On 2015-10-15 15:26, Tony Harminc wrote: > >> I recall struggling to backport some code >> which used IPM...SPM to older hardware that lacked those instructions. > > Must've been *very* old hardware... SPM is original with S/360. IPM is > much later (XA, iirc, because of issues with BALR and the high byte in > 31-bit mode). Before that BALR was the standard way to capture the CC > in a register. > Yup. That old. (Just like me.)
Compatibility bind. Couldn't use IPM on 370; BALR didn't capture CC in AMODE 31. Had to tread lightly and not stomp on CC. I suppose I could have used BALR ,0 and tested bit 0: if 0, CC is captured; if 1, I could use IPM. Oops. Can't test bit 0 without altering CC. >> I refractured the intervening code so it never changed CC. > > Fracking...? -- gil
