RFR: JDK-8286666: JEP 429: Implementation of Scoped Values (Incubator) [v33]

[Dean Long]

On Tue, 29 Nov 2022 11:49:10 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Unused variable
>
> src/jdk.incubator.concurrent/share/classes/jdk/incubator/concurrent/ScopedValue.java line 385:
> 
>> 383:             try {
>> 384:                 JLA.setScopedValueBindings(newSnapshot);
>> 385:                 JLA.ensureMaterializedForStackWalk(newSnapshot);
> 
> Question: is it necessary here to invoke `ensureMaterializedForStackWalk()` It's really only there to prevent the new `Snapshot` from being scalar replaced. But we know that it cannot be scalar replaced, because it really does escape: a pointer to it is stored in the current `Thread`. So should we simply remove the call to `ensureMaterializedForStackWalk()`, on the grounds that it cannot have any effect?

It does seem unnecessary here, but I'm not an expert on current and future C2 escape analysis.  @vnkozlov, do you agree?

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PR: https://git.openjdk.org/jdk/pull/10952