[Llvm-bgq-discuss] New bgclang nighty builds (and other updates)
Hal Finkel
hfinkel at anl.gov
Mon May 11 11:30:33 CDT 2015
Hi Erik,
This has now been fixed upstream, and the r236977-20150511 nightly build contains the fix. Thanks again for sending the reduced test case.
-Hal
----- Original Message -----
> From: "Erik Lindahl" <erik.lindahl at gmail.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: llvm-bgq-discuss at lists.alcf.anl.gov, "Mark Abraham" <mark.j.abraham at gmail.com>
> Sent: Sunday, May 10, 2015 10:41:26 AM
> Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and other updates)
>
>
> Oops, hit the “send” instead of “attach” button by mistake. Here we
> go.
>
>
> The output with xlc at all optimization levels, and clang at -O0 is
> "v: 1 2 3 4”.
>
>
> With clang and -O3 I get “v: 0.0078125 32 0 0”
>
>
> Cheers,
>
>
> E.
>
>
>
> From: Erik Lindahl <erik.lindahl at gmail.com>
> Reply: Erik Lindahl <erik.lindahl at gmail.com>>
> Date: 10 May 2015 at 17:40:02
> To: Hal Finkel <hfinkel at anl.gov>>
> Cc: Mark Abraham <mark.j.abraham at gmail.com>> ,
> llvm-bgq-discuss at lists.alcf.anl.gov
> <llvm-bgq-discuss at lists.alcf.anl.gov>>
> Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and other
> updates)
>
>
>
>
>
>
>
> Hi Hal,
>
>
> See attachment!
>
>
>
>
>
> From: Hal Finkel <hfinkel at anl.gov>
> Reply: Hal Finkel <hfinkel at anl.gov>>
> Date: 10 May 2015 at 17:22:52
> To: Erik Lindahl <erik.lindahl at gmail.com>>
> Cc: llvm-bgq-discuss at lists.alcf.anl.gov
> <llvm-bgq-discuss at lists.alcf.anl.gov>> , Mark Abraham
> <mark.j.abraham at gmail.com>>
> Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and other
> updates)
>
>
>
>
>
> Hi Erik,
>
> If you could send this trivial piece of code, that would be greatly
> appreciated.
>
> Thanks again,
> Hal
>
> ----- Original Message -----
> > From: "Erik Lindahl" <erik.lindahl at gmail.com>
> > To: "Hal Finkel" <hfinkel at anl.gov>, "Mark Abraham"
> > <mark.j.abraham at gmail.com>
> > Cc: llvm-bgq-discuss at lists.alcf.anl.gov
> > Sent: Sunday, May 10, 2015 9:25:34 AM
> > Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and
> > other updates)
> >
> >
> > Hi,
> >
> >
> > Super-brief summary:
> >
> >
> > The bug occurs at high optimization (-O3) with the vec_ld() or
> > vec_st() functions when calling the (overloaded) version with
> > single-precision arguments (i.e., float pointers).
> >
> >
> > This is reproducible even with a trivial piece of code that tries
> > to
> > load from single precision memory and then write out the contents
> > of
> > the (double precision) vector4doubles by storing to a double
> > variable.
> >
> >
> > - Everything works fine with the double-precision functions,
> > regardless of optimization
> > - It works fine with clang in single precision without optimization
> > - It works fine with xlc.
> >
> >
> > Cheers,
> >
> >
> > Erik
> >
> >
> >
> >
> > From: Mark Abraham <mark.j.abraham at gmail.com>
> > Reply: Mark Abraham <mark.j.abraham at gmail.com>>
> > Date: 10 May 2015 at 16:04:51
> > To: Hal Finkel <hfinkel at anl.gov>>
> > Cc: llvm-bgq-discuss at lists.alcf.anl.gov
> > <llvm-bgq-discuss at lists.alcf.anl.gov>> , Erik Lindahl
> > <erik.lindahl at gmail.com>>
> > Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and
> > other
> > updates)
> >
> >
> >
> >
> >
> >
> >
> > Hi,
> >
> > Bump. Erik Lindahl has also observed this on bgclang on JUQUEEN. Is
> > it helpful if I produce a small piece of code that reproduces some
> > of the issues on bgclang 3.6?
