RFR: 8371464: C2: assert(no_dead_loop) failed: dead loop detected [v2]

[Roland Westrelin]

On Mon, 1 Dec 2025 08:02:47 GMT, Damon Fenacci <dfenacci at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
>> 
>>  - review
>>  - Merge branch 'master' into JDK-8371464
>>  - test
>>  - fix
>
> src/hotspot/share/opto/cfgnode.cpp line 1404:
> 
>> 1402:       Node* other_phi_input = in(j);
>> 1403:       if (other_phi_input != nullptr && other_phi_input == merge_mem->base_memory() && !is_data_loop(region, phi_input, igvn)) {
>> 1404:         // merge_mem is a successor memory to other_phi_input, and is not pinned inside the diamond, so push it out.
> 
> Do you think it might be worth adding an additional reason for `!is_data_loop` in the comment?

I added a comment in the new commit. Can you have a look?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28554#discussion_r2580274083