John,

This is the first time I have had to take exception to a fact that you said and 
that is on the comment that we need a 8i multiple.

Even with 64-bit addressing, it doesn't change the length of a branch or jump, 
they are still 4 bytes.  A jump long is 6 bytes, so maybe 6i is possible, but 
that is a weird number to deal with in a binary environment.

Of course you could use 8i with the following

         B     *+4(R15)
         JLU   COND0
         NOPR  0          never executed, just here to fill space
         JLU   COND8
         NOPR  0
         JLU   COND16
         NOPR  0
         ...

I think I will continue to prefer the more traditional 4i solution.

Chris Blaicher
Principal Software Engineer, Software Development
Syncsort Incorporated
50 Tice Boulevard, Woodcliff Lake, NJ 07677
P: 201-930-8260  |  M: 512-627-3803
E: cblaic...@syncsort.com


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf 
Of John Gilmore
Sent: Wednesday, May 08, 2013 2:39 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Return codes

There are also situations in which one wants to be able to set more than one of 
the diagnostic bits in a return code additively and unambiguously, and the 
alternative use of 0, 2, 4, 8, 16,  . . . , i.e., the sequence 2^i, i = 0, 1, 
2, . . . , powers of 2, permits this to be done.

Still, the fact that successive branch-table addresses always differed by four 
bytes in probably explains the 4i, i = 0, 1, 2, . . .
convention best.

Now, of course, we need 8i, i= 0, 1, . . . , i.e.,  0, 8, 16, 24, . . .

John Gilmore, Ashland, MA 01721 - USA

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