RFR: 8144505: Change G1ParCopyHelper to inherit OopClosure
stefan.johansson at oracle.com
Wed Dec 2 15:55:01 UTC 2015
Please review this change for:
When iterating objects with oop_iterate() there is a special case for
InstanceRefKlass, if the closure overrides
apply_to_weak_ref_discovered_field() to return true, the closure will be
applied to the discovered field, even if the normal checks prevents it.
This special treatment is needed in certain situations, but it is not
obvious if it should be done when iterating the object. Currently only
G1 closures override apply_to_weak_ref_discovered_field() and many of
them seem to do it without any reason. My initial plan  was to remove
all usage of this special casing but after discussions I realized it
would be easier to see the effects if doing this one closure at a time.
G1ParCopyClosure is only used as a normal OopClosure. It inherits from
G1ParCopyHelper which in turn inherits G1ParClosureSuper.
G1ParClosureSuper overrides apply_to_weak_ref_discovered_field() to
return true but since G1ParCopyClosure is never used with oop_iterate()
it doesn't need to inherit this functionality. G1ParCopyHelper can
instead be changed to inherit directly from OopClosure, and this way we
have one closure less depending on apply_to_weak_ref_discovered_field().
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