On Tue, 16 Feb 2016 19:17:10 +0000, Gibney, David Allen,Jr wrote: >I am finding this interesting. One thing I think you are missing was the >advisability >to use STMG/LMG to save and restore all 64 bits of the registers. Not a lot of >stuff >running above the bar as yet, but it will be there sooner than we expect. :)
It isn't because of things running above the bar. Nor is it about referencing storage above the bar Your program can't know whether your caller or anyone who called him is using the high halves of the registers for anything, so the linkage conventions require that if you alter the high halves in any way, you must restore them. For example, if your program issues a LG, XGR, or AG instruction, among many others, you should save and restore the high halves. It isn't hard to do it correctly when you are passed a 144-byte save area, as this exit is. By the way, for a long time (z/OS 1.3 maybe, but I'm not sure), the system provides any program that it calls with a 144-byte save area. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
