Merge topic 'cuda_clang_toolkit_path' into release-3.18

ec59fb6c31 CUDA: Determine CUDA toolkit location for NVCC
0a056246a1 CUDA: Pass toolkit path to Clang
9c43972127 FindCUDAToolkit: Avoid unnecessary temporary variable computing binary dir
9eebb5b8b2 FindCUDAToolkit: Remove unnecessary checks around searches
8f01fe7bf1 FindCUDAToolkit: Use list(SORT) to sort in natural order
8c144fe9ad FindCUDAToolkit: Compute CUDAToolkit_INCLUDE_DIR instead of searching
403f8d31e3 FindCUDAToolkit: Add CUDAToolkit_LIBRARY_ROOT
6636693134 FindCUDAToolkit: Re-unify with Internal/CUDAToolkit

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4828

8 files changed, 448 insertions, 260 deletions

diff --git a/Help/release/3.18.rst b/Help/release/3.18.rst
index 71f9d85b39..db5f62a7c0 100644
--- a/Help/release/3.18.rst
+++ b/Help/release/3.18.rst
@@ -194,6 +194,14 @@ Modules
 
 .. _`SWIG-Fortran`: https://github.com/swig-fortran/swig
 
+* The :module:`FindCUDAToolkit` module:
+
+  * gained the variable
+    ``CUDAToolkit_LIBRARY_ROOT``, which is the directory containing the
+    ``nvvm`` directory and ``version.txt``.
+
+  * uses toolkit and library root found during ``CUDA`` compiler detection.
+
 Generator Expressions
 ---------------------
 
diff --git a/Modules/CMakeCUDACompiler.cmake.in b/Modules/CMakeCUDACompiler.cmake.in
index 64fb4696ce..704ad09fdf 100644
--- a/Modules/CMakeCUDACompiler.cmake.in
+++ b/Modules/CMakeCUDACompiler.cmake.in
@@ -43,6 +43,9 @@ if(CMAKE_CUDA_LIBRARY_ARCHITECTURE)
   set(CMAKE_LIBRARY_ARCHITECTURE "@CMAKE_CUDA_LIBRARY_ARCHITECTURE@")
 endif()
 
+set(CMAKE_CUDA_COMPILER_TOOLKIT_ROOT "@CMAKE_CUDA_COMPILER_TOOLKIT_ROOT@")
+set(CMAKE_CUDA_COMPILER_LIBRARY_ROOT "@CMAKE_CUDA_COMPILER_LIBRARY_ROOT@")
+
 set(CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES "@CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES@")
 
 set(CMAKE_CUDA_HOST_IMPLICIT_LINK_LIBRARIES "@CMAKE_CUDA_HOST_IMPLICIT_LINK_LIBRARIES@")
diff --git a/Modules/CMakeDetermineCUDACompiler.cmake b/Modules/CMakeDetermineCUDACompiler.cmake
index 1273831ef6..a0f7202b0b 100644
--- a/Modules/CMakeDetermineCUDACompiler.cmake
+++ b/Modules/CMakeDetermineCUDACompiler.cmake
@@ -65,18 +65,144 @@ if(NOT CMAKE_CUDA_COMPILER_ID_RUN)
   set(CMAKE_CXX_COMPILER_ID_TOOL_MATCH_INDEX 2)
   set(CMAKE_CUDA_COMPILER_ID_FLAGS_ALWAYS "-v")
 
-  # nvcc
-  set(nvcc_test_flags "--keep --keep-dir tmp")
-  if(CMAKE_CUDA_HOST_COMPILER)
-    string(APPEND nvcc_test_flags " -ccbin=${CMAKE_CUDA_HOST_COMPILER}")
+  # We determine the vendor to help with find the toolkit and use the right flags for detection right away.
+  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerId.cmake)
+  CMAKE_DETERMINE_COMPILER_ID_VENDOR(CUDA "--version")
+
+  # Find the CUDA toolkit. We store the CMAKE_CUDA_COMPILER_TOOLKIT_ROOT and CMAKE_CUDA_COMPILER_LIBRARY_ROOT
+  # in CMakeCUDACompiler.cmake, so FindCUDAToolkit can avoid searching on future runs and the toolkit stays the same.
+  # This is very similar to FindCUDAToolkit, but somewhat simplified since we can issue fatal errors
+  # if we fail to find things we need and we don't need to account for searching the libraries.
+
+  # For NVCC we can easily deduce the SDK binary directory from the compiler path.
+  if(CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
+    get_filename_component(_CUDA_BIN_DIR "${CMAKE_CUDA_COMPILER}" DIRECTORY)
+    find_program(CUDAToolkit_NVCC_EXECUTABLE
+      NAMES nvcc nvcc.exe
+      PATHS ${_CUDA_BIN_DIR}
+      NO_DEFAULT_PATH
+    )
+    unset(_CUDA_BIN_DIR)
   endif()
 
