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Re: recent binutils and mips64-linux

To: Zack Weinberg <zack@codesourcery.com>
Subject: Re: recent binutils and mips64-linux
From: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
Date: Tue, 23 Sep 2003 22:03:37 +0200
Cc: Eric Christopher <echristo@redhat.com>, Alexandre Oliva <aoliva@redhat.com>, "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, Atsushi Nemoto <nemoto@toshiba-tops.co.jp>, linux-mips@linux-mips.org, binutils@sources.redhat.com
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Zack Weinberg wrote:
> Daniel Jacobowitz <dan@debian.org> writes:
> 
> > On Tue, Sep 23, 2003 at 11:01:11AM -0700, Eric Christopher wrote:
> >> 
> >> I'm still trying to figure out why you are going through such weird
> >> contortions at all. I understand not having an elf64 loader. That's what
> >> the objcopy comment was for, everything else I don't understand. Why not
> >> compile for the abi you want?
> >
> > Compare the optimal way to load an address into a register when you
> > have a full 64-bit address space and when you know that addresses are
> > sign extended.  I'm told it saves over 100K of code.
> 
> Maybe what you really want is an -mdata-model=kernel switch (or some
> such spelling)

Well, an ELF64 kernel loaded in the 64bit address space is also legal,
and desireable on some (bigger) hardware. Btw, it would have to be
-mtext-model=kernel, the data is the same. :-)

> that tells gcc to do the right thing in the first place?

Gcc still generates MIPS assembler macros, so such a switch would
do nothing yet. Gcc should be changed to do the expansion itself
(and improve code quality by that), but that's a much larger task.


Thiemo

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