[Libomptarget] Remove dependency on the DeviceRTL from the GPU plugins

[jhuber6]

Summary

The GPU plugins have a dependency on the device libraries. Sometimes we
cannot build the device libraries because the user does not have a valid
clang to use or it was explicitly disabled. Currently this leads to a
transitive failure because we cannot meet this dependency. This patch
simply removes that dependency.

Fixes https://github.com/llvm/llvm-project/issues/60457

[h-vetinari]

Thanks for this!

[tianshilei1992]

I don't understand why a host library depends on a device library?

[jhuber6]

In D143196#4101531, @tianshilei1992 wrote:

I don't understand why a host library depends on a device library?

Well, I guess it's possible to use OpenMP without the device runtime. We could potentially just keep them completely separate. My guess is that whoever wrote the code first didn't know how to make the dependency build so they put it on the plugins.

[tianshilei1992]

The build of plugins don't need device runtime right? We set dependences in CMake for build and test running only.

[jhuber6]

Updating to just remove the dependency. I think it should be fine to build these anyway. Not sure why we need to depend on the DeviceRTL.

[h-vetinari]

Just to confirm: I applied this patch to rc1 (& rc2) and then things build fine again. Thanks!

[tianshilei1992]

LGTM

openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt

add_llvm_library(omptarget.rtl.amdgpu.nextgen SHARED
   PluginInterface
   ${LIBOMPTARGET_DEP_LIBRARIES}
   ${OPENMP_PTHREAD_LIB}
   "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports"
   ${LDFLAGS_UNDEFINED}
 
   NO_INSTALL_RPATH
 )
-add_dependencies(omptarget.rtl.amdgpu.nextgen omptarget.devicertl.amdgpu)
 
 target_include_directories(
   omptarget.rtl.amdgpu.nextgen
   PRIVATE
   ${LIBOMPTARGET_INCLUDE_DIR}
   ${CMAKE_CURRENT_SOURCE_DIR}/utils
 )
 
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.amdgpu.nextgen LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.amdgpu.nextgen PROPERTIES
   INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
   CXX_VISIBILITY_PRESET protected)

openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt

 if(LIBOMPTARGET_DEP_CUDA_FOUND AND NOT LIBOMPTARGET_FORCE_DLOPEN_LIBCUDA)
   libomptarget_say("Building CUDA plugin linked against libcuda")
   target_link_libraries(omptarget.rtl.cuda.nextgen PRIVATE CUDA::cuda_driver)
 else()
   libomptarget_say("Building CUDA plugin for dlopened libcuda")
   target_include_directories(omptarget.rtl.cuda.nextgen PRIVATE ../../plugins/cuda/dynamic_cuda)
   target_sources(omptarget.rtl.cuda.nextgen PRIVATE ../../plugins/cuda/dynamic_cuda/cuda.cpp)
 endif()
-add_dependencies(omptarget.rtl.cuda.nextgen omptarget.devicertl.nvptx)
 
 # Define debug prefix. TODO: This should be automatized in the Debug.h but it
 # requires changing the original plugins.
 target_compile_definitions(omptarget.rtl.cuda.nextgen PRIVATE TARGET_NAME="CUDA")
 target_compile_definitions(omptarget.rtl.cuda.nextgen PRIVATE DEBUG_PREFIX="TARGET CUDA RTL")
 
 target_include_directories(omptarget.rtl.cuda.nextgen PRIVATE ${LIBOMPTARGET_INCLUDE_DIR})
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.cuda.nextgen LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.cuda.nextgen PROPERTIES
   INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
   CXX_VISIBILITY_PRESET protected)

openmp/libomptarget/plugins/amdgpu/CMakeLists.txt

add_llvm_library(omptarget.rtl.amdgpu SHARED
   elf_common
   ${LIBOMPTARGET_DEP_LIBRARIES}
   ${OPENMP_PTHREAD_LIB}
   "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports"
   ${LDFLAGS_UNDEFINED}
 
   NO_INSTALL_RPATH
 )
-add_dependencies(omptarget.rtl.amdgpu omptarget.devicertl.amdgpu)
 
 target_include_directories(
   omptarget.rtl.amdgpu
   PRIVATE
   ${LIBOMPTARGET_INCLUDE_DIR}
   ${CMAKE_CURRENT_SOURCE_DIR}/impl
   ${CMAKE_CURRENT_SOURCE_DIR}/../../plugins-nextgen/amdgpu/utils
 )

openmp/libomptarget/plugins/cuda/CMakeLists.txt

 if(LIBOMPTARGET_DEP_CUDA_FOUND AND NOT LIBOMPTARGET_FORCE_DLOPEN_LIBCUDA)
   libomptarget_say("Building CUDA plugin linked against libcuda")
   target_link_libraries(omptarget.rtl.cuda PRIVATE CUDA::cuda_driver)
 else()
   libomptarget_say("Building CUDA plugin for dlopened libcuda")
   target_include_directories(omptarget.rtl.cuda PRIVATE dynamic_cuda)
   target_sources(omptarget.rtl.cuda PRIVATE dynamic_cuda/cuda.cpp)
 endif()
-add_dependencies(omptarget.rtl.cuda omptarget.devicertl.nvptx)
 
 # Define the suffix for the runtime messaging dumps.
 target_compile_definitions(omptarget.rtl.cuda PRIVATE TARGET_NAME="CUDA")
 target_include_directories(omptarget.rtl.cuda PRIVATE ${LIBOMPTARGET_INCLUDE_DIR})
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.cuda LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.cuda PROPERTIES