Cycles: some warning fixes, cpu device task tweaks, avoid unnecessary

tonemap in non-viewport render, and some utility functions.

intern/cycles/util/util_cuda.cpp

@@ -19,6 +19,8 @@
 #include "util_cuda.h"
 #include "util_debug.h"
 #include "util_dynlib.h"
+#include "util_path.h"
+#include "util_string.h"
 
 /* function defininitions */
 
@@ -375,5 +377,17 @@ bool cuLibraryInit()
 	return result;
 }
 
+string cuCompilerPath()
+{
+		/* todo: better nvcc detection */
+#ifdef _WIN32
+	string nvcc = "C:/CUDA/bin/nvcc.exe";
+#else
+	string nvcc = "/usr/local/cuda/bin/nvcc";
+#endif
+
+	return (path_exists(nvcc))? nvcc: "";
+}
+
 CCL_NAMESPACE_END