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

Wed Nov 25 19:52:02 UTC 2020

On Wed, 25 Nov 2020 18:34:28 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> From this conversation the only change I can do is 'Turn (on_weak || on_phantom) into !on_strong'.
>> @fisk Is this correct? I am concern that it will include `unknown` decorator too.
>> I agree with Erik to keep !no_keepalive because he prefer it and this is code supported by GC group.
>
> Well if on_weak || on_phantom then it is provably a weak access. But I think the absence of the strong decorator does not prove it is weak, as it could have an unknown strength (via unsafe), in which case we need some extra logic to see if we can prove that an unknown strength access can't be weak.

Okay. I will leave changes as it is.

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