"I use instructions for what they do, not for their motivation or nomenclature."
+1 OR LA 1,1(,1) if you like. On Tue, 8 Feb 2022 at 11:23, Seymour J Metz <sme...@gmu.edu> wrote: > I have certainly been accused of being a pedant, and I freely use LA as an > add immediate instruction for constants less than 4096. I use instructions > for what they do, not for their motivation or nomenclature. Do you find it > improper to use UNPK for purposes other than decimal arithmetic, e.g., > converting binary to hexadecimal for display? BCTR to decrement a register > without testing it? > > > -- > Shmuel (Seymour J.) Metz > http://mason.gmu.edu/~smetz3 > > ________________________________________ > From: IBM Mainframe Assembler List [ASSEMBLER-LIST@LISTSERV.UGA.EDU] on > behalf of Paul Gilmartin [00000014e0e4a59b-dmarc-requ...@listserv.uga.edu] > Sent: Tuesday, February 8, 2022 10:44 AM > To: ASSEMBLER-LIST@LISTSERV.UGA.EDU > Subject: Re: Making Encoded Bits Human Readable > > On Feb 7, 2022, at 23:10:49, Bob Raicer wrote: > > > > Just for fun, here is yet one more variation on Peter's scheme, using > > only S/360 instructions. In the comments, YY and ZZ represent the two > > bit pairs of interest, lower case x represents bits or bytes of unknown > > value. Bit strings are enclosed in square brackets. Bytes are separated > > by underscore characters. > > > > XR R14,R14 R14 = 00_00_00_00. > > > Is that the fastest way to clear R14 on S/360? > > > ... > > LA R14,X'F1'(,R14) * Scale x'00' through x'03' > > LA R15,X'F1'(,R15) * to x'F1' through x'F4' > > > Is that more transparent than: > LA R14,C'1'(,R14) > LA R15,C'1'(,R15) > ??? When I'm wearing my Pascal hat I loathe arithmetic operations > on character operands. When I wear my C hat they come naturally. > > A pedant insisted (here? lately?) that LA should be used only with > operands referring to storage addresses. I believe the rationale > is that reckless use of LA in lieu of Immediate instructions, which > have existed only recently, risks unexpected truncation to 24 bits > or 31 bits. > > -- > gil >
