RFR: 8365205: C2: Optimize popcount value computation using knownbits [v9]

[Jatin Bhateja]

On Fri, 19 Sep 2025 09:37:45 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> As I'm about to board my plane for a 3-week vacation, I'm leaving a last little **note for the reviewers**.
> 
> I think this is a really nice addition, so thanks for doing it @jatin-bhateja 😊 . Though it will only reach its full potential once we implement more "basic" KnownBits optimizations such as [JDK-8367341](https://bugs.openjdk.org/browse/JDK-8367341).
> 

Correct, currently KnownBits information is constrained as they are generated for limited value ranges, as discussed in 
https://github.com/openjdk/jdk/pull/27075#discussion_r2337215333

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PR Comment: https://git.openjdk.org/jdk/pull/27075#issuecomment-3311500441