-  # Clang
-  if(CMAKE_CROSSCOMPILING)
-    # Need to pass the host target and include directories if we're crosscompiling.
-    set(clang_test_flags "--sysroot=\"${CMAKE_SYSROOT}\" --target=${CMAKE_CUDA_COMPILER_TARGET}")
-  else()
-    set(clang_test_flags)
+  # Search using CUDAToolkit_ROOT and then CUDA_PATH for equivalence with FindCUDAToolkit.
+  # In FindCUDAToolkit CUDAToolkit_ROOT is searched automatically due to being in a find_package().
+  # First we search candidate non-default paths to give them priority.
+  find_program(_CUDA_NVCC_EXECUTABLE
+    NAMES nvcc nvcc.exe
+    PATHS ${CUDAToolkit_ROOT}
+    ENV CUDAToolkit_ROOT
+    ENV CUDA_PATH
+    PATH_SUFFIXES bin
+    NO_DEFAULT_PATH
+  )
+
+  # If we didn't find NVCC, then try the default paths.
+  find_program(_CUDA_NVCC_EXECUTABLE
+    NAMES nvcc nvcc.exe
+    PATH_SUFFIXES bin
+  )
+
+  # If the user specified CUDAToolkit_ROOT but nvcc could not be found, this is an error.
+  if(NOT _CUDA_NVCC_EXECUTABLE AND (DEFINED CUDAToolkit_ROOT OR DEFINED ENV{CUDAToolkit_ROOT}))
+    set(fail_base "Could not find nvcc executable in path specified by")
+
+    if(DEFINED CUDAToolkit_ROOT)
+      message(FATAL_ERROR "${fail_base} CUDAToolkit_ROOT=${CUDAToolkit_ROOT}")
+    elseif(DEFINED ENV{CUDAToolkit_ROOT})
+      message(FATAL_ERROR "${fail_base} environment variable CUDAToolkit_ROOT=$ENV{CUDAToolkit_ROOT}")
+    endif()
+  endif()
+
+  # CUDAToolkit_ROOT cmake/env variable not specified, try platform defaults.
+  #
+  # - Linux: /usr/local/cuda-X.Y
+  # - macOS: /Developer/NVIDIA/CUDA-X.Y
+  # - Windows: C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\vX.Y
+  #
+  # We will also search the default symlink location /usr/local/cuda first since
+  # if CUDAToolkit_ROOT is not specified, it is assumed that the symlinked
+  # directory is the desired location.
+  if(NOT _CUDA_NVCC_EXECUTABLE)
+    if(UNIX)
+      if(NOT APPLE)
+        set(platform_base "/usr/local/cuda-")
+      else()
+        set(platform_base "/Developer/NVIDIA/CUDA-")
+      endif()
+    else()
+      set(platform_base "C:\\Program Files\\NVIDIA GPU Computing Toolkit\\CUDA\\v")
+    endif()
+
+    # Build out a descending list of possible cuda installations, e.g.
+    file(GLOB possible_paths "${platform_base}*")
+    # Iterate the glob results and create a descending list.
+    set(versions)
+    foreach(p ${possible_paths})
+      # Extract version number from end of string
+      string(REGEX MATCH "[0-9][0-9]?\\.[0-9]$" p_version ${p})
+      if(IS_DIRECTORY ${p} AND p_version)
+        list(APPEND versions ${p_version})
+      endif()
+    endforeach()
+
+    # Sort numerically in descending order, so we try the newest versions first.
+    list(SORT versions COMPARE NATURAL ORDER DESCENDING)
+
+    # With a descending list of versions, populate possible paths to search.
+    set(search_paths)
+    foreach(v ${versions})
+      list(APPEND search_paths "${platform_base}${v}")
+    endforeach()
+
+    # Force the global default /usr/local/cuda to the front on Unix.
+    if(UNIX)
+      list(INSERT search_paths 0 "/usr/local/cuda")
+    endif()
+
+    # Now search for nvcc again using the platform default search paths.
+    find_program(_CUDA_NVCC_EXECUTABLE
+      NAMES nvcc nvcc.exe
+      PATHS ${search_paths}
+      PATH_SUFFIXES bin
+    )
+
+    # We are done with these variables now, cleanup.
+    unset(platform_base)
+    unset(possible_paths)
+    unset(versions)
+    unset(search_paths)
+
+    if(NOT _CUDA_NVCC_EXECUTABLE)
+      message(FATAL_ERROR "Could not find nvcc, please set CUDAToolkit_ROOT.")
+    endif()
+  endif()
+
+  get_filename_component(CMAKE_CUDA_COMPILER_TOOLKIT_ROOT "${_CUDA_NVCC_EXECUTABLE}" DIRECTORY)
+  get_filename_component(CMAKE_CUDA_COMPILER_TOOLKIT_ROOT "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}" DIRECTORY ABSOLUTE)
+
+  # CMAKE_CUDA_COMPILER_LIBRARY_ROOT contains the device library and version file.
+  # In a non-scattered installation this is equivalent to CMAKE_CUDA_COMPILER_TOOLKIT_ROOT.
+  # We first check for a non-scattered installation to prefer it over a scattered installation.
+  if(EXISTS "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}/version.txt")
+    set(CMAKE_CUDA_COMPILER_LIBRARY_ROOT "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}")
+  elseif(CMAKE_SYSROOT_LINK AND EXISTS "${CMAKE_SYSROOT_LINK}/usr/lib/cuda/version.txt")
+    set(CMAKE_CUDA_COMPILER_LIBRARY_ROOT "${CMAKE_SYSROOT_LINK}/usr/lib/cuda")
+  elseif(EXISTS "${CMAKE_SYSROOT}/usr/lib/cuda/version.txt")
+    set(CMAKE_CUDA_COMPILER_LIBRARY_ROOT "${CMAKE_SYSROOT}/usr/lib/cuda")
+  endif()
+
+  if(CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
+    set(nvcc_test_flags "--keep --keep-dir tmp")
+    if(CMAKE_CUDA_HOST_COMPILER)
+      string(APPEND nvcc_test_flags " -ccbin=${CMAKE_CUDA_HOST_COMPILER}")
+    endif()
+  elseif(CMAKE_CUDA_COMPILER_ID STREQUAL "Clang")
+    set(clang_test_flags "--cuda-path=\"${CMAKE_CUDA_COMPILER_LIBRARY_ROOT}\"")
+    if(CMAKE_CROSSCOMPILING)
+      # Need to pass the host target and include directories if we're crosscompiling.
+      string(APPEND clang_test_flags " --sysroot=\"${CMAKE_SYSROOT}\" --target=${CMAKE_CUDA_COMPILER_TARGET}")
+    endif()
   endif()
 
