diff -up firefox-57.0b5/js/src/jit/AtomicOperations.h.jit-atomic-lucky firefox-57.0b5/js/src/jit/AtomicOperations.h

--- firefox-57.0b5/js/src/jit/AtomicOperations.h.jit-atomic-lucky	2017-10-06 12:34:02.338973607 +0200

+++ firefox-57.0b5/js/src/jit/AtomicOperations.h	2017-10-06 12:38:24.632622215 +0200

@@ -415,7 +415,7 @@ AtomicOperations::isLockfreeJS(int32_t s

 #elif defined(__s390__) || defined(__s390x__)

 # include "jit/none/AtomicOperations-feeling-lucky.h"

 #else

-# error "No AtomicOperations support provided for this platform"

+# include "jit/none/AtomicOperations-feeling-lucky.h"

 #endif

 #endif // jit_AtomicOperations_h

diff -up firefox-57.0b5/js/src/jit/none/AtomicOperations-feeling-lucky.h.jit-atomic-lucky firefox-57.0b5/js/src/jit/none/AtomicOperations-feeling-lucky.h

--- firefox-57.0b5/js/src/jit/none/AtomicOperations-feeling-lucky.h.jit-atomic-lucky	2017-09-19 06:18:28.000000000 +0200

+++ firefox-57.0b5/js/src/jit/none/AtomicOperations-feeling-lucky.h	2017-10-06 12:34:02.338973607 +0200

@@ -79,6 +79,14 @@

 #  define GNUC_COMPATIBLE

 #endif

+#ifdef __s390__

+#  define GNUC_COMPATIBLE

+#endif

+

+#ifdef __s390x__

+#  define GNUC_COMPATIBLE

+#endif

+

 // The default implementation tactic for gcc/clang is to use the newer

 // __atomic intrinsics added for use in C++11 <atomic>.  Where that

 // isn't available, we use GCC's older __sync functions instead.