RFR (XXL): 8223347: Integration of Vector API (Incubator): General HotSpot changes

[Vladimir Ivanov]

> Typo, it's --add-modules

Good catch, Remi. Thanks for the correction.

> 
>> When user does that, JVM automatically enables Vector API support.
>> It improves usability (user doesn't need to separately "open" the API
>> and enable JVM support) while minimizing risks of destabilitzation from
>> new code when the API is not used.
> 
> Question, what if i declare a module-info that requires "jdk.incubator.vector", because in that case, i don't have to add --add-modules jdk.incubator.vector on the command line, but does the VM will enable the Vector API support ?

Good point. JEP 11: "Incubator Modules" [1] states the following:

"Applications on the class path must use the --add-modules command-line 
option to request that an incubator module be resolved. Applications 
developed as modules can specify requires or requires transitive 
dependences upon an incubator module directly."

Current implementation doesn't distinguish whether the module is 
resolved for an application on the class path or by another module, so 
JVM support will be enabled by default in both cases. Do you see any 
problems with that?

Best regards,
Vladimir Ivanov

[1] https://openjdk.java.net/jeps/11

>> That's it! Will be happy to answer any questions.
>>
>> And thanks in advance for any feedback!
> 
> regards,
> Rémi
> 
>>
>> Best regards,
>> Vladimir Ivanov
>>
>> [0]
>> https://mail.openjdk.java.net/pipermail/core-libs-dev/2020-March/065345.html
>>
>> [1]
>> https://mail.openjdk.java.net/pipermail/hotspot-dev/2020-April/041228.html
>>
>> [2] https://openjdk.java.net/jeps/338
>>
>> [3] https://openjdk.java.net/projects/panama/
>>
>> [4]
>> http://cr.openjdk.java.net/~vlivanov/panama/vector/jep338/hotspot.shared/webrev.00/01.intrinsics/src/java.base/share/classes/jdk/internal/vm/vector/VectorSupport.java.html
>>
>> [5] http://cr.openjdk.java.net/~vlivanov/talks/2018_JVMLS_VectorAPI.pdf
>>
>> [6] http://hg.openjdk.java.net/panama/dev/shortlog/92bbd44386e9
>>
>>       $ hg clone http://hg.openjdk.java.net/panama/dev/ -b vector-unstable