The trick with (0) also works for other RX instructions, such as arithmetic and logical instructions. It also works for unaligned macro operand addresses which will be referenced using RX-type instructions, where the original instruction is not under the programmer's control (although there is of course a risk then that the macro expansion may change in future). ICM/STCM only covers the L/ST cases, although ICM sets the condition code which may be an unwanted side-effect.
Jonathan Scott -----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Jon Perryman Sent: 02 September 2025 20:09 To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Using (0) to suppress alignment checks in HLASM On Tue, 2 Sep 2025 17:16:38 +0100, Rupert Reynolds <rupertreyno...@gmail.com> wrote: >I was politely asked to avoid that, and to use > ICM R0,B'1111', X_UNAL Sensible comment I now wonder if there >was/is a performance penalty for ICM. ICM is commonly used to avoid this message. I suspect that ICM and L against an unaligned field is similar. If you didn't care about alignment impact, then why be worried about the negligible performance difference.
