diff -up firefox-43.0.3/js/src/configure.in.rhbz-1219542-s390 firefox-43.0.3/js/src/configure.in
--- firefox-43.0.3/js/src/configure.in.rhbz-1219542-s390	2015-12-23 17:11:01.000000000 -0500
+++ firefox-43.0.3/js/src/configure.in	2016-01-03 08:08:27.139956990 -0500
@@ -1466,7 +1466,7 @@ case "$host" in
 
 *-linux*|*-kfreebsd*-gnu|*-gnu*)
     HOST_CFLAGS="$HOST_CFLAGS -DXP_UNIX"
-    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O3}"
+    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O1}"
     ;;
 
 *)
@@ -1649,8 +1649,8 @@ ia64*-hpux*)
         # while; Intel recommends against using it.
         MOZ_OPTIMIZE_FLAGS="-O2"
     elif test "$GNU_CC" -o "$GNU_CXX"; then
-        MOZ_PGO_OPTIMIZE_FLAGS="-O3"
-        MOZ_OPTIMIZE_FLAGS="-O3"
+        MOZ_PGO_OPTIMIZE_FLAGS="-O1"
+        MOZ_OPTIMIZE_FLAGS="-O1"
         if test -z "$CLANG_CC"; then
            MOZ_OPTIMIZE_FLAGS="-freorder-blocks $MOZ_OPTIMIZE_FLAGS"
         fi