6873800: enable compressed oops by default

Summary: enable compressed oops by default
Reviewed-by: never, ysr

src/share/vm/runtime/arguments.cpp

@@ -1233,10 +1233,8 @@ void Arguments::set_ergonomics_flags() {
   // Check that UseCompressedOops can be set with the max heap size allocated
   // by ergonomics.
   if (MaxHeapSize <= max_heap_for_compressed_oops()) {
-    if (FLAG_IS_DEFAULT(UseCompressedOops)) {
-      // Turn off until bug is fixed.
-      // the following line to return it to default status.
-      // FLAG_SET_ERGO(bool, UseCompressedOops, true);
+    if (FLAG_IS_DEFAULT(UseCompressedOops) && !UseG1GC) {
+      FLAG_SET_ERGO(bool, UseCompressedOops, true);
     }
 #ifdef _WIN64
     if (UseLargePages && UseCompressedOops) {