Index: libcxx/include/atomic
===================================================================
--- libcxx/include/atomic
+++ libcxx/include/atomic
@@ -642,20 +642,22 @@
 
 } // namespace __gcc_atomic
 
+#define __cxx_atomic_is_lock_free(x) __atomic_is_lock_free(x, 0)
+
 template <typename _Tp>
-static inline
+static _LIBCPP_INLINE_VISIBILITY inline
 typename enable_if<
     __gcc_atomic::__can_assign<volatile _Atomic(_Tp)*, _Tp>::value>::type
-__c11_atomic_init(volatile _Atomic(_Tp)* __a,  _Tp __val) {
+__cxx_atomic_init(volatile _Atomic(_Tp)* __a,  _Tp __val) {
   __a->__a_value = __val;
 }
 
 template <typename _Tp>
-static inline
+static _LIBCPP_INLINE_VISIBILITY inline
 typename enable_if<
     !__gcc_atomic::__can_assign<volatile _Atomic(_Tp)*, _Tp>::value &&
      __gcc_atomic::__can_assign<         _Atomic(_Tp)*, _Tp>::value>::type
-__c11_atomic_init(volatile _Atomic(_Tp)* __a,  _Tp __val) {
+__cxx_atomic_init(volatile _Atomic(_Tp)* __a,  _Tp __val) {
   // [atomics.types.generic]p1 guarantees _Tp is trivially copyable. Because
   // the default operator= in an object is not volatile, a byte-by-byte copy
   // is required.
@@ -668,34 +670,34 @@
 }
 
 template <typename _Tp>
-static inline void __c11_atomic_init(_Atomic(_Tp)* __a,  _Tp __val) {
+static _LIBCPP_INLINE_VISIBILITY inline void __cxx_atomic_init(_Atomic(_Tp)* __a,  _Tp __val) {
   __a->__a_value = __val;
 }
 
-static inline void __c11_atomic_thread_fence(memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline void __cxx_atomic_thread_fence(memory_order __order) {
   __atomic_thread_fence(__gcc_atomic::__to_gcc_order(__order));
 }
 
-static inline void __c11_atomic_signal_fence(memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline void __cxx_atomic_signal_fence(memory_order __order) {
   __atomic_signal_fence(__gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline void __c11_atomic_store(volatile _Atomic(_Tp)* __a,  _Tp __val,
+static _LIBCPP_INLINE_VISIBILITY inline void __cxx_atomic_store(volatile _Atomic(_Tp)* __a,  _Tp __val,
                                       memory_order __order) {
-  return __atomic_store(&__a->__a_value, &__val,
-                        __gcc_atomic::__to_gcc_order(__order));
+  __atomic_store(&__a->__a_value, &__val,
+                 __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline void __c11_atomic_store(_Atomic(_Tp)* __a,  _Tp __val,
+static _LIBCPP_INLINE_VISIBILITY inline void __cxx_atomic_store(_Atomic(_Tp)* __a,  _Tp __val,
                                       memory_order __order) {
   __atomic_store(&__a->__a_value, &__val,
                  __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_load(const volatile _Atomic(_Tp)* __a,
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_load(const volatile _Atomic(_Tp)* __a,
                                     memory_order __order) {
   _Tp __ret;
   __atomic_load(&__a->__a_value, &__ret,
@@ -704,7 +706,7 @@
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_load(const _Atomic(_Tp)* __a, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_load(const _Atomic(_Tp)* __a, memory_order __order) {
   _Tp __ret;
   __atomic_load(&__a->__a_value, &__ret,
                 __gcc_atomic::__to_gcc_order(__order));
@@ -712,7 +714,7 @@
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_exchange(volatile _Atomic(_Tp)* __a,
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_exchange(volatile _Atomic(_Tp)* __a,
                                         _Tp __value, memory_order __order) {
   _Tp __ret;
   __atomic_exchange(&__a->__a_value, &__value, &__ret,
@@ -721,7 +723,7 @@
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_exchange(_Atomic(_Tp)* __a, _Tp __value,
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_exchange(_Atomic(_Tp)* __a, _Tp __value,
                                         memory_order __order) {
   _Tp __ret;
   __atomic_exchange(&__a->__a_value, &__value, &__ret,
@@ -730,7 +732,7 @@
 }
 
 template <typename _Tp>
-static inline bool __c11_atomic_compare_exchange_strong(
+static _LIBCPP_INLINE_VISIBILITY inline bool __cxx_atomic_compare_exchange_strong(
     volatile _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value,
     memory_order __success, memory_order __failure) {
   return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
@@ -740,7 +742,7 @@
 }
 
