FindCUDAToolkit: Factor out discovery code into a separate file

This allows for re-use in other parts of the code, that require the CUDA
toolkit location, but can't or may not want to use the full
`FindCUDAToolkit`.

Modules/FindCUDAToolkit.cmake

@@ -473,168 +473,8 @@ Result variables
 #
 ###############################################################################
 
-# 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()
+# Include shared CUDA toolkit location code.
+include(Internal/CUDAToolkit)
 
 if(CUDAToolkit_NVCC_EXECUTABLE AND
    CUDAToolkit_NVCC_EXECUTABLE STREQUAL CMAKE_CUDA_COMPILER)
@@ -658,72 +498,22 @@ else()
   unset(NVCC_OUT)
 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)
+if(NOT CUDA_CUDART AND NOT CUDAToolkit_FIND_QUIETLY)
+  message(STATUS "Unable to find cudart library.")
 endif()
 
-
-# Find the include/ directory
-find_path(CUDAToolkit_INCLUDE_DIR
-  NAMES cuda_runtime.h
-)
-
-# And find the CUDA Runtime Library libcudart
+# Find the CUDA Runtime Library libcudart
 find_library(CUDA_CUDART
   NAMES cudart
   PATH_SUFFIXES lib64 lib/x64
 )
-if (NOT CUDA_CUDART)
+if(NOT CUDA_CUDART)
   find_library(CUDA_CUDART
     NAMES cudart
     PATH_SUFFIXES lib64/stubs lib/x64/stubs
   )
 endif()
 
-if (NOT CUDA_CUDART AND NOT CUDAToolkit_FIND_QUIETLY)
-  message(STATUS "Unable to find cudart library.")
-endif()
-
 unset(CUDAToolkit_ROOT_DIR)
 if(_CUDAToolkit_Pop_Prefix)
   list(REMOVE_AT CMAKE_PREFIX_PATH -1)
@@ -749,8 +539,8 @@ mark_as_advanced(CUDA_CUDART
 #-----------------------------------------------------------------------------
 # Construct result variables
 if(CUDAToolkit_FOUND)
- set(CUDAToolkit_INCLUDE_DIRS ${CUDAToolkit_INCLUDE_DIR})
- get_filename_component(CUDAToolkit_LIBRARY_DIR ${CUDA_CUDART} DIRECTORY ABSOLUTE)
+  set(CUDAToolkit_INCLUDE_DIRS ${CUDAToolkit_INCLUDE_DIR})
+  get_filename_component(CUDAToolkit_LIBRARY_DIR ${CUDA_CUDART} DIRECTORY ABSOLUTE)
 endif()
 
 #-----------------------------------------------------------------------------

Modules/Internal/CUDAToolkit.cmake

@@ -0,0 +1,225 @@
+# 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")
+  set(CUDAToolkit_LIBRARY_DIR "${CUDAToolkit_TARGET_DIR}/lib")
+endif()