diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -2932,7 +2932,10 @@
   }
   case Builtin::BI__builtin_bswap16:
   case Builtin::BI__builtin_bswap32:
-  case Builtin::BI__builtin_bswap64: {
+  case Builtin::BI__builtin_bswap64:
+  case Builtin::BI_byteswap_ushort:
+  case Builtin::BI_byteswap_ulong:
+  case Builtin::BI_byteswap_uint64: {
     return RValue::get(emitUnaryBuiltin(*this, E, Intrinsic::bswap));
   }
   case Builtin::BI__builtin_bitreverse8:
diff --git a/clang/test/Headers/ms-arm64-intrin.cpp b/clang/test/Headers/ms-arm64-intrin.cpp
--- a/clang/test/Headers/ms-arm64-intrin.cpp
+++ b/clang/test/Headers/ms-arm64-intrin.cpp
@@ -2,7 +2,7 @@
 
 // RUN: %clang_cc1 -triple arm64-windows -O1 \
 // RUN: -fms-compatibility -fms-compatibility-version=17.00 \
-// RUN: -ffreestanding -fsyntax-only -Werror \
+// RUN: -fsyntax-only -Werror \
 // RUN: -isystem %S/Inputs/include %s -S -o - -emit-llvm 2>&1 \
 // RUN: | FileCheck %s
 
@@ -14,16 +14,16 @@
 }
 
 unsigned short check_byteswap_ushort(unsigned short val) {
-// CHECK: call i16 @_byteswap_ushort(i16 noundef %val)
+// CHECK: call i16 @llvm.bswap.i16(i16 %val)
   return _byteswap_ushort(val);
 }
 
 unsigned long check_byteswap_ulong(unsigned long val) {
-// CHECK: call i32 @_byteswap_ulong(i32 noundef %val)
+// CHECK: call i32 @llvm.bswap.i32(i32 %val)
   return _byteswap_ulong(val);
 }
 
 unsigned __int64 check_byteswap_uint64(unsigned __int64 val) {
-// CHECK: call i64 @_byteswap_uint64(i64 noundef %val)
+// CHECK: call i64 @llvm.bswap.i64(i64 %val)
   return _byteswap_uint64(val);
 }