[Openmp-dev] clang 6.0.0 and libomptarget

[Jonas Hahnfeld via Openmp-dev]

Hi,

as I wrote a few hours ago there are still some bits missing, so don't 
expect this to work at the moment.
Some more comments inline, just for future reference...

Am 2017-10-17 18:01, schrieb Jost, Gabriele (ARC-TNE)[CSRA, LLC] via 
Openmp-dev:
> Hello,
> 
> I have installed
> clang version 6.0.0 (trunk 315725) (llvm/trunk 315713)
> 
> on my system. When trying to build a simple example I get the following 
> error:
> 
> + clang -c -Iclang-install/lib/clang/6.0.0/include -fopenmp=libomp
> -fopenmp-targets=nvptx64-nvidia-cuda -march=sm_35 -Xopenmp-target
> --cuda-path=/cuda/8.0/bin example.c
> clang-6.0: error: cannot find libdevice for sm_20. Provide path to
> different CUDA installation via --cuda-path, or pass -nocudalib to
> build without linking with libdevice.

In my last e-mail I wrote '-Xopenmp-target -march=sm_60', the order is 
important here.
(Also note that current top of trunk defaults to sm_30 for OpenMP since 
this morning.)
--cuda-path doesn't seem right, maybe you meant something like 
/usr/local/cuda? This is the default location and will be tried by Clang 
automatically.

> 
> I am now looking at some older instruction for clang + openm4 (not 
> 4.5).
> There is one step I did not do:
> 
> $ cd $HOME/forge/openmp4
> $ git clone https://github.com/clang-omp/libomptarget.git
> $ cd libomptarget
> $ mkdir build
> $ cd build
> $ cmake -DCMAKE_INSTALL_PREFIX=$HOME/forge/openmp4/llvm/install
> -DOMPTARGET_NVPTX_SM=30,35 ..
> $ make -j12
> $ cp -rf lib/libomptarget* $HOME/forge/openmp4/llvm/install/lib/
> 
> Is this still necessary for the latest and greatest clang?
> 
> (website is
> https://parallel-computing.pro/index.php/9-cuda/43-openmp-4-0-on-nvidia-cuda-gpus)

This won't work as this version is heavily out-dated and current Clang 
calls incompatible runtime functions.
Again, not all pieces are upstreamed yet but mixing very old stuff also 
won't work.

Cheers,
Jonas

> 
> Note: If you feel that I am sending too many questions to this forum,
> please let me know =.
> 
> Gabriele
> 
> 
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