   # First try with the user-specified architectures.
@@ -108,7 +234,12 @@ if(NOT CMAKE_CUDA_COMPILER_ID_RUN)
   # Finally also try the default.
   list(APPEND CMAKE_CUDA_COMPILER_ID_TEST_FLAGS_FIRST "${clang_test_flags}")
 
-  include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerId.cmake)
+  # We perform compiler identification for a second time to extract implicit linking info and host compiler for NVCC.
+  # We also use it to verify that CMAKE_CUDA_ARCHITECTURES and additionaly on Clang that CUDA toolkit path works.
+  # The latter could be done during compiler testing in the future to avoid doing this for Clang.
+  # We need to unset the compiler ID otherwise CMAKE_DETERMINE_COMPILER_ID() doesn't work.
+  unset(CMAKE_CUDA_COMPILER_ID)
+
   CMAKE_DETERMINE_COMPILER_ID(CUDA CUDAFLAGS CMakeCUDACompilerId.cu)
 
   _cmake_find_compiler_sysroot(CUDA)
@@ -157,12 +288,54 @@ elseif(CMAKE_CUDA_COMPILER_ID STREQUAL "Clang")
     endforeach()
   endif()
 
+  # Find target directory. Account for crosscompiling.
+  if(CMAKE_CROSSCOMPILING)
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL "armv7-a")
+      # Support for NVPACK
+      set(_CUDA_TARGET_NAME "armv7-linux-androideabi")
+    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm")
+      set(_CUDA_TARGET_NAME "armv7-linux-gnueabihf")
+    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
+      if(ANDROID_ARCH_NAME STREQUAL "arm64")
+        set(_CUDA_TARGET_NAME "aarch64-linux-androideabi")
+      else()
+        set(_CUDA_TARGET_NAME "aarch64-linux")
+      endif()
+    elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
+      set(_CUDA_TARGET_NAME "x86_64-linux")
+    endif()
+
+    if(EXISTS "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}/targets/${_CUDA_TARGET_NAME}")
+      set(_CUDA_TARGET_DIR "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}/targets/${_CUDA_TARGET_NAME}")
+    endif()
+  else()
+    set(_CUDA_TARGET_DIR "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}")
+  endif()
+
+  # We can't use find_library() yet at this point, so try a few guesses.
+  if(EXISTS "${_CUDA_TARGET_DIR}/lib64")
+    set(_CUDA_LIBRARY_DIR "${_CUDA_TARGET_DIR}/lib64")
+  elseif(EXISTS "${_CUDA_TARGET_DIR}/lib/x64")
+    set(_CUDA_LIBRARY_DIR "${_CUDA_TARGET_DIR}/lib/x64")
+  elseif(EXISTS "${_CUDA_TARGET_DIR}/lib")
+    set(_CUDA_LIBRARY_DIR "${_CUDA_TARGET_DIR}/lib")
+  else()
+    message(FATAL_ERROR "Unable to find _CUDA_LIBRARY_DIR based on _CUDA_TARGET_DIR=${_CUDA_TARGET_DIR}")
+  endif()
+
+  # _CUDA_TARGET_DIR always points to the directory containing the include directory.
+  # On a scattered installation /usr, on a non-scattered something like /usr/local/cuda or /usr/local/cuda-10.2/targets/aarch64-linux.
+  if(EXISTS "${_CUDA_TARGET_DIR}/include/cuda_runtime.h")
+    set(_CUDA_INCLUDE_DIR "${_CUDA_TARGET_DIR}/include")
+  else()
+    message(FATAL_ERROR "Unable to find cuda_runtime.h in \"${_CUDA_TARGET_DIR}/include\" for _CUDA_INCLUDE_DIR.")
+  endif()
+
   # Clang does not add any CUDA SDK libraries or directories when invoking the host linker.
   # Add the CUDA toolkit library directory ourselves so that linking works.
   # The CUDA runtime libraries are handled elsewhere by CMAKE_CUDA_RUNTIME_LIBRARY.
-  include(Internal/CUDAToolkit)
-  set(CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES "${CUDAToolkit_INCLUDE_DIR}")
-  set(CMAKE_CUDA_HOST_IMPLICIT_LINK_DIRECTORIES "${CUDAToolkit_LIBRARY_DIR}")
+  set(CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES "${_CUDA_INCLUDE_DIR}")
+  set(CMAKE_CUDA_HOST_IMPLICIT_LINK_DIRECTORIES "${_CUDA_LIBRARY_DIR}")
   set(CMAKE_CUDA_HOST_IMPLICIT_LINK_LIBRARIES "")
   set(CMAKE_CUDA_HOST_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES "")
 elseif(CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
@@ -382,7 +555,14 @@ endif()
 configure_file(${CMAKE_ROOT}/Modules/CMakeCUDACompiler.cmake.in
   ${CMAKE_PLATFORM_INFO_DIR}/CMakeCUDACompiler.cmake
   @ONLY
-  )
+)
+
+# Don't leak variables unnecessarily to user code.
+unset(_CUDA_INCLUDE_DIR CACHE)
+unset(_CUDA_NVCC_EXECUTABLE CACHE)
+unset(_CUDA_LIBRARY_DIR)
+unset(_CUDA_TARGET_DIR)
+unset(_CUDA_TARGET_NAME)
 
 set(CMAKE_CUDA_COMPILER_ENV_VAR "CUDACXX")
 set(CMAKE_CUDA_HOST_COMPILER_ENV_VAR "CUDAHOSTCXX")
diff --git a/Modules/FindCUDAToolkit.cmake b/Modules/FindCUDAToolkit.cmake
index 7d4e168a1a..00d1a504c4 100644
--- a/Modules/FindCUDAToolkit.cmake
+++ b/Modules/FindCUDAToolkit.cmake
@@ -421,6 +421,10 @@ Result variables
     The path to the CUDA Toolkit library directory that contains the CUDA
     Runtime library ``cudart``.
 
