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Re: recent binutils and mips64-linux

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: recent binutils and mips64-linux
From: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
Date: Fri, 19 Sep 2003 19:40:39 +0200
Cc: Eric Christopher <echristo@redhat.com>, Atsushi Nemoto <nemoto@toshiba-tops.co.jp>, Daniel Jacobowitz <dan@debian.org>, linux-mips@linux-mips.org, binutils@sources.redhat.com
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Maciej W. Rozycki wrote:
> On Fri, 19 Sep 2003, Thiemo Seufer wrote:
> 
> > > > A third answer is to add a -msign-extend-addresses switch in the 
> > > > assembler.
> > > > Together with -mabi=64 this would produce optimized ELF64 output.
> > > 
> > >  Hmm, what do you exactly mean -- is that what I am worrying about?
> > 
> > The idea is to use the assembler's 32bit macro expansions for addresses.
> 
>  So it is...
> 
> > This reduces the .text size of a n64 kernel and improves the performance,
> > without tricks like -Wa,32.
> 
>  What if the final link leads to segments being mapped outside the 32-bit
> address range?  We won't know about it when assembling.

Then the resulting code is broken. It's the programmers responsibility
to care about it. IMHO that's not a problem, this feature is only
useful for kernels, and the tricks currently done there are worse.

>  If the idea were to be implemented, there should be a flag added to the
> header of object files that would forbid the linker to map addresses
> outside the 32-bit range.

Please don't add any header flag. An additional (.note?) section would
be nice, but is not a priority for me.


Thiemo

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