RFR: 8254354: Add a withInvokeExactBehavior() VarHandle combinator [v9]

[Jorn Vernee]

On Fri, 30 Oct 2020 15:23:28 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
>> 
>>  - Update Javadoc, and rename asExact and asGeneric to withInvokeExactBehaviour and withInvokeBehaviour
>>  - Merge branch 'master' into Exact_VarHandle
>>  - Use AccessType ordinal in guard checks instead of the AccessMode ordinal
>>  - Update accessModeType to use the AccessType ordinal directly.
>>  - Add benchmarks
>>  - - Update javadoc
>>    - Make isExact() public
>>  - Fixes failing tests, and enable verifier on Exact test
>>  - Fix whitespace
>>  - Comment out VarHandleGuards generator code
>>  - Makes exactness a property of a VarHandle, not a VarForm, since the latter are shared. Use handle.accessModeType to get the exact type of the VarHandle.
>>  - ... and 2 more: https://git.openjdk.java.net/jdk/compare/84ce7081...3c707bc7
>
> Looks good. There is just one difference between the spec and implementation. The spec states: 
>> If this VarHandle already has invoke{-exact} behaviour this VarHandle is returned.
> 
> I prefer this behaviour, but feel free to update the spec if you like e.g. If ... already has XXX then a new VH with exactly the same behaviour as this VH is returned.
> 
> I just realized i used "behaviour", the english spelling. We should use the US spelling, "behavior", which is more commonly used throughout the JDK documentation.

@ChrisHegarty Thanks for the comments. I've implemented them.

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PR: https://git.openjdk.java.net/jdk/pull/843