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

[Christian Hagedorn]

On Thu, 27 Nov 2025 21:06:18 GMT, Kangcheng Xu <kxu at openjdk.org> wrote:

>> 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!

Thanks @tabjy for the update. Was too busy this week with the mainline fork but I'm happy to take another look next week :-)

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PR Comment: https://git.openjdk.org/jdk/pull/24458#issuecomment-3617590462