RFR: 8256999: Add C2 intrinsic for Reference.refersTo and PhantomReference::refersTo [v2]

[Aleksey Shipilev]

On Sat, 28 Nov 2020 09:43:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Vladimir Kozlov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8256999
>>  - Added ZLoadBarrierElided = 0 definition.
>>    Removed is_exact argument in load_field_from_object().
>>    Added Shenandoah support for narrow phantom accesses.
>>  - 8256999: Add C2 intrinsic for Reference.refersTo and PhantomReference::refersTo
>
> Yes, still looks good for me.

You might want to pull from master to get clean `x86_32` test runs.

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PR: https://git.openjdk.java.net/jdk/pull/1425