RFR: 8256831: MIPS Zero builds fail with undefined __atomic_compare_exchange_8 [v3]

[Magnus Ihse Bursie]

On Mon, 23 Nov 2020 22:35:05 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> If you try to build `linux-mipsel-zero-fastdebug`, this happens:
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>> I think it relates to [JDK-8253970](https://bugs.openjdk.java.net/browse/JDK-8253970) that introduced `atomic_compare_exchange` on those paths, but maybe the issue exists for longer. 
>> 
>> Various other reports for build failures like this suggest the binary should link with `libatomic`. GCC's `libatomic` is the library that provides runtime support for atomics not supported in hardware, which seems to include 8-byte CAS for MIPS, but not any other OpenJDK platform.
>> 
>> The alternative would be to massage the otherwise generic Zero code to unimplement the 8-byte CAS.
>> 
>> Attention @DamonFool, who must be running into this problem for their MIPS builds?
>> 
>> Testing:
>>  - [x] Linux mipsel Zero fastdebug build (together with JDK-8256829 fix)
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
> 
>  - Merge branch 'master' into JDK-8256831-mips-8-byte-cas
>  - Move the library addition to LIB_SETUP_LIBRARIES
>  - Merge branch 'master' into JDK-8256831-mips-8-byte-cas
>  - 8256831: MIPS Zero builds fail with undefined __atomic_compare_exchange_8

Marked as reviewed by ihse (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/1375