[TBAA] Add test showing tbaa.struct being generated with relaxed-alias.

Add test showing that tbaa.struct is generated when using TSan with
relaxed-aliasing.

(cherry-picked from 167b90d)

Author: fhahn

clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp

@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm -o - -O1 -relaxed-aliasing -fsanitize=thread -disable-llvm-optzns %s | \
+// RUN:     FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -new-struct-path-tbaa \
+// RUN:     -emit-llvm -o - -O1 -relaxed-aliasing -fsanitize=thread -disable-llvm-optzns %s | \
+// RUN:     FileCheck %s
+//
+// Check that we do not create tbaa for instructions generated for copies.
+// FIXME: !tbaa.struct is generated with null node as tag.
+
+// CHECK: !tbaa.struct
+// CHECK-NOT: !tbaa
+
+struct A {
+  short s;
+  int i;
+  char c;
+  int j;
+};
+
+void copyStruct(A *a1, A *a2) {
+  *a1 = *a2;
+}
+
+void copyInt(int *a, int *b) {
+  *a = *b;
+}