RFR: 8255040: Replace __sync_add_and_fetch with __atomic_add_fetch to avoid build errors with clang

[Jie Fu]

On Thu, 22 Oct 2020 11:45:18 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> Hi all,
> 
> It's time to replace __sync_add_and_fetch with __atomic_add_fetch to avoid build errors. 
> 
> After JDK-8252221, build errors with clang were observed [1] due to the use of __sync_add_and_fetch, which is legacy and will be deprecated in the future.
> It can be reproduced by building macos-x86-zero or linux-x86-zero with clang.
> 
> The fix was prepared by learning from aarch64's implementation [2].
> Please review it.
> 
> Thanks
> Best regards,
> Jie
> 
> [1] https://bugs.openjdk.java.net/browse/JDK-8255040
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.hpp#L39

This bug was exposed after JDK-8252221.
Hope the author and reviewers of JDK-8252221 ( @amitdpawar , @tschatzl and @kimbarrett ) can first take a look at this.
Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/803