 template <typename _Tp>
-static inline bool __c11_atomic_compare_exchange_strong(
+static _LIBCPP_INLINE_VISIBILITY inline bool __cxx_atomic_compare_exchange_strong(
     _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value, memory_order __success,
     memory_order __failure) {
   return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
@@ -750,7 +752,7 @@
 }
 
 template <typename _Tp>
-static inline bool __c11_atomic_compare_exchange_weak(
+static _LIBCPP_INLINE_VISIBILITY inline bool __cxx_atomic_compare_exchange_weak(
     volatile _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value,
     memory_order __success, memory_order __failure) {
   return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
@@ -760,7 +762,7 @@
 }
 
 template <typename _Tp>
-static inline bool __c11_atomic_compare_exchange_weak(
+static _LIBCPP_INLINE_VISIBILITY inline bool __cxx_atomic_compare_exchange_weak(
     _Atomic(_Tp)* __a, _Tp* __expected, _Tp __value, memory_order __success,
     memory_order __failure) {
   return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
@@ -783,74 +785,162 @@
 struct __skip_amt<_Tp[n]> { };
 
 template <typename _Tp, typename _Td>
-static inline _Tp __c11_atomic_fetch_add(volatile _Atomic(_Tp)* __a,
-                                         _Td __delta, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_add(volatile _Atomic(_Tp)* __a,
+                           _Td __delta, memory_order __order) {
   return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp, typename _Td>
-static inline _Tp __c11_atomic_fetch_add(_Atomic(_Tp)* __a, _Td __delta,
-                                         memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_add(_Atomic(_Tp)* __a, _Td __delta,
+                           memory_order __order) {
   return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp, typename _Td>
-static inline _Tp __c11_atomic_fetch_sub(volatile _Atomic(_Tp)* __a,
-                                         _Td __delta, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_sub(volatile _Atomic(_Tp)* __a,
+                           _Td __delta, memory_order __order) {
   return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp, typename _Td>
-static inline _Tp __c11_atomic_fetch_sub(_Atomic(_Tp)* __a, _Td __delta,
-                                         memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_sub(_Atomic(_Tp)* __a, _Td __delta,
+                           memory_order __order) {
   return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_and(volatile _Atomic(_Tp)* __a,
-                                         _Tp __pattern, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_and(volatile _Atomic(_Tp)* __a,
+                           _Tp __pattern, memory_order __order) {
   return __atomic_fetch_and(&__a->__a_value, __pattern,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_and(_Atomic(_Tp)* __a,
-                                         _Tp __pattern, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_and(_Atomic(_Tp)* __a,
+                           _Tp __pattern, memory_order __order) {
   return __atomic_fetch_and(&__a->__a_value, __pattern,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_or(volatile _Atomic(_Tp)* __a,
-                                        _Tp __pattern, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_or(volatile _Atomic(_Tp)* __a,
+                          _Tp __pattern, memory_order __order) {
   return __atomic_fetch_or(&__a->__a_value, __pattern,
                            __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_or(_Atomic(_Tp)* __a, _Tp __pattern,
-                                        memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_or(_Atomic(_Tp)* __a, _Tp __pattern,
+                          memory_order __order) {
   return __atomic_fetch_or(&__a->__a_value, __pattern,
                            __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_xor(volatile _Atomic(_Tp)* __a,
-                                         _Tp __pattern, memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_xor(volatile _Atomic(_Tp)* __a,
+                           _Tp __pattern, memory_order __order) {
   return __atomic_fetch_xor(&__a->__a_value, __pattern,
                             __gcc_atomic::__to_gcc_order(__order));
 }
 
