recommit b58f6bb120

Add a test for UsedDeclVisitor

This test is reduced from mlir/lib/Transforms/AffineDataCopyGeneration.cpp
to make sure there is no assertion due to UsedDeclVisitor.

clang/test/CodeGenCXX/used-decl-visitor.cpp

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -triple x86_64 -emit-llvm -o %t %s
+
+// Make sure there is no assertion due to UsedDeclVisitor.
+
+struct A {
+  int a;
+};
+
+static A a;
+
+struct B {
+  B(int b = a.a) {}
+};
+
+
+void foo() {
+  B();
+}