RFR: 8353290: C2: Refactor PhaseIdealLoop::is_counted_loop() [v21]

[Christian Hagedorn]

On Wed, 12 Nov 2025 14:31:44 GMT, Kangcheng Xu <kxu at openjdk.org> wrote:

>> This PR refactors `PhaseIdealLoop::is_counted_loop()` into (mostly) `CountedLoopConverter::is_counted_loop()` and `CountedLoopConverter::convert()` to decouple the detection and conversion code. This enables us to try different loop configurations easily and finally convert once a counted loop is found. 
>> 
>> A nested `PhaseIdealLoop::CountedLoopConverter` class is created to handle the context, but I'm not if this is the best name or place for it. Please let me know what you think.
>> 
>> Blocks [JDK-8336759](https://bugs.openjdk.org/browse/JDK-8336759).
>
> Kangcheng Xu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add missed minor changes

Thanks for the (ongoing?) updates! Let me know, when it's ready to be reviewed again 👍

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PR Comment: https://git.openjdk.org/jdk/pull/24458#issuecomment-3526550324