From: Robert Hancock <hancockrwd@gmail.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Make shr to divide by power of 2
Date: Fri, 07 Aug 2009 21:09:36 -0600 [thread overview]
Message-ID: <4A7CEC70.4050806@gmail.com> (raw)
In-Reply-To: <87d478i0d7.fsf@basil.nowhere.org>
On 08/07/2009 12:50 AM, Andi Kleen wrote:
> Sergey Senozhatsky<sergey.senozhatsky@gmail.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..
next prev parent reply other threads:[~2009-08-08 3:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-06 18:09 [PATCH] Make shr to divide by power of 2 Sergey Senozhatsky
2009-08-07 6:50 ` Andi Kleen
2009-08-07 7:42 ` Sergey Senozhatsky
2009-08-08 3:09 ` Robert Hancock [this message]
2009-08-08 7:35 ` Andi Kleen
2009-08-09 9:40 ` Sergey Senozhatsky
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