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Message-ID: <20120710013027.GA4731@openwall.com>
Date: Tue, 10 Jul 2012 05:30:27 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: Rotate and bitselect investigation
On Mon, Jul 09, 2012 at 12:42:47PM +0530, Sayantan Datta wrote:
> On Mon, Jul 9, 2012 at 12:00 PM, Solar Designer <solar@...nwall.com> wrote:
>
> > Also, I guess this change should hurt on NVIDIA (does
> > it?), so you'll need to wrap it in some #ifdef.
>
> Yes I did wrap it in #ifdef.
So you use USE_LIBRARY_BITSELECT, which has to be manually (un)defined.
Maybe we should use the same approach that magnum uses in rar_kernel.cl:
#ifdef cl_nv_pragma_unroll
#define NVIDIA
#endif
[...]
#ifdef NVIDIA
#define F(x,y,z) (z ^ (x & (y ^ z)))
#else
#define F(x,y,z) bitselect(z, y, x)
#endif
This won't detect CPUs, though - where we also don't want to use
bitselect() most of the time (the instruction is only available with XOP
and is probably not used by current OpenCL SDKs since I think only
Intel's does vectorization) - but this code is mostly just for AMD and
NVIDIA GPUs now. We have faster MSCash2 code on CPU anyway.
Alexander
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