diff --git a/clang/lib/Headers/x86intrin.h b/clang/lib/Headers/x86intrin.h
index be9e71d3a500..21a43daf3c2d 100644
--- a/clang/lib/Headers/x86intrin.h
+++ b/clang/lib/Headers/x86intrin.h
@@ -76,6 +76,6 @@
 #include <f16cintrin.h>
 #endif
 
-// FIXME: LWP
+/* FIXME: LWP */
 
 #endif /* __X86INTRIN_H */
diff --git a/clang/lib/Headers/xmmintrin.h b/clang/lib/Headers/xmmintrin.h
index e777ec0171ea..c9befcb456f6 100644
--- a/clang/lib/Headers/xmmintrin.h
+++ b/clang/lib/Headers/xmmintrin.h
@@ -34,8 +34,8 @@ typedef int __v4si __attribute__((__vector_size__(16)));
 typedef float __v4sf __attribute__((__vector_size__(16)));
 typedef float __m128 __attribute__((__vector_size__(16)));
 
-// This header should only be included in a hosted environment as it depends on
-// a standard library to provide allocation routines.
+/* This header should only be included in a hosted environment as it depends on
+ * a standard library to provide allocation routines. */
 #if __STDC_HOSTED__
 #include <mm_malloc.h>
 #endif
@@ -589,7 +589,7 @@ _mm_set1_ps(float __w)
   return (__m128){ __w, __w, __w, __w };
 }
 
-// Microsoft specific.
+/* Microsoft specific. */
 static __inline__ __m128 __attribute__((__always_inline__, __nodebug__))
 _mm_set_ps1(float __w)
 {