Add support for compiling CUDA with clang++

UoB-HPC · Apr 16, 2024 · cf5ad17 · cf5ad17
1 parent 3f7075b
commit cf5ad17
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Showing 2 changed files with 22 additions and 7 deletions.
diff --git a/src/ci-test-compile.sh b/src/ci-test-compile.sh
@@ -234,6 +234,11 @@ build_clang() {
   else
     echo "Skipping RAJA models due to CMake version requirement"
   fi
+
+  run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${CLANG_CXX:?} -DCUDA_ARCH=$NV_ARCH -DCUDA_CLANG_DRIVER=ON"
+  run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${CLANG_CXX:?} -DCUDA_ARCH=$NV_ARCH -DCUDA_CLANG_DRIVER=ON -DMEM=MANAGED"
+  run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${CLANG_CXX:?} -DCUDA_ARCH=$NV_ARCH -DCUDA_CLANG_DRIVER=ON -DMEM=PAGEFAULT"
+
   run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${NVHPC_NVCC:?} -DCUDA_ARCH=$NV_ARCH"
   run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${NVHPC_NVCC:?} -DCUDA_ARCH=$NV_ARCH -DMEM=MANAGED"
   run_build $name "${CLANG_CXX:?}" cuda "$cxx -DCMAKE_CUDA_COMPILER=${NVHPC_NVCC:?} -DCUDA_ARCH=$NV_ARCH -DMEM=PAGEFAULT"

diff --git a/src/cuda/model.cmake b/src/cuda/model.cmake
@@ -16,29 +16,39 @@ register_flag_required(CMAKE_CUDA_COMPILER
 register_flag_required(CUDA_ARCH
         "Nvidia architecture, will be passed in via `-arch=` (e.g `sm_70`) for nvcc")
 
+register_flag_optional(CUDA_CLANG_DRIVER
+        "Disable any nvcc-specific flags so that setting CMAKE_CUDA_COMPILER to clang++ can compile successfully"
+        "OFF")
+
 register_flag_optional(CUDA_EXTRA_FLAGS
-        "Additional CUDA flags passed to nvcc, this is appended after `CUDA_ARCH`"
+        "Additional CUDA flags passed to the CUDA compiler, this is appended after `CUDA_ARCH`"
         "")
 
 
 macro(setup)
 
     # XXX CMake 3.18 supports CMAKE_CUDA_ARCHITECTURES/CUDA_ARCHITECTURES but we support older CMakes
-    if(POLICY CMP0104)
+    if (POLICY CMP0104)
         cmake_policy(SET CMP0104 OLD)
-    endif()
+    endif ()
 
-    enable_language(CUDA)
     register_definitions(${MEM})
 
-    # add -forward-unknown-to-host-compiler for compatibility reasons
-    set(CMAKE_CUDA_FLAGS ${CMAKE_CUDA_FLAGS} "-forward-unknown-to-host-compiler" "-arch=${CUDA_ARCH}" ${CUDA_EXTRA_FLAGS})
+    if (CUDA_CLANG_DRIVER)
+        set(CMAKE_CUDA_FLAGS "${CMAKE_CUDA_FLAGS} -std=c++17 --cuda-gpu-arch=${CUDA_ARCH} ${CUDA_EXTRA_FLAGS}")
+    else ()
+        # add -forward-unknown-to-host-compiler for compatibility reasons
+        # add -std=c++17 manually as older CMake seems to omit this (source gets treated as C otherwise)
+        set(CMAKE_CUDA_FLAGS "${CMAKE_CUDA_FLAGS} -std=c++17 -forward-unknown-to-host-compiler -arch=${CUDA_ARCH} ${CUDA_EXTRA_FLAGS}")
+    endif ()
     string(REPLACE ";" " " CMAKE_CUDA_FLAGS "${CMAKE_CUDA_FLAGS}")
 
+    enable_language(CUDA)
+
     # CMake defaults to -O2 for CUDA at Release, let's wipe that and use the global RELEASE_FLAG
     # appended later
     wipe_gcc_style_optimisation_flags(CMAKE_CUDA_FLAGS_${BUILD_TYPE})
 
-    message(STATUS "NVCC flags: ${CMAKE_CUDA_FLAGS} ${CMAKE_CUDA_FLAGS_${BUILD_TYPE}}")
+    message(STATUS "CUDA compiler flags: ${CMAKE_CUDA_FLAGS} ${CMAKE_CUDA_FLAGS_${BUILD_TYPE}}")
 endmacro()