diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2553,7 +2553,7 @@
         '/', '/', '/', '/',  '/', '/', '/', '/'
       };
       while (CurPtr+16 <= BufferEnd &&
-             !vec_any_eq(*(const vector unsigned char*)CurPtr, Slashes))
+             !vec_any_eq(*(const __vector unsigned char*)CurPtr, Slashes))
         CurPtr += 16;
 #else
       // Scan for '/' quickly.  Many block comments are very large.