RFR: 8325482: Test that distinct seeds produce distinct traces for compiler stress flags [v3]

[Damon Fenacci]

On Mon, 4 Aug 2025 12:44:21 GMT, Saranya Natarajan <snatarajan at openjdk.org> wrote:

>> The existing test (`compiler/debug/TestStress.java`) verifies that compiler stress options produce consistent traces when using the same seed. However, there is currently no test to ensure that different seeds result in different traces.
>> 
>> ### Solution
>> Added a test case to assess the distinctness of traces generated from different seeds. This fix addresses the fragility concern highlighted in [JDK-8325482](https://bugs.openjdk.org/browse/JDK-8325482) by verifying that traces produced using N (in this case 10) distinct seeds are all not identical.
>> 
>> ### Changes to `compiler/debug/TestStress.java`
>> While investigating this issue, I observed that in `compiler/debug/TestStress.java`, the stress options for macro expansion and macro elimination were not being triggered because there were fewer than 2 macro nodes. Note that the  `shuffle_macro_nodes()` in` compile.cpp` is only meaningful when there are more than two macro nodes. The generated traces for macro expansion and macro elimination in `TestStress.java` were empty. I have proposed changes to address this problem.
>
> Saranya Natarajan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   addressing review comments on camelCase

Thanks for looking at this and for the clarifications @sarannat.
LGTM

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Marked as reviewed by dfenacci (Committer).

PR Review: https://git.openjdk.org/jdk/pull/26554#pullrequestreview-3087141514