RFR: 8274004: Change 'nonleaf' rank name

[Daniel D.Daugherty]

On Wed, 6 Oct 2021 23:27:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> 8273956: Add checking for rank values
> 
> This change does 3 things.  I could separate them but this has all been tested together and most of the change is mechanical.  The first is a simple rename of nonleaf => safepoint.  The second change is to add the enum class Rank which only allows subtraction from a base rank, and some additional type checking so that rank arithmetic doesn't overlap with a different rank.  Ie if you say nosafepoint-n, that doesn't overlap with oopstorage.   The third change is to remove the _safepoint_check_always/never flag.  That is now intrinsic in the ranking, as all nosafepoint ranks are lower than all safepoint ranks.
> 
> Future changes could add rank names in the middle of nosafepoint and safepoint, like handshake.  As of now, the rank subtractions isn't unmanageable.  There are actually not many nested Mutex.
> 
> This is the last of the planned subtasks for Mutex ranking cleanup.  If you have other ideas or suggestions, please let me know.
> 
> Tested with tier1-8 at one point in time and just retested with tier1-6.

The PR description mentions:
`8273956: Add checking for rank values`
but the PR synopsis is:
`8274004: Change 'nonleaf' rank name`

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PR: https://git.openjdk.java.net/jdk/pull/5845