diff --git a/modules/fdlibm/src/math_private.h b/modules/fdlibm/src/math_private.h
--- a/modules/fdlibm/src/math_private.h
+++ b/modules/fdlibm/src/math_private.h
@@ -14,20 +14,21 @@
  * $FreeBSD$
  */
 
 #ifndef _MATH_PRIVATE_H_
 #define	_MATH_PRIVATE_H_
 
 #include <stdint.h>
 #include <sys/types.h>
-#include <machine/endian.h>
 
 #include "fdlibm.h"
 
+#include "mozilla/EndianUtils.h"
+
 /*
  * The original fdlibm code used statements like:
  *	n0 = ((*(int*)&one)>>29)^1;		* index of high word *
  *	ix0 = *(n0+(int*)&x);			* high word of x *
  *	ix1 = *((1-n0)+(int*)&x);		* low word of x *
  * to dig two 32 bit words out of the 64 bit IEEE floating point
  * value.  That is non-ANSI, and, moreover, the gcc instruction
  * scheduler gets it wrong.  We instead use the following macros.
@@ -36,27 +37,17 @@
  * endianness at run time.
  */
 
 /*
  * A union which permits us to convert between a double and two 32 bit
  * ints.
  */
 
-#ifdef __arm__
-#if defined(__VFP_FP__) || defined(__ARM_EABI__)
-#define	IEEE_WORD_ORDER	BYTE_ORDER
-#else
-#define	IEEE_WORD_ORDER	BIG_ENDIAN
-#endif
-#else /* __arm__ */
-#define	IEEE_WORD_ORDER	BYTE_ORDER
-#endif
-
-#if IEEE_WORD_ORDER == BIG_ENDIAN
+#if MOZ_BIG_ENDIAN
 
 typedef union
 {
   double value;
   struct
   {
     u_int32_t msw;
     u_int32_t lsw;
@@ -64,17 +55,17 @@ typedef union
   struct
   {
     u_int64_t w;
   } xparts;
 } ieee_double_shape_type;
 
 #endif
 
-#if IEEE_WORD_ORDER == LITTLE_ENDIAN
+#if MOZ_LITTLE_ENDIAN
 
 typedef union
 {
   double value;
   struct
   {
     u_int32_t lsw;
     u_int32_t msw;