RFR: 8221554: aarch64 cross-modifying code

[David Holmes]

On Mon, 12 Oct 2020 12:47:46 GMT, Alan Hayward <github.com+4146708+a74nh at openjdk.org> wrote:

>> Patch updated.
>> 
>> * cross_modify_fence now calls cross_modify_fence_impl as suggested.
>> 
>> * ISBs in the JNI calls have been removed. This means that it is currently unsafe to merge until
>>   https://github.com/openjdk/jdk/pull/296 has been merged.
>
> https://github.com/openjdk/jdk/pull/296 has been merged to head.
> 
> Rebased this request and re-tested.
> All review comments have been addressed.
> Note that with VerifyCrossModifyFence set, testing took longer by a factor of *2.5.

@a74nh Please do not force-push commits on an open PR as it breaks the commit history and prevents reviewers from
seeing what has changed since they last reviewed things. If you need to "rebase" you can just merge your branch with an
updated master branch and push the merge commit to your personal fork. The skara tooling will flatten the commits into
a single clean commit when integration happens. Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/428