RFR: 8271579: G1: Move copy before CAS in do_copy_to_survivor_space [v2]

[Hamlin Li]

On Thu, 5 Aug 2021 14:56:57 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hamlin Li has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.
>
> We are currently trying to reproduce these improvements on aarch64 and x64.
> 
> Also, please revert the change to the age calculation and file this separately. I think I remember the reason for incrementing the age the way it is done is/was that it is supposed to avoid some forced reloads of the mark word which may or may not be important. Either way it is completely unrelated to this change.

@tschatzl Hi Thomas, may I ask how's test result on aarch64 and x64?

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PR: https://git.openjdk.java.net/jdk/pull/4983