Index: include/clang/Basic/BuiltinsAArch64.def
===================================================================
--- include/clang/Basic/BuiltinsAArch64.def
+++ include/clang/Basic/BuiltinsAArch64.def
@@ -104,6 +104,7 @@
 TARGET_HEADER_BUILTIN(_InterlockedXor64,         "LLiLLiD*LLi", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
 
 TARGET_HEADER_BUILTIN(_ReadWriteBarrier, "v", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
+TARGET_HEADER_BUILTIN(__getReg, "ULLii", "nh", "intrin.h", ALL_MS_LANGUAGES, "")
 
 #undef BUILTIN
 #undef LANGBUILTIN
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -6582,6 +6582,30 @@
     return Builder.CreateCall(F, {StoreVal, StoreAddr}, "stxr");
   }
 
+  if (BuiltinID == AArch64::BI__getReg) {
+    APSInt Value;
+    if (!E->getArg(0)->EvaluateAsInt(Value, CGM.getContext()))
+      CGM.Error(E->getArg(0)->getBeginLoc(),
+                "__getReg expects a constant input parameter");
+
+    if (Value < 0 || Value > 31)
+      CGM.Error(E->getArg(0)->getBeginLoc(),
+                "__getReg expects an input parameter between 0 and 31");
+
+    LLVMContext &Context = CGM.getLLVMContext();
+    SmallString<8> StrVal;
+    Value.toString(StrVal);
+    std::string Reg = "x" + std::string(StrVal.c_str());
+
+    llvm::Metadata *Ops[] = {llvm::MDString::get(Context, Reg)};
+    llvm::MDNode *RegName = llvm::MDNode::get(Context, Ops);
+    llvm::Value *Metadata = llvm::MetadataAsValue::get(Context, RegName);
+
+    llvm::Value *F =
+        CGM.getIntrinsic(llvm::Intrinsic::read_register, {Int64Ty});
+    return Builder.CreateCall(F, Metadata);
+  }
+
   if (BuiltinID == AArch64::BI__builtin_arm_clrex) {
     Function *F = CGM.getIntrinsic(Intrinsic::aarch64_clrex);
     return Builder.CreateCall(F);
Index: lib/Headers/intrin.h
===================================================================
--- lib/Headers/intrin.h
+++ lib/Headers/intrin.h
@@ -865,6 +865,13 @@
 #endif
 
 /*----------------------------------------------------------------------------*\
+|* MS AArch64 specific
+\*----------------------------------------------------------------------------*/
+#if defined(__aarch64__)
+unsigned __int64 __getReg(int);
+#endif
+
+/*----------------------------------------------------------------------------*\
 |* Privileged intrinsics
 \*----------------------------------------------------------------------------*/
 #if defined(__i386__) || defined(__x86_64__)
Index: test/CodeGen/arm64-microsoft-intrinsics.c
===================================================================
--- test/CodeGen/arm64-microsoft-intrinsics.c
+++ test/CodeGen/arm64-microsoft-intrinsics.c
@@ -66,3 +66,42 @@
 
 // CHECK-MSVC: fence syncscope("singlethread")
 // CHECK-LINUX: error: implicit declaration of function '_ReadWriteBarrier'
+
+unsigned __int64 check_getReg() {
+  unsigned volatile __int64 reg;
+  reg = __getReg(0);
+  reg = __getReg(1);
+  reg = __getReg(2);
+  reg = __getReg(3);
+  reg = __getReg(4);
+  reg = __getReg(5);
+  reg = __getReg(6);
+  reg = __getReg(7);
+  reg = __getReg(8);
+  reg = __getReg(9);
+  reg = __getReg(10);
+  reg = __getReg(11);
+  reg = __getReg(12);
+  reg = __getReg(13);
+  reg = __getReg(14);
+  reg = __getReg(15);
+  reg = __getReg(16);
+  reg = __getReg(17);
+  reg = __getReg(18);
+  reg = __getReg(19);
+  reg = __getReg(20);
+  reg = __getReg(21);
+  reg = __getReg(22);
+  reg = __getReg(23);
+  reg = __getReg(24);
+  reg = __getReg(25);
+  reg = __getReg(26);
+  reg = __getReg(27);
+  reg = __getReg(28);
+  reg = __getReg(29);
+  reg = __getReg(30);
+  reg = __getReg(31);
+  return reg;
+}
+
+// CHECK-MSVC: llvm.read_register.i64