Index: include/atomic
===================================================================
--- include/atomic
+++ include/atomic
@@ -89,6 +89,7 @@
 template <class T>
 struct atomic
 {
+    static constexpr bool is_always_lock_free;
     bool is_lock_free() const volatile noexcept;
     bool is_lock_free() const noexcept;
     void store(T desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -127,6 +128,7 @@
 template <>
 struct atomic<integral>
 {
+    static constexpr bool is_always_lock_free;
     bool is_lock_free() const volatile noexcept;
     bool is_lock_free() const noexcept;
     void store(integral desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -202,6 +204,7 @@
 template <class T>
 struct atomic<T*>
 {
+    static constexpr bool is_always_lock_free;
     bool is_lock_free() const volatile noexcept;
     bool is_lock_free() const noexcept;
     void store(T* desr, memory_order m = memory_order_seq_cst) volatile noexcept;
@@ -825,6 +828,17 @@
     return __y;
 }
 
+#define ATOMIC_BOOL_LOCK_FREE      __GCC_ATOMIC_BOOL_LOCK_FREE
+#define ATOMIC_CHAR_LOCK_FREE      __GCC_ATOMIC_CHAR_LOCK_FREE
+#define ATOMIC_CHAR16_T_LOCK_FREE  __GCC_ATOMIC_CHAR16_T_LOCK_FREE
+#define ATOMIC_CHAR32_T_LOCK_FREE  __GCC_ATOMIC_CHAR32_T_LOCK_FREE
+#define ATOMIC_WCHAR_T_LOCK_FREE   __GCC_ATOMIC_WCHAR_T_LOCK_FREE
+#define ATOMIC_SHORT_LOCK_FREE     __GCC_ATOMIC_SHORT_LOCK_FREE
+#define ATOMIC_INT_LOCK_FREE       __GCC_ATOMIC_INT_LOCK_FREE
+#define ATOMIC_LONG_LOCK_FREE      __GCC_ATOMIC_LONG_LOCK_FREE
+#define ATOMIC_LLONG_LOCK_FREE     __GCC_ATOMIC_LLONG_LOCK_FREE
+#define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
+
 // general atomic<T>
 
 template <class _Tp, bool = is_integral<_Tp>::value && !is_same<_Tp, bool>::value>
@@ -832,6 +846,10 @@
 {
     mutable _Atomic(_Tp) __a_;
 
+#if defined(__cpp_lib_atomic_is_always_lock_free)
+  static _LIBCPP_CONSTEXPR bool is_always_lock_free = __atomic_always_lock_free(sizeof(__a_), 0);
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
     bool is_lock_free() const volatile _NOEXCEPT
     {
@@ -1789,17 +1807,6 @@
 #define ATOMIC_FLAG_INIT {false}
 #define ATOMIC_VAR_INIT(__v) {__v}
 
