[llvm-dev] building with openmp target nvptx with llvm 12 versus 11

[Johannes Doerfert via llvm-dev]

This was an oversight and we'll make sure the runtime will be 
freestanding in the future.
That said, Ye Luo fixed this by installing gcc-multilib, maybe that 
helps you too.

If not, we'll have to come up with a hotfix.

~ Johannes


On 4/29/21 8:04 AM, KESTENER Pierre via llvm-dev wrote:
> Hello,
>
> I have succesfully built and used clang with OpenMP offload target for Nivida architecture (sm_80) using llvm-11.0.1 release sources.
>
> However, using release 12.0.0, I have a strange compile error.
>
> Here is how I configure the openmp support with cmake:
> ccmake  -DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_80 -DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=80 -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;libcxx;libcxxabi;lld;openmp" -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=/opt/local/llvm-12-omptarget -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ../openmp
>
> here clang and clang++ are actually clang-12 and clang++-12 (built previously, I crossed check that I was able to compile cuda code, it is ok).
>
> The compile error in building openmp support is
>
> [ 24%] Building LLVM bitcode target_impl.cu-cuda_112-sm_80.bc
> cd /home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/build-openmp/libomptarget/deviceRTLs/nvptx && /opt/local/llvm-12-omptarget/bin/clang -S -x c++ -O1 -std=c++14 -target nvptx64 -Xclang -emit-llvm-bc -Xclang -aux-triple -Xclang x86_64-unknown-linux-gnu -fopenmp -fopenmp-cuda-mode -Xclang -fopenmp-is-device -D__CUDACC__ -I/home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/openmp/libomptarget/deviceRTLs -I/home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/openmp/libomptarget/deviceRTLs/nvptx/src -DOMPTARGET_NVPTX_DEBUG=0 -Xclang -target-cpu -Xclang sm_80 -D__CUDA_ARCH__=800 -Xclang -target-feature -Xclang +ptx70 -DCUDA_VERSION=11200 /home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.cu -o target_impl.cu-cuda_112-sm_80.bc
> In file included from /home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.cu:14:
> In file included from /home/kestener/install/llvm/llvm-project-llvmorg-12.0.0/openmp/libomptarget/deviceRTLs/nvptx/src/target_impl.h:15:
> In file included from /usr/include/assert.h:35:
> /usr/include/features.h:461:12: fatal error: 'sys/cdefs.h' file not found
> #  include <sys/cdefs.h>
>             ^~~~~~~~~~~~~
>
> I don't know why this header is not found, it is actually present in my system (Ubuntu 20.04)
>
> Did I miss something here ? It was building fine with llvm-11.0.1.
>
> Thanks for your help.
>
> Pierre
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