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

[Roland Westrelin]

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

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

> 347:             int init1 = rng.nextInt();
> 348:             int init2 = rng.nextInt(Integer.MIN_VALUE + i + 1, i);
> 349:             long init1L = rng.nextLong(Long.MIN_VALUE + i + 1, i);

I understand the init2 computation I think (i - init2 should not overflow max signed int value) but I don't understand the `init1L` one. As far as I can tell, `init1L` is used the same way `init1` is used but one is for a test with a long variable and the other for a int variable. Why don't they use the same initialization pattern then?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18489#discussion_r1778500313