 template <typename _Tp>
-static inline _Tp __c11_atomic_fetch_xor(_Atomic(_Tp)* __a, _Tp __pattern,
-                                         memory_order __order) {
+static _LIBCPP_INLINE_VISIBILITY inline _Tp __cxx_atomic_fetch_xor(_Atomic(_Tp)* __a, _Tp __pattern,
+                           memory_order __order) {
   return __atomic_fetch_xor(&__a->__a_value, __pattern,
                             __gcc_atomic::__to_gcc_order(__order));
 }
+
+#else //_LIBCPP_HAS_GCC_ATOMIC_IMP
+
+#define __cxx_atomic_is_lock_free(x) __c11_atomic_is_lock_free(x)
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_init(_Ap __a,  _Tp __val) {
+  __c11_atomic_init(__a, __val);
+}
+
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_thread_fence(memory_order __order) {
+  __c11_atomic_thread_fence(__order);
+}
+
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_signal_fence(memory_order __order) {
+  __c11_atomic_signal_fence(__order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_store(_Ap __a,  _Tp __val, memory_order __order) {
+  __c11_atomic_store(__a, __val, __order);
+}
+
+template <typename _Ap, typename _Tp = typename remove_const<typename remove_pointer<_Ap>::type>::type>
+static _LIBCPP_INLINE_VISIBILITY inline 
+auto __cxx_atomic_load(_Ap __a, memory_order __order) 
+    -> decltype(__c11_atomic_load((_Ap)0, memory_order_relaxed)) {
+  return __c11_atomic_load(const_cast<_Tp*>(__a), __order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_exchange(_Ap __a, _Tp __value, memory_order __order) {
+  return __c11_atomic_exchange(__a, __value, __order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_strong(_Ap __a, _Tp* __expected, _Tp __value,
+                                          memory_order __success, memory_order __failure) {
+  return __c11_atomic_compare_exchange_strong(__a, __expected, __value,
+                                              __success, __failure);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_weak(_Ap __a, _Tp* __expected, _Tp __value,
+                                        memory_order __success, memory_order __failure) {
+  return __c11_atomic_compare_exchange_weak(__a, __expected, __value,
+                                              __success, __failure);
+}
+
+template <typename _Ap, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+auto __cxx_atomic_fetch_add(_Ap __a, _Td __delta, memory_order __order) 
+    -> decltype(__c11_atomic_load((_Ap)0, memory_order_relaxed)) {
+  return __c11_atomic_fetch_add(__a, __delta, __order);
+}
+
+template <typename _Ap, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+auto __cxx_atomic_fetch_sub(_Ap __a, _Td __delta, memory_order __order) 
+    -> decltype(__c11_atomic_load((_Ap)0, memory_order_relaxed)) {
+  return __c11_atomic_fetch_sub(__a, __delta, __order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_and(_Ap __a, _Tp __pattern, memory_order __order) {
+  return __c11_atomic_fetch_and(__a, __pattern, __order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_or(_Ap __a, _Tp __pattern, memory_order __order) {
+  return __c11_atomic_fetch_or(__a, __pattern, __order);
+}
+
+template <typename _Ap, typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_xor(_Ap __a, _Tp __pattern, memory_order __order) {
+  return __c11_atomic_fetch_xor(__a, __pattern, __order);
+}
+
 #endif // _LIBCPP_HAS_GCC_ATOMIC_IMP
 
 template <class _Tp>
@@ -885,91 +975,402 @@
 # define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
 #endif
 
