diff --git a/compiler-rt/lib/builtins/assembly.h b/compiler-rt/lib/builtins/assembly.h
--- a/compiler-rt/lib/builtins/assembly.h
+++ b/compiler-rt/lib/builtins/assembly.h
@@ -194,7 +194,8 @@
 #elif __ARM_ARCH >= 6
 #define DMB mcr p15, #0, r0, c7, c10, #5
 #else
-#error only supported on ARMv6+
+#warning DMB is only supported on ARMv6+
+#define DMB
 #endif
 
 #if defined(USE_THUMB_2)