RFR: 8353290: C2: Refactor PhaseIdealLoop::is_counted_loop() [v23]

[Kangcheng Xu]

On Fri, 21 Nov 2025 16:34:03 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Kangcheng Xu has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix trip counter loop-variant detection
>
> Was too busy this week, will try to come back to this next week!

@chhagedorn Thank you reviewing. I'm glad to hear I'm making progress. Please see [my pervious comment](https://github.com/openjdk/jdk/pull/24458#discussion_r2569790528) regarding iteratively uncasting `xphi()`.

> [...] give your patch a spin in our standard testing [...]

Yes please. I've addressed last few suggestions and merged in the master. 

> [...] run some more extended testing with your old vs. new counted loop transformation state [...]

Good idea. I've updated the old vs. new code based on the latest patch on this pr. Please find it on the [`counted-loop-refactor-old-vs-new` branch](https://github.com/tabjy/jdk/commits/counted-loop-refactor-old-vs-new/). 

Please let me know how the testing goes. Thank you very much once again!

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PR Comment: https://git.openjdk.org/jdk/pull/24458#issuecomment-3587271888