Path: chuka.playstation.co.uk!news
From: gil@snsys.com (Gil Jaysmith)
Newsgroups: scee.yaroze.programming.gnu_compiler
Subject: Re: Optimise Problem - trunced data
Date: Thu, 07 Aug 1997 16:08:07 GMT
Organization: SN Systems
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Message-ID: <5scri7$oj11@chuka.playstation.co.uk>
References: <333d7fd9.23907964@news.playstation.co.uk> <33424023.72C4@interactive.sony.com> <33D5B732.3AC9@dial.pipex.com> <01bc9c44$3fe961e0$ca2c9ac2@martin.snsys.com> <33E39782.6C3F@dial.pipex.com> <01bca0db$fb8dfdc0$ca2c9ac2@martin.snsys.com> <33E8377F.366F@dial.pipex.com> <5s9g9e$oj8@chuka.playstation.co.uk> <33E98CFC.522B@dial.pipex.com>
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Chris Chadwick <xjk18@dial.pipex.com> wrote:
>I wondered why the GP register was set to point to the *middle* and
>indexed with a signed offset instead of simply pointing to the base
>and using an unsigned offset. I didn't realize this section was
>shared! I guess, then, negative offsets index into .sdata and positive
>offsets index into .sbss (or vice versa)...

Not necessarily the middle... the total size of .sdata and .sbss is
limited to 64K, so (assuming .sdata and .sbss occur in that order) the
startup code can set GP to .sdata + 32768. So if you have really small
.sdata and .sbss sections, all the offsets created by the linker will
be sizeable and negative.


Gil Jaysmith
SN Systems Software Ltd, makers of Psy-Q... http://www.snsys.com
Disclaimer: What I say when I post here represents me, not my employers.