Add OpenCL error that a kernel function must have void return type. Includes a test case.

llvm-svn: 173963
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index c94bf5f..24dffc0 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -6227,7 +6227,14 @@
       Diag(D.getIdentifierLoc(), diag::err_static_kernel);
       D.setInvalidType();
     }
-
+    
+    // OpenCL v1.2, s6.9 -- Kernels can only have return type void.
+    if (!NewFD->getResultType()->isVoidType()) {
+      Diag(D.getIdentifierLoc(),
+           diag::err_expected_kernel_void_return_type);
+      D.setInvalidType();
+    }
+    
     for (FunctionDecl::param_iterator PI = NewFD->param_begin(),
          PE = NewFD->param_end(); PI != PE; ++PI) {
       ParmVarDecl *Param = *PI;