My favorite (not!) is MODESET which generates (IIRC) in-line data and a branch around it and a LOAD from storage. I know it is nothing but it just annoyed me so much that I created my own that uses LHI and no branch.
Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Keith Moe Sent: Wednesday, August 1, 2018 3:58 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Instruction/Data Cache Usage (was EQU *) "(working storage or stack storage)" I interpret this is mean storage that is being ALTERED, not CONSTANTS. I would think that duplicate unchanged cache lines in the instruction and data caches would not have the same SERIOUS penalty as altering data would. But I am not a hardware engineer nor do I know if this is true or not. I've noticed that IBM has been changing many of their macros to generate fewer inline constants with branches around them and use more literals (which can sometime surprise you with unexpected addressability problems when the data suddenly move from being very local) presumably to reduce the double cache usage (with or without the move/copy penalty), but one of the most glaring mixture of instructions and data that is (potentially) updated are the CVTEXIT and CVTBRET instructions. Programs invoked via system linkage have Register 14 pointing to CVTEXIT. The CVT is in the read/write nucleus and is not even cache line aligned!
