[Pkg-opencl-devel] Moving to LLVM 3.9 (was: pocl)

[Ghislain Vaillant]

On Tue, 2016-12-20 at 16:04 +0100, Andreas Boll wrote:
> Hi,
> 
> we are currently in the same situation again. Mesa has moved to LLVM 3.9
> and thus beignet will automatically switch with the next upload/binNMU
> to LLVM 3.9 too [1]. Unfortunately pocl 0.13 isn't compatible with LLVM
> 3.9. There's a git commit with fixes for 3.9 but I don't know if it's
> enough [2]. Fedora Rawhide has moved to a git snapshot of pocl 0.14 to
> get compatibility with LLVM 3.9 [3].
> 
> What should we do with pocl?

The positive thing here is that we know a git snapshot should work
since Fedora successfully tried it.

Perhaps, we could also ask upstream how comfortable they are in making
a release soon? Or at least point us to a specific commit they feel
happy about packaging?

> There're already reports of random crashes with:
> - Blender + mesa-opencl-icd + pocl [4]
> - Blender + beignet-opencl-icd [5]
> - Related: kdevelop (was LLVM 3.8) + mesa (LLVM 3.9) crashed [6]
> 
> And there's a LLVM bug which might cause these issues [7].
> 
> Thanks,
> Andreas
> 
> [1] https://sources.debian.net/src/beignet/1.2.1-1/debian/rules/#L16
> [2] https://github.com/pocl/pocl/commit/08742e77004ec4ffdb081d2c493ef994b075cfcb
> [3] https://apps.fedoraproject.org/packages/pocl/changelog/
> [4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=846162#5
> [5] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=848792
> [6] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847447
> [7] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=848368
> 
> 2016-04-23 11:37 GMT+02:00 Giuseppe Bilotta <giuseppe.bilotta at gmail.com>:
> > My limited experience with building pocl manually in debian unstable
> > has taught me a couple of things:
> > 
> > * all ICDs based on LLVM have to be built using the same version of
> > LLVM, or one will get random crashes and segfaults during execution;
> > this means that Pocl must be built with the same LLVM as
> > mesa-opencl-icd and beignet;
> > * Pocl needs at least LLVM 3.7, but Debian defaults to LLVM 3.6, so
> > the LLVM version must be specified manually (by the way, why is 3.6
> > still the default in Debian?)
> > * automatic build dependencies are affected by
> > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=792842
> > * there is a known issue with LLVM 3.7 (at least the version that
> > ships in Debian unstable) producing the wrong shift/rotation
> > instructions for short/ushort vector types on Haswell CPUs, which
> > causes some tests to fail.