The BarrierSet class has an embedded enum named Flags. That type and the associated enum tags are unused.

The Flags enum was added as part of the fix for
6627983: G1: Bad oop deference during marking

However, there were no uses of the Flags enum type or either of its tags in that changeset. Instead, there are a number of functions which were given new "bool dest_uninitialized" parameters. Perhaps the intent was that the new parameter should have Flags as its type and use the enum tags as arguments, for better type safety and self-documentation of the code. If so, that didn't happen.

We should either change the code to use the Flags enum or eliminate it.