. HLASM tries to avoid updating new instruction set tables after they have been defined, as this could impact existing programs. In this case, the architects made it clear that there is a definite possibility of an instruction with this mnemonic being made available before the next major hardware level, so HLASM has defined that instruction for the z15 level to avoid any incompatible change. The fact that HLASM was provided with the definition of this instruction mnemonic makes it clear that if this instruction is made available, it will also be documented for use by assembler programmers. Jonathan Scott, HLASM IBM Hursley, UK
