RFR: 8328528: C2 should optimize long-typed parallel iv in an int counted loop [v18]

[Roland Westrelin]

On Fri, 27 Sep 2024 21:55:26 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:
> 
>   Update TestParallelIvInIntCountedLoop.java

test/hotspot/jtreg/compiler/loopopts/parallel_iv/TestParallelIvInIntCountedLoop.java line 349:

> 347:             // also test with random init and init2
> 348:             int init1 = rng.nextInt();
> 349:             int init2 = rng.nextInt(Integer.MIN_VALUE + i + 1, i); // Similarly, avoid (i - init2) from overflowing.

What does the "similarly" refer to? To comment line 347 or line 321? It's unclear to me. I would remove it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18489#discussion_r1781010905