RFR: CODETOOLS-7903004: JMH: Compiler Blackholes auto-detection [v6]

[Claes Redestad]

On Wed, 4 Aug 2021 09:05:08 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This is another step towards better [compiler blackholes](https://shipilev.net/jvm/anatomy-quarks/27-compiler-blackholes/) support. This time, we can enable JMH to auto-detect the support and enable it, if JVM supports it. 
>> 
>> The upside is that users would have much more fidelity in benchmarks and would be be exposed to eventual default Blackhole mode early.
>> 
>> The flip side is that JDK 17+ benchmarks would suddenly become faster without any user prompt, and maybe run into higher risk for VM bugs in the new blackhole code. I have ran the entire JDK microbenchmark corpus without problems, however, so that possibility should be low.
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minor touchups

LGTM (Not a codetools Reviewer)

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Marked as reviewed by redestad (no project role).

PR: https://git.openjdk.java.net/jmh/pull/48