RFR: 8350097: Make Compilation::current() and Compile::current() safer

[Dean Long]

On Fri, 14 Feb 2025 14:48:34 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Somewhat trivial.
> 
> I recently hunted a bug for an hour until I realized that I had accessed ciEnv::compiler_data() as C2 `Compile` when, in fact, it was C1 `Compilation`. Stupid mistake, but an assert is easy to do and saves time.

If we derive C2 Compile and C1 Compilation from a common superclass, then ciEnv::compiler_data() could return that superclass and self-identify using a type field or virtual function.  When looking into how we handle failure messages and how complicated it is, I thought moving some fields into a common superclass would be useful.  Eventually we could even look into making ciEnv the common superclass, because the lifetimes are almost identical.

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PR Comment: https://git.openjdk.org/jdk/pull/23635#issuecomment-2660623476