>Have you looked at the SUBDLA/SUBDL/SUBDLR macros? They allow you to take 64 >bit addresses in register pairs (and/or a data area) and subtract them. They are in >HCPOM2 MACLIB. I use them a lot for TRACK support of 64 bit.
Okay, so I didn't answer the actual question - doh! I am wondering if you could use COMPDxx macro(s) to verify/validate for a possible overflow condition. I am not positive if/how SUBDxx handles an overflow, but I believe given the basic commands in the macros, the condition code may still be useful to check. _______________________________________ James Vincent Systems Engineering Consultant Nationwide Services Co., Technology Infrastructure Engineering Mainframe, z/VM and z/Linux Support One Nationwide Plaza 3-25-02 Columbus OH 43215-2220 U.S.A Voice: (614) 249-5547 Fax: (614) 677-7681 mailto:[EMAIL PROTECTED] VM/ESA and z/VM Discussions <[email protected]> wrote on 11/30/2005 11:19:11 AM: > [email protected] > > I'm trying to implement a 64-bit subtract with overflow detection > using 32-bit instructions and I can't seem to crack it. Without > overflow detection it's trivial but I can't get a reliable mechanism > for detecting overflow. Does anyone have a simple s/390 algorithm > they'd like to share? > Neale
