[SYCL][OpenMP] Build issue with configuring SYCL & OpenMP

[abagusetty]

Describe the bug

I am trying to configure buildbot with SYCL (for instance, CUDA runtime) and OpenMP (CPU-only, no offload). Tried with two options: --llvm-external-projects openmp and --cmake-opt=-DLLVM_ENABLE_RUNTIMES="openmp"

Using --llvm-external-projects openmp, this option only leads to OpenMP project being enabled.

CUDA_LIB_PATH=${CUDA_HOME} python3 $DPCPP_HOME/llvm/buildbot/configure.py 
--shared-libs --cmake-gen "Unix Makefiles" -DCUDAToolkit_ROOT=${CUDA_HOME} 
--native_cpu --cuda -t Release --llvm-external-projects openmp

With the above configure option, -- openmp project is enabled but leads to a warning and an error:

CMake Warning at CMakeLists.txt:204 (message):
  Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will become a
  fatal error in the LLVM 21 release.  Please use
  -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at
  https://openmp.llvm.org/ for building the runtimes.



CMake Error at cmake/modules/LLVMExternalProjectUtils.cmake:471 (add_custom_target):
  add_custom_target cannot create target "check-openmp" because another
  target with the same name already exists.  The existing target is a custom
  target created in source directory "/home/abagusetty/today/llvm/openmp".
  See documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
  runtimes/CMakeLists.txt:263 (llvm_ExternalProject_Add)
  runtimes/CMakeLists.txt:557 (runtime_default_target)

When I tried with `

CUDA_LIB_PATH=${CUDA_HOME} python3 $DPCPP_HOME/llvm/buildbot/configure.py 
--shared-libs --cmake-gen "Unix Makefiles" -DCUDAToolkit_ROOT=${CUDA_HOME} 
--native_cpu --cuda -t Release --cmake-opt=-DLLVM_ENABLE_RUNTIMES="openmp"

Apparently, OpenMP project is not enabled via the above option

[sarnex]

Hi @abagusetty,

I wasn't able to reproduce those CMake failures, I was able to successfully build with both build commands. Could you please provide the commit hash of this repo you're using?

Thanks

[abagusetty]

Hi @sarnex

Thanks for taking time to look into this. I using this commit hash: 72b85b6

Please let me know if you need any info.

Thanks!

[sarnex]

Unfortunately the build worked using that commit too. Could you attach the full build log from when it errors? Thanks

[abagusetty]

Please find the logs and CMakeCache.txt files for each build. Please note that the machine is Cray based, so system paths might be bit off.

(a) Using --llvm-external-projects openmp -- Configure failed
(b) Using --cmake-opt=-DLLVM_ENABLE_RUNTIMES="openmp" -- Configured fine, but OpenMP got disabled

b-buildlog.txt
a-buildlog.txt

b-CMakeCache.txt
a-CMakeCache.txt

[sarnex]

I'm looking at case (a) and I see the following in the CMake cache:

LLVM_ENABLE_RUNTIMES:STRING=openmp

I don't see that in my CMake cache with the same configure/cmake arguments, however I do see the same error as you if I do add it manually.

Did you clear the build directory before running the commands for case (a)? If not can you try with a clean build directory and see if it happens again and if so update the logs? Thanks

[sarnex]

@abagusetty Did you get a chance to try out my reply above? Thanks

[abagusetty]

@sarnex Thanks for the above snippet and taking time. Yes, I was able to configure but build fails at linking step. Attached is the log, was wondering if you have any pointers.

make sycl-toolchain pointed me to this error. There isnt a directory under build/tools/clc

[ 88%] Generating ../../lib/clc/libspirv-nvptx64--nvidiacl.bc
cd /home/abagusetty/today/llvm/build/tools/libclc && ../../bin/prepare_builtins -o /home/abagusetty/today/llvm/build/./lib/clc/libspirv-nvptx64--nvidiacl.bc /home/abagusetty/today/llvm/build/tools/libclc/obj.libclc.dir/nvptx64--nvidiacl/builtins.opt.libspirv-nvptx64--nvidiacl.bc
No such file or directory
make[3]: *** [tools/libclc/CMakeFiles/prepare-libspirv-nvptx64--nvidiacl.bc.dir/build.make:74: lib/clc/libspirv-nvptx64--nvidiacl.bc] Error 1
make[3]: Leaving directory '/home/abagusetty/today/llvm/build'
make[2]: *** [CMakeFiles/Makefile2:118231: tools/libclc/CMakeFiles/prepare-libspirv-nvptx64--nvidiacl.bc.dir/all] Error 2
make[2]: Leaving directory '/home/abagusetty/today/llvm/build'
make[1]: *** [CMakeFiles/Makefile2:124802: tools/sycl/CMakeFiles/sycl-toolchain.dir/rule] Error 2
make[1]: Leaving directory '/home/abagusetty/today/llvm/build'

[sarnex]

@abagusetty Sorry for the late reply, I was able to reproduce the issue and it seems the failure only occurs when using make. With make it fails for me every time, but ninja works for some reason. Do you have access to ninja so you can try -GNinja instead and confirm my results? I filed a bug for this, really weird one.

[abagusetty]

@sarnex No worries, thanks for your time. I did try with ninja build and it worked. However, I was able to trigger an other issue with native_cpu backend. Reported here

[sarnex]

Thanks, btw it should work with Make in HEAD, a fix was submitted in #20063. I'll close this one as completed and we can track the new problem in that issue, thanks again.