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Path: utzoo!utcs!lsuc!pesnta!amd!masscomp!carter
From: carter@masscomp.UUCP (Jeff Carter)
Newsgroups: net.arch,net.micro.68k
Subject: Re: M680*0 "small model"
Message-ID: <722@masscomp.UUCP>
Date: Mon, 17-Jun-85 23:04:31 EDT
Article-I.D.: masscomp.722
Posted: Mon Jun 17 23:04:31 1985
Date-Received: Tue, 18-Jun-85 08:45:34 EDT
References: <167@mot.UUCP> <1069@peora.UUCP>
Reply-To: carter@masscomp.UUCP (Jeff Carter)
Organization: Masscomp - Westford, MA
Lines: 33
Xref: utcs net.arch:1394 net.micro.68k:928

In article <1069@peora.UUCP> joel@peora.UUCP (Joel Upchurch) writes:
>>      The M680*0 small model is not generally supported in M680*0 systems
>> and compilers for the following resons:
>>   .........etc.......etc.....etc......
>
>It sounds to me like what the 68000 needs is an optimizing assembler.
>On Perkin-Elmer 3200 series computers there are several addressing
>modes, using from 2 to 6 bytes per instruction. The assembler
>.......etc....etc
>referenceing allowing a more compact addressing format to be used.
>
>It seems to me that such a optimizer could be used as a post-processor
>for the compiler allowing all languages to use this technique.  (etc.)

Or perhaps I could suggest a different method. Rather than add another
postprocessor to the 6 stages of processing already involved in
such *Wonderful* Unix utilities as pcc, why not modify the assembler
to choose the shortest possible address mode for jumps and branches, 
etc. so that the compiler doesn't have to to know such things?
The compiler says "branch to location _xxA3" and if this label
is "close enough" for the small model to apply, then the assembler
generates the proper short branch. This will work for all references
inside of a given program unit. Now, for global references from external
program units is another problem....... (Post-process the a.out file? :-))

[The views expressed herein have no relationship to reality, as neither
 does the author]

Jeff Carter
MASSCOMP 
1 Technology Park,
Westford, MA 01886
UUCP: .....!{ihnp4 | decvax | allegra |harpo}!masscomp!carter