Index: lib/Headers/xmmintrin.h
===================================================================
--- lib/Headers/xmmintrin.h
+++ lib/Headers/xmmintrin.h
@@ -2823,6 +2823,8 @@
 
 #ifdef _MSC_VER
 #define _MM_ALIGN16 __declspec(align(16))
+#else
+#define _MM_ALIGN16 __attribute__((aligned(16)))
 #endif
 
 #define _MM_SHUFFLE(z, y, x, w) (((z) << 6) | ((y) << 4) | ((x) << 2) | (w))
Index: test/Headers/xmmintrin.c
===================================================================
--- test/Headers/xmmintrin.c
+++ test/Headers/xmmintrin.c
@@ -7,6 +7,9 @@
 // REQUIRES: x86-registered-target
 #include <xmmintrin.h>
 
+// CHECK: @c = common global i8 0, align 16
+_MM_ALIGN16 char c;
+
 // Make sure the last step of _mm_cvtps_pi16 converts <4 x i32> to <4 x i16> by
 // checking that clang emits PACKSSDW instead of PACKSSWB.