RFR: 8296139: Make GrowableBitMap the base class of all implementations [v4]

[Axel Boldt-Christmas]

On Sat, 5 Nov 2022 00:53:51 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> BitMap is an abstract class. All subclasses provide their own allocators. It is the allocator brings the capability to 'resize' the container. 
>> I would like to add a new 'GrowableBitmap' and make it the common base class. 
>> 
>> To substitute 'VectorSet', we also need to merge ResourceBitMap and ArenaBitMap because VectorSet supports Resource and Arena storage at the same time. 
>> This patch unifies them.  ResourceBitMap is a specialized ArenaBitMap whose allocator is with NULL arena.
>> 
>> All subclasses of GrowableBitMap are elastic. I will add new interface like VectorSet::test_set(index). It will grow to include the new index.
>
> Xin Liu has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains eight commits:
> 
>  - Merge branch 'master' into JDK-8296139
>  - Bring back verify_size to the constructor of BitMap.
>    
>    Also resume the underlying member data to be private. Subclasses of
>    GrowableBitMap update them using update(map, size).
>  - Reivew comments from stefank
>  - Refactor GrowableBitMap using C++ CRTP
>    
>    With CPTP, we don't need to have explicit Allocators. Subclasses expose
>    allocate/free member functions upward to GrowableBitMap<BitMapWithAllocator>. This
>    aproach is similar to GrowableArray.
>  - Add unittest for Arena.
>  - Avoid polluting namespace.
>    
>    uses qualified bm_word_t and idx_t.
>  - Change ResourceBitMap to subclass of ArenaBitMap.
>  - Add GrowableBitMap.

Lgtm. 

Just one comment, on one comment.

src/hotspot/share/utilities/bitMap.hpp line 401:

> 399:   bm_word_t* allocate(idx_t size_in_words) const;
> 400:   void free(bm_word_t* map, idx_t size_in_words) const {
> 401:     // ArenaBitMaps currently don't free memory.

s/ArenaBitMaps/ResourceBitMap/

Or keep the old `Don't free resource allocated arrays.` comment

-------------

Marked as reviewed by aboldtch (Committer).

PR: https://git.openjdk.org/jdk/pull/10941