RFR: 8292170: Convert CodeRootSetTable to use ResourceHashtable

[Coleen Phillimore]

On Wed, 14 Dec 2022 13:45:51 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

> I am replacing the old hash table with ResourceHashtable. In the process I am also removing the redundant `_length` field. By removing the `_length` field, a lot of asserts can be removed as the length will trivially match the length of the underlying table.
> 
> I would like to have feedback on the addition of `unlink_destruct(Function&& should_remove)`. I added it because I prefer to use a functor object that can be used by lambdas instead of an iterator object. However, I did add code to "destruct" resource objects when they are removed instead of just letting them be to reflect that we use `delete` on c-heap objects. Maybe I should remove this "improvement" and then maybe implement the function by calling the existing unlink?

I'm happy to see this change coming!

src/hotspot/share/utilities/resourceHash.hpp line 277:

> 275:   }
> 276: 
> 277:   // The argument should_remove() have the signature: bool Function(K const&, V const&).

Can you make the unlink a separate change?  I think unlink with the Function argument should be an overload of unlink() and implemented like the iterate function. I don't immediately understand the additional &&s.
If it's a separate change, we can fix the other callers to use lambdas, which would be nicer.
Also, I think calling the ResourceObj destructor is another discussion - they are not typically used and I think the discussion should be somewhere else.

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PR: https://git.openjdk.org/jdk/pull/11675