linux-kernel - Re: [PATCH] Change ZERO_SIZE_PTR to point at unmapped space

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Date:	Sat, 30 May 2009 16:00:22 -0700
From:	"Larry H." <research@...reption.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-mm@...ck.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Change ZERO_SIZE_PTR to point at unmapped space

On 15:29 Sat 30 May     , Linus Torvalds wrote:
> 
> 
> On Sat, 30 May 2009, Larry H. wrote:
> > 
> > The ZERO_OR_NULL_PTR macro is changed accordingly. This patch does
> > not modify its behavior nor has any performance nor functionality
> > impact.
> 
> I'm sure it makes a code generation difference, with (a) big constants and 
> (b) no longer possible to merge the conditional into one single one.

Like I said in the reply to Peter, this is 3 extra bytes for amd64 with
gcc 4.3.3. I can't be bothered to check other architectures at the
moment.

	Larry
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