CUDA: Add CMAKE_CUDA_HOST_COMPILER support on Windows non-VS generators

Help/envvar/CUDAHOSTCXX.rst

@@ -15,6 +15,10 @@ ignored if the :variable:`CMAKE_CUDA_HOST_COMPILER` variable is defined.
 This environment variable is primarily meant for use with projects that
 enable ``CUDA`` as a first-class language.
 
+.. note::
+
+  Ignored when using :ref:`Visual Studio Generators`.
+
 .. versionadded:: 3.13
   The :module:`FindCUDA`
   module will use this variable to initialize its ``CUDA_HOST_COMPILER`` setting.

Help/variable/CMAKE_CUDA_HOST_COMPILER.rst

@@ -23,3 +23,7 @@ is read-only and changes to it are undefined behavior.
   :variable:`CMAKE_CUDA_COMPILER_ID <CMAKE_<LANG>_COMPILER_ID>` is ``NVIDIA``,
   it does not make sense to set ``CMAKE_CUDA_HOST_COMPILER`` without also
   setting ``CMAKE_CUDA_COMPILER`` to NVCC.
+
+.. note::
+
+  Ignored when using :ref:`Visual Studio Generators`.

Modules/CMakeCUDAInformation.cmake

@@ -110,13 +110,6 @@ include(CMakeCommonLanguageInclude)
 # CMAKE_CUDA_COMPILE_SEPARABLE_COMPILATION
 # CMAKE_CUDA_LINK_EXECUTABLE
 
-if(CMAKE_CUDA_HOST_COMPILER AND CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
-  # FIXME: This is too late for the Platform/Windows-NVIDIA-CUDA module to
-  # see it, so we do not support CMAKE_CUDA_HOST_COMPILER on Windows.
-  # Move this to Compiler/NVIDIA-CUDA and update the VS generator too.
-  string(APPEND _CMAKE_CUDA_EXTRA_FLAGS " -ccbin=<CMAKE_CUDA_HOST_COMPILER>")
-endif()
-
 # create a shared library
 if(NOT CMAKE_CUDA_CREATE_SHARED_LIBRARY)
   set(CMAKE_CUDA_CREATE_SHARED_LIBRARY

Modules/CMakeDetermineCUDACompiler.cmake

@@ -11,6 +11,9 @@ if( NOT ( ("${CMAKE_GENERATOR}" MATCHES "Make") OR
 endif()
 
 if(${CMAKE_GENERATOR} MATCHES "Visual Studio")
+  if(DEFINED ENV{CUDAHOSTCXX} OR DEFINED CMAKE_CUDA_HOST_COMPILER)
+    message(WARNING "Visual Studio does not support specifying CUDAHOSTCXX or CMAKE_CUDA_HOST_COMPILER. Using the C++ compiler provided by Visual Studio.")
+  endif()
 else()
   if(NOT CMAKE_CUDA_COMPILER)
     set(CMAKE_CUDA_COMPILER_INIT NOTFOUND)
@@ -39,13 +42,13 @@ else()
   endif()
 
   mark_as_advanced(CMAKE_CUDA_COMPILER)
-endif()
 
-#Allow the user to specify a host compiler
-if(NOT $ENV{CUDAHOSTCXX} STREQUAL "")
-  get_filename_component(CMAKE_CUDA_HOST_COMPILER $ENV{CUDAHOSTCXX} PROGRAM)
-  if(NOT EXISTS ${CMAKE_CUDA_HOST_COMPILER})
-    message(FATAL_ERROR "Could not find compiler set in environment variable CUDAHOSTCXX:\n$ENV{CUDAHOSTCXX}.\n${CMAKE_CUDA_HOST_COMPILER}")
+  #Allow the user to specify a host compiler except for Visual Studio
+  if(NOT $ENV{CUDAHOSTCXX} STREQUAL "")
+    get_filename_component(CMAKE_CUDA_HOST_COMPILER $ENV{CUDAHOSTCXX} PROGRAM)
+    if(NOT EXISTS ${CMAKE_CUDA_HOST_COMPILER})
+      message(FATAL_ERROR "Could not find compiler set in environment variable CUDAHOSTCXX:\n$ENV{CUDAHOSTCXX}.\n${CMAKE_CUDA_HOST_COMPILER}")
+    endif()
   endif()
 endif()
 

Modules/Compiler/NVIDIA-CUDA.cmake

@@ -24,21 +24,17 @@ else()
   set(_CMAKE_CUDA_EXTRA_DEVICE_LINK_FLAGS "")
 endif()
 
+if(CMAKE_CUDA_HOST_COMPILER AND NOT CMAKE_GENERATOR MATCHES "Visual Studio")
+  string(APPEND _CMAKE_CUDA_EXTRA_FLAGS " -ccbin=<CMAKE_CUDA_HOST_COMPILER>")
+endif()
+
 if (CMAKE_CUDA_COMPILER_VERSION VERSION_GREATER_EQUAL 10.2.89)
   # The -MD flag was only added to nvcc in 10.2 so
   # before that we had to invoke the compiler twice
   # to get header dependency information
   set(CMAKE_DEPFILE_FLAGS_CUDA "-MD -MT <DEP_TARGET> -MF <DEP_FILE>")
 else()
-  if(CMAKE_CUDA_HOST_COMPILER AND NOT CMAKE_SYSTEM_NAME STREQUAL "Windows")
-    # FIXME: Move the main -ccbin= flag from CMakeCUDAInformation to
-    # a block above, remove this copy, and update the VS generator too.
-    set(_CMAKE_CUDA_EXTRA_FLAGS_LOCAL " -ccbin=<CMAKE_CUDA_HOST_COMPILER>")
-  else()
-    set(_CMAKE_CUDA_EXTRA_FLAGS_LOCAL "")
-  endif()
-  set(CMAKE_CUDA_DEPENDS_EXTRA_COMMANDS "<CMAKE_CUDA_COMPILER> ${_CMAKE_CUDA_EXTRA_FLAGS}${_CMAKE_CUDA_EXTRA_FLAGS_LOCAL} <DEFINES> <INCLUDES> <FLAGS> ${_CMAKE_COMPILE_AS_CUDA_FLAG} -M <SOURCE> -MT <OBJECT> -o <DEP_FILE>")
-  unset(_CMAKE_CUDA_EXTRA_FLAGS_LOCAL)
+  set(CMAKE_CUDA_DEPENDS_EXTRA_COMMANDS "<CMAKE_CUDA_COMPILER> ${_CMAKE_CUDA_EXTRA_FLAGS} <DEFINES> <INCLUDES> <FLAGS> ${_CMAKE_COMPILE_AS_CUDA_FLAG} -M <SOURCE> -MT <OBJECT> -o <DEP_FILE>")
 endif()
 set(CMAKE_CUDA_DEPFILE_FORMAT gcc)
 if((NOT DEFINED CMAKE_DEPENDS_USE_COMPILER OR CMAKE_DEPENDS_USE_COMPILER)