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Date: Mon, 29 Apr 2013 00:05:36 +0400
From: Solar Designer <>
Subject: Re: AMD GCN ISA development

Daniel, Sayantan -

On Sun, Apr 28, 2013 at 09:43:51PM +0200, D?niel Bali wrote:
> My name is Daniel Bali and I started a thread earlier about GPU support for
> JtR under Windows. I'm interested in working with Openwall during this
> year's GSoC programme, but GPU support for Windows alone isn't a big enough
> task for a GSoC project.

You're right.

> I started looking into AMD's GCN ISA architecture a couple of days ago, but
> I still can't find much info about getting started with it

Right.  Our suggested low-level GPU programming project would involve
figuring this out, and creating approaches and tools as necessary -
well, unless you choose to stay at the (higher) IL level and demonstrate
that it's sufficient to achieve our goals.  (I think IL may be
sufficient for some goals, but not for all.)

> and I have a couple of questions. I found this:

Oh, thank you for reminding us about this wiki page.  I did not recall
it existed. :-(  I've now added a link to it to our ideas page.

Sayantan was the one to create this wiki page (thanks, Sayantan!)

> Which describes how to write AMD IL code, but I was wondering if this works
> for GCN ISA. Does anybody have experience with this? (Or with GCN ISA
> development in general?)

I'm not sure what you mean by "if this works for GCN ISA".  Whether it's
possible to have GCN ISA code generated from IL as described on this
wiki page?  Perhaps.  And even if there's some hurdle, perhaps it can be
taken care of.  However, IL level development is not the same as GCN ISA
level development.  It's similar to how GCN ISA code is generated from
OpenCL code - but there are reasons why we want to try writing GCN ISA
code directly.

IL may be a good start, though.

> I also checked out HetPas:
> I was able to run AMD IL code with it, but it gives me a BSOD when I try to
> run the GCN_OpenCL_HelloWorld example. Maybe this is because my GPU is a
> Radeon HD 7670M, but it is supposed to have the "Souther Islands" (=GCN)
> architecture too. Did anybody manage to get this work for GCN ISA?

We did not experiment with this tool, in part because it's for Windows
and because it's closed-source, and in part because we did not seriously
approach the task yet.  I guess Sayantan can test it on his 7970 under
Windows 7 x64, which he has just mentioned he has.



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