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.