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 r363337, reverted in r363352.

llvm-svn: 363429

3 files changed, 59 insertions, 10 deletions

diff --git a/clang/test/Analysis/nullptr.cpp b/clang/test/Analysis/nullptr.cpp
index 38e099b7fbd..e9b975c148a 100644
--- a/clang/test/Analysis/nullptr.cpp
+++ b/clang/test/Analysis/nullptr.cpp
@@ -128,18 +128,10 @@ void shouldNotCrash() {
   decltype(nullptr) p; // expected-note{{'p' declared without an initial value}}
   if (getSymbol()) // expected-note   {{Assuming the condition is false}}
                    // expected-note@-1{{Taking false branch}}
-                   // expected-note@-2{{Assuming the condition is false}}
-                   // expected-note@-3{{Taking false branch}}
-                   // expected-note@-4{{Assuming the condition is true}}
-                   // expected-note@-5{{Taking true branch}}
-    invokeF(p); // expected-warning{{1st function call argument is an uninitialized value}}
-                // expected-note@-1{{1st function call argument is an uninitialized value}}
-  if (getSymbol()) // expected-note   {{Assuming the condition is false}}
-                   // expected-note@-1{{Taking false branch}}
                    // expected-note@-2{{Assuming the condition is true}}
                    // expected-note@-3{{Taking true branch}}
-    invokeF(nullptr); // expected-note   {{Calling 'invokeF'}}
-                      // expected-note@-1{{Passing null pointer value via 1st parameter 'x'}}
+    invokeF(p);    // expected-note   {{Calling 'invokeF'}}
+                   // expected-note@-1{{Passing null pointer value via 1st parameter 'x'}}
   if (getSymbol()) {  // expected-note  {{Assuming the condition is true}}
                       // expected-note@-1{{Taking true branch}}
     X *xx = Type().x; // expected-note   {{Null pointer value stored to field 'x'}}
diff --git a/clang/test/CXX/drs/dr21xx.cpp b/clang/test/CXX/drs/dr21xx.cpp
index 83c59d01202..7f76440de2e 100644
--- a/clang/test/CXX/drs/dr21xx.cpp
+++ b/clang/test/CXX/drs/dr21xx.cpp
@@ -32,6 +32,16 @@ namespace dr2120 { // dr2120: 7
   static_assert(!__is_standard_layout(E), "");
 }
 
+namespace dr2140 { // dr2140: 9
+#if __cplusplus >= 201103L
+  union U { int a; decltype(nullptr) b; };
+  constexpr int *test(U u) {
+    return u.b;
+  }
+  static_assert(!test({123}), "u.b should be valid even when b is inactive");
+#endif
+}
+
 namespace dr2170 { // dr2170: 9
 #if __cplusplus >= 201103L
   void f() {
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); }
+}