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

[Serguei Spitsyn]

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.

Thank you for one more unification update! Looks good.

-------------

Marked as reviewed by sspitsyn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22246#pullrequestreview-2535297355