RFR: 8261027: AArch64: Support for LSE atomics C++ HotSpot code

[Ludovic Henry]

On Mon, 8 Feb 2021 11:24:00 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> I suppose you could just move it to `os_cpu/linux_aarch64/` as these are only called from the Linux atomics?
>
> They're probably needed on Windows, or I'd have put them in linux_aarch64.

I can confirm that assembly code targeted at Linux generally won't compile out of the box on Windows. For `windows_aarch64`, could we have simple fallbacks in C++ code that simply call `InterlockedAdd`, `InterlockedExchange`, and `InterlockedCompareExchange`? It would be similar to [atomic_windows_aarch64.hpp](https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/windows_aarch64/atomic_windows_aarch64.hpp)

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PR: https://git.openjdk.java.net/jdk/pull/2434