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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 11:14:09 -0400
Cc: Hartvig Ekner <hartvige@mips.com>, "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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References: <20020905145954.GA17383@nevyn.them.org> <Pine.GSO.3.96.1020905170830.7444E-100000@delta.ds2.pg.gda.pl>
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On Thu, Sep 05, 2002 at 05:10:51PM +0200, Maciej W. Rozycki wrote:
> On Thu, 5 Sep 2002, Daniel Jacobowitz wrote:
> 
> > No - the point is that all data types have the same size in N32.  It
> > was created explicitly as a transitional sop for people who didn't want
> > to fix their code, but wanted a performance increase from their 64-bit
> > hardware.
> 
>  Well, what's the performance increase of n32 over o32?  The increased
> number of argument registers?  I doubt it's noticeable in most cases.

N32 supports saving and restoring 64-bit registers, which O32 doesn't -
according to some comments in GCC, O32 is in fact incompatible with
using 64-bit operations.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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