RFR: 8276799: Implementation of JEP 422: Linux/RISC-V Port [v2]

[Fei Yang]

On Tue, 22 Mar 2022 04:13:17 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Fei Yang 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 two additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'upstream/master' into JDK-8276799
>>  - 8276799: Implementation of JEP 422: Linux/RISC-V Port
>
> make/autoconf/libraries.m4 line 152:
> 
>> 150:   fi
>> 151: 
>> 152:   # Programs which use C11 or C++11 atomics, like #include <atomic>,
> 
> Use of C++ atomics is not allowed in hotspot code base. See the style guide:
> https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md
> 
> That said, I don't see any actual use of C++ atomics. ??

I think the old code comment here is a bit too general. It does not mean we introduce any use of C++ atomics here.
The fact is that RISC-V only has word-sized atomics, it requries libatomic where other common architectures do not [1].
So atomic support would require explicit linking against -latomic on RISC-V. Otherwise we got build errors like:

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PR: https://git.openjdk.java.net/jdk/pull/6294