+``CUDAToolkit_LIBRARY_ROOT``
+    The path to the CUDA Toolkit directory containing the nvvm directory and
+    version.txt.
+
 ``CUDAToolkit_TARGET_DIR``
     The path to the CUDA Toolkit directory including the target architecture
     when cross-compiling. When not cross-compiling this will be equivalant to
@@ -473,8 +477,207 @@ Result variables
 #
 ###############################################################################
 
-# Include shared CUDA toolkit location code.
-include(Internal/CUDAToolkit)
+# The toolkit is located during compiler detection for CUDA and stored in CMakeCUDACompiler.cmake as
+# CMAKE_CUDA_COMPILER_TOOLKIT_ROOT and CMAKE_CUDA_COMPILER_LIBRARY_ROOT.
+# We compute the rest based on those here to avoid re-searching and to avoid finding a possibly
+# different installation.
+if(CMAKE_CUDA_COMPILER_TOOLKIT_ROOT)
+  set(CUDAToolkit_ROOT_DIR "${CMAKE_CUDA_COMPILER_TOOLKIT_ROOT}")
+  set(CUDAToolkit_LIBRARY_ROOT "${CMAKE_CUDA_COMPILER_LIBRARY_ROOT}")
+  set(CUDAToolkit_BIN_DIR "${CUDAToolkit_ROOT_DIR}/bin")
+  set(CUDAToolkit_NVCC_EXECUTABLE "${CUDAToolkit_BIN_DIR}/nvcc${CMAKE_EXECUTABLE_SUFFIX}")
+else()
+  # For NVCC we can easily deduce the SDK binary directory from the compiler path.
+  if(CMAKE_CUDA_COMPILER_LOADED AND NOT CUDAToolkit_BIN_DIR AND CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
+    get_filename_component(CUDAToolkit_BIN_DIR "${CMAKE_CUDA_COMPILER}" DIRECTORY)
+    set(CUDAToolkit_BIN_DIR "${CUDAToolkit_BIN_DIR}" CACHE PATH "")
+    mark_as_advanced(CUDAToolkit_BIN_DIR)
+  endif()
+
+  # Try language- or user-provided path first.
+  if(CUDAToolkit_BIN_DIR)
+    find_program(CUDAToolkit_NVCC_EXECUTABLE
+      NAMES nvcc nvcc.exe
+      PATHS ${CUDAToolkit_BIN_DIR}
+      NO_DEFAULT_PATH
+    )
+  endif()
+
+  # Search using CUDAToolkit_ROOT
+  find_program(CUDAToolkit_NVCC_EXECUTABLE
+    NAMES nvcc nvcc.exe
+    PATHS ENV CUDA_PATH
+    PATH_SUFFIXES bin
+  )
+
+  # If the user specified CUDAToolkit_ROOT but nvcc could not be found, this is an error.
+  if(NOT CUDAToolkit_NVCC_EXECUTABLE AND (DEFINED CUDAToolkit_ROOT OR DEFINED ENV{CUDAToolkit_ROOT}))
+    # Declare error messages now, print later depending on find_package args.
+    set(fail_base "Could not find nvcc executable in path specified by")
+    set(cuda_root_fail "${fail_base} CUDAToolkit_ROOT=${CUDAToolkit_ROOT}")
+    set(env_cuda_root_fail "${fail_base} environment variable CUDAToolkit_ROOT=$ENV{CUDAToolkit_ROOT}")
+
+    if(CUDAToolkit_FIND_REQUIRED)
+      if(DEFINED CUDAToolkit_ROOT)
+        message(FATAL_ERROR ${cuda_root_fail})
+      elseif(DEFINED ENV{CUDAToolkit_ROOT})
+        message(FATAL_ERROR ${env_cuda_root_fail})
+      endif()
+    else()
+      if(NOT CUDAToolkit_FIND_QUIETLY)
+        if(DEFINED CUDAToolkit_ROOT)
+          message(STATUS ${cuda_root_fail})
+        elseif(DEFINED ENV{CUDAToolkit_ROOT})
+          message(STATUS ${env_cuda_root_fail})
+        endif()
+      endif()
+      set(CUDAToolkit_FOUND FALSE)
+      unset(fail_base)
+      unset(cuda_root_fail)
+      unset(env_cuda_root_fail)
+      return()
+    endif()
+  endif()
+
+  # CUDAToolkit_ROOT cmake / env variable not specified, try platform defaults.
+  #
+  # - Linux: /usr/local/cuda-X.Y
+  # - macOS: /Developer/NVIDIA/CUDA-X.Y
+  # - Windows: C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\vX.Y
+  #
+  # We will also search the default symlink location /usr/local/cuda first since
+  # if CUDAToolkit_ROOT is not specified, it is assumed that the symlinked
+  # directory is the desired location.
+  if(NOT CUDAToolkit_NVCC_EXECUTABLE)
+    if(UNIX)
+      if(NOT APPLE)
+        set(platform_base "/usr/local/cuda-")
+      else()
+        set(platform_base "/Developer/NVIDIA/CUDA-")
+      endif()
+    else()
+      set(platform_base "C:\\Program Files\\NVIDIA GPU Computing Toolkit\\CUDA\\v")
+    endif()
+
+    # Build out a descending list of possible cuda installations, e.g.
+    file(GLOB possible_paths "${platform_base}*")
+    # Iterate the glob results and create a descending list.
+    set(versions)
+    foreach(p ${possible_paths})
+      # Extract version number from end of string
+      string(REGEX MATCH "[0-9][0-9]?\\.[0-9]$" p_version ${p})
+      if(IS_DIRECTORY ${p} AND p_version)
+        list(APPEND versions ${p_version})
+      endif()
+    endforeach()
+
+    # Sort numerically in descending order, so we try the newest versions first.
+    list(SORT versions COMPARE NATURAL ORDER DESCENDING)
