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Re: 2GB userspace limitation in ABI N32

To: David Daney <ddaney.cavm@gmail.com>
Subject: Re: 2GB userspace limitation in ABI N32
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Wed, 10 Oct 2012 18:10:03 +0100 (BST)
Cc: Rich Felker <dalias@aerifal.cx>, linux-mips@linux-mips.org, "Pinski, Andrew" <Andrew.Pinski@caviumnetworks.com>
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On Wed, 10 Oct 2012, David Daney wrote:

> The only disadvantage of doing this is that the code will be slightly
> larger/slower as it takes three instructions to load a zero extended 32-bit
> pointer verses two for n32-2GB.

 And of course such code will only run on 64-bit processors that not only 
support 64-bit data, but 64-bit addressing as well.  That is implement the 
CP0.Status.UX bit rather than CP0.Status.PX only -- the latters are still 
compatible with the true n32 ABI.  See also CP0.Config.AT.

  Maciej

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