Index: lib/Headers/intrin.h
===================================================================
--- lib/Headers/intrin.h
+++ lib/Headers/intrin.h
@@ -557,15 +557,9 @@
 int _ReadStatusReg(int);
 void _WriteStatusReg(int, int);
 
-static inline unsigned short _byteswap_ushort (unsigned short val) {
-  return __builtin_bswap16(val);
-}
-static inline unsigned long _byteswap_ulong (unsigned long val) {
-  return __builtin_bswap32(val);
-}
-static inline unsigned __int64 _byteswap_uint64 (unsigned __int64 val) {
-  return __builtin_bswap64(val);
-}
+unsigned short __cdecl _byteswap_ushort(unsigned short val);
+unsigned long __cdecl _byteswap_ulong (unsigned long val);
+unsigned __int64 __cdecl _byteswap_uint64(unsigned __int64 val);
 #endif
 
 /*----------------------------------------------------------------------------*\
Index: test/Headers/ms-arm64-intrin.cpp
===================================================================
--- test/Headers/ms-arm64-intrin.cpp
+++ test/Headers/ms-arm64-intrin.cpp
@@ -14,16 +14,16 @@
 }
 
 unsigned short check_byteswap_ushort(unsigned short val) {
-// CHECK: call i16 @llvm.bswap.i16(i16 %val)
+// CHECK: call i16 @_byteswap_ushort(i16 %val)
   return _byteswap_ushort(val);
 }
 
 unsigned long check_byteswap_ulong(unsigned long val) {
-// CHECK: call i32 @llvm.bswap.i32(i32 %val)
+// CHECK: call i32 @_byteswap_ulong(i32 %val)
   return _byteswap_ulong(val);
 }
 
 unsigned __int64 check_byteswap_uint64(unsigned __int64 val) {
-// CHECK: call i64 @llvm.bswap.i64(i64 %val)
+// CHECK: call i64 @_byteswap_uint64(i64 %val)
   return _byteswap_uint64(val);
 }