+
+    # With a descending list of versions, populate possible paths to search.
+    set(search_paths)
+    foreach(v ${versions})
+      list(APPEND search_paths "${platform_base}${v}")
+    endforeach()
+
+    # Force the global default /usr/local/cuda to the front on Unix.
+    if(UNIX)
+      list(INSERT search_paths 0 "/usr/local/cuda")
+    endif()
+
+    # Now search for nvcc again using the platform default search paths.
+    find_program(CUDAToolkit_NVCC_EXECUTABLE
+      NAMES nvcc nvcc.exe
+      PATHS ${search_paths}
+      PATH_SUFFIXES bin
+    )
+
+    # We are done with these variables now, cleanup for caller.
+    unset(platform_base)
+    unset(possible_paths)
+    unset(versions)
+    unset(search_paths)
+
+    if(NOT CUDAToolkit_NVCC_EXECUTABLE)
+      if(CUDAToolkit_FIND_REQUIRED)
+        message(FATAL_ERROR "Could not find nvcc, please set CUDAToolkit_ROOT.")
+      elseif(NOT CUDAToolkit_FIND_QUIETLY)
+        message(STATUS "Could not find nvcc, please set CUDAToolkit_ROOT.")
+      endif()
+
+      set(CUDAToolkit_FOUND FALSE)
+      return()
+    endif()
+  endif()
+
+  if(NOT CUDAToolkit_BIN_DIR AND CUDAToolkit_NVCC_EXECUTABLE)
+    get_filename_component(CUDAToolkit_BIN_DIR "${CUDAToolkit_NVCC_EXECUTABLE}" DIRECTORY)
+    set(CUDAToolkit_BIN_DIR "${CUDAToolkit_BIN_DIR}" CACHE PATH "" FORCE)
+    mark_as_advanced(CUDAToolkit_BIN_DIR)
+  endif()
+
+  get_filename_component(CUDAToolkit_ROOT_DIR ${CUDAToolkit_BIN_DIR} DIRECTORY ABSOLUTE)
+
+  # CUDAToolkit_LIBRARY_ROOT contains the device library and version file.
+  # In a non-scattered installation this is equivalent to CUDAToolkit_ROOT_DIR.
+  # We first check for a non-scattered installation to prefer it over a scattered installation.
+  if(EXISTS "${CUDAToolkit_ROOT_DIR}/version.txt")
+    set(CUDAToolkit_LIBRARY_ROOT "${CUDAToolkit_ROOT_DIR}")
+  elseif(CMAKE_SYSROOT_LINK AND EXISTS "${CMAKE_SYSROOT_LINK}/usr/lib/cuda/version.txt")
+    set(CUDAToolkit_LIBRARY_ROOT "${CMAKE_SYSROOT_LINK}/usr/lib/cuda")
+  elseif(EXISTS "${CMAKE_SYSROOT}/usr/lib/cuda/version.txt")
+    set(CUDAToolkit_LIBRARY_ROOT "${CMAKE_SYSROOT}/usr/lib/cuda")
+  endif()
+endif()
+
+# Handle cross compilation
+if(CMAKE_CROSSCOMPILING)
+  if(CMAKE_SYSTEM_PROCESSOR STREQUAL "armv7-a")
+    # Support for NVPACK
+    set(CUDAToolkit_TARGET_NAME "armv7-linux-androideabi")
+  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm")
+    # Support for arm cross compilation
+    set(CUDAToolkit_TARGET_NAME "armv7-linux-gnueabihf")
+  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
+    # Support for aarch64 cross compilation
+    if(ANDROID_ARCH_NAME STREQUAL "arm64")
+      set(CUDAToolkit_TARGET_NAME "aarch64-linux-androideabi")
+    else()
+      set(CUDAToolkit_TARGET_NAME "aarch64-linux")
+    endif(ANDROID_ARCH_NAME STREQUAL "arm64")
+  elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
+    set(CUDAToolkit_TARGET_NAME "x86_64-linux")
+  endif()
+
+  if(EXISTS "${CUDAToolkit_ROOT_DIR}/targets/${CUDAToolkit_TARGET_NAME}")
+    set(CUDAToolkit_TARGET_DIR "${CUDAToolkit_ROOT_DIR}/targets/${CUDAToolkit_TARGET_NAME}")
+    # add known CUDA target root path to the set of directories we search for programs, libraries and headers
+    list(PREPEND CMAKE_FIND_ROOT_PATH "${CUDAToolkit_TARGET_DIR}")
+
+    # Mark that we need to pop the root search path changes after we have
+    # found all cuda libraries so that searches for our cross-compilation
+    # libraries work when another cuda sdk is in CMAKE_PREFIX_PATH or
+    # PATh
+    set(_CUDAToolkit_Pop_ROOT_PATH True)
+  endif()
+else()
+  # Not cross compiling
+  set(CUDAToolkit_TARGET_DIR "${CUDAToolkit_ROOT_DIR}")
+  # Now that we have the real ROOT_DIR, find components inside it.
+  list(APPEND CMAKE_PREFIX_PATH ${CUDAToolkit_ROOT_DIR})
+
+  # Mark that we need to pop the prefix path changes after we have
+  # found the cudart library.
+  set(_CUDAToolkit_Pop_Prefix True)
+endif()
+
+# CUDAToolkit_TARGET_DIR always points to the directory containing the include directory.
+# On a scattered installation /usr, on a non-scattered something like /usr/local/cuda or /usr/local/cuda-10.2/targets/aarch64-linux.
+if(EXISTS "${CUDAToolkit_TARGET_DIR}/include/cuda_runtime.h")
+  set(CUDAToolkit_INCLUDE_DIR "${CUDAToolkit_TARGET_DIR}/include")
+elseif(NOT CUDAToolkit_FIND_QUIETLY)
+  message(STATUS "Unable to find cuda_runtime.h in \"${CUDAToolkit_TARGET_DIR}/include\" for CUDAToolkit_INCLUDE_DIR.")
+endif()
 
