> ST r0,var(,r13,160) I assume that should be either ST r0,var or ST r0,160var(,r13) and that var has an offset of 160 from the DSA. If the programmer's guide documents the format of SYSPRINT that may be APARable.
Yes, the code is bloated. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List [[email protected]] on behalf of Phil Smith III [[email protected]] Sent: Thursday, November 11, 2021 6:58 PM To: [email protected] Subject: Curious compiler optimization IBM XLC on z/OS 2.4, under USS. With NOOPT: * int var = 0; LA r4,0 LR r0,r4 ST r0,var(,r13,160) That's an interesting way to clear a fullword, no? And I'm unclear what var(,r13,160) is supposed to be-the actual generated opcodes are 5000 D0A0 Which makes sense. Feels like there's an extra comma in there and an extra offset. Maybe this is the compiler's way of saying "This is tinkering with var, which is at offset 160"? I.e., it explicitly mentions both the variable name and the 160 for readability? With OPT(3): * int var = 0; MVHI var(r13,160),H'0' LA r0,0 Saner, but still a bit curious-halfword?? Maybe it's so clever it's reusing something that it knows is already half cleared!?! The LA r0,0 is in preparation for using it in a subsequent instruction, though that doesn't explain the redundant register tinkering in the NOOPT version. None of this matters-it all works fine-but it struck me as odd.
