llvm dev - Jun 2009 - [LLVMdev] Some understanding of LLVM vs gCC vs Intel C++ Compilers

On Monday 15 June 2009 01:32, me22 wrote:
> My (possibly faultly) understanding is that intel's has good support
> for numerics, presumably through auto-vectorization and such, but only
Yes, that's true.
> works for intel's architectures and is only excellent on intel chips.
That used to be the case, but not so anymore.  Intel compilers generate
just fine code for AMD processors.  Since AMD doesn't produce their
own compilers, it's likely on par with any other vendor producing an
AMD compiler.

Well, except for Cray, that is.  :)

*ducks*

But hey, we use LLVM to do it!

                                      -Dave

2009/6/15 David Greene <dag at cray.com>:
> On Monday 15 June 2009 01:32, me22 wrote:
>> [...] works for intel's architectures and is only excellent on
intel chips.
>
> That used to be the case, but not so anymore.  Intel compilers generate
> just fine code for AMD processors.  Since AMD doesn't produce their
> own compilers, it's likely on par with any other vendor producing an
> AMD compiler.
>
"On par with any other vendor" doesn't count as
"excellent", to me,
but fair enough.

On Monday 15 June 2009 19:02, me22 wrote:
> 2009/6/15 David Greene <dag at cray.com>:
> > On Monday 15 June 2009 01:32, me22 wrote:
> >> [...] works for intel's architectures and is only excellent on
intel
> >> chips.
> >
> > That used to be the case, but not so anymore.  Intel compilers
generate
> > just fine code for AMD processors.  Since AMD doesn't produce
their
> > own compilers, it's likely on par with any other vendor producing
an
> > AMD compiler.
>
> "On par with any other vendor" doesn't count as
"excellent", to me,
> but fair enough.
Intel doesn't have the internal AMD designs so it can't make use of 
proprietary knowledge as it can for Intel chips.  But then, no AMD
compiler vendor can, so they're all operating on a level playing
field.  That's all I meant.  It is faster on some codes than other
AMD compilers.  On other codes, it's slower.  This is no different
than any other compiler.

                                  -Dave

On Mon, Jun 15, 2009 at 4:43 PM, David Greene<dag at cray.com>
wrote:
> On Monday 15 June 2009 01:32, me22 wrote:
>
>> My (possibly faultly) understanding is that intel's has good
support
>> for numerics, presumably through auto-vectorization and such, but only
>
> Yes, that's true.
>
>> works for intel's architectures and is only excellent on intel
chips.
>
> That used to be the case, but not so anymore.  Intel compilers generate
> just fine code for AMD processors.
Per http://www.agner.org/optimize/, Intel's compiler doesn't use
vectorized codepaths on AMD chips by default; I don't know whether
that has changed in more recent versions.

-Eli

On Tuesday 16 June 2009 00:43:58 David Greene wrote:
> But hey, we use LLVM to do it!
Hello David,

I just noticed your post and was wondering what Cray are doing with LLVM? Are 
you using it in production?

I am trying to keep an eye on the fast moving LLVM project and like to keep up 
to date with respect to its industrial applications...

-- 
Dr Jon Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/?e

Are there any papers in the works which benchmark some specification suite
of C programs on GCC, LLVM-GCC, and CLANG?
The only stuff I have seen so far are some bar charts in a few LLVM
presentations, would be nice to have something a little more comprehensive.

Cheers,

Granville

On Tue, Jun 16, 2009 at 6:51 AM, Jon Harrop <jon at ffconsultancy.com>
wrote:
> On Tuesday 16 June 2009 00:43:58 David Greene wrote:
> > But hey, we use LLVM to do it!
>
> Hello David,
>
> I just noticed your post and was wondering what Cray are doing with LLVM?
> Are
> you using it in production?
>
> I am trying to keep an eye on the fast moving LLVM project and like to keep
> up
> to date with respect to its industrial applications...
>
> --
> Dr Jon Harrop, Flying Frog Consultancy Ltd.
> http://www.ffconsultancy.com/?e
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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On Tuesday 16 June 2009 00:51, Jon Harrop wrote:
> I just noticed your post and was wondering what Cray are doing with LLVM?
> Are you using it in production?
>
> I am trying to keep an eye on the fast moving LLVM project and like to keep
> up to date with respect to its industrial applications...
We're on the LLVM users page, but that probably needs an update.  I'll
look at
checking something in.

The Cray X86 compiler is in use by customers today.  The first release 
happened in December with an update coming RSN.  It's being used for real
science, today, on massively parallel supercomputers.  We're talking tens of
thousands of processors.

So all you LLVM developers, put another feather in your cap.  Our (yours and 
Cray compiler devlopers') code is being used to solve the world's most
challenging and groundbreaking scientific problems!

                               -Dave