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Date: Fri, 12 Sep 2014 19:17:19 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: nVidia Maxwell support (especially descrypt)?

On Thu, Sep 11, 2014 at 09:00:17PM +0200, magnum wrote:
> On 2014-09-11 10:39, Solar Designer wrote:
> >On Thu, Sep 11, 2014 at 09:54:39AM +0200, magnum wrote:
> >>BTW I just dropped the DEScrypt-opencl format to the broken/
> >>subdirectory because it keeps giving me problems.
> >
> >Ouch.  It worked for me before.
> 
> AMD driver (even the one on Super) spews a screenful of complaints about 
> the goto's ("warning: goto statement may cause irreducible control 
> flow"),

Sure, this was always the case, but then the format just works.

> and latest stable (as well as 14.4 iirc) finally fails building 
> because of just that.

That's worse.

> >I'd say it's a compiler problem, but yes we may have to workaround it by
> >stopping to use goto, even though this kernel's uses of goto are
> >reasonable.  Code size might increase if we express the same things with
> >structured programming constructs, and thus speed might be lower.
> 
> Perhaps it also might be faster? Like you said in the other post, GPU's 
> are weird.

Yes.

> >Those goto's are not data-dependent (they depend on the current
> >iteration number only, which is the same for all work-items), so they are
> >OK for GPUs' hardware.
> 
> Even if that is true we're facing a reality of poor compliers.

Right.

> >> To use it, simply move the files back from src/broken to src,
> >> reconfigure and re-build. I hope Sayantan will fix it (as well as the
> >> memory leak discussed before) at some point in time.
> 
> It now hit me we could put it back in the tree but add it as a "disabled 
> format" in default john.conf instead. That way, enabling it is a soft 
> change. Also, the format is actually there if you spell it out with 
> "-format:descrypt-opencl", but only then. That's much better, I'll do 
> this change now.

OK.  Thanks!

Alexander

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