Add a __builtin_addressof that performs the same functionality as the built-in
& operator (ignoring any overloaded operator& for the type). The purpose of
this builtin is for use in std::addressof, to allow it to be made constexpr;
the existing implementation technique (reinterpret_cast to some reference type,
take address, reinterpert_cast back) does not permit this because
reinterpret_cast between reference types is not permitted in a constant
expression in C++11 onwards.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186053 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst
index d7f46b5..bfc5feb 100644
--- a/docs/LanguageExtensions.rst
+++ b/docs/LanguageExtensions.rst
@@ -1533,6 +1533,22 @@
implementation details of ``__sync_lock_test_and_set()``. The
``__sync_swap()`` builtin is a full barrier.
+``__builtin_addressof``
+-----------------------
+
+``__builtin_addressof`` performs the functionality of the built-in ``&``
+operator, ignoring any ``operator&`` overload. This is useful in constant
+expressions in C++11, where there is no other way to take the address of an
+object that overloads ``operator&``.
+
+**Example of use**:
+
+.. code-block:: c++
+
+ template<typename T> constexpr T *addressof(T &value) {
+ return __builtin_addressof(value);
+ }
+
Multiprecision Arithmetic Builtins
----------------------------------