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Re: lwl-lwr

To: Gilad Benjamini <yaelgilad@myrealbox.com>
Subject: Re: lwl-lwr
From: Will Jhun <wjhun@cisco.com>
Date: Tue, 20 May 2003 11:34:36 -0700
Cc: linux-mips@linux-mips.org
In-reply-to: <1053455551.996c4860yaelgilad@myrealbox.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1053455551.996c4860yaelgilad@myrealbox.com>
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Some free or "MIPS-like" CPUs don't implement it because of a patent
problem. I've seen at least one implementation on opencores.org that has
this (missing) feature.

Probably if the compiler were to emit lwl and lwr code via
__attribute__((packed)), these instructions would have to be emulated by
the kernel on such a CPU. I imagine this would be quite a bit worse than
just doing two normal loads and extracting the desired word.

Will

On Tue, May 20, 2003 at 06:32:31PM +0000, Gilad Benjamini wrote:
> Hi,
> About two months ago there was a discussion
> here about disabling lwl-lwr.
> 
> Can someone shed some light on why the discussion
> emerged ?
> 
> Is this a performance issue, a processor which 
> doesn't support it, or something else ?
> 
> If this is a performance issue, I'll be happy
> to hear more details.
> 
> TIA
> 
> 
> 

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