 if(CUDAToolkit_NVCC_EXECUTABLE AND
    CUDAToolkit_NVCC_EXECUTABLE STREQUAL CMAKE_CUDA_COMPILER)
@@ -488,7 +691,7 @@ if(CUDAToolkit_NVCC_EXECUTABLE AND
   endif()
 else()
   # Compute the version by invoking nvcc
-  execute_process (COMMAND ${CUDAToolkit_NVCC_EXECUTABLE} "--version" OUTPUT_VARIABLE NVCC_OUT)
+  execute_process(COMMAND ${CUDAToolkit_NVCC_EXECUTABLE} "--version" OUTPUT_VARIABLE NVCC_OUT)
   if(NVCC_OUT MATCHES [=[ V([0-9]+)\.([0-9]+)\.([0-9]+)]=])
     set(CUDAToolkit_VERSION_MAJOR "${CMAKE_MATCH_1}")
     set(CUDAToolkit_VERSION_MINOR "${CMAKE_MATCH_2}")
@@ -503,12 +706,10 @@ find_library(CUDA_CUDART
   NAMES cudart
   PATH_SUFFIXES lib64 lib/x64
 )
-if(NOT CUDA_CUDART)
-  find_library(CUDA_CUDART
-    NAMES cudart
-    PATH_SUFFIXES lib64/stubs lib/x64/stubs
-  )
-endif()
+find_library(CUDA_CUDART
+  NAMES cudart
+  PATH_SUFFIXES lib64/stubs lib/x64/stubs
+)
 
 if(NOT CUDA_CUDART AND NOT CUDAToolkit_FIND_QUIETLY)
   message(STATUS "Unable to find cudart library.")
@@ -559,16 +760,14 @@ if(CUDAToolkit_FOUND)
       PATH_SUFFIXES nvidia/current lib64 lib/x64 lib
                     ${arg_EXTRA_PATH_SUFFIXES}
     )
-    # Don't try any stub directories intil we have exhausted all other
+    # Don't try any stub directories until we have exhausted all other
     # search locations.
-    if(NOT CUDA_${lib_name}_LIBRARY)
-      find_library(CUDA_${lib_name}_LIBRARY
-        NAMES ${search_names}
-        HINTS ${CUDAToolkit_LIBRARY_DIR}
-              ENV CUDA_PATH
-        PATH_SUFFIXES lib64/stubs lib/x64/stubs lib/stubs stubs
-      )
-    endif()
+    find_library(CUDA_${lib_name}_LIBRARY
+      NAMES ${search_names}
+      HINTS ${CUDAToolkit_LIBRARY_DIR}
+            ENV CUDA_PATH
+      PATH_SUFFIXES lib64/stubs lib/x64/stubs lib/stubs stubs
+    )
 
     mark_as_advanced(CUDA_${lib_name}_LIBRARY)
 
