FindCUDA: Added CUDA_HOST_COMPILER variable.

Added a new CUDA variable for specifying the CUDA_HOST_COMPILER.  This will allow users to
be able to specify which host compiler to use for invoking NVCC with.  By default it will
use the compiler used for host compilation.  This is convenient for when you want to
specify a different compiler than the default compiler.  You end up using the same
compiler for both the NVCC compilation and the host compilation instead of using the
default compiler in the path for NVCC.

Modules/FindCUDA.cmake

@@ -68,6 +68,13 @@
 #  CUDA_HOST_COMPILATION_CPP (Default ON)
 #  -- Set to OFF for C compilation of host code.
 #
+#  CUDA_HOST_COMPILER (Default CMAKE_C_COMPILER, $(VCInstallDir)/bin for VS)
+#  -- Set the host compiler to be used by nvcc.  Ignored if -ccbin or
+#     --compiler-bindir is already present in the CUDA_NVCC_FLAGS or
+#     CUDA_NVCC_FLAGS_<CONFIG> variables.  For Visual Studio targets
+#     $(VCInstallDir)/bin is a special value that expands out to the path when
+#     the command is run from withing VS.
+#
 #  CUDA_NVCC_FLAGS
 #  CUDA_NVCC_FLAGS_<CONFIG>
 #  -- Additional NVCC command line arguments.  NOTE: multiple arguments must be
@@ -390,6 +397,12 @@ option(CUDA_HOST_COMPILATION_CPP "Generated file extension" ON)
 # Extra user settable flags
 set(CUDA_NVCC_FLAGS "" CACHE STRING "Semi-colon delimit multiple arguments.")
 
+if(CMAKE_GENERATOR MATCHES "Visual Studio")
+  set(CUDA_HOST_COMPILER "$(VCInstallDir)bin" CACHE FILEPATH "Host side compiler used by NVCC")
+else()
+  set(CUDA_HOST_COMPILER "${CMAKE_C_COMPILER}" CACHE FILEPATH "Host side compiler used by NVCC")
+endif()
+
 # Propagate the host flags to the host compiler via -Xcompiler
 option(CUDA_PROPAGATE_HOST_FLAGS "Propage C/CXX_FLAGS and friends to the host compiler via -Xcompile" ON)
 
@@ -938,12 +951,11 @@ macro(CUDA_WRAP_SRCS cuda_target format generated_files)
   endif()
 
   # This needs to be passed in at this stage, because VS needs to fill out the
-  # value of VCInstallDir from within VS.
+  # value of VCInstallDir from within VS.  Note that CCBIN is only used if
+  # -ccbin or --compiler-bindir isn't used and CUDA_HOST_COMPILER matches
+  # $(VCInstallDir)/bin.
   if(CMAKE_GENERATOR MATCHES "Visual Studio")
-    if( CMAKE_SIZEOF_VOID_P EQUAL 8 )
-      # Add nvcc flag for 64b Windows
-      set(ccbin_flags -D "\"CCBIN:PATH=$(VCInstallDir)bin\"" )
-    endif()
+    set(ccbin_flags -D "\"CCBIN:PATH=$(VCInstallDir)bin\"" )
   endif()
 
   # Figure out which configure we will use and pass that in as an argument to

Modules/FindCUDA/run_nvcc.cmake

@@ -62,6 +62,7 @@ set(cmake_dependency_file "@cmake_dependency_file@") # path
 set(CUDA_make2cmake "@CUDA_make2cmake@") # path
 set(CUDA_parse_cubin "@CUDA_parse_cubin@") # path
 set(build_cubin @build_cubin@) # bool
+set(CUDA_HOST_COMPILER "@CUDA_HOST_COMPILER@") # bool
 # We won't actually use these variables for now, but we need to set this, in
 # order to force this file to be run again if it changes.
 set(generated_file_path "@generated_file_path@") # path
@@ -102,8 +103,15 @@ endif()
 # Add the build specific configuration flags
 list(APPEND CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS_${build_configuration}})
 
-if(DEFINED CCBIN)
-  set(CCBIN -ccbin "${CCBIN}")
+# Any -ccbin existing in CUDA_NVCC_FLAGS gets highest priority
+list( FIND CUDA_NVCC_FLAGS "-ccbin" ccbin_found0 )
+list( FIND CUDA_NVCC_FLAGS "--compiler-bindir" ccbin_found1 )
+if( ccbin_found0 LESS 0 AND ccbin_found1 LESS 0 )
+  if (CUDA_HOST_COMPILER STREQUAL "$(VCInstallDir)bin" AND DEFINED CCBIN)
+    set(CCBIN -ccbin "${CCBIN}")
+  else()
+    set(CCBIN -ccbin "${CUDA_HOST_COMPILER}")
+  endif()
 endif()
 
 # cuda_execute_process - Executes a command with optional command echo and status message.