Bug: C2 crash on Derby with -XX:-ShenandoahNoBarriersForConst

[Roland Westrelin]

> Even after the recent Roland's fix, Derby fails with ShNoBarriersForConst:
>
> $ java -jar target/benchmarks.jar Derby --jvmArgs "-XX:+UseShenandoahGC -Xmx4g
> -Xms4g -XX:+UnlockExperimentalVMOptions -XX:-ShenandoahNoBarriersForConst" -f 1 -t 8

This one should be fixed now.

Roland.