[OpenCL] Add test for atomic pointers.

[Anastasia]

Sorry for delay... Does this test anything OpenCL specific? As far as I remember we don't have any changes to PointerType with an atomic pointee type.

[Fznamznon]

Yes, we don't have anything OpenCL specific for atomic pointers.
But we have OpenCL specific in pointers and atomics separately and we have address spaces.
Why not to test all at once?

[Anastasia]

In D42844#1004663, @Fznamznon wrote:

Yes, we don't have anything OpenCL specific for atomic pointers.
But we have OpenCL specific in pointers and atomics separately and we have address spaces.
Why not to test all at once?

We don't typically do integration testing in Clang to keep the runtime of tests within reasonable bounds. Even though this test is quite small I would say if it doesn't increase our code coverage (test a program path which is not tested yet) I wouldn't be so keen to add it. As for the pointer type implementation I don't think this test is testing any new behavior to what we already cover by C pointer tests. I don't remember any special rule in OpenCL wrt operations on either atomics or local pointers.

test/SemaOpenCL/atomic-ptr.cl

+// RUN: %clang_cc1 -O0 -cl-std=CL2.0 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+void __kernel test_atomic_ptrs(void){
+  // Null assignment to atomic pointer is legal
+  local atomic_int *p1 = 0;
+
+  // Array aliasing is permitted
+  local atomic_int a[16];
+  local atomic_int *p2 = a;
+
+  // Test pointer arithmetics
+  local atomic_int *p3 = p1 + 1;
+
+  // Test implicit cast to pointer
+  local atomic_int *p4 = a + 1;
+}