[Openmp-dev] Compiling OpenMP code with CUDA support using libc++

[G Zhao via Openmp-dev]

Hi,

I just compiled LLVM and enable NVPTX by
-DLLVM_TARGETS_TO_BUILD="X86;NVPTX". But when I compiled my code using the
below command:

clang++ main.cpp -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda -o a_gpu.exe

I got the below error:

/usr/lib64/gcc/x86_64-pc-linux-gnu/9.2.1/../../../../include/c++/9.2.1/bits/std_abs.h:75:3:
error: declaration conflicts with target of using declaration already in
scope
  abs(float __x)

I think the reason is I am using GCC-9. I did a bit search and someone said
using libc++ can address this. So I compiled libcxx and libcxxabi, and used
the below command to compile my code again:

clang++ stdlib=libc++  main.cpp -fopenmp
-fopenmp-targets=nvptx64-nvidia-cuda -o a_gpu.exe

I got different errors:

nvlink error   : Undefined reference to
'_ZNKSt3__120__vector_base_commonILb1EE20__throw_length_errorEv' in
'/tmp/main-42e0a6.cubin'
nvlink error   : Undefined reference to 'abort' in '/tmp/main-42e0a6.cubin'

I think the reason here is nvlink don't know we should link libc++ with
those cubin files together. But I don't know how to solve this.

Any one know a workaround to this?

Thanks!
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