PR23833, DR2140: an lvalue-to-rvalue conversion on a glvalue of type

nullptr_t does not access memory.

We now reuse CK_NullToPointer to represent a conversion from a glvalue
of type nullptr_t to a prvalue of nullptr_t where necessary.

This reinstates r345562, reverted in r346065, now that CodeGen's
handling of non-odr-used variables has been fixed.

llvm-svn: 363337

1 files changed, 47 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/nullptr.cpp b/clang/test/CodeGenCXX/nullptr.cpp
index e93f7061bdd..823c0d7d18a 100644
--- a/clang/test/CodeGenCXX/nullptr.cpp
+++ b/clang/test/CodeGenCXX/nullptr.cpp
@@ -22,3 +22,50 @@ void g() {
 const std::type_info& f2() {
   return typeid(nullptr_t);
 }
+
+union U {
+  int n;
+  nullptr_t b;
+};
+// CHECK-LABEL: define {{.*}}pr23833_a
+// CHECK: store
+// CHECK: load
+// CHECK-NOT: load
+// CHECK: ret i1 false
+bool pr23833_a(U &u) { return u.b; }
+
+// CHECK-LABEL: define {{.*}}pr23833_b
+// CHECK: store
+// CHECK: load
+// CHECK-NOT: load
+// CHECK: ret i8* null
+nullptr_t pr23833_b(nullptr_t &n) { return n; }
+
+struct X1 { operator int*(); };
+struct X2 { operator const nullptr_t&(); };
+
+// CHECK-LABEL: define {{.*}}pr23833_c
+// CHECK: call {{.*}}X1
+// CHECK: call {{.*}}X2
+// CHECK-NOT: load
+// CHECK: ret i32
+int pr23833_c() {
+  return X1() != X2();
+}
+
+// CHECK-LABEL: define {{.*}}pr23833_d
+// CHECK: call {{.*}}X2
+// CHECK-NOT: load
+// CHECK: store
+// CHECK: load
+// CHECK: ret i32*
+int *pr23833_d() {
+  int *p = X2();
+  return p;
+}
+
+namespace PR39528 {
+  constexpr nullptr_t null = nullptr;
+  void f(nullptr_t);
+  void g() { f(null); }
+}