diff -r 9dc4a391dd6d mpi/generic/mpi-asm-defs.h
--- a/mpi/generic/mpi-asm-defs.h	Tue Jul 29 16:44:47 2014 +0200
+++ b/mpi/generic/mpi-asm-defs.h	Tue Jul 29 16:47:43 2014 +0200
@@ -1,7 +1,12 @@
-/* This file defines some basic constants for the MPI machinery.  We
- * need to define the types on a per-CPU basis, so it is done with
- * this file here.  */
+/* AMD64 compiled with x32 fails in assembly due to incorrect 
+ * size of long detected. Using compiler information to detect
+ * this since it is no longer per-architecture
+ */
+#if defined(__GNUC__) && __GNUC__ >= 3 && defined(__x86_64__) && defined(__ILP32__)
+#define BYTES_PER_MPI_LIMB 8
+#else
 #define BYTES_PER_MPI_LIMB  (SIZEOF_UNSIGNED_LONG)
+#endif