RFR: 8282469: Allow considered use of C++ thread_local in Hotspot

[David Holmes]

On Mon, 7 Mar 2022 17:23:18 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> This patch provides a means for using C++ `thread_local` when it is essential - see JBS for more details.
>> 
>> There are three parts:
>> 
>> 1. Add the new #define for `thread_local`
>> 2. Remove `operator_new.cpp` as use of C++ `thread_local` with a non-trival cleanup actions requires use of global operators new/delete. These are still excluded for hotspot use via a link-time check.
>> 3. Remove the prohibition on using `thread_local` from the hotspot style guide
>> 
>> Due to the way hotspot style guide changes must be done, part 3 is being done under a sub-task in PR https://github.com/openjdk/jdk/pull/7720 and the two PR's will integrate at the same time.
>> 
>> Testing:
>>   - manual testing of the Panama usecase as referenced in the JBS issue
>>   - Tiers 1-3
>> 
>> Thanks,
>> David
>
> Looks good.

Thanks for the review @kimbarrett !

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PR: https://git.openjdk.java.net/jdk/pull/7719