Index: cfe/trunk/include/clang/Basic/BuiltinsAArch64.def
===================================================================
--- cfe/trunk/include/clang/Basic/BuiltinsAArch64.def
+++ cfe/trunk/include/clang/Basic/BuiltinsAArch64.def
@@ -103,6 +103,8 @@
 TARGET_HEADER_BUILTIN(_InterlockedOr64,          "LLiLLiD*LLi", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
 TARGET_HEADER_BUILTIN(_InterlockedXor64,         "LLiLLiD*LLi", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
 
+TARGET_HEADER_BUILTIN(_ReadWriteBarrier, "v", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
+
 #undef BUILTIN
 #undef LANGBUILTIN
 #undef TARGET_HEADER_BUILTIN
Index: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGBuiltin.cpp
+++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp
@@ -6581,6 +6581,10 @@
     return Builder.CreateCall(F);
   }
 
+  if (BuiltinID == AArch64::BI_ReadWriteBarrier)
+    return Builder.CreateFence(llvm::AtomicOrdering::SequentiallyConsistent,
+                               llvm::SyncScope::SingleThread);
+
   // CRC32
   Intrinsic::ID CRCIntrinsicID = Intrinsic::not_intrinsic;
   switch (BuiltinID) {
Index: cfe/trunk/test/CodeGen/arm64-microsoft-intrinsics.c
===================================================================
--- cfe/trunk/test/CodeGen/arm64-microsoft-intrinsics.c
+++ cfe/trunk/test/CodeGen/arm64-microsoft-intrinsics.c
@@ -59,3 +59,10 @@
 
 // CHECK-MSVC: @llvm.aarch64.hint(i32 5)
 // CHECK-LINUX: error: implicit declaration of function '__sevl'
+
+void check_ReadWriteBarrier() {
+  _ReadWriteBarrier();
+}
+
+// CHECK-MSVC: fence syncscope("singlethread")
+// CHECK-LINUX: error: implicit declaration of function '_ReadWriteBarrier'