> >
> >
> >
> > Mark
> >
> > On Wed, Mar 25, 2015 at 4:16 PM Mark Abraham <
> > mark.j.abraham at gmail.com > wrote:
> >
> >
> >
> >
> >
> > On Tue, Mar 24, 2015 at 7:29 PM, Hal Finkel < hfinkel at anl.gov >
> > wrote:
> >
> >
> > ----- Original Message -----
> > > From: "Mark Abraham" < mark.j.abraham at gmail.com >
> > > To: "Hal Finkel" < hfinkel at anl.gov >
> > > Cc: llvm-bgq-discuss at lists.alcf.anl.gov
> > > Sent: Tuesday, March 24, 2015 12:35:20 PM
> > > Subject: Re: [Llvm-bgq-discuss] New bgclang nighty builds (and
> > > other updates)
> > >
> > >
> > > Hi Hal,
> > >
> > >
> > > Thanks very much for the update & effort.
> > >
> >
> > You're very welcome.
> >
> > >
> > > I tried out the default bgclang 3.6.0 on vesta, but found a bunch
> > > of
> > > the GROMACS SIMD-layer unit tests failing. These need correct QPX
> > > vector intrinsics available. From memory, things worked fine with
> > > bgclang in ~August last year, but I no longer have those results.
> > > Is
> > > there a simple way I can compile on vesta with older bgclang to
> > > see
> > > where a problem might lie? Otherwise / depending what I learn,
> > > I'll
> > > break out a debugger.
> >
> > The old builds are still all installed. Just use the MPI wrappers
> > from:
> >
> > /home/projects/llvm/<whatever>/mpi/bgclang/bin -- I don't know
> > exactly which build you were using in August of last year,
> > r209570-20140527 maybe?
> >
> >
> >
> >
> >
> >
> > Yes, that was it, looking at some cruft in my former build script.
> > In
> > any case, the latest GROMACS SIMD single-precision unit tests pass
> > on that old compiler version (3.5.0), and many of them fail in a
> > release build on the default 3.6.0 bgclang on vesta. For some of
> > the
> > cases, it looks like some junk memory gets loaded, somehow. A few
> > tests pass, but no theme for passing or failing tests leaps out at
> > me. Double precision unit tests are OK, though.
> >
> >
> > Naturally, in debug mode most of the tests pass. However, the two I
> > looked at in ddt were fine up until they called vec_extract(x, 0)
> > e.g. on lines
> > https://github.com/gromacs/gromacs/blob/master/src/gromacs/simd/impl_ibm_qpx/impl_ibm_qpx.h#L315
> > (where a SIMD vector of 1 2 3 1 was summed to 3, rather than 7) and
> > https://github.com/gromacs/gromacs/blob/master/src/gromacs/simd/impl_ibm_qpx/impl_ibm_qpx.h#L462
> > (where a SIMD vector dot product of the first 3 lanes returns a
> > garbage answer). So maybe that is a productive lead?
> >
> >
> > I couldn't inspect the disassembly in ddt, so I'm not sure where we
> > can take this from here, Hal. Tarball of test results attached.
> >
> >
> > Thanks,
> >
> >
> > Mark
> >
> >
> >
> >
> >
> >
> >
> > -Hal
> >
> >
> >
> > >
> > >
> > > Thanks,
> > >
> > >
> > > Mark
> > >
> > >
> > >
> > >
> > > On Fri, Mar 20, 2015 at 12:15 AM, Hal Finkel < hfinkel at anl.gov >
> > > wrote:
> > >
> > >
> > > Hello everyone,
> > >
> > > First, let me apologize to everyone, this is a few months late...
> > > but, hopefully, this will never be a problem again...
