RFR: 8294729: [s390] Implement nmethod entry barriers [v2]

[Martin Doerr]

On Thu, 27 Oct 2022 14:15:39 GMT, Tyler Steele <tsteele at openjdk.org> wrote:

>> This draft PR implements native method barriers on s390. When complete, this will fix the build, and bring the other benefits of [JDK-8290025](https://bugs.openjdk.org/browse/JDK-8290025) to that platform.
>
> Tyler Steele has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixup comments

Ok, this is the version which looks correct. Please consider moving the nmethod entry barrier implementation to the end such that you don't have to move it in your next PR.

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Marked as reviewed by mdoerr (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10558