From: Marc Bevand <bevand_m@epita.fr>
To: dean gaudet <dean-list-linux-kernel@arctic.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [rc4-amd64] RC4 optimized for AMD64
Date: Tue, 2 Nov 2004 00:01:03 +0100 [thread overview]
Message-ID: <20041101230103.GA656@iah.epita.fr> (raw)
In-Reply-To: <Pine.LNX.4.61.0411011249550.25856@twinlark.arctic.org>
dean gaudet wrote:
|
| [...]
| ack... it's too early on a monday morning -- i misread the documentation.
| this ZF assumption is actually defined and portable... still kind of ugly.
| how much benefit do you see?
When "dec" is placed before "ror", throughput goes up by about 5%
on my test system (Opteron 244 rev C0). I don't find it "ugly"
because the optimization no intrusive at all (only 1 moved instruction).
Concerning the "dec / sub $1" case, it makes absolutely no difference
on the Opteron, I just used "dec" because the opcode is 3 bytes length
instead of 4.
--
Marc Bevand http://www.epita.fr/~bevand_m
Computer Science School EPITA - System, Network and Security Dept.
next prev parent reply other threads:[~2004-11-01 23:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-01 6:57 [rc4-amd64] RC4 optimized for AMD64 Marc Bevand
2004-11-01 7:36 ` James Morris
2004-11-01 12:24 ` Marc Bevand
2004-11-01 20:44 ` dean gaudet
2004-11-01 20:51 ` dean gaudet
2004-11-01 23:01 ` Marc Bevand [this message]
[not found] ` <200411020854.21629.vda@port.imtp.ilyichevsk.odessa.ua>
2004-11-02 18:52 ` dean gaudet
2004-11-02 21:45 ` Denis Vlasenko
2004-11-03 10:07 ` Marc Bevand
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