RFR: 8352565: Add native method implementation of Reference.get() [v6]

[Kim Barrett]

On Thu, 29 May 2025 18:45:20 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Yes, I find it much cleaner when intrinsic is non-virtual.
>> 
>>> Or maybe that's better done as a later cleanup?
>> 
>> Up to you. I'm fine with the current PR if you remove the comment referring to C2.
>
> FTR the special case in `compile.cpp` you referred to is not used right now because there are no stand-alone compilations of `Reference::get` happening (I believe because it is also intrinsified in interpreter).

Much of the point of this change is to let us later remove the interpreter/c1
intrinsics for this function. I think what you are saying is that might be
tricky if `get()` is the intrinsic. So maybe I should just go ahead now with
making the native `get0()` be the intrinsic. I'll take a look at it and see
how widespread the renaming changes are.

If `get0()` is the intrinsic, then I think that referenced snippet from the
Compile ctor can go away? Rather than being changed to refer to the get0
intrinsic.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24315#discussion_r2115737025