RFR: 8265702: ZGC on macOS/aarch64 [v2]

[Gerard Ziemski]

On Thu, 22 Apr 2021 06:43:45 GMT, Per Liden <pliden at openjdk.org> wrote:

>> This patch enables ZGC on macOS/aarch64. It does three things:
>> 1) Enables building of ZGC on this platform.
>> 2) Adds `os::processor_id()`, which for now always returns 0.
>> 3) Fixes a WX issue in `OptoRuntime::handle_exception_C()`, where the stackwater mark might unnecessarily process a frame when the thread is in WXExec mode. In this case, the we're not touching any oops, so we don't need to process any frames.
>> 
>> Testing: Passes the same tests as macOS/x86_64 (with the exception of pre-existing issues unrelated to ZGC).
>
> Per Liden has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comment to #else

Marked as reviewed by gziemski (Committer).

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PR: https://git.openjdk.java.net/jdk/pull/3609