diff --git a/lib/compiler-rt/builtins/int_endianness.h b/lib/compiler-rt/builtins/int_endianness.h
new file mode 100644
index 0000000..e2586c5
--- /dev/null
+++ b/lib/compiler-rt/builtins/int_endianness.h
@@ -0,0 +1,116 @@
+/* ===-- int_endianness.h - configuration header for compiler-rt ------------===
+ *
+ *		       The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file is a configuration header for compiler-rt.
+ * This file is not part of the interface of this library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#ifndef INT_ENDIANNESS_H
+#define INT_ENDIANNESS_H
+
+#if defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && \
+    defined(__ORDER_LITTLE_ENDIAN__)
+
+/* Clang and GCC provide built-in endianness definitions. */
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define _YUGA_LITTLE_ENDIAN 0
+#define _YUGA_BIG_ENDIAN    1
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+#endif /* __BYTE_ORDER__ */
+
+#else /* Compilers other than Clang or GCC. */
+
+#if defined(__SVR4) && defined(__sun)
+#include <sys/byteorder.h>
+
+#if defined(_BIG_ENDIAN)
+#define _YUGA_LITTLE_ENDIAN 0
+#define _YUGA_BIG_ENDIAN    1
+#elif defined(_LITTLE_ENDIAN)
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+#else /* !_LITTLE_ENDIAN */
+#error "unknown endianness"
+#endif /* !_LITTLE_ENDIAN */
+
+#endif /* Solaris and AuroraUX. */
+
+/* .. */
+
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__DragonFly__) ||   \
+    defined(__minix)
+#include <sys/endian.h>
+
+#if _BYTE_ORDER == _BIG_ENDIAN
+#define _YUGA_LITTLE_ENDIAN 0
+#define _YUGA_BIG_ENDIAN    1
+#elif _BYTE_ORDER == _LITTLE_ENDIAN
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+#endif /* _BYTE_ORDER */
+
+#endif /* *BSD */
+
+#if defined(__OpenBSD__)
+#include <machine/endian.h>
+
+#if _BYTE_ORDER == _BIG_ENDIAN
+#define _YUGA_LITTLE_ENDIAN 0
+#define _YUGA_BIG_ENDIAN    1
+#elif _BYTE_ORDER == _LITTLE_ENDIAN
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+#endif /* _BYTE_ORDER */
+
+#endif /* OpenBSD */
+
+/* .. */
+
+/* Mac OSX has __BIG_ENDIAN__ or __LITTLE_ENDIAN__ automatically set by the
+ * compiler (at least with GCC) */
+#if defined(__APPLE__) || defined(__ellcc__ )
+
+#ifdef __BIG_ENDIAN__
+#if __BIG_ENDIAN__
+#define _YUGA_LITTLE_ENDIAN 0
+#define _YUGA_BIG_ENDIAN    1
+#endif
+#endif /* __BIG_ENDIAN__ */
+
+#ifdef __LITTLE_ENDIAN__
+#if __LITTLE_ENDIAN__
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+#endif
+#endif /* __LITTLE_ENDIAN__ */
+
+#endif /* Mac OSX */
+
+/* .. */
+
+#if defined(_WIN32)
+
+#define _YUGA_LITTLE_ENDIAN 1
+#define _YUGA_BIG_ENDIAN    0
+
+#endif /* Windows */
+
+#endif /* Clang or GCC. */
+
+/* . */
+
+#if !defined(_YUGA_LITTLE_ENDIAN) || !defined(_YUGA_BIG_ENDIAN)
+#error Unable to determine endian
+#endif /* Check we found an endianness correctly. */
+
+#endif /* INT_ENDIANNESS_H */