+namespace __cxx_detail {
+#if defined(__cpp_lib_atomic_is_always_lock_free)
+    template<typename _Tp> struct __is_always_lock_free {
+        enum { __value = __atomic_always_lock_free(sizeof(_Tp), 0) }; };
+#else
+    template<typename _Tp> struct __is_always_lock_free { enum { __value = false }; };
+    template<> struct __is_always_lock_free<bool> { enum { __value = 2 == ATOMIC_BOOL_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<signed char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<unsigned char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<char16_t> { enum { __value = 2 == ATOMIC_CHAR16_T_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<char32_t> { enum { __value = 2 == ATOMIC_CHAR32_T_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<wchar_t> { enum { __value = 2 == ATOMIC_WCHAR_T_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<short> { enum { __value = 2 == ATOMIC_SHORT_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<unsigned short> { enum { __value = 2 == ATOMIC_SHORT_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<int> { enum { __value = 2 == ATOMIC_INT_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<unsigned int> { enum { __value = 2 == ATOMIC_INT_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<long> { enum { __value = 2 == ATOMIC_LONG_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<unsigned long> { enum { __value = 2 == ATOMIC_LONG_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<long long> { enum { __value = 2 == ATOMIC_LLONG_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<unsigned long long> { enum { __value = 2 == ATOMIC_LLONG_LOCK_FREE }; };
+    template<typename _Tp> struct __is_always_lock_free<_Tp*> { enum { __value = 2 == ATOMIC_POINTER_LOCK_FREE }; };
+    template<> struct __is_always_lock_free<nullptr_t> { enum { __value = 2 == ATOMIC_POINTER_LOCK_FREE }; };
+#endif
+}
+
+#ifdef LIBCXX_FREESTANDING
+
+template<typename _Tp>
+struct __cxx_locked_atomic_type {
+
+#if _GNUC_VER >= 501
+    static_assert(is_trivially_copyable<_Tp>::value,
+      "std::atomic<Tp> requires that 'Tp' be a trivially copyable type");
+#endif
+
+  _LIBCPP_INLINE_VISIBILITY
+    __cxx_locked_atomic_type() _NOEXCEPT 
+    : __a_value(), __a_lock(0) {}
+  _LIBCPP_CONSTEXPR explicit __cxx_locked_atomic_type(_Tp value) _NOEXCEPT
+    : __a_value(value), __a_lock(0) {}
+
+  _Tp __a_value;
+  mutable _Atomic(int) __a_lock;
+
+    template<typename _Function>
+    _LIBCPP_INLINE_VISIBILITY inline void reader_section(_Function && __f) const volatile {
+        while(1 == __cxx_atomic_exchange(&__a_lock, 1, memory_order_acquire));
+        __f(__a_value);
+        __cxx_atomic_store(&__a_lock, 0, memory_order_release);
+    }
+    template<typename _Function>
+    _LIBCPP_INLINE_VISIBILITY inline void reader_section(_Function && __f) const {
+        while(1 == __cxx_atomic_exchange(&__a_lock, 1, memory_order_acquire));
+        __f(__a_value);
+        __cxx_atomic_store(&__a_lock, 0, memory_order_release);
+    }
+    template<typename _Function>
+    _LIBCPP_INLINE_VISIBILITY inline void writer_section(_Function && __f) volatile {
+        while(1 == __cxx_atomic_exchange(&__a_lock, 1, memory_order_acquire));
+        __f(__a_value);
+        __cxx_atomic_store(&__a_lock, 0, memory_order_release);
+    }
+    template<typename _Function>
+    _LIBCPP_INLINE_VISIBILITY inline void writer_section(_Function && __f) {
+        while(1 == __cxx_atomic_exchange(&__a_lock, 1, memory_order_acquire));
+        __f(__a_value);
+        __cxx_atomic_store(&__a_lock, 0, memory_order_release);
+    }
+};
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_init(volatile __cxx_locked_atomic_type<_Tp>* __a,  _Tp __val) {
+  __a->__a_value = __val;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_init(__cxx_locked_atomic_type<_Tp>* __a,  _Tp __val) {
+  __a->__a_value = __val;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_store(volatile __cxx_locked_atomic_type<_Tp>* __a,  _Tp __val, 
+                        memory_order) {
+  __a->writer_section([&](_Tp volatile& __a_value){ __a_value = __val; });
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+void __cxx_atomic_store(__cxx_locked_atomic_type<_Tp>* __a,  _Tp __val,
+                        memory_order) {
+  __a->writer_section([&](_Tp & __a_value){ __a_value = __val; });
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_load(const volatile __cxx_locked_atomic_type<_Tp>* __a,
+                      memory_order) {
+  _Tp __val;
+  __a->reader_section([&](_Tp const volatile& __a_value){ __val = __a_value; });
+  return __val;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_load(const __cxx_locked_atomic_type<_Tp>* __a, memory_order) {
+  _Tp __val;
+  __a->reader_section([&](_Tp const& __a_value){ __val = __a_value; });
+  return __val;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_exchange(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                          _Tp __value, memory_order) {
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      _Tp __temp = __a_value;
+      __a_value = __value;
+      __value = __temp; 
