RFR: 8363996: Obsolete UseCompressedClassPointers [v3]

[Andrew Haley]

On Thu, 4 Dec 2025 14:03:26 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> src/hotspot/share/cds/aotMappedHeapLoader.hpp line 55:
>> 
>>> 53:   static bool can_use() { return can_map() || can_load(); }
>>> 54: 
>>> 55:   // Can this VM map archived heap region? Currently only G1+compressed{oops,cp}
>> 
>> Suggestion:
>> 
>>   // Can this VM map archived heap region? Currently only G1.
>
> After thinking about this, I got confused. Should heap archiving not actually depend on CompressedOops, too, in addition to CompressedClassPointers? Otherwise we would have the heap region at runtime at exactly the same address as at compile time...
> 
> That would be a preexisting bug. It may just be one of the old "UseCompressedClassPointers is tied to UseCompressedOops" bugs. But if true, we would have seen CDT crashes e.g. with G1 and heaps > 32g.
> 
> I'll take a look.

Sorry, my mistake. Just compressed CP. Maybe just delete the comment, which violates

Rule 1: Comments should not duplicate the code

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PR Review Comment: https://git.openjdk.org/jdk/pull/28366#discussion_r2589349492