CUDA: MSVC will now state files are cuda files when needed

The MSVC CUDA build customizations before CUDA 9 would not explicitly
add the -x cu option when building. This caused .cpp and .c files
invoked with CudaCompile to be compiled as host code and not
cuda. Now when we detect CUDA < 9 we will explicitly add this
option to correct this bug.

Source/cmVisualStudio10TargetGenerator.cxx

@@ -2646,6 +2646,7 @@ bool cmVisualStudio10TargetGenerator::ComputeCudaOptions(
     cudaOptions.AddFlag("GPUDebugInfo", "false");
   }
 
+  bool notPtx = true;
   if (this->GeneratorTarget->GetPropertyAsBool("CUDA_SEPARABLE_COMPILATION")) {
     cudaOptions.AddFlag("GenerateRelocatableDeviceCode", "true");
   } else if (this->GeneratorTarget->GetPropertyAsBool(
@@ -2654,6 +2655,16 @@ bool cmVisualStudio10TargetGenerator::ComputeCudaOptions(
     // We drop the %(Extension) component as CMake expects all PTX files
     // to not have the source file extension at all
     cudaOptions.AddFlag("CompileOut", "$(IntDir)%(Filename).ptx");
+    notPtx = false;
+  }
+
+  if (notPtx &&
+      cmSystemTools::VersionCompareGreaterEq(
+        "8.0", this->GlobalGenerator->GetPlatformToolsetCudaString())) {
+    // Explicitly state that we want this file to be treated as a
+    // CUDA file no matter what the file extensions is
+    // This is only needed for < CUDA 9
+    cudaOptions.AppendFlagString("AdditionalOptions", "-x cu");
   }
 
   // CUDA automatically passes the proper '--machine' flag to nvcc

Tests/CudaOnly/WithDefs/CMakeLists.txt

@@ -21,14 +21,8 @@ set(release_compile_defs DEFREL)
 #this verifies we can pass things such as '_','(' to nvcc
 add_definitions("-DPACKED_DEFINE=__attribute__((packed))")
 
-if(CMAKE_GENERATOR MATCHES "Visual Studio")
-  # CUDA MSBuild rules do not pass '-x cu' to nvcc
-  set(main main_for_vs.cu)
-else()
-  set(main main.notcu)
-  set_source_files_properties(main.notcu PROPERTIES LANGUAGE CUDA)
-endif()
-add_executable(CudaOnlyWithDefs ${main})
+add_executable(CudaOnlyWithDefs main.notcu)
+set_source_files_properties(main.notcu PROPERTIES LANGUAGE CUDA)
 
 target_compile_options(CudaOnlyWithDefs
   PRIVATE

Tests/CudaOnly/WithDefs/main_for_vs.cu

@@ -1 +0,0 @@
-#include "main.notcu"