RFR: 8303882: Refactor some iterators in jdk.compiler [v3]

[Pavel Rappo]

On Mon, 13 Mar 2023 10:49:37 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Pavel Rappo has updated the pull request incrementally with four additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'myjdk/8303882' into 8303882
>>  - Squeeze a few extra drops of perf
>>  - Add a recursive test
>>  - Try squeeze more performance
>
> Looks good - some minor (optional) comments on the test

@mcimadamore, I have updated the test. Please check if that's what you had in mind.

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PR: https://git.openjdk.org/jdk/pull/12949