diff --git a/Modules/Internal/CUDAToolkit.cmake b/Modules/Internal/CUDAToolkit.cmake
deleted file mode 100644
index 291bb0146d..0000000000
--- a/Modules/Internal/CUDAToolkit.cmake
+++ /dev/null
@@ -1,227 +0,0 @@
-# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
-# file Copyright.txt or https://cmake.org/licensing for details.
-
-# This file is for sharing code for finding basic CUDA toolkit information between
-# CMakeDetermineCUDACompiler.cmake and FindCUDAToolkit.cmake.
-
-# For NVCC we can easily deduce the SDK binary directory from the compiler path.
-if(CMAKE_CUDA_COMPILER_LOADED AND NOT CUDAToolkit_BIN_DIR AND CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
-  get_filename_component(cuda_dir "${CMAKE_CUDA_COMPILER}" DIRECTORY)
-  set(CUDAToolkit_BIN_DIR "${cuda_dir}" CACHE PATH "")
-  mark_as_advanced(CUDAToolkit_BIN_DIR)
-  unset(cuda_dir)
-endif()
-
-# Try language- or user-provided path first.
-if(CUDAToolkit_BIN_DIR)
-  find_program(CUDAToolkit_NVCC_EXECUTABLE
-    NAMES nvcc nvcc.exe
-    PATHS ${CUDAToolkit_BIN_DIR}
-    NO_DEFAULT_PATH
-    )
-endif()
-
-# Search using CUDAToolkit_ROOT
-find_program(CUDAToolkit_NVCC_EXECUTABLE
-  NAMES nvcc nvcc.exe
-  PATHS ENV CUDA_PATH
-  PATH_SUFFIXES bin
-)
-
-# If the user specified CUDAToolkit_ROOT but nvcc could not be found, this is an error.
-if(NOT CUDAToolkit_NVCC_EXECUTABLE AND (DEFINED CUDAToolkit_ROOT OR DEFINED ENV{CUDAToolkit_ROOT}))
-  # Declare error messages now, print later depending on find_package args.
-  set(fail_base "Could not find nvcc executable in path specified by")
-  set(cuda_root_fail "${fail_base} CUDAToolkit_ROOT=${CUDAToolkit_ROOT}")
-  set(env_cuda_root_fail "${fail_base} environment variable CUDAToolkit_ROOT=$ENV{CUDAToolkit_ROOT}")
-
-  if(CUDAToolkit_FIND_REQUIRED)
-    if(DEFINED CUDAToolkit_ROOT)
-      message(FATAL_ERROR ${cuda_root_fail})
-    elseif(DEFINED ENV{CUDAToolkit_ROOT})
-      message(FATAL_ERROR ${env_cuda_root_fail})
-    endif()
-  else()
-    if(NOT CUDAToolkit_FIND_QUIETLY)
-      if(DEFINED CUDAToolkit_ROOT)
-        message(STATUS ${cuda_root_fail})
-      elseif(DEFINED ENV{CUDAToolkit_ROOT})
-        message(STATUS ${env_cuda_root_fail})
-      endif()
-    endif()
-    set(CUDAToolkit_FOUND FALSE)
-    unset(fail_base)
-    unset(cuda_root_fail)
-    unset(env_cuda_root_fail)
-    return()
-  endif()
-endif()
-
-# CUDAToolkit_ROOT cmake / env variable not specified, try platform defaults.
-#
-# - Linux: /usr/local/cuda-X.Y
-# - macOS: /Developer/NVIDIA/CUDA-X.Y
-# - Windows: C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\vX.Y
-#
-# We will also search the default symlink location /usr/local/cuda first since
-# if CUDAToolkit_ROOT is not specified, it is assumed that the symlinked
-# directory is the desired location.
-if(NOT CUDAToolkit_NVCC_EXECUTABLE)
-  if(UNIX)
-    if(NOT APPLE)
-      set(platform_base "/usr/local/cuda-")
-    else()
-      set(platform_base "/Developer/NVIDIA/CUDA-")
-    endif()
-  else()
-    set(platform_base "C:\\Program Files\\NVIDIA GPU Computing Toolkit\\CUDA\\v")
-  endif()
-
-  # Build out a descending list of possible cuda installations, e.g.
-  file(GLOB possible_paths "${platform_base}*")
-  # Iterate the glob results and create a descending list.
-  set(possible_versions)
-  foreach (p ${possible_paths})
-    # Extract version number from end of string
-    string(REGEX MATCH "[0-9][0-9]?\\.[0-9]$" p_version ${p})
-    if(IS_DIRECTORY ${p} AND p_version)
-      list(APPEND possible_versions ${p_version})
-    endif()
-  endforeach()
-
-  # Cannot use list(SORT) because that is alphabetical, we need numerical.
-  # NOTE: this is not an efficient sorting strategy.  But even if a user had
-  # every possible version of CUDA installed, this wouldn't create any
-  # significant overhead.
-  set(versions)
-  foreach (v ${possible_versions})
-    list(LENGTH versions num_versions)
-    # First version, nothing to compare with so just append.
-    if(num_versions EQUAL 0)
-      list(APPEND versions ${v})
-    else()
-      # Loop through list.  Insert at an index when comparison is
-      # VERSION_GREATER since we want a descending list.  Duplicates will not
-      # happen since this came from a glob list of directories.
-      set(i 0)
-      set(early_terminate FALSE)
-      while (i LESS num_versions)
-        list(GET versions ${i} curr)
-        if(v VERSION_GREATER curr)
-          list(INSERT versions ${i} ${v})
-          set(early_terminate TRUE)
-          break()
-        endif()
-        math(EXPR i "${i} + 1")
-      endwhile()
-      # If it did not get inserted, place it at the end.
-      if(NOT early_terminate)
-        list(APPEND versions ${v})
-      endif()
-    endif()
-  endforeach()
-
-  # With a descending list of versions, populate possible paths to search.
-  set(search_paths)
-  foreach (v ${versions})
-    list(APPEND search_paths "${platform_base}${v}")
-  endforeach()
-
-  # Force the global default /usr/local/cuda to the front on Unix.
-  if(UNIX)
-    list(INSERT search_paths 0 "/usr/local/cuda")
-  endif()
-
-  # Now search for nvcc again using the platform default search paths.
-  find_program(CUDAToolkit_NVCC_EXECUTABLE
-    NAMES nvcc nvcc.exe
-    PATHS ${search_paths}
-    PATH_SUFFIXES bin
-  )
-
-  # We are done with these variables now, cleanup for caller.
-  unset(platform_base)
-  unset(possible_paths)
-  unset(possible_versions)
-  unset(versions)
-  unset(i)
-  unset(early_terminate)
-  unset(search_paths)
-
-  if(NOT CUDAToolkit_NVCC_EXECUTABLE)
-    if(CUDAToolkit_FIND_REQUIRED)
-      message(FATAL_ERROR "Could not find nvcc, please set CUDAToolkit_ROOT.")
-    elseif(NOT CUDAToolkit_FIND_QUIETLY)
-      message(STATUS "Could not find nvcc, please set CUDAToolkit_ROOT.")
-    endif()
-
-    set(CUDAToolkit_FOUND FALSE)
-    return()
-  endif()
-endif()
-
-if(NOT CUDAToolkit_BIN_DIR AND CUDAToolkit_NVCC_EXECUTABLE)
-  get_filename_component(cuda_dir "${CUDAToolkit_NVCC_EXECUTABLE}" DIRECTORY)
-  set(CUDAToolkit_BIN_DIR "${cuda_dir}" CACHE PATH "" FORCE)
-  mark_as_advanced(CUDAToolkit_BIN_DIR)
-  unset(cuda_dir)
-endif()
-
-get_filename_component(CUDAToolkit_ROOT_DIR ${CUDAToolkit_BIN_DIR} DIRECTORY ABSOLUTE)
-
-# Handle cross compilation
-if(CMAKE_CROSSCOMPILING)
-  if(CMAKE_SYSTEM_PROCESSOR STREQUAL "armv7-a")
-    # Support for NVPACK
-    set(CUDAToolkit_TARGET_NAME "armv7-linux-androideabi")
-  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm")
-    # Support for arm cross compilation
-    set(CUDAToolkit_TARGET_NAME "armv7-linux-gnueabihf")
-  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
-    # Support for aarch64 cross compilation
-    if(ANDROID_ARCH_NAME STREQUAL "arm64")
-      set(CUDAToolkit_TARGET_NAME "aarch64-linux-androideabi")
-    else()
-      set(CUDAToolkit_TARGET_NAME "aarch64-linux")
-    endif(ANDROID_ARCH_NAME STREQUAL "arm64")
-  elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
-      set(CUDAToolkit_TARGET_NAME "x86_64-linux")
-  endif()
-
-  if(EXISTS "${CUDAToolkit_ROOT_DIR}/targets/${CUDAToolkit_TARGET_NAME}")
-    set(CUDAToolkit_TARGET_DIR "${CUDAToolkit_ROOT_DIR}/targets/${CUDAToolkit_TARGET_NAME}")
-    # add known CUDA target root path to the set of directories we search for programs, libraries and headers
-    list(PREPEND CMAKE_FIND_ROOT_PATH "${CUDAToolkit_TARGET_DIR}")
-
-    # Mark that we need to pop the root search path changes after we have
-    # found all cuda libraries so that searches for our cross-compilation
-    # libraries work when another cuda sdk is in CMAKE_PREFIX_PATH or
-    # PATh
-    set(_CUDAToolkit_Pop_ROOT_PATH True)
-  endif()
-else()
-  # Not cross compiling
-  set(CUDAToolkit_TARGET_DIR "${CUDAToolkit_ROOT_DIR}")
-  # Now that we have the real ROOT_DIR, find components inside it.
-  list(APPEND CMAKE_PREFIX_PATH ${CUDAToolkit_ROOT_DIR})
-
-  # Mark that we need to pop the prefix path changes after we have
-  # found the cudart library.
-  set(_CUDAToolkit_Pop_Prefix True)
-endif()
-
-# Find the include/ directory
-find_path(CUDAToolkit_INCLUDE_DIR
-  NAMES cuda_runtime.h
-)
-
-# Find a tentative CUDAToolkit_LIBRARY_DIR. FindCUDAToolkit overrides it by searching for the CUDA runtime,
-# but we can't do that here, as CMakeDetermineCUDACompiler wants to use it before the variables necessary
-# for find_library() have been initialized.
-if(EXISTS "${CUDAToolkit_TARGET_DIR}/lib64")
-  set(CUDAToolkit_LIBRARY_DIR "${CUDAToolkit_TARGET_DIR}/lib64")
-elseif(EXISTS "${CUDAToolkit_TARGET_DIR}/lib/x64")
-  set(CUDAToolkit_LIBRARY_DIR "${CUDAToolkit_TARGET_DIR}/lib/x64")
-elseif(EXISTS "${CUDAToolkit_TARGET_DIR}/lib")
-  set(CUDAToolkit_LIBRARY_DIR "${CUDAToolkit_TARGET_DIR}/lib")
-endif()
diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 54d34baabd..f2011ee665 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -37,6 +37,7 @@
 #include "cmLocalGenerator.h"
 #include "cmMakefile.h"
 #include "cmMessageType.h"
+#include "cmOutputConverter.h"
 #include "cmPropertyMap.h"
 #include "cmRange.h"
 #include "cmSourceFile.h"
@@ -3152,6 +3153,28 @@ void cmGeneratorTarget::AddCUDAArchitectureFlags(std::string& flags) const
   }
 }
 
