RFR: Fix satb barrier for object array copy [v3]

[Kelvin Nilsen]

On Fri, 31 Mar 2023 15:43:23 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> The satb barrier for overwritten arrays residing in old-gen must be unconditional during young GC.
>> 
>> During old GC, the satb barrier is only needed for overwritten old-gen arrays if the array is below TAMS within its old-gen region.
>
> Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:
> 
>  - Merge remote-tracking branch 'github/master' into fix-satb-barrier-for-object-array-copy
>  - Fix typo in comment
>  - Tidy up branch to make consistent with recompute-generation_usage PR
>  - Integrate improvements to region-usage-accounting after full gc
>  - Change name of phase5_restore_generation_usage
>  - Fix comparison between array address and TAMS for old-gen collection
>  - Merge remote-tracking branch 'GitFarmBranch/fix-satb-barrier-for-objectarray-copy' into fix-satb-barrier-for-object-array-copy
>  - Restore generation budgets following fullgc
>  - Fix implementation of SATB barrier for objectarray copy
>    
>    Original code ommitted SATB barrier for old-gen arrays that were above
>    the old-gen TAMS.  That was an error.

Have merged from master to clean up redundancy.

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PR Comment: https://git.openjdk.org/shenandoah/pull/237#issuecomment-1492216645