-#define ATOMIC_BOOL_LOCK_FREE      __GCC_ATOMIC_BOOL_LOCK_FREE
-#define ATOMIC_CHAR_LOCK_FREE      __GCC_ATOMIC_CHAR_LOCK_FREE
-#define ATOMIC_CHAR16_T_LOCK_FREE  __GCC_ATOMIC_CHAR16_T_LOCK_FREE
-#define ATOMIC_CHAR32_T_LOCK_FREE  __GCC_ATOMIC_CHAR32_T_LOCK_FREE
-#define ATOMIC_WCHAR_T_LOCK_FREE   __GCC_ATOMIC_WCHAR_T_LOCK_FREE
-#define ATOMIC_SHORT_LOCK_FREE     __GCC_ATOMIC_SHORT_LOCK_FREE
-#define ATOMIC_INT_LOCK_FREE       __GCC_ATOMIC_INT_LOCK_FREE
-#define ATOMIC_LONG_LOCK_FREE      __GCC_ATOMIC_LONG_LOCK_FREE
-#define ATOMIC_LLONG_LOCK_FREE     __GCC_ATOMIC_LLONG_LOCK_FREE
-#define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_ATOMIC
Index: test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
===================================================================
--- /dev/null
+++ test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads, c++98, c++03, c++11, c++14
+
+// <atomic>
+
+// static constexpr bool is_always_lock_free;
+
+#include <atomic>
+#include <cassert>
+
+template <typename T> void checkAlwaysLockFree() {
+  if (std::atomic<T>::is_always_lock_free)
+    assert(std::atomic<T>().is_lock_free());
+}
+
+int main()
+{
+// structs and unions can't be defined in the template invocation.
+// Work around this with a typedef.
+#define CHECK_ALWAYS_LOCK_FREE(T)                                              \
+  do {                                                                         \
+    typedef T type;                                                            \
+    checkAlwaysLockFree<type>();                                               \
+  } while (0)
+
+    CHECK_ALWAYS_LOCK_FREE(bool);
+    CHECK_ALWAYS_LOCK_FREE(char);
+    CHECK_ALWAYS_LOCK_FREE(signed char);
+    CHECK_ALWAYS_LOCK_FREE(unsigned char);
+    CHECK_ALWAYS_LOCK_FREE(char16_t);
+    CHECK_ALWAYS_LOCK_FREE(char32_t);
+    CHECK_ALWAYS_LOCK_FREE(wchar_t);
+    CHECK_ALWAYS_LOCK_FREE(short);
+    CHECK_ALWAYS_LOCK_FREE(unsigned short);
+    CHECK_ALWAYS_LOCK_FREE(int);
+    CHECK_ALWAYS_LOCK_FREE(unsigned int);
+    CHECK_ALWAYS_LOCK_FREE(long);
+    CHECK_ALWAYS_LOCK_FREE(unsigned long);
+    CHECK_ALWAYS_LOCK_FREE(long long);
+    CHECK_ALWAYS_LOCK_FREE(unsigned long long);
+    CHECK_ALWAYS_LOCK_FREE(std::nullptr_t);
+    CHECK_ALWAYS_LOCK_FREE(void*);
+    CHECK_ALWAYS_LOCK_FREE(float);
+    CHECK_ALWAYS_LOCK_FREE(double);
+    CHECK_ALWAYS_LOCK_FREE(long double);
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(1 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(2 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(4 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(16 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(int __attribute__((vector_size(32 * sizeof(int)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(1 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(2 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(4 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(16 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(float __attribute__((vector_size(32 * sizeof(float)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(1 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(2 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(4 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(16 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(double __attribute__((vector_size(32 * sizeof(double)))));
+    CHECK_ALWAYS_LOCK_FREE(struct{});
+    CHECK_ALWAYS_LOCK_FREE(struct{ int i; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ int i[2]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[2]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[4]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[8]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ long long int i[16]; });
+    CHECK_ALWAYS_LOCK_FREE(struct{ char c; /* padding */ long long int i; });
+    CHECK_ALWAYS_LOCK_FREE(union{ int i; float f; });
+
+    // C macro and static constexpr must be consistent.
+    static_assert(std::atomic<bool>::is_always_lock_free == (2 == ATOMIC_BOOL_LOCK_FREE));
+    static_assert(std::atomic<char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<signed char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<unsigned char>::is_always_lock_free == (2 == ATOMIC_CHAR_LOCK_FREE));
+    static_assert(std::atomic<char16_t>::is_always_lock_free == (2 == ATOMIC_CHAR16_T_LOCK_FREE));
+    static_assert(std::atomic<char32_t>::is_always_lock_free == (2 == ATOMIC_CHAR32_T_LOCK_FREE));
+    static_assert(std::atomic<wchar_t>::is_always_lock_free == (2 == ATOMIC_WCHAR_T_LOCK_FREE));
+    static_assert(std::atomic<short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE));
+    static_assert(std::atomic<unsigned short>::is_always_lock_free == (2 == ATOMIC_SHORT_LOCK_FREE));
+    static_assert(std::atomic<int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE));
+    static_assert(std::atomic<unsigned int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE));
+    static_assert(std::atomic<long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE));
+    static_assert(std::atomic<unsigned long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE));
+    static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE));
+    static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE));
+    static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
+    static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
+}