linux-kernel - Re: [PATCH 1/4] sound/isa: use unsigned for loop index

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Message-ID: <20080511172225.GA19791@martell.zuzino.mipt.ru>
Date:	Sun, 11 May 2008 21:22:25 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Ricardo Martins <ricardo@...rybox.net>
Cc:	julia@...u.dk, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, perex@...ex.cz
Subject: Re: [PATCH 1/4] sound/isa: use unsigned for loop index

On Sun, May 11, 2008 at 05:08:32PM +0100, Ricardo Martins wrote:
> On Sun, 11 May 2008 20:43, Alexey Dobriyan wrote:
> > On Sun, May 11, 2008 at 02:50:33PM +0200, Julia Lawall wrote:
> > > A few more cases in the spirit of the patch "Trivial: Replacement of always
> > > >0 ints with unsigned ints" submitted by Ricardo Martins <ricardo@...rybox.net>
> > 
> > And rationale for those would be ...?
> 
> Acccording to the kernel-janitors TODO [1], Jeff Garzik suggested the following:
> 
>   2) "unsigned int" is preferred to "int", it generates better asm code
>   on all platforms except sh5. This replacement needs to be done manually,
>   because often 'int' is required due to negative values -Exxx commonly
>   passed as error values.
> 
> Since (most) loop counters such as "int i" are always either zero or a positive
> number, they are perfect candidates for using unsigned int instead, imho.
> It goes without saying, that each case must be considered separately in
> case a negative value is indeed needed.
> 
> [1] http://kernelnewbies.org/KernelJanitors/Todo

So you've checked disassembly in both cases and saw it's better?

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