RFR (M): 8189737: Make HeapRegion not derive from Space

[Kim Barrett]

> On Nov 6, 2019, at 2:21 PM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi,
> 
> On 06.11.19 12:03, Stefan Johansson wrote:
>> Hi Thomas,
> [...]
>>>> 
>>>> I think this looks really good in general, so nice to get rid of this inheritance.
>>>> 
>>>> I have one question/comment though. I took a look at the HeapRegion implementation in the SA and there it still extends CompactibleSpace (which extends Space), I think we should remove this and add _bottom and _top for HeapRegion in vmStructs_g1.hpp. This also has the effect that the PrintRegionClosure needs to be updated to not depend on space either. It is only used by G1 so I think it should simply be moved from shared to g1 and changed to not depend on space.
>>> 
>>> Good catch. Changed in
>>> 
>>> http://cr.openjdk.java.net/~tschatzl/8189737/webrev.0_to_1/ (diff)
>>> http://cr.openjdk.java.net/~tschatzl/8189737/webrev.1 (full)
>> Thanks for fixing this, looks good. I don't think we need to add _compaction_top, from what I can see it is not used. I don't need a new webrev for this if I'm right.
> 
> Updated in place.
> 
> Thanks,
>  Thomas

Still looks good.