Add compiler test.

Author: hvdijk

clang/test/CodeGen/callingconv-native_cpu.cpp

@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -triple native_cpu -aux-triple x86_64-unknown-linux-gnu -fsycl-is-device -emit-llvm -o - %s | FileCheck %s
+
+struct S {
+  char c;
+  short s;
+};
+using short16 = short __attribute__((ext_vector_type(16)));
+
+__attribute__((sycl_device))
+S foo(short16, S);
+
+__attribute__((sycl_device, libclc_call))
+S bar(short16, S);
+
+// CHECK: define noundef <16 x i16> @_Z3bazRDv16_sR1S(ptr noundef nonnull align 32 dereferenceable(32) %x, ptr noundef nonnull align 2 dereferenceable(4) %y)
+__attribute__((sycl_device))
+short16 baz(short16 &x, S &y) {
+  // Host ABI:
+  //   short16 argument is passed by reference.
+  //   S is passed by value.
+  //   S is returned by value.
+  // CHECK: call i32 @_Z3fooDv16_s1S(ptr noundef byval(<16 x i16>) align 32 {{%.*}}, i32 {{%.*}})
+  y = foo(x, y);
+  // Libclc ABI:
+  //   short16 is passed by value.
+  //   S is passed by reference.
+  //   S is returned by reference.
+  // CHECK: call void @_Z3barDv16_s1S(ptr dead_on_unwind writable sret(%struct.S) align 2 {{%.*}}, <16 x i16> noundef {{%.*}}, ptr noundef byval(%struct.S) align 2 {{%.*}})
+  y = bar(x, y);
+  return x;
+}