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Date:      Thu, 11 Apr 2002 09:42:42 -0400 (EDT)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Denis Serenyi <dserenyi@panasas.com>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: SSE bcopy
Message-ID:  <15541.37586.404951.505010@grasshopper.cs.duke.edu>
In-Reply-To: <B3B2200B-4CD1-11D6-9B98-003065675568@panasas.com>
References:  <B3B2200B-4CD1-11D6-9B98-003065675568@panasas.com>

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Denis Serenyi writes:
 > I've been looking at adding an SSE bcopy that runs at user-level to a 
 > program that I'm working on. I'm using FreeBSD 4.3 currently.
 > 
 > I wrote the routine, and when I execute it, I get an illegal instruction 
 > exception when I try to execute the first SSE instruction (movups).
 > 
 > After searching the hackers archives, I'm guessing that this is because 
 > FreeBSD 4.3 does not execute the instructions at boot time to enable SSE 
 > instructions to be executed, and also because FreeBSD 4.3 does not save 
 > the 128-bit SIMD registers on context switches.
 > 
 > Am I correct in this assessment?
 > 
 > It also seems like this support has been added to FreeBSD 4.5. Is this 
 > correct?
 > 
 > Assuming yes, in what release was SSE support added to FreeBSD? Has 
 > anyone done a patch that can be applied to FreeBSD 4.3, or are the 
 > changes non-trivial?
 > 

As David says, have a look at
http://kobe1995.net/~kaz/FreeBSD/SSE.en.html  There is a patch there
for 4.3.

What are the performance implications to an SSE bcopy?  How much
faster is it than a normal bcopy?   

Would you consider releasing your code under a BSD license so that
others could play with it, and possibly integrate it (or something
based on it) into FreeBSD?

Thanks,

Drew

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