RFR: 8248238: Implementation of JEP: Windows AArch64 Support [v10]

[Bernhard Urban-Forster]

On Mon, 28 Sep 2020 19:28:10 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

>> The idea is that the naming should suggest that `r18` shouldn't be used on that particular platform. Same is true for
>> macOS, but the ABI docs suggest a different usage, hence we have something like that in our internal branch for macOS:
>> Suggestion:
>>     "r17", NOT_R18_RESERVED("r18") WIN64_ONLY("rtls") MACOS_ONLY("rplatform"), "r19",
>> Are you suggesting it should rather be something like this eventually?
>> Suggestion:
>> 
>>     "r17", LINUX_ONLY("r18") WIN64_ONLY("rtls") MACOS_ONLY("rplatform"), "r19",
>
> this looks better I think, if it's done right from beginning, we won't have to modify it later.
> The Question is, can we do it ahead of JEP-391 ?
> If we can't then maybe better to leave it this way for now:
> WIN64_ONLY("rtls") NOT_WIN64("r18")
> 
> as r18 is supposed to be reserved register on aarch64, linux is just an exception where it's allowed.

Let us go with the following in this PR as that's the extend of this PR:
Suggestion:

    "r17", LINUX_ONLY("r18") WIN64_ONLY("rtls"), "r19",
We can update it accordingly in a PR for JEP-391.

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PR: https://git.openjdk.java.net/jdk/pull/212