RFR: 8328528: C2 should optimize long-typed parallel iv in an int counted loop [v17]

[Kangcheng Xu]

On Thu, 26 Sep 2024 16:19:27 GMT, Kangcheng Xu <kxu at openjdk.org> wrote:

>> Currently, parallel iv optimization only happens in an int counted loop with int-typed parallel iv's. This PR adds support for long-typed iv to be optimized. 
>> 
>> Additionally, this ticket contributes to the resolution of [JDK-8275913](https://bugs.openjdk.org/browse/JDK-8275913). Meanwhile, I'm working on adding support for parallel IV replacement for long counted loops which will depend on this PR.
>
> Kangcheng Xu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix wrong expect values in test

Random tests were unstable. The latest commit addressed wrong expected values being computed if the loop variable overflows (which the formula used for computing expected values are not accounted for). Stricter upper and lower bounds for RNG were added to avoid such an overflow.

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PR Comment: https://git.openjdk.org/jdk/pull/18489#issuecomment-2377415901