RFR: Add flag to prevent multiple deopts on the same nmethod.

[Coleen Phillimore]

On Tue, 9 Nov 2021 13:25:50 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> I added a flag to prevent the same nmethod from being optimized multiple times.  It might be better to have a new MarkForDeoptimizationStatus enum but wasn't sure how that would interact with the deoptimize_update state.  Advice welcome.
> I also don't know why the sweeper is so slow to get rid of these entries.
> This makes ctw_2 test run in an hour on my machine, just like mainline jdk/jdk (machine is slow!) in fastdebug.

I had a look again and can add the flag to MarkForDeoptimizationStatus which I left as a u1.

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PR: https://git.openjdk.java.net/loom/pull/81