Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!xanth!mcnc!rti!xyzzy!tiktok!meissner
From: meissner@tiktok.dg.com (Michael Meissner)
Newsgroups: comp.arch
Subject: Re: 68000 architecture
Message-ID: <7233@xyzzy.UUCP>
Date: 19 Jun 89 15:33:04 GMT
References: <65416@<1989Jun4> <28200334@mcdurb>
Sender: usenet@xyzzy.UUCP
Reply-To: meissner@tiktok.UUCP (Michael Meissner)
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 27

In article <28200334@mcdurb> aglew@mcdurb.Urbana.Gould.COM writes:
| 
| >| Actually, I don't mind the absolute addresses being signed; it's a
| >| fairly minor issue.  It's the signed offsets in base+offset mode that
| >| burn me up.
| >
| >It's useful on occasion. For example, Amiga shared libraries have shared
| >data at positive offsets, and a jump table at negative offsets.
| 
| The 88K does not have signed offsets (except for branches).
| 
| I recall (but do not have the reference handy) a paper by some fellows from
| Tektronix who were porting Scheme to the 88K that listed lack of signed 
| offsets as one of the things that made their task slightly more difficult.
| However, lack of signed offsets certainly has not prevented LISP and other
| AI type languages from being ported to the 88K.

I don't about AI languages on the 88000, but not having negative
literals was an extreme pain in finishing the GNU C 88000 port.  The
compiler internally expects to have a frame where local variables are
on one side of the frame, and arguments' stack slots are on the other
side.  This certainly is my biggest gripe about the 88000, though
signed division is close behind.
--
Michael Meissner, Data General.
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