linux-kernel - Re: [PATCH] Make shr to divide by power of 2

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Date:	Fri, 07 Aug 2009 21:09:36 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make shr to divide by power of 2

On 08/07/2009 12:50 AM, Andi Kleen wrote:
> Sergey Senozhatsky<sergey.senozhatsky@...il.com>  writes:
>> Of course, compiler supposed to do something like
>> 	add    $0x7,%eax
>> 	shr    $0x3,%eax
>> instead of div. Should we rely on this?
>
> Yes. We should rely on this.

It may depend on the selected CPU type that gcc is optimizing for - I 
believe that on some P4s the shift may actually be slower than the divide..
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