Make std::get constexpr

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@186525 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__tuple b/include/__tuple
index 1213262..9a6b6e0 100644
--- a/include/__tuple
+++ b/include/__tuple
@@ -79,47 +79,47 @@
 template <class _Tp, size_t _Size> struct __tuple_like<array<_Tp, _Size> > : true_type {};
 
 template <size_t _Ip, class ..._Tp>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(tuple<_Tp...>&) _NOEXCEPT;
 
 template <size_t _Ip, class ..._Tp>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(const tuple<_Tp...>&) _NOEXCEPT;
 
 template <size_t _Ip, class ..._Tp>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, tuple<_Tp...> >::type&&
 get(tuple<_Tp...>&&) _NOEXCEPT;
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(pair<_T1, _T2>&) _NOEXCEPT;
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(const pair<_T1, _T2>&) _NOEXCEPT;
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
 get(pair<_T1, _T2>&&) _NOEXCEPT;
 
 template <size_t _Ip, class _Tp, size_t _Size>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _Tp&
 get(array<_Tp, _Size>&) _NOEXCEPT;
 
 template <size_t _Ip, class _Tp, size_t _Size>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const _Tp&
 get(const array<_Tp, _Size>&) _NOEXCEPT;
 
 template <size_t _Ip, class _Tp, size_t _Size>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _Tp&&
 get(array<_Tp, _Size>&&) _NOEXCEPT;