[libc] Search for the CUDA patch explicitly when testing

The packaged version of the `libc` library does not depend on the CUDA
installation because it only uses `clang` and emits LLVM-IR. However,
for testing we directly need the CUDA toolkit to emit and execute the
files. This patch explicitly passes `--cuda-path` to the relevant
compilations for NVPTX testing.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D147653

Author: jhuber6

libc/cmake/modules/LLVMLibCObjectRules.cmake

@@ -195,7 +195,9 @@ function(_build_gpu_objects fq_target_name internal_target_name)
     if(LIBC_GPU_TARGET_ARCHITECTURE_IS_AMDGPU)
       target_compile_options(${internal_target_name} PRIVATE -mcpu=${LIBC_GPU_TARGET_ARCHITECTURE} -flto)
     elseif(LIBC_GPU_TARGET_ARCHITECTURE_IS_NVPTX)
-      target_compile_options(${internal_target_name} PRIVATE -march=${LIBC_GPU_TARGET_ARCHITECTURE})
+      target_compile_options(${internal_target_name} PRIVATE
+                             -march=${LIBC_GPU_TARGET_ARCHITECTURE}
+                             --cuda-path=${LIBC_CUDA_ROOT})
     endif()
     target_include_directories(${internal_target_name} PRIVATE ${include_dirs})
     if(full_deps_list)

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -507,6 +507,7 @@ function(add_integration_test test_name)
                            --target=${LIBC_GPU_TARGET_TRIPLE})
   elseif(LIBC_GPU_TARGET_ARCHITECTURE_IS_NVPTX)
     target_compile_options(${fq_build_target_name} PRIVATE
+                           --cuda-path=${LIBC_CUDA_ROOT}
                            -march=${LIBC_GPU_TARGET_ARCHITECTURE}
                            --target=${LIBC_GPU_TARGET_TRIPLE})
   endif()

libc/cmake/modules/prepare_libc_gpu_build.cmake

@@ -98,3 +98,11 @@ elseif("${gpu_test_architecture}" IN_LIST all_nvptx_architectures)
 else()
   message(FATAL_ERROR "Unknown GPU architecture '${gpu_test_architecture}'")
 endif()
+
+if(LIBC_GPU_TARGET_ARCHITECTURE_IS_NVPTX)
+  find_package(CUDAToolkit QUIET)
+  if(CUDAToolkit_FOUND)
+    get_filename_component(LIBC_CUDA_ROOT "${CUDAToolkit_BIN_DIR}" DIRECTORY ABSOLUTE)
+    message(WARNING ${LIBC_CUDA_ROOT})
+  endif()
+endif()

libc/startup/gpu/nvptx/CMakeLists.txt

@@ -10,6 +10,7 @@ add_startup_object(
     -nogpulib # Do not include any GPU vendor libraries.
     -march=${LIBC_GPU_TARGET_ARCHITECTURE}
     --target=${LIBC_GPU_TARGET_TRIPLE}
+    --cuda-path=${LIBC_CUDA_ROOT}
   NO_GPU_BUNDLE # Compile this file directly without special GPU handling.
 )
 get_fq_target_name(crt1 fq_name)
@@ -19,4 +20,5 @@ target_link_libraries(${fq_name}
   PUBLIC
   "-march=${LIBC_GPU_TARGET_ARCHITECTURE}"
   "--target=${LIBC_GPU_TARGET_TRIPLE}"
+  "--cuda-path=${LIBC_CUDA_ROOT}"
 )

libc/test/IntegrationTest/CMakeLists.txt

@@ -8,6 +8,7 @@ elseif(LIBC_GPU_TARGET_ARCHITECTURE_IS_NVPTX)
   set(TEST_COMPILE_FLAGS
     -march=${LIBC_GPU_TARGET_ARCHITECTURE}
     --target=${LIBC_GPU_TARGET_TRIPLE}
+    --cuda-path=${LIBC_CUDA_ROOT}
   )
 endif()