Index: include/new
===================================================================
--- include/new
+++ include/new
@@ -46,6 +46,8 @@
 new_handler set_new_handler(new_handler new_p) noexcept;
 new_handler get_new_handler() noexcept;
 
+// 21.6.4, pointer optimization barrier
+template <class T> constexpr T* launder(T* p) noexcept; // C++17
 }  // std
 
 void* operator new(std::size_t size);                                   // replaceable
@@ -166,6 +168,11 @@
 #endif
 #endif
 
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp* launder(_Tp* __p) noexcept { return __p;}
+#endif
 }  // std
 
 #if defined(_LIBCPP_CXX03_LANG)
Index: test/std/language.support/support.dynamic/ptr.launder/launder.fail.cpp
===================================================================
--- test/std/language.support/support.dynamic/ptr.launder/launder.fail.cpp
+++ test/std/language.support/support.dynamic/ptr.launder/launder.fail.cpp
@@ -0,0 +1,27 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <new>
+
+// template <class T> constexpr T* launder(T* p) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <new>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main ()
+{
+    int *p = nullptr;
+    std::launder(p);  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}
Index: test/std/language.support/support.dynamic/ptr.launder/launder.pass.cpp
===================================================================
--- test/std/language.support/support.dynamic/ptr.launder/launder.pass.cpp
+++ test/std/language.support/support.dynamic/ptr.launder/launder.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <new>
+
+// template <class T> constexpr T* launder(T* p) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+#include <new>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr int gi = 5;
+constexpr float gf = 8.f;
+
+int main() {
+	static_assert(std::launder(&gi) == &gi, "" );
+	static_assert(std::launder(&gf) == &gf, "" );
+
+  	const int *i = &gi;
+  	const float *f = &gf;
+    static_assert(std::is_same<decltype(i), decltype(std::launder(i))>::value, "");
+    static_assert(std::is_same<decltype(f), decltype(std::launder(f))>::value, "");
+
+	assert(std::launder(i) == i);
+	assert(std::launder(f) == f);
+}
Index: www/cxx1z_status.html
===================================================================
--- www/cxx1z_status.html
+++ www/cxx1z_status.html
@@ -104,6 +104,7 @@
 	<tr><td><a href="https://wg21.link/p0083r3">p0083r3</a></td><td>LWG</td><td>Splicing Maps and Sets</td><td>Oulu</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/p0084r2">p0084r2</a></td><td>LWG</td><td>Emplace Return Type</td><td>Oulu</td><td>Complete</td><td>4.0</td></tr>
 	<tr><td><a href="https://wg21.link/p0088r3">p0088r3</a></td><td>LWG</td><td>Variant: a type-safe union for C++17</td><td>Oulu</td><td>Complete</td><td>4.0</td></tr>
+	<tr><td><a href="https://wg21.link/p0137r1">p0137r1</a></td><td>CWG</td><td>Core Issue 1776: Replacement of class objects containing reference members</td><td>Oulu</td><td>Complete</td><td>6.0</td></tr>
 	<tr><td><a href="https://wg21.link/p0163r0">p0163r0</a></td><td>LWG</td><td>shared_ptr::weak_type</td><td>Oulu</td><td>Complete</td><td>3.9</td></tr>
 	<tr><td><a href="https://wg21.link/p0174r2">p0174r2</a></td><td>LWG</td><td>Deprecating Vestigial Library Parts in C++17</td><td>Oulu</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/p0175r1">p0175r1</a></td><td>LWG</td><td>Synopses for the C library</td><td>Oulu</td><td></td><td></td></tr>