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

[G Zhao via Openmp-dev]

Thanks! I didn't notice this. The code is from a legacy project and I just
checked all the target regions. It did use STL vectors. I just replaced all
those vectors with arrays. Now it can successfully compile. But When I run
it, there is another error:

Libomptarget fatal error 1: failure of target construct while offloading is
mandatory

I tried it on a simple vector add example, and got the same error.

Below is the debug information with LIBOMPTARGET_DEBUG=1:

Libomptarget --> Loading RTLs...
Libomptarget --> Loading library 'libomptarget.rtl.ppc64.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.ppc64.so':
libomptarget.rtl.ppc64.so: cannot open shared object file: No such file or
directory!
Libomptarget --> Loading library 'libomptarget.rtl.x86_64.so'...
Libomptarget --> Successfully loaded library 'libomptarget.rtl.x86_64.so'!
Libomptarget --> Registering RTL libomptarget.rtl.x86_64.so supporting 4
devices!
Libomptarget --> Loading library 'libomptarget.rtl.cuda.so'...
Target CUDA RTL --> Start initializing CUDA
Libomptarget --> Successfully loaded library 'libomptarget.rtl.cuda.so'!
Libomptarget --> Registering RTL libomptarget.rtl.cuda.so supporting 1
devices!
Libomptarget --> Loading library 'libomptarget.rtl.aarch64.so'...
Libomptarget --> Unable to load library 'libomptarget.rtl.aarch64.so':
libomptarget.rtl.aarch64.so: cannot open shared object file: No such file
or directory!
Libomptarget --> RTLs loaded!
Libomptarget --> Image 0x000000000041ad20 is NOT compatible with RTL
libomptarget.rtl.x86_64.so!
Libomptarget --> Image 0x000000000041ad20 is compatible with RTL
libomptarget.rtl.cuda.so!
Libomptarget --> RTL 0x00000000015b3c40 has index 0!
Libomptarget --> Registering image 0x000000000041ad20 with RTL
libomptarget.rtl.cuda.so!
Libomptarget --> Done registering entries!
Libomptarget --> Call to omp_get_num_devices returning 1
Libomptarget --> Default TARGET OFFLOAD policy is now mandatory (devices
were found)
Libomptarget --> Checking whether device 0 is ready.
Libomptarget --> Is the device 0 (local ID 0) initialized? 0
Target CUDA RTL --> Init requires flags to 1
Target CUDA RTL --> Getting device 0
Target CUDA RTL --> Max CUDA blocks per grid 2147483647 exceeds the hard
team limit 65536, capping at the hard limit
Target CUDA RTL --> Using 1024 CUDA threads per block
Target CUDA RTL --> Max number of CUDA blocks 65536, threads 1024 & warp
size 32
Target CUDA RTL --> Default number of teams set according to library's
default 128
Target CUDA RTL --> Default number of threads set according to library's
default 128
Libomptarget --> Device 0 is ready to use.
Target CUDA RTL --> Load data from image 0x000000000041ad20
Target CUDA RTL --> Error when loading CUDA module
Target CUDA RTL --> CUDA error is: device kernel image is invalid
Libomptarget --> Unable to generate entries table for device id 0.
Libomptarget --> Failed to init globals on device 0
Libomptarget --> Failed to get device 0 ready
Libomptarget fatal error 1: failure of target construct while offloading is
mandatory
Libomptarget --> Unloading target library!
Libomptarget --> Image 0x000000000041ad20 is compatible with RTL
0x00000000015b3c40!
Libomptarget --> Unregistered image 0x000000000041ad20 from RTL
0x00000000015b3c40!
Libomptarget --> Done unregistering images!
Libomptarget --> Removing translation table for descriptor
0x0000000000440810
Libomptarget --> Done unregistering library!
Libomptarget --> Deinit target library!

Any hints about this?

Regards,
Gang Zhao

Alexey Bataev <a.bataev at hotmail.com> 于2020年3月5日周四 上午5:44写道：

> Neither libc++, nor libstdc++ cannot be linked with nvlink. NVidia does
> not provide implementations for either libc++, or libstdc++. You must
> exclude the use of the standard c++ library from target regions.
>
> Best regards,
> Alexey Bataev
>
> > 5 марта 2020 г., в 00:25, G Zhao via Openmp-dev <
> openmp-dev at lists.llvm.org> написал(а):
> >
> > 
> > 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!
> >
> >
> >
> >
> > _______________________________________________
> > Openmp-dev mailing list
> > Openmp-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
>
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