+void cmGeneratorTarget::AddCUDAToolkitFlags(std::string& flags) const
+{
+  std::string const& compiler =
+    this->Makefile->GetSafeDefinition("CMAKE_CUDA_COMPILER_ID");
+
+  if (compiler == "Clang") {
+    // Pass CUDA toolkit explicitly to Clang.
+    // Clang's searching for the system CUDA toolkit isn't very good and it's
+    // expected the user will explicitly pass the toolkit path.
+    // This also avoids Clang having to search for the toolkit on every
+    // invocation.
+    std::string toolkitRoot =
+      this->Makefile->GetSafeDefinition("CMAKE_CUDA_COMPILER_LIBRARY_ROOT");
+
+    if (!toolkitRoot.empty()) {
+      flags += " --cuda-path=" +
+        this->LocalGenerator->ConvertToOutputFormat(toolkitRoot,
+                                                    cmOutputConverter::SHELL);
+    }
+  }
+}
+
 //----------------------------------------------------------------------------
 std::string cmGeneratorTarget::GetFeatureSpecificLinkRuleVariable(
   std::string const& var, std::string const& lang,
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index a7201dcae0..3aedbf53e6 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -426,6 +426,7 @@ public:
                      std::vector<std::string>& archVec) const;
 
   void AddCUDAArchitectureFlags(std::string& flags) const;
+  void AddCUDAToolkitFlags(std::string& flags) const;
 
   std::string GetFeatureSpecificLinkRuleVariable(
     std::string const& var, std::string const& lang,
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index fba9cdb317..f7488227b2 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1986,6 +1986,7 @@ void cmLocalGenerator::AddLanguageFlags(std::string& flags,
     }
   } else if (lang == "CUDA") {
     target->AddCUDAArchitectureFlags(flags);
+    target->AddCUDAToolkitFlags(flags);
 
     std::string const& compiler =
       this->Makefile->GetSafeDefinition("CMAKE_CUDA_COMPILER_ID");