6920970: Zero build fixes after 6849984 and 6911204
Summary: Two recent commits broke the build on Zero.
Reviewed-by: twisti
Contributed-by: Gary Benson <gbenson@redhat.com>
6920090: G1: Disable ReduceInitialCardMarks at least until 6920109 is fixed
Summary: G1 now answers "no" to the query can_elide_initializing_store_barrier() in the product build. A debug flag allows alternate behaviour in debug builds.
Reviewed-by: iveresov, tonyp