Index: include/clang/Basic/TargetInfo.h
===================================================================
--- include/clang/Basic/TargetInfo.h
+++ include/clang/Basic/TargetInfo.h
@@ -1223,7 +1223,7 @@
   enum CallingConvKind {
     CCK_Default,
     CCK_ClangABI4OrPS4,
-    CCK_MicrosoftX86_64
+    CCK_MicrosoftWin64
   };
 
   virtual CallingConvKind getCallingConvKind(bool ClangABICompat4) const;
Index: lib/Basic/Targets/AArch64.h
===================================================================
--- lib/Basic/Targets/AArch64.h
+++ lib/Basic/Targets/AArch64.h
@@ -126,6 +126,8 @@
                               MacroBuilder &Builder) const;
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override;
+  TargetInfo::CallingConvKind
+  getCallingConvKind(bool ClangABICompat4) const override;
 };
 
 // ARM64 MinGW target
Index: lib/Basic/Targets/AArch64.cpp
===================================================================
--- lib/Basic/Targets/AArch64.cpp
+++ lib/Basic/Targets/AArch64.cpp
@@ -533,6 +533,11 @@
   getVisualStudioDefines(Opts, Builder);
 }
 
+TargetInfo::CallingConvKind
+MicrosoftARM64TargetInfo::getCallingConvKind(bool ClangABICompat4) const {
+  return CCK_MicrosoftWin64;
+}
+
 MinGWARM64TargetInfo::MinGWARM64TargetInfo(const llvm::Triple &Triple,
                                            const TargetOptions &Opts)
     : WindowsARM64TargetInfo(Triple, Opts) {
Index: lib/Basic/Targets/X86.h
===================================================================
--- lib/Basic/Targets/X86.h
+++ lib/Basic/Targets/X86.h
@@ -752,7 +752,7 @@
 
   TargetInfo::CallingConvKind
   getCallingConvKind(bool ClangABICompat4) const override {
-    return CCK_MicrosoftX86_64;
+    return CCK_MicrosoftWin64;
   }
 };
 
Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -827,6 +827,7 @@
     return RAA_Default;
 
   case llvm::Triple::x86_64:
+  case llvm::Triple::aarch64:
     return !canCopyArgument(RD) ? RAA_Indirect : RAA_Default;
   }
 
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -5831,7 +5831,7 @@
     return !D->hasNonTrivialDestructorForCall() &&
            !D->hasNonTrivialCopyConstructorForCall();
 
-  if (CCK == TargetInfo::CCK_MicrosoftX86_64) {
+  if (CCK == TargetInfo::CCK_MicrosoftWin64) {
     bool CopyCtorIsTrivial = false, CopyCtorIsTrivialForCall = false;
     bool DtorIsTrivialForCall = false;
 
Index: test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
===================================================================
--- test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
+++ test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
@@ -2,6 +2,7 @@
 // RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple=i386-pc-win32 -mconstructor-aliases -fno-rtti | FileCheck -check-prefix WIN32 %s
 // RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple=thumb-pc-win32 -mconstructor-aliases -fno-rtti | FileCheck -check-prefix WOA %s
 // RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple=x86_64-pc-win32 -mconstructor-aliases -fno-rtti | FileCheck -check-prefix WIN64 %s
+// RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple=aarch64-windows-msvc -mconstructor-aliases -fno-rtti | FileCheck -check-prefix WOA64 %s
 
 struct Empty {};
 
@@ -163,6 +164,9 @@
 // WIN64: define dso_local void @"?small_arg_with_dtor@@YAXUSmallWithDtor@@@Z"(i32 %s.coerce) {{.*}} {
 // WIN64:   call void @"??1SmallWithDtor@@QEAA@XZ"
 // WIN64: }
+// WOA64: define dso_local void @"?small_arg_with_dtor@@YAXUSmallWithDtor@@@Z"(i64 %s.coerce) {{.*}} {
+// WOA64:   call void @"??1SmallWithDtor@@QEAA@XZ"
+// WOA64: }
 
 // FIXME: MSVC incompatible!
 // WOA: define dso_local arm_aapcs_vfpcc void @"?small_arg_with_dtor@@YAXUSmallWithDtor@@@Z"(%struct.SmallWithDtor* %s) {{.*}} {
@@ -227,12 +231,14 @@
 // LINUX-LABEL: define void @_Z22small_arg_with_vftable16SmallWithVftable(%struct.SmallWithVftable* %s)
 // WIN32: define dso_local void @"?small_arg_with_vftable@@YAXUSmallWithVftable@@@Z"(<{ %struct.SmallWithVftable }>* inalloca)
 // WIN64: define dso_local void @"?small_arg_with_vftable@@YAXUSmallWithVftable@@@Z"(%struct.SmallWithVftable* %s)
+// WOA64: define dso_local void @"?small_arg_with_vftable@@YAXUSmallWithVftable@@@Z"(%struct.SmallWithVftable* %s)
 
 void medium_arg_with_copy_ctor(MediumWithCopyCtor s) {}
 // LINUX-LABEL: define void @_Z25medium_arg_with_copy_ctor18MediumWithCopyCtor(%struct.MediumWithCopyCtor* %s)
 // WIN32: define dso_local void @"?medium_arg_with_copy_ctor@@YAXUMediumWithCopyCtor@@@Z"(<{ %struct.MediumWithCopyCtor }>* inalloca)
 // WIN64: define dso_local void @"?medium_arg_with_copy_ctor@@YAXUMediumWithCopyCtor@@@Z"(%struct.MediumWithCopyCtor* %s)
 // WOA: define dso_local arm_aapcs_vfpcc void @"?medium_arg_with_copy_ctor@@YAXUMediumWithCopyCtor@@@Z"(%struct.MediumWithCopyCtor* %s)
+// WOA64: define dso_local void @"?medium_arg_with_copy_ctor@@YAXUMediumWithCopyCtor@@@Z"(%struct.MediumWithCopyCtor* %s)
 
 void big_arg(Big s) {}
 // LINUX-LABEL: define void @_Z7big_arg3Big(%struct.Big* byval align 4 %s)