RFR: 8304303: implement VirtualThread class notifyJvmti methods as C2 intrinsics [v4]

[Serguei Spitsyn]

On Fri, 17 Mar 2023 17:33:46 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> Overall, compiler changes look good.
> Any performance numbers to justify the intrinsification?

Thank you for review and your guidance and help with C2 intrinsification!
My goal was to move the notifyJvmtiEvents checks from Java to VM side without a performance penalty.
I do not observe any performance degradation with customized Skynet benchmark executing 5 million virtual threads.
Used `time` utility to measure total execution time (in milliseconds) of 10 runs on Oracle Linux server:
- without intrinsics: 6083, 5405, 5270, 5700, 5004, 5402, 5536, 5031, 4902, 5124
- with intrinsics:       5904, 5287, 5470, 5672, 5298, 5053, 6154, 4992, 6237, 5155

-------------

PR: https://git.openjdk.org/jdk/pull/13054