[LLVMdev] Status of PTX Backend

[Justin Holewinski]

Helge,

Thanks for the link.  I was able to get it to build against the LLVM SVN
revision listed in the README file.  I've only run some simple tests through
it, but it seems to be working.  Is this backend still being actively worked
on?  Is there an effort to get it to work with LLVM 2.8?

Che-Liang,

I am very interested in this project.  Are you re-coding and upstreaming an
existing version, or is it currently being written from scratch?  If you
would like some help, I would be willing to put some time into this.

Thanks,

Justin Holewinski

On Thu, Oct 7, 2010 at 1:19 PM, Helge Rhodin <helge.rhodin at alice-dsl.net>wrote:

>
>  Hi,
>
> The PTX backend we developed (CBackend approach, does not use the target
> independent code generator) is already more advanced.
> An older version is published here:
> http://sourceforge.net/projects/llvmptxbackend/
>
> We recently eliminated a bug which increased the number of required
> registers per thread. Surprisingly, without that bug the generated code is
> already comparable to code generated by the official nvcc copiler.  Of cause
> the nvcc compiler is superior in a lot of cases, however only by a small
> margin. And there are even cases(e.g. a phong surface shader) where our PTX
> backend is faster, without any particular optimization! It seems like the
> NVIDIA driver does a good job at late optimizations liker register
> allocation etc. I can give you some numbers if you are intrested.
> I'll push the newest version of the backend to sourceforge during the next
> days.
>
> What kind of optimizations are you planning to do? If you want to apply
> high level (on llvm bitcode) optimizations, you can start with our PTX
> backend and shwitch over to the new backend approach later on (If it turns
> out that the new approach is really faster).
>
> best, Helge
>
>
>
> Am 06.10.2010 17:39, schrieb Che-Liang Chiou:
>
>  Hi Justin,
>>
>> I am upstreaming the PTX backend.
>> My plan is to have a working prototype (that mean you may compile
>> non-trivial code with some workarounds) by the end of this year or by
>> January 2011.
>> I hope I could catch up next release of LLVM (version 2.9), so I will
>> adjust my plan according to the release schedule once it is announced.
>>
>> Regards,
>> Che-Liang
>>
>> On Wed, Oct 6, 2010 at 11:16 PM, Justin Holewinski
>> <justin.holewinski at gmail.com>  wrote:
>>
>>> I read on the archives that a PTX back-end was discussed around August
>>> and I
>>> see that some initial code has been checked into LLVM trunk.  What is the
>>> status of this project?  Is it being actively worked on?
>>> I am ultimately interested in using LLVM for GPU code
>>> optimization/generation and am very interested in this particular
>>> project.
>>>
>>> --
>>>
>>> Thanks,
>>> Justin Holewinski
>>>
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>


-- 

Thanks,

Justin Holewinski
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