RFR: 8296477: Foreign linker implementation update following JEP 434 [v4]

[Jorn Vernee]

On Tue, 15 Nov 2022 18:07:18 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Tried this before when `Register` wasn't as `constexpr` friendly due to the reinterpret casts. Seems to work now though (thanks! :)) I'll change all these to `constexpr`.
>
> Err, looks like this works for MSVC, but with GCC I hit a snag eventually (it also require putting `constexpr` on a lot of the `Register`/`VMReg` API).
> 
> This error occurs:
> 
> 
> * For target hotspot_variant-server_libjvm_objs_downcallLinker.o:
> In file included from /mnt/h/openjdk/foreign-abi/src/hotspot/share/prims/vmstorage.inline.hpp:100,
>                  from /mnt/h/openjdk/foreign-abi/src/hotspot/share/prims/foreignGlobals.hpp:29,
>                  from /mnt/h/openjdk/foreign-abi/src/hotspot/share/prims/downcallLinker.hpp:27,
>                  from /mnt/h/openjdk/foreign-abi/src/hotspot/share/prims/downcallLinker.cpp:25:

I guess there's also the possibility that this might trip up compilers on other platforms, even if I can manage to fix it here.

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PR: https://git.openjdk.org/jdk/pull/11019