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Date: Sun, 8 Jul 2012 13:18:04 +0400
From: Solar Designer <>
Subject: Re: Rotate and bitselect investigation

On Sun, Jul 08, 2012 at 02:41:08PM +0530, Sayantan Datta wrote:
> So the results are little slow on 570 and also on 4890. So if you want we
> can have two binary kernel specifiaclly tailored for these two and one
> general kernel for all other devices. Or we may go the opposite way too i.e
> using binary for 7970.

No, let's not bother with multiple kernel versions just because of this.

Rather, if you have time, you may try optimizing SHA1_digest() further
(based on the known constants for some W[] elements), such that it
relies on the optimizer less.  I suspect that it's this reliance on the
optimizer that results in bitselect() hurting performance on some cards.
This suggests that the overall speedup we're seeing on 7970 is less than
full as well - in other words, that there's some slowdown (more limited
propagation of the known constants in the optimizer) and a greater
speedup from bitselect() itself at once.  The slowdown portion may be
avoided by better written source code.

> Do you want me to commit it and push to git repo?

Yes, please.  Thanks.


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