Unrevert r147271, reverted in r147361.

Also temporarily remove the assumption from IR gen that we can emit IR for every
constant we can fold, since it isn't currently true in C++11, to fix PR11676.

Original comment from r147271:

constexpr: perform zero-initialization prior to / instead of performing a
constructor call when appropriate. Thanks to Eli for spotting this.

llvm-svn: 147384

1 files changed, 31 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/constexpr-value-init.cpp b/clang/test/SemaCXX/constexpr-value-init.cpp
new file mode 100644
index 00000000000..efa9e94da12
--- /dev/null
+++ b/clang/test/SemaCXX/constexpr-value-init.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 %s -std=c++11 -fsyntax-only -verify
+
+struct A {
+  constexpr A() : a(b + 1), b(a + 1) {} // expected-note {{uninitialized}}
+  int a;
+  int b;
+};
+struct B {
+  A a;
+};
+
+constexpr A a; // ok, zero initialization preceeds static initialization
+void f() {
+  constexpr A a; // expected-error {{constant expression}} expected-note {{in call to 'A()'}}
+}
+
+constexpr B b1; // expected-error {{requires a user-provided default constructor}}
+constexpr B b2 = B(); // ok
+static_assert(b2.a.a == 1, "");
+static_assert(b2.a.b == 2, "");
+
+struct C {
+  int c;
+};
+struct D : C { int d; };
+constexpr C c1; // expected-error {{requires a user-provided default constructor}}
+constexpr C c2 = C(); // ok
+constexpr D d1; // expected-error {{requires a user-provided default constructor}}
+constexpr D d2 = D(); // expected-error {{constant expression}} expected-note {{non-literal type 'const D'}}
+static_assert(D().c == 0, "");
+static_assert(D().d == 0, "");