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Re: 64-bit and N32 kernel interfaces

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: 64-bit and N32 kernel interfaces
From: Daniel Jacobowitz <dan@debian.org>
Date: Thu, 5 Sep 2002 11:14:49 -0400
Cc: "Kevin D. Kissell" <kevink@mips.com>, Tor Arntsen <tor@spacetec.no>, Carsten Langgaard <carstenl@mips.com>, Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
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On Thu, Sep 05, 2002 at 05:08:06PM +0200, Maciej W. Rozycki wrote:
> On Thu, 5 Sep 2002, Daniel Jacobowitz wrote:
> 
> > Well, here's one - while we all know that C code which assumes a
> > pointer and int are the same size is buggy, it makes everything
> > substantially simpler if long and void* are the same size.  That's true
> > for both normal LP64 and ILP32 models.  Since n32 was mostly a
> > transitional tool (SGI was primarily interested in n64 as I understand
> > it), I imagine they wanted path of least damage...
> 
>  I see.  But do we need the SGI's traditional n32 in Linux then?  Having
> most experiences in the server world I'd vote for a pure 64-bit setup
> (with an optional ability to execute o32 stuff), but I understand there
> are people who consider it a waste of resources.
> 
>  Therefore, I believe we may choose another way and use an IP32 (if I
> encode it right) data model, where we have 32-bit ints and pointers for
> these who are short on memory, 64-bit longs for the maximum native
> precision (you don't choose long for the type for your favourite "i" loop
> counter unless you really need it) and an ability to have double-precision
> 128-bit long longs in the distant future (if needed). 
> 
>  Any opinions?

My opinion is that N32 is good enough for people who are short on
space.  We have too many MIPS ABIs already!

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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