RFR: 8242440: use separate, destroyable JavaVM instances per libgraal compiler thread [v3]

[Doug Simon]

On Tue, 19 Apr 2022 09:06:54 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> The declaration was wrong for that usage - it should have been "volatile pointer to X" (`JavaVM* volatile`) but was declared "pointer to volatile X" (`volatile JavaVM*`).  That also wasn't a correct implementation of DCLP.  Good thing you are changing this.  So yes, the volatile should be nuked and this cast and the similar one in destroy_shared_library_javavm can be removed.
>
> Thanks for the correction. I have removed `volatile` altogether now. It's also a good reminder of the subtleties in C++ that do not exist in Java.

Fixed: https://github.com/openjdk/jdk/pull/8262/commits/8aacbbaa2c3909694e83000ca0f8366fc6dc7931

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PR: https://git.openjdk.java.net/jdk/pull/8262