linux-kernel - Re: Trying to convert old modules to newer kernels

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Date:	Wed, 26 Dec 2007 19:17:02 -0500
From:	Bill Davidsen <davidsen@....com>
To:	James Courtier-Dutton <James@...erbug.co.uk>
CC:	"J.A. Magallón" <jamagallon@....com>,
	"linux-os (Dick Johnson)" <linux-os@...logic.com>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: Trying to convert old modules to newer kernels

James Courtier-Dutton wrote:
> J.A. Magallón wrote:
>>>>>
>>>>> I need to get rid of -mregparm=3 on gcc's command line. It
>>>>> is completely incompatible with the standard calling conventions
>>>>> used in all our assembly-language files in our drivers. We make
>>>>> very high-speed number-crunching drivers that munge high-speed
>>>>> data into images. We need to do that in assembly as we have
>>>>> always done.
>>>>>         
>>
>> Just for curiosity... yep, I understand now you have everything written
>> in assembler, but why not consider start writing it in C and stop
>> doing the compiler work (such as pipelining, out of order reordering,
>> loop unrolling for specific processor, and so on...)
>>
>> That's what everyone taught me, nowadays you won't be better than the
>> compiler in anything longer than three lines...
>>
>>   
> 
> Not true for image processing. compilers are not too good with 
> optimizing mmx and sse algorithms. This is why user space libraries like 
> ffmpeg still use assembly code.

If half of what I read about the Intel compiler is true, that may no 
longer be true.

> That being said, I don't think sse and mmx are available in kernel 
> space, so I would have suggested doing all the grunt work in userspace 
> would be better for this persons application so that he could use sse 
> and mmx etc.

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

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