On 2015-07-02 14:58, glen herrmannsfeldt wrote: > someone wrote: > >> I was raised to do single-instruction branches thus: >> TM FLAG,BIT Is the flag bit set? >> BO *+8 Yes, skip next instruction >> L R15,SOMEVAL No, get the value >> *+8 DS 0H > >> Yes, of course I realize that the "DS 0H" is meaningless, but it helps >> readability. > I believe it's evil in that it might mislead the careless reader to believe it's a real label and that the length of the intervening instruction sequence may safely be changed.
I've even heard a tale (legend) that the technique was invented to deceive automated standards checkers (Lint?) that otherwise required definition of all apparent labels. As such, it's not only overly clever and evil but also unethical. > (the : indicates it is a label). Local labels are unique only between > two ordinary labels, making them convenient for the little branches > like this discussion. That is a little easier than thinking up new > names for each label. > > I don't know if anyone ever did it for S/360 and descendants, but: > > (the : indicates it is a label). Local labels are unique only between > two ordinary labels, making them convenient for the little branches > like this discussion. That is a little easier than thinking up new > names for each label. > > I don't know if anyone ever did it for S/360 and descendants, but: > > (the : indicates it is a label). Local labels are unique only between > two ordinary labels, making them convenient for the little branches > like this discussion. That is a little easier than thinking up new > names for each label. > > I don't know if anyone ever did it for S/360 and descendants, but: > ... "What I tell you three times is true." -- C. L. Dodgson -- gil
