RFR: 8365823: Revert storing abstract and interface Klasses to non-class metaspace [v3]

[Coleen Phillimore]

On Mon, 15 Sep 2025 15:06:04 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove CFP.is_abstract().
>
> src/hotspot/share/ci/ciKlass.hpp line 112:
> 
>> 110:     assert(is_in_encoding_range, "sanity");
>> 111:     return is_in_encoding_range;
>> 112:   }
> 
> I thought about this method, and it _looks_ to be just:
> 
> 
>   bool is_in_encoding_range() {
>     assert(CompressedKlassPointers::is_encodable(get_Klass()), "sanity");
>     return true;
>   }
> 
> 
> But I think your version is better, since it is more paranoid and actually checks if we are dealing with the class within the class range.

I was on the verge of removing this but that snowballed into removing all sorts of other things that maybe can be removed later.  This was sort of where I cut it off and I did like the variable name.

> src/hotspot/share/memory/allocation.cpp line 76:
> 
>> 74:   // Klass has its own operator new
>> 75:   assert(type != ClassType, "class has its own operator new");
>> 76:   return Metaspace::allocate(loader_data, word_size, type, /*use_class_space*/ false, THREAD);
> 
> Question: now that `ArrayKlass` and `InstanceKlass` do not have `::new`, the assert above is still valid? I am guessing all these inherit `Klass::new`?

Yes, all Klass allocation should call Klass::operator new().  Klass is derived from Metadata that's derived from MetaspaceObj.  The Klass operator new _hides_ the one in MetaspaceObj.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27295#discussion_r2349433048
PR Review Comment: https://git.openjdk.org/jdk/pull/27295#discussion_r2349449119