Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!MAINE.BITNET!MICHAEL
From: MICHAEL@MAINE.BITNET (Michael Johnson)
Newsgroups: comp.lang.asm370
Subject: Re: Addressibility problems
Message-ID: <8906011713.AA20509@jade.berkeley.edu>
Date: 1 Jun 89 13:01:18 GMT
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Reply-To: IBM 370 Assembly Programming Discussion List <ASM370%UCF1VM.bitnet@jade.berkeley.edu>
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While moving data areas to the end of the program MAY be only a stopgap
solution, it does have merit. It is a lot less work than reorganizing the
code entirely and will usually do the job nicely. Which isn't to say that your
solution isn't elegent, Leonard. It's a pretty standard way to write code for
large systems.

One problem that the solutions proposed so far have is that they generated
address constants. In release 6 of CMS this is not a problem at all, since
there are fully relocatable modules in R6. But for earlier releases, being
free of address constants can be important. You can avoid address constants
by coding something like this..

  BASE    CSECT ,
          USING BASE,R12
          .
          .
          L    Rx,ADATA
          ALR  Rx,R12
          .
          .
  ADATA   DC   AL4(DATA-BASE)

While this approach uses an extra two byte instruction, it has the advantage
of not generating a relocatable address constant. I've used this many times in
code that I wanted to be absolutely ADCON free.

Michael Johnson                           "We are the Priests of the Temples
University of Maine System                 of Syrinx. Our great computers fill
Computing and Data Processing Services     the hallowed halls." - Neil Peart