RFR: 8252505: C1/C2 compiler support for blackholes [v19]

[Aleksey Shipilev]

On Thu, 3 Dec 2020 12:48:30 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 33 commits:
>> 
>>  - Merge branch 'master' into JDK-8252505-blackholes
>>  - Handle null-checks in intrinsics to maintain the semantics
>>  - Blackhole takes precedence over all other intrinsics
>>  - Print Blackhole format
>>  - Formatting touchups
>>  - Make sure null-checks are handled correctly after blackholed methods
>>  - Parallelize and ID the tests properly
>>  - Multiple arguments tests
>>  - Remodel blackhole hook as fake intrinsic
>>  - Remodel CallBlackhole as Blackhole membar
>>  - ... and 23 more: https://git.openjdk.java.net/jdk/compare/56b15fbb...1c4b1706
>
> Looks good!

I think testing is all-green in GH Actions. I also passed tier{1,2} locally. Also passes JMH validation tests. I think we are ready to integrate this. @theRealAph, @adinn, @cl4es, want to ack the current patch?

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PR: https://git.openjdk.java.net/jdk/pull/1203