RFR: 8252898: remove bulk registration of JFR CompilerPhaseType names

[Doug Simon]

On Tue, 8 Sep 2020 15:07:04 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

> The changes made in [JDK-8193210](https://bugs.openjdk.java.net/browse/JDK-8193210) support only [bulk
> registration](https://github.com/openjdk/jdk/blob/4e6a4af1866d0007d368b78bf78b6a8e1c8be425/src/hotspot/share/compiler/compilerEvent.hpp#L75)
> of compiler phase names with JFR. However, Graal only registers compiler phase names upon first execution of the phase
> since the set of phases is not known during VM initialization. This means registration of a Graal phase name needs to
> do unnecessary work, wrapping a single name into an array to conform to the bulk registration API. This pull request
> updates the registration API to be in terms of a registering a single phase name.

@jamsheedcm could you please have a look at this change.

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PR: https://git.openjdk.java.net/jdk/pull/77