RFR: 8309717: C2: Remove Arena::move_contents usage

[Johan Sjölen]

On Fri, 9 Jun 2023 10:17:46 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Hi,
> 
> Instead of using `Arena::move_contents` we can just see the arena swap as a form of double buffering, reducing this to a pointer swap and a clear. This allows us to remove `Arena::move_contents`, cleaning up the arena code.
> 
> Since this requires allocating another pointer for `Compile`, I took the time to move some members around in order to reduce the padding. This means that this patch does *not* introduce a size change for `Compile`.
> 
> I'm currently running tier1-3 tests.
> 
> Thanks for considering this,
> Johan

Thanks Tobias, I took your changes and applied them.

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PR Comment: https://git.openjdk.org/jdk/pull/14391#issuecomment-1591097852