CUDA host device code with two code paths

Summary:
Allow CUDA host device functions with two code paths using __CUDA_ARCH__
to differentiate between code path being compiled.

For example:
  __host__ __device__ void host_device_function(void) {
  #ifdef __CUDA_ARCH__
    device_only_function();
  #else
    host_only_function();
  #endif
  }

Patch by Jacques Pienaar.

Reviewed By: rnk

Differential Revision: http://reviews.llvm.org/D6457

llvm-svn: 223271

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1349,6 +1349,9 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   if (Args.hasArg(OPT_fno_operator_names))
     Opts.CXXOperatorNames = 0;
 
+  if (Args.hasArg(OPT_fcuda_is_device))
+    Opts.CUDAIsDevice = 1;
+
   if (Opts.ObjC1) {
     if (Arg *arg = Args.getLastArg(OPT_fobjc_runtime_EQ)) {
       StringRef value = arg->getValue();