[cfe-users] How to tell Clang which version of CUDA to use ?

[Justin Lebar via cfe-users]

Sorry for the delayed response, just got back from vacation.

I just installed cuda 9 to /usr/local/cuda-9.0 and couldn't reproduce
this problem.  I also tried redirecting /usr/local/cuda to
/usr/local/cuda-9.0 and passing an explicit
--cuda-path=/usr/local/cuda-8.0, and things still worked as expected.

Very strange what you're seeing, although I believe there's a decent
chance it's a bug in clang.  Hopefully the -v output will be
revealing.

-Justin

On Tue, Aug 29, 2017 at 12:49 AM, Jean-Loup Tastet
<jean-loup.tastet at epfl.ch> wrote:
> As a workaround, we have temporarily disabled the CUDA 9.0 install (by
> renaming its directory to /usr/local/_cuda-9.0). Now the program compiles as
> expected (I also recompiled Clang in the meantime).
>
> As soon as I manage to convince my sysadmin to enable CUDA 9.0 again, I will
> retry with the `-v` command-line option and post the output here.
>
> On Mon, 2017-08-28 at 11:42 -0700, Justin Lebar wrote:
>
> --cuda-path is the right flag to pass.  Strange it's not doing the
> right thing for you.
>
> Can you include the output of running the same command line with -v?
>
> On Fri, Aug 18, 2017 at 3:55 AM, Jean-Loup Tastet via cfe-users
> <cfe-users at lists.llvm.org> wrote:
>
> Hi,
>
> I am trying to use Clang to compile CUDA device code. I followed the
> instructions in [1] and compiled the latest Clang trunk [2].
>
> However, my system has both CUDA 8.0 and 9.0 RC installed, in
> `/usr/local/cuda-{8.0,9.0}`. The default `/usr/local/cuda` is symlinked
> to `/usr/local/cuda-8.0`.
>
> Clang only supports version 8.0, however it seems to incorrectly pick
> version 9.0, even when manually specifying the `--cuda-path`. For
> instance, trying to compile a trivial CUDA program (with no kernel):
> ```
> $ cat main.cu
> #include <cuda.h>
> #include <iostream>
>
> int main(int argc, char* argv[])
> {
>     std::cout << "Hello, World!" << std::endl;
> }
>
> $ clang++ -o main main.cu \
>     --cuda-path=/usr/local/cuda-8.0 \
>     -I/usr/local/cuda-8.0/include \
>     -L/usr/local/cuda-8.0/lib64 \
>     -lcudart_static -ldl -lrt -pthread
> ```
> generates the following error:
> ```
> /home/jtastet/.local/stow/llvm_gcc-
> 6.3/lib/clang/6.0.0/include/__clang_cuda_runtime_wrapper.h:66:2: error:
> "Unsupported CUDA version!"
> #error "Unsupported CUDA version!"
>  ^
> In file included from <built-in>:1:
> In file included from /home/jtastet/.local/stow/llvm_gcc-
> 6.3/lib/clang/6.0.0/include/__clang_cuda_runtime_wrapper.h:169:
> /usr/local/cuda-9.0/targets/x86_64-
> linux/include/device_functions.hpp:218:10: error: reference to
> __device__ function '__nvvm_bar0_popc' in __host__ function
>   return __nvvm_bar0_popc(predicate);
>          ^
> /usr/local/cuda-9.0/targets/x86_64-
> linux/include/device_functions.hpp:218:10: note: '__nvvm_bar0_popc'
> declared here
> /usr/local/cuda-9.0/targets/x86_64-
> linux/include/device_functions.hpp:223:10: error: reference to
> __device__ function '__nvvm_bar0_and' in __host__ function
>   return __nvvm_bar0_and(predicate);
>          ^
> [...output truncated...]
> ```
> Note the reference to CUDA 9.0 in the path.
>
> Do you know how to tell Clang which version of CUDA to use ? Does it
> have to be specified at compile-time or as a command-line option ?
>
> Uninstalling CUDA 9.0 is not an option here, since I do not have
> privileged access to the machine.
>
> Thanks in advance for your help !
>
> Best regards,
> Jean-Loup Tastet
>
>
> [1] https://llvm.org/docs/CompileCudaWithLLVM.html
> [2] For reference, I compiled revision 311091 with the following
> configuration:
> ```
> cmake -G "Unix Makefiles" \
>     -D CMAKE_INSTALL_PREFIX=/home/jtastet/.local/stow/llvm_gcc-6.3 \
>     -D CMAKE_BUILD_TYPE=Release \
>     -D GCC_INSTALL_PREFIX=/afs/cern.ch/sw/lcg/external/gcc/6.3/x86_64-
> centos7 \
>     ..
> ```
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