llvm dev - Jun 2015 - [LLVMdev] NVPTX questions

Hi,

I started experimenting with the NVPTX backend and have been successful so far,
however I ran into two issues:


1.       How do I access createNVVMReflectPass properly? The header in which it
is defined is not installed along with other headers when (using CMake, if that
matters), so I am currently declaring it directly in my code.

2.       When using mathematical functions like powf or sqrtf, I need to use
__nv_powf and __nv_sqrtf from libdevice. This works fine but unlike powf,
expressions like powf(x, 0.5f), where .5f is constant are not optimized/strength
reduced.
Is there any way to call powf, then optimize then rename these calls later on
(and probably optimize again...)? Or is there a better approach?

Regards
Johannes

--
Johannes S. Mueller-Roemer, MSc
Wiss. Mitarbeiter - Interactive Engineering Technologies (IET)

Fraunhofer-Institut für Graphische Datenverarbeitung IGD
Fraunhoferstr. 5  |  64283 Darmstadt  |  Germany
Tel +49 6151 155-606  |  Fax +49 6151 155-139
johannes.mueller-roemer at igd.fraunhofer.de  |  www.igd.fraunhofer.de

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On Thu, Jun 11, 2015 at 10:31 AM, Mueller-Roemer, Johannes Sebastian <
Johannes.Sebastian.Mueller-Roemer at igd.fraunhofer.de> wrote:
>  Hi,
>
>
>
> I started experimenting with the NVPTX backend and have been successful so
> far, however I ran into two issues:
>
>
>
> 1.       How do I access createNVVMReflectPass properly? The header in
> which it is defined is not installed along with other headers when (using
> CMake, if that matters), so I am currently declaring it directly in my
code.
>
Yes, that is an unfortunate part of the current implementation.  I've been
thinking of how to address this better.  For now, just declaring the init
function prototype in your source file is fine.

>  2.       When using mathematical functions like powf or sqrtf, I need to
> use __nv_powf and __nv_sqrtf from libdevice. This works fine but unlike
> powf, expressions like powf(x, 0.5f), where .5f is constant are not
> optimized/strength reduced.
> Is there any way to call powf, then optimize then rename these calls later
> on (and probably optimize again…)? Or is there a better approach?
>
How are you linking with libdevice?  The recommended way is to link the IR
before calling any optimization passes to allow the optimizers to see the
implementation.  Or are you referring to LLVM not understanding that
__nv_powf is a "built-in" function like libm's powf?


>
>
> Regards
>
> Johannes
>
>
>
> --
>
> Johannes S. Mueller-Roemer, MSc
>
> Wiss. Mitarbeiter - Interactive Engineering Technologies (IET)
>
>
>
> Fraunhofer-Institut für Graphische Datenverarbeitung IGD
>
> Fraunhoferstr. 5  |  64283 Darmstadt  |  Germany
>
> Tel +49 6151 155-606  |  Fax +49 6151 155-139
>
> johannes.mueller-roemer at igd.fraunhofer.de  |  www.igd.fraunhofer.de
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>

-- 

Thanks,

Justin Holewinski
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