RFR: 8297503: Merge FilteringDCTOC into ContiguousSpaceDCTOC

[Thomas Schatzl]

On Wed, 23 Nov 2022 13:40:55 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple cleanup of trimming unnecessary type hierarchy levels.
> 
> Test: hotspot_gc

Lgtm, some minor comments to be fixed as you want.

src/hotspot/share/gc/shared/space.hpp line 547:

> 545: // sub-classes). It knows how to filter out objects that are outside of the
> 546: // _boundary.
> 547: //

Suggestion:

//
// Assumptions:

src/hotspot/share/gc/shared/space.hpp line 555:

> 553: class ContiguousSpaceDCTOC : public DirtyCardToOopClosure {
> 554: protected:
> 555:   // Overrides.

Instead of the `overrides` comment, both methods could be decorated with the `override` specifier.

src/hotspot/share/gc/shared/space.hpp line 573:

> 571:   void walk_mem_region_with_cl(MemRegion mr,
> 572:                                HeapWord* bottom, HeapWord* top,
> 573:                                FilteringClosure* cl);

These do not need to be `protected` afaict

src/hotspot/share/gc/shared/space.hpp line 577:

> 575: public:
> 576:   ContiguousSpaceDCTOC(ContiguousSpace* sp, OopIterateClosure* cl,
> 577:                        CardTable::PrecisionStyle precision,

That's a pre-existing (different) issue, but the only `PrecisionStyle` this code is ever used with seems to be `ObjHeadPreciseArray`.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11322