diff -up mozjs-38.0.0/js/src/configure.in.rhbz-1219542-s390 mozjs-38.0.0/js/src/configure.in
--- mozjs-38.0.0/js/src/configure.in.rhbz-1219542-s390	2015-09-17 22:12:18.000000000 +0200
+++ mozjs-38.0.0/js/src/configure.in	2015-11-26 12:32:05.000000000 +0100
@@ -1492,7 +1492,7 @@ case "$host" in
 *-linux*|*-kfreebsd*-gnu|*-gnu*)
     HOST_CFLAGS="$HOST_CFLAGS -DXP_UNIX"
     HOST_NSPR_MDCPUCFG='\"md/_linux.cfg\"'
-    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O3}"
+    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O1}"
     ;;
 
 *)
@@ -1674,8 +1674,8 @@ 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 $MOZ_OPTIMIZE_FLAGS"
         fi
diff -up mozjs-38.0.0/js/src/configure.rhbz-1219542-s390 mozjs-38.0.0/js/src/configure
--- mozjs-38.0.0/js/src/configure.rhbz-1219542-s390	2015-09-17 22:38:10.000000000 +0200
+++ mozjs-38.0.0/js/src/configure	2015-11-26 13:01:59.000000000 +0100
@@ -7444,7 +7444,7 @@ case "$host" in
 *-linux*|*-kfreebsd*-gnu|*-gnu*)
     HOST_CFLAGS="$HOST_CFLAGS -DXP_UNIX"
     HOST_NSPR_MDCPUCFG='\"md/_linux.cfg\"'
-    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O3}"
+    HOST_OPTIMIZE_FLAGS="${HOST_OPTIMIZE_FLAGS=-O1}"
     ;;
 
 *)
@@ -7774,8 +7774,8 @@ EOF
         # 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