RFR: 8339113: AccessFlags can be u2 in metadata [v13]

[Coleen Phillimore]

On Tue, 7 Jan 2025 02:36:36 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Please review this change that makes AccessFlags and modifier_flags u2 types and removes the last remnants of Hotspot adding internal access flags.  This change moves AccessFlags and modifier_flags in Klass to alignment gaps saving 16 bytes.  From pahole: so it's a bit better.
>> 
>> before:
>> 
>>         /* size: 216, cachelines: 4, members: 25, static members: 17 */
>>         /* sum members: 194, holes: 3, sum holes: 18 */
>> 
>> 
>> after:
>> 
>>         /* size: 200, cachelines: 4, members: 25, static members: 17 */
>>         /* sum members: 188, holes: 4, sum holes: 12 */
>> 
>> 
>> We may eventually move the modifiers to java.lang.Class but that's WIP.
>> 
>> Tested with tier1-7 on oracle platforms.  Did test builds on other platforms (please try these changes ppc/arm32 and s390).  Also requires minor Graal changes.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make more AccessFlags fetches more specific and remove an assert and remove this->s.

> IMO you could just call as_int() here. All other usages of ciFlags::as_int() are in printing code.
> Ideally, ciField::print() could use ciFlags::print(), but such cleanup can be done separately.

This does seem like a good future cleanup.  Thanks for reviewing Vladimir.

Thanks for reviewing David, Yudi and Serguei.  I reran tiers 1-7 on this change.

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PR Comment: https://git.openjdk.org/jdk/pull/22246#issuecomment-2576308012
PR Comment: https://git.openjdk.org/jdk/pull/22246#issuecomment-2576309500