if(NOT LIBC_TARGET_OS_IS_GPU)
  message(FATAL_ERROR
          "libc build: Invalid attempt to set up GPU architectures.")
endif()

# Ensure the compiler is a valid clang when building the GPU target.
set(req_ver "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
if(LLVM_VERSION_MAJOR AND NOT (CMAKE_CXX_COMPILER_ID MATCHES "[Cc]lang" AND
   ${CMAKE_CXX_COMPILER_VERSION} VERSION_EQUAL "${req_ver}"))
  message(FATAL_ERROR "Cannot build libc for GPU. CMake compiler "
                      "'${CMAKE_CXX_COMPILER_ID} ${CMAKE_CXX_COMPILER_VERSION}' "
                      " is not 'Clang ${req_ver}'.")
endif()
if(NOT LLVM_LIBC_FULL_BUILD)
  message(FATAL_ERROR "LLVM_LIBC_FULL_BUILD must be enabled to build libc for "
                      "GPU.")
endif()

# Set the required flags globally so standard CMake utilities can compile.
if(LIBC_TARGET_TRIPLE)
  set(CMAKE_REQUIRED_FLAGS "--target=${LIBC_TARGET_TRIPLE}")
endif()
if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nogpulib")
elseif(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
  set(CMAKE_REQUIRED_FLAGS
      "${CMAKE_REQUIRED_FLAGS} -flto -c -Wno-unused-command-line-argument")
endif()

# Optionally set up a job pool to limit the number of GPU tests run in parallel.
# This is sometimes necessary as running too many tests in parallel can cause
# the GPU or driver to run out of resources.
set(LIBC_GPU_TEST_JOBS "" CACHE STRING "Number of jobs to use for GPU tests")
if(LIBC_GPU_TEST_JOBS)
  set_property(GLOBAL PROPERTY JOB_POOLS LIBC_GPU_TEST_POOL=${LIBC_GPU_TEST_JOBS})
  set(LIBC_HERMETIC_TEST_JOB_POOL JOB_POOL LIBC_GPU_TEST_POOL)
else()
  set_property(GLOBAL PROPERTY JOB_POOLS LIBC_GPU_TEST_POOL=1)
  set(LIBC_HERMETIC_TEST_JOB_POOL JOB_POOL LIBC_GPU_TEST_POOL)
endif()

set(LIBC_GPU_TEST_ARCHITECTURE "" CACHE STRING "Architecture for the GPU tests")
if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
  check_cxx_compiler_flag(-mcpu=native PLATFORM_HAS_GPU)
elseif(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
  check_cxx_compiler_flag(-march=native PLATFORM_HAS_GPU)
endif()

set(gpu_test_architecture "")
if(DEFINED LLVM_TARGETS_TO_BUILD AND LIBC_TARGET_ARCHITECTURE_IS_AMDGPU
   AND NOT "AMDGPU" IN_LIST LLVM_TARGETS_TO_BUILD)
  set(LIBC_GPU_TESTS_DISABLED TRUE)
  message(STATUS "AMDGPU backend is not available, tests will not be built")
elseif(DEFINED LLVM_TARGETS_TO_BUILD AND LIBC_TARGET_ARCHITECTURE_IS_NVPTX
       AND NOT "NVPTX" IN_LIST LLVM_TARGETS_TO_BUILD)
  set(LIBC_GPU_TESTS_DISABLED TRUE)
  message(STATUS "NVPTX backend is not available, tests will not be built")
elseif(LIBC_GPU_TEST_ARCHITECTURE)
  set(LIBC_GPU_TESTS_DISABLED FALSE)
  set(gpu_test_architecture ${LIBC_GPU_TEST_ARCHITECTURE})
  message(STATUS "Using user-specified GPU architecture for testing: "
                 "'${gpu_test_architecture}'")
elseif(PLATFORM_HAS_GPU)
  set(LIBC_GPU_TESTS_DISABLED FALSE)
  set(gpu_test_architecture "native")
  message(STATUS "Using GPU architecture detected on the system for testing: "
                 "'native'")
else()
  set(LIBC_GPU_TESTS_DISABLED TRUE)
  message(STATUS "No GPU architecture detected or provided, tests will not be "
                 "built")
endif()
set(LIBC_GPU_TARGET_ARCHITECTURE "${gpu_test_architecture}")

# Identify the GPU loader utility used to run tests.
set(LIBC_GPU_LOADER_EXECUTABLE "" CACHE STRING "Executable for the GPU loader.")
if(LIBC_GPU_LOADER_EXECUTABLE)
  set(gpu_loader_executable ${LIBC_GPU_LOADER_EXECUTABLE})
elseif(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
  find_program(LIBC_AMDHSA_LOADER_EXECUTABLE
               NAMES amdhsa-loader NO_DEFAULT_PATH
               PATHS ${LLVM_BINARY_DIR}/bin ${compiler_path})
  if(LIBC_AMDHSA_LOADER_EXECUTABLE)
    set(gpu_loader_executable ${LIBC_AMDHSA_LOADER_EXECUTABLE})
  endif()
elseif(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
  find_program(LIBC_NVPTX_LOADER_EXECUTABLE
               NAMES nvptx-loader NO_DEFAULT_PATH
               PATHS ${LLVM_BINARY_DIR}/bin ${compiler_path})
  if(LIBC_NVPTX_LOADER_EXECUTABLE)
    set(gpu_loader_executable ${LIBC_NVPTX_LOADER_EXECUTABLE})
  endif()
endif()
if(NOT TARGET libc.utils.gpu.loader AND gpu_loader_executable)
  add_custom_target(libc.utils.gpu.loader)
  set_target_properties(
    libc.utils.gpu.loader
    PROPERTIES
      EXECUTABLE "${gpu_loader_executable}"
  )
endif()

if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
  # The AMDGPU environment uses different code objects to encode the ABI for
  # kernel calls and intrinsic functions. We want to specify this manually to
  # conform to whatever the test suite was built to handle.
  set(LIBC_GPU_CODE_OBJECT_VERSION 5)
endif()

if(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
  # FIXME: This is a hack required to keep the CUDA package from trying to find
  #        pthreads. We only link the CUDA driver, so this is unneeded.
  add_library(CUDA::cudart_static_deps IMPORTED INTERFACE)

  find_package(CUDAToolkit QUIET)
  if(CUDAToolkit_FOUND)
    get_filename_component(LIBC_CUDA_ROOT "${CUDAToolkit_BIN_DIR}" DIRECTORY ABSOLUTE)
  endif()
endif()