+    });
+  return __value;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_exchange(__cxx_locked_atomic_type<_Tp>* __a, _Tp __value,
+                          memory_order) {
+  __a->writer_section([&](_Tp & __a_value){
+      _Tp __temp = __a_value;
+      __a_value = __value;
+      __value = __temp; 
+    });
+  return __value;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_strong(volatile __cxx_locked_atomic_type<_Tp>* __a, 
+                                          _Tp* __expected, _Tp __value,
+    memory_order, memory_order) {
+  bool __ret;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __ret = __a_value == *__expected;
+      if(__ret)
+        __a_value = __value;
+      else
+        *__expected = __a_value; });
+  return __ret;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_strong(__cxx_locked_atomic_type<_Tp>* __a, 
+                                          _Tp* __expected, _Tp __value,
+    memory_order, memory_order) {
+  bool __ret;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __ret = __a_value == *__expected;
+      if(__ret)
+        __a_value = __value;
+      else
+        *__expected = __a_value; });
+  return __ret;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_weak(volatile __cxx_locked_atomic_type<_Tp>* __a, 
+                                        _Tp* __expected, _Tp __value,
+    memory_order, memory_order) {
+  bool __ret;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __ret = __a_value == *__expected;
+      if(__ret)
+        __a_value = __value;
+      else
+        *__expected = __a_value; });
+  return __ret;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+bool __cxx_atomic_compare_exchange_weak(__cxx_locked_atomic_type<_Tp>* __a, 
+                                        _Tp* __expected, _Tp __value,
+    memory_order, memory_order) {
+  bool __ret;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __ret = __a_value == *__expected;
+      if(__ret)
+        __a_value = __value;
+      else
+        *__expected = __a_value; });
+  return __ret;
+}
+
+template <typename _Tp, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_add(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                           _Td __delta, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __old = __a_value;
+      __a_value += __delta; });
+  return __old;
+}
+
+template <typename _Tp, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_add(__cxx_locked_atomic_type<_Tp>* __a,
+                           _Td __delta, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __old = __a_value;
+      __a_value += __delta; });
+  return __old;
+}
+
+template <typename _Tp, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_sub(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                           _Td __delta, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __old = __a_value;
+      __a_value -= __delta; });
+  return __old;
+}
+
+template <typename _Tp, typename _Td>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_sub(__cxx_locked_atomic_type<_Tp>* __a,
+                           _Td __delta, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __old = __a_value;
+      __a_value -= __delta; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_and(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                           _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __old = __a_value;
+      __a_value &= __pattern; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_and(__cxx_locked_atomic_type<_Tp>* __a,
+                           _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __old = __a_value;
+      __a_value &= __pattern; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_or(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                          _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __old = __a_value;
+      __a_value |= __pattern; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_or(__cxx_locked_atomic_type<_Tp>* __a,
+                          _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __old = __a_value;
+      __a_value |= __pattern; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_xor(volatile __cxx_locked_atomic_type<_Tp>* __a,
+                           _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp volatile& __a_value){ 
+      __old = __a_value;
+      __a_value ^= __pattern; });
+  return __old;
+}
+
+template <typename _Tp>
+static _LIBCPP_INLINE_VISIBILITY inline 
+_Tp __cxx_atomic_fetch_xor(__cxx_locked_atomic_type<_Tp>* __a,
+                           _Tp __pattern, memory_order) {
+  _Tp __old;
+  __a->writer_section([&](_Tp & __a_value){ 
+      __old = __a_value;
+      __a_value ^= __pattern; });
+  return __old;
+}
+
+template <class _Tp>
+using __atomic_type = typename conditional<__cxx_detail::__is_always_lock_free<_Tp>::__value, 
+                                  _Atomic(_Tp), 
+                                  __cxx_locked_atomic_type<_Tp>>::type;
+#else
+template <class _Tp>
+using __atomic_type = _Atomic(_Tp);
+#endif //LIBCXX_FREESTANDING
+
 // general atomic<T>
 