> > >
> > > I now have a system setup which automatically pulls in upstream
> > > changes and tries to merge those with the bgclang-specific
> > > patches,
> > > and then builds the resulting suite of bgclang RPMs. When this
> > > succeeds, the RPMs should be posted automatically to:
> > >
> > > http://www.mcs.anl.gov/~hfinkel/bgclang/
> > > (note that installing a build from here now also requires both
> > > the
> > > 'stage1' and 'stage2' RPMs as well)
> > >
> > > The first such nightly build, r232720-20150319, has been posted
> > > to
> > > that page.
> > >
> > > And, for the curious, the local repositories used for version
> > > control
> > > are now mirrored to github:
> > >
> > > https://github.com/hfinkel/clang-bgq
> > > https://github.com/hfinkel/llvm-bgq
> > > https://github.com/hfinkel/bgclang-aux
> > > https://github.com/hfinkel/compiler-rt-bgq
> > > https://github.com/hfinkel/libcxx-bgq
> > > https://github.com/hfinkel/openmp-bgq
> > > https://github.com/hfinkel/sleef-bgq
> > >
> > > Compared to the latest "released" version (r220548-20141024), the
> > > most-recent nightly build does show some performance regressions,
> > > and there are a few things I've not even tested yet (LTO, ASan,
> > > etc.), but it also contains a number of bug fixes and
> > > improvements,
> > > so feel free to test on your applications.
> > >
> > > One particular noteworthy improvement is that our OpenMP runtime
> > > library now has affinity support enabled. This means that all of
> > > the
> > > OpenMP 4 affinity features should work, and also that the default
> > > thread<->core bindings are now sensible.
> > >
> > > The bgclang wrapper script no longer disables 'fast-isel'
> > > instruction
> > > selection at -O0, so your debug builds should now be faster too.
> > > Also, the automated vectorization of math functions using our
> > > SLEEF
> > > library adaptation is controlled using the new -fveclib flag (so
> > > the
> > > wrapper script contains -fveclib=SLEEF, and you can add
> > > -fveclib=none to turn it off if desired for whatever reason).
> > >
> > > Also, the core QPX support has been contributed upstream
> > > (although
> > > not yet the Clang-level intrinsics support); so if you're using
> > > LLVM
> > > as a library, and want to just build from upstream sources
> > > instead
> > > of depending on the bgclang builds, that is now possible.
> > >
> > > Thanks again everyone, and please let me know if you experience
> > > any
> > > difficulties,
> > > Hal
> > >
> > > --
> > > Hal Finkel
> > > Assistant Computational Scientist
> > > Leadership Computing Facility
> > > Argonne National Laboratory
> > > _______________________________________________
> > > llvm-bgq-discuss mailing list
> > > llvm-bgq-discuss at lists.alcf.anl.gov
> > > https://lists.alcf.anl.gov/mailman/listinfo/llvm-bgq-discuss
> > >
> > >
> >
> > --
> > Hal Finkel
> > Assistant Computational Scientist
> > Leadership Computing Facility
> > Argonne National Laboratory
> >
> >
> > --
> > Erik Lindahl < erik.lindahl at gmail.com >
> > Professor of Biophysics, Dept. Biochemistry & Biophysics, Stockholm
> > University
> > Professor of Theoretical biophysics, Dept. Theoretical Physics,
> > Royal
> > Inst. Technology
> > Science for Life Laboratory, Box 1031, 17121 Solna, Sweden
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
>
> --
> Erik Lindahl < erik.lindahl at gmail.com >
> Professor of Biophysics, Dept. Biochemistry & Biophysics, Stockholm
> University
> Professor of Theoretical biophysics, Dept. Theoretical Physics, Royal
> Inst. Technology
> Science for Life Laboratory, Box 1031, 17121 Solna, Sweden
>
> --
> Erik Lindahl < erik.lindahl at gmail.com >
> Professor of Biophysics, Dept. Biochemistry & Biophysics, Stockholm
> University
> Professor of Theoretical biophysics, Dept. Theoretical Physics, Royal
> Inst. Technology
> Science for Life Laboratory, Box 1031, 17121 Solna, Sweden
--
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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