Index: include/clang/Basic/TokenKinds.def
===================================================================
--- include/clang/Basic/TokenKinds.def	(revision 155632)
+++ include/clang/Basic/TokenKinds.def	(working copy)
@@ -501,6 +501,7 @@
 ALIAS("__int16"      , short      , KEYMS)
 ALIAS("__int32"      , int        , KEYMS)
 ALIAS("_asm"         , asm        , KEYMS)
+ALIAS("_alignof"     , __alignof  , KEYMS)
 ALIAS("_cdecl"       , __cdecl    , KEYMS | KEYBORLAND)
 ALIAS("_fastcall"    , __fastcall , KEYMS | KEYBORLAND)
 ALIAS("_stdcall"     , __stdcall  , KEYMS | KEYBORLAND)
Index: test/Parser/MicrosoftExtensions.c
===================================================================
--- test/Parser/MicrosoftExtensions.c	(revision 155632)
+++ test/Parser/MicrosoftExtensions.c	(working copy)
@@ -29,6 +29,10 @@
 }
 _inline int foo99() { return 99; }
 
+void test_ms_alignof_alias() {
+  unsigned int s = _alignof(int);
+}
+
 void *_alloca(int);
 
 void foo() {