[libomptarget] Check for library with CUDA Driver API

[Hahnfeld]

Summary

That's what we really need to link the CUDA plugin against,
not the CUDA runtime API in CUDA_LIBRARIES! While the latter
comes with the CUDA SDK, the Driver API is installed with
the kernel driver and there is at most one per system. As
fallback we can use the stubs library distributed with the
CUDA SDK for linking.

[tra]

You may want to consider linking with <CUDA>/lib64/stubs/libcuda.so. This way you don't really care whether nvidia's driver is installed on the system you compile on and all you need for compilation is a CUDA installation. At runtime dynamic linker will pick the real libcuda.so from wherever it's installed.

[Hahnfeld]

In D42643#991096, @tra wrote:

You may want to consider linking with <CUDA>/lib64/stubs/libcuda.so. This way you don't really care whether nvidia's driver is installed on the system you compile on and all you need for compilation is a CUDA installation. At runtime dynamic linker will pick the real libcuda.so from wherever it's installed.

That's great, thanks for the pointer! I'll update this patch when I find time.

[grokos]

libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake

118

So LIBOMPTARGET_DEP_CUDA_LIBRARIES is no longer a dependency we care about. It can be removed.

124

Remove.

[Hahnfeld]

Use stubs library for linking and remove LIBOMPTARGET_DEP_CUDA_LIBRARIES.

[grokos]

Looks good!

libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake

mark_as_advanced(
   LIBOMPTARGET_DEP_LIBFFI_LIBRARIES)
   
 ################################################################################
 # Looking for CUDA...
 ################################################################################
 find_package(CUDA QUIET)
 
 set(LIBOMPTARGET_DEP_CUDA_FOUND ${CUDA_FOUND})
 set(LIBOMPTARGET_DEP_CUDA_LIBRARIES ${CUDA_LIBRARIES})
 set(LIBOMPTARGET_DEP_CUDA_INCLUDE_DIRS ${CUDA_INCLUDE_DIRS})
 
 mark_as_advanced(
   LIBOMPTARGET_DEP_CUDA_FOUND 
   LIBOMPTARGET_DEP_CUDA_INCLUDE_DIRS
   LIBOMPTARGET_DEP_CUDA_LIBRARIES)
+
+################################################################################
+# Looking for CUDA Driver API... (needed for CUDA plugin)
+################################################################################
+
+find_library (
+    LIBOMPTARGET_DEP_CUDA_DRIVER_LIBRARIES
+  NAMES
+    cuda
+  PATHS
+    /lib64)
+
+find_package_handle_standard_args(
+  LIBOMPTARGET_DEP_CUDA_DRIVER
+  DEFAULT_MSG
+  LIBOMPTARGET_DEP_CUDA_DRIVER_LIBRARIES)
+
+mark_as_advanced(LIBOMPTARGET_DEP_CUDA_DRIVER_LIBRARIES)

libomptarget/plugins/cuda/CMakeLists.txt

 ##===----------------------------------------------------------------------===##
 # 
 #                     The LLVM Compiler Infrastructure
 #
 # This file is dual licensed under the MIT and the University of Illinois Open
 # Source Licenses. See LICENSE.txt for details.
 # 
 ##===----------------------------------------------------------------------===##
 #
 # Build a plugin for a CUDA machine if available.
 #
 ##===----------------------------------------------------------------------===##
-if(LIBOMPTARGET_DEP_LIBELF_FOUND)
-  if(LIBOMPTARGET_DEP_CUDA_FOUND)
-    if(CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64)|(ppc64le)$" AND CMAKE_SYSTEM_NAME MATCHES "Linux")
-    
-      libomptarget_say("Building CUDA offloading plugin.")
-    
-      # Define the suffix for the runtime messaging dumps.
-      add_definitions(-DTARGET_NAME=CUDA)
-    
-      if(LIBOMPTARGET_CMAKE_BUILD_TYPE MATCHES debug)
-          add_definitions(-DCUDA_ERROR_REPORT)
-      endif()
-      
-      include_directories(${LIBOMPTARGET_DEP_CUDA_INCLUDE_DIRS})
-      include_directories(${LIBOMPTARGET_DEP_LIBELF_INCLUDE_DIRS})
-    
-      add_library(omptarget.rtl.cuda SHARED src/rtl.cpp)
-      
-      # Install plugin under the lib destination folder.
-      install(TARGETS omptarget.rtl.cuda LIBRARY DESTINATION lib${OPENMP_LIBDIR_SUFFIX})
-      
-      target_link_libraries(omptarget.rtl.cuda 
-        ${LIBOMPTARGET_DEP_CUDA_LIBRARIES} 
-        cuda 
-        ${LIBOMPTARGET_DEP_LIBELF_LIBRARIES}
-        "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports")
-    
-      # Report to the parent scope that we are building a plugin for CUDA.
-      set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS} nvptx64-nvidia-cuda" PARENT_SCOPE)
-    else()
-      libomptarget_say("Not building CUDA offloading plugin: only support CUDA in Linux x86_64 or ppc64le hosts.")
-    endif()
-  else()
-    libomptarget_say("Not building CUDA offloading plugin: CUDA not found in system.")
-  endif()
-else(LIBOMPTARGET_DEP_LIBELF_FOUND)
-  libomptarget_say("Not building CUDA offloading plugin: libelf dependency not found.")
-endif(LIBOMPTARGET_DEP_LIBELF_FOUND)
+if (NOT(CMAKE_SYSTEM_PROCESSOR MATCHES "(x86_64)|(ppc64le)$" AND CMAKE_SYSTEM_NAME MATCHES "Linux"))
+  libomptarget_say("Not building CUDA offloading plugin: only support CUDA in Linux x86_64 or ppc64le hosts.")
+  return()
+elseif (NOT LIBOMPTARGET_DEP_LIBELF_FOUND)
+  libomptarget_say("Not building CUDA offloading plugin: libelf dependency not found.")
+  return()
+elseif(NOT LIBOMPTARGET_DEP_CUDA_FOUND)
+  libomptarget_say("Not building CUDA offloading plugin: CUDA not found in system.")
+  return()
+elseif(NOT LIBOMPTARGET_DEP_CUDA_DRIVER_FOUND)
+  libomptarget_say("Not building CUDA offloading plugin: CUDA Driver API not found in system.")
+  return()
+endif()
+target_link_libraries(omptarget.rtl.cuda
+  ${LIBOMPTARGET_DEP_CUDA_DRIVER_LIBRARIES}