During work on and review of https://git.openjdk.org/jdk/pull/12453 it was made apparent that array.clone() is sometimes a smidge slower than System.arraycopy, so for that patch we opted to keep helper methods and code around to call arraycopy.

One candidate is that zeroing is not properly eliminated for clone, making this related to https://bugs.openjdk.org/browse/JDK-8146828