diff --git a/libcxx/include/__atomic_support b/libcxx/include/__atomic_support
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__atomic_support
@@ -0,0 +1,31 @@
+// -*- C++ -*-
+//===------------------------ __atomic_support -----------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ATOMIC_SUPPORT
+#define _LIBCPP___ATOMIC_SUPPORT
+
+#include <__config>
+
+template<typename T>
+T __libcpp_sync_add_and_fetch(T *ptr, T value) {
+  return __sync_add_and_fetch(ptr, value);
+}
+
+template<typename T>
+T __libcpp_sync_fetch_and_add(T *ptr, T value) {
+  return __sync_fetch_and_add(ptr, value);
+}
+
+template<typename T>
+T __libcpp_sync_lock_test_and_set(T *ptr, T value) {
+  return __sync_lock_test_and_set(ptr, value);
+}
+
+#endif //_LIBCPP___ATOMIC_SUPPORT
diff --git a/libcxx/include/__refstring b/libcxx/include/__refstring
--- a/libcxx/include/__refstring
+++ b/libcxx/include/__refstring
@@ -14,6 +14,7 @@
 #include <stdexcept>
 #include <cstddef>
 #include <cstring>
+#include <__atomic_support>
 #ifdef __APPLE__
 #include <dlfcn.h>
 #include <mach-o/dyld.h>
@@ -83,7 +84,7 @@
     : __imp_(s.__imp_)
 {
     if (__uses_refcount())
-        __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+        __libcpp_sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
 }
 
 inline
@@ -92,10 +93,10 @@
     struct _Rep_base *old_rep = rep_from_data(__imp_);
     __imp_ = s.__imp_;
     if (__uses_refcount())
-        __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+        __libcpp_sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
     if (adjust_old_count)
     {
-        if (__sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
+        if (__libcpp_sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
         {
             ::operator delete(old_rep);
         }
@@ -107,7 +108,7 @@
 __libcpp_refstring::~__libcpp_refstring() {
     if (__uses_refcount()) {
         _Rep_base* rep = rep_from_data(__imp_);
-        if (__sync_add_and_fetch(&rep->count, count_t(-1)) < 0) {
+        if (__libcpp_sync_add_and_fetch(&rep->count, count_t(-1)) < 0) {
             ::operator delete(rep);
         }
     }
diff --git a/libcxx/src/locale.cpp b/libcxx/src/locale.cpp
--- a/libcxx/src/locale.cpp
+++ b/libcxx/src/locale.cpp
@@ -28,6 +28,7 @@
 #define _CTYPE_DISABLE_MACROS
 #endif
 #include "cwctype"
+#include "__atomic_support"
 #include "__sso_allocator"
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
 #include "support/win32/locale_win32.h"
@@ -667,7 +668,7 @@
 void
 locale::id::__init()
 {
-    __id_ = __sync_add_and_fetch(&__next_id, 1);
+    __id_ = __libcpp_sync_add_and_fetch(&__next_id, 1);
 }
 
 // template <> class collate_byname<char>
diff --git a/libcxx/src/support/runtime/exception_fallback.ipp b/libcxx/src/support/runtime/exception_fallback.ipp
--- a/libcxx/src/support/runtime/exception_fallback.ipp
+++ b/libcxx/src/support/runtime/exception_fallback.ipp
@@ -9,6 +9,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <cstdio>
+#include <__atomic_support>
 
 namespace std {
 
@@ -20,13 +21,13 @@
 unexpected_handler
 set_unexpected(unexpected_handler func) _NOEXCEPT
 {
-  return __sync_lock_test_and_set(&__unexpected_handler, func);
+  return __libcpp_sync_lock_test_and_set(&__unexpected_handler, func);
 }
 
 unexpected_handler
 get_unexpected() _NOEXCEPT
 {
-  return __sync_fetch_and_add(&__unexpected_handler, (unexpected_handler)0);
+  return __libcpp_sync_fetch_and_add(&__unexpected_handler, (unexpected_handler)0);
 
 }
 
@@ -41,14 +42,13 @@
 terminate_handler
 set_terminate(terminate_handler func) _NOEXCEPT
 {
-  return __sync_lock_test_and_set(&__terminate_handler, func);
+  return __libcpp_sync_lock_test_and_set(&__terminate_handler, func);
 }
 
 terminate_handler
 get_terminate() _NOEXCEPT
 {
-  return __sync_fetch_and_add(&__terminate_handler, (terminate_handler)0);
-
+  return __libcpp_sync_fetch_and_add(&__terminate_handler, (terminate_handler)0);
 }
 
 #ifndef __EMSCRIPTEN__ // We provide this in JS
diff --git a/libcxx/src/support/runtime/new_handler_fallback.ipp b/libcxx/src/support/runtime/new_handler_fallback.ipp
--- a/libcxx/src/support/runtime/new_handler_fallback.ipp
+++ b/libcxx/src/support/runtime/new_handler_fallback.ipp
@@ -8,6 +8,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <__atomic_support>
+
 namespace std {
 
 _LIBCPP_SAFE_STATIC static std::new_handler __new_handler;
@@ -15,13 +17,13 @@
 new_handler
 set_new_handler(new_handler handler) _NOEXCEPT
 {
-    return __sync_lock_test_and_set(&__new_handler, handler);
+    return __libcpp_sync_lock_test_and_set(&__new_handler, handler);
 }
 
 new_handler
 get_new_handler() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__new_handler, nullptr);
+    return __libcpp_sync_fetch_and_add<new_handler>(&__new_handler, nullptr);
 }
 
 } // namespace std