RFR: 8367981: Update CompactHashtable comments [v2]

[Hamlin Li]

On Tue, 23 Sep 2025 18:32:15 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> src/hotspot/share/classfile/compactHashtable.hpp line 174:
>> 
>>> 172: // For regular buckets, each entry is 8 bytes in the entries[]:
>>> 173: //   u4 hash;    // entry hash
>>> 174: //   u4 value;   // it could be offset or index or any payload.
>> 
>> I think `value` is confusing, as it's not the same as the template type `V`. I would suggest changing the declaration to 
>> 
>> 
>> class CompactHashtableWriter: public StackObj {
>> public:
>>   class Entry {
>>     unsigned int _hash;
>> -   u4 _value;
>> +   u4 _encoded_value;
>> 
>> 
>> All parameters of `offset` should be changed to `encoded_value`.
>> 
>> This comment should be updated:
>> 
>> 
>> u4 encoded_value; // A 32-bit encoding of the template type V. The template parameter DECODE
>>                   // converts this to type V. Many CompactHashtables encode a pointer as a 32-bit offset, where
>>                   //   V entry = (V)(base_address + offset)
>>                   // see StringTable, SymbolTable and AdapterHandlerLibrary for examples
>> 
>>  
>> I think we should consider a future clean up of adding an `ENCODE` template parameter so that the various table dumping functions can be consolidated.
>
>> All parameters of offset should be changed to encoded_value.
> 
> I guess you mean change from `value` to encoded_value in `CompactHashtable`?
> I did not touch the parameter name `offset` in read_value_from_compact_hashtable (which is used in OffsetCompactHashtable), as I think it means `offset` intentionally.
> But please correct me if I'm understanding wrongly.

Modify from `offset`/`value` to `encoded_value` in CompactHashtable template parameters.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27360#discussion_r2373201842