 template <class _Tp, bool = is_integral<_Tp>::value && !is_same<_Tp, bool>::value>
 struct __atomic_base  // false
 {
-    mutable _Atomic(_Tp) __a_;
+    mutable __atomic_type<_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);
+  static _LIBCPP_CONSTEXPR bool is_always_lock_free = __cxx_detail::__is_always_lock_free<_Tp>::__value;
 #endif
 
     _LIBCPP_INLINE_VISIBILITY
     bool is_lock_free() const volatile _NOEXCEPT
-    {
-#if defined(_LIBCPP_HAS_C_ATOMIC_IMP)
-    return __c11_atomic_is_lock_free(sizeof(_Tp));
-#else
-    return __atomic_is_lock_free(sizeof(_Tp), 0);
-#endif
-    }
+            {return __cxx_atomic_is_lock_free(sizeof(_Tp));}
     _LIBCPP_INLINE_VISIBILITY
     bool is_lock_free() const _NOEXCEPT
         {return static_cast<__atomic_base const volatile*>(this)->is_lock_free();}
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
       _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
-        {__c11_atomic_store(&__a_, __d, __m);}
+        {__cxx_atomic_store(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
       _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
-        {__c11_atomic_store(&__a_, __d, __m);}
+        {__cxx_atomic_store(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
       _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
-        {return __c11_atomic_load(&__a_, __m);}
+        {return __cxx_atomic_load(&__a_, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const _NOEXCEPT
       _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
-        {return __c11_atomic_load(&__a_, __m);}
+        {return __cxx_atomic_load(&__a_, __m);}
     _LIBCPP_INLINE_VISIBILITY
     operator _Tp() const volatile _NOEXCEPT {return load();}
     _LIBCPP_INLINE_VISIBILITY
     operator _Tp() const _NOEXCEPT          {return load();}
     _LIBCPP_INLINE_VISIBILITY
     _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_exchange(&__a_, __d, __m);}
+        {return __cxx_atomic_exchange(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_exchange(&__a_, __d, __m);}
+        {return __cxx_atomic_exchange(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) volatile _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) volatile _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                               memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                               memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
 #ifndef _LIBCPP_CXX03_LANG
@@ -1005,40 +1406,44 @@
 {
     typedef __atomic_base<_Tp, false> __base;
     _LIBCPP_INLINE_VISIBILITY
-    __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT
+#ifndef _LIBCPP_CXX03_LANG
+    __atomic_base() _NOEXCEPT = default;
+#else
+    __atomic_base() _NOEXCEPT : __base() {}
+#endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __atomic_base(_Tp __d) _NOEXCEPT : __base(__d) {}
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_fetch_and(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_and(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_fetch_or(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_or(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_fetch_xor(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_xor(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp operator++(int) volatile _NOEXCEPT      {return fetch_add(_Tp(1));}
@@ -1086,7 +1491,11 @@
 {
     typedef __atomic_base<_Tp> __base;
     _LIBCPP_INLINE_VISIBILITY
-    atomic() _NOEXCEPT _LIBCPP_DEFAULT
+#ifndef _LIBCPP_CXX03_LANG
+    atomic() _NOEXCEPT = default;
+#else
+    atomic() _NOEXCEPT : __base() {}
+#endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR atomic(_Tp __d) _NOEXCEPT : __base(__d) {}
 
@@ -1106,7 +1515,11 @@
 {
     typedef __atomic_base<_Tp*> __base;
     _LIBCPP_INLINE_VISIBILITY
-    atomic() _NOEXCEPT _LIBCPP_DEFAULT
+#ifndef _LIBCPP_CXX03_LANG
+    atomic() _NOEXCEPT = default;
+#else
+    atomic() _NOEXCEPT : __base() {}
+#endif // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR atomic(_Tp* __d) _NOEXCEPT : __base(__d) {}
 
@@ -1120,17 +1533,17 @@
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst)
                                                                         volatile _NOEXCEPT
-        {return __c11_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst)
                                                                         volatile _NOEXCEPT
-        {return __c11_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp* operator++(int) volatile _NOEXCEPT            {return fetch_add(1);}
@@ -1183,7 +1596,7 @@
 void
 atomic_init(volatile atomic<_Tp>* __o, _Tp __d) _NOEXCEPT
 {
-    __c11_atomic_init(&__o->__a_, __d);
+    __cxx_atomic_init(&__o->__a_, __d);
 }
 
 template <class _Tp>
@@ -1191,7 +1604,7 @@
 void
 atomic_init(atomic<_Tp>* __o, _Tp __d) _NOEXCEPT
 {
-    __c11_atomic_init(&__o->__a_, __d);
+    __cxx_atomic_init(&__o->__a_, __d);
 }
 
 // atomic_store
@@ -1723,16 +2136,16 @@
 
     _LIBCPP_INLINE_VISIBILITY
     bool test_and_set(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __c11_atomic_exchange(&__a_, true, __m);}
+        {return __cxx_atomic_exchange(&__a_, true, __m);}
     _LIBCPP_INLINE_VISIBILITY
     bool test_and_set(memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __c11_atomic_exchange(&__a_, true, __m);}
+        {return __cxx_atomic_exchange(&__a_, true, __m);}
     _LIBCPP_INLINE_VISIBILITY
     void clear(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {__c11_atomic_store(&__a_, false, __m);}
+        {__cxx_atomic_store(&__a_, false, __m);}
     _LIBCPP_INLINE_VISIBILITY
     void clear(memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {__c11_atomic_store(&__a_, false, __m);}
+        {__cxx_atomic_store(&__a_, false, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
 #ifndef _LIBCPP_CXX03_LANG
@@ -1818,14 +2231,14 @@
 void
 atomic_thread_fence(memory_order __m) _NOEXCEPT
 {
-    __c11_atomic_thread_fence(__m);
+    __cxx_atomic_thread_fence(__m);
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
 void
 atomic_signal_fence(memory_order __m) _NOEXCEPT
 {
-    __c11_atomic_signal_fence(__m);
+    __cxx_atomic_signal_fence(__m);
 }
 
 // Atomics for standard typedef types