RFR: 8367627: C2: Missed Ideal() optimization opportunity with MemBar [v3]

[Benoît Maillard]

On Wed, 10 Dec 2025 11:44:31 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Benoît Maillard 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 six additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8367627
>>  - Add notification in Node::has_special_unique_user
>>  - Add run with -XX:+AlwaysIncrementalInline, and add intermediate run for -XX:-DoEscapeAnalysis
>>  - Record in GraphKit::insert_mem_bar_volatile for consistency
>>  - Improve test and fix
>>  - Add test
>
> test/hotspot/jtreg/compiler/c2/igvn/TestMissingOptMemBarRemovePrecedentEdge.java line 2:
> 
>> (failed to retrieve contents of file, check the PR for context)
> Should the test go into an `igvn` directory? Or something else a bit more specific?

Moved it to `compiler/c2/igvn`

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PR Review Comment: https://git.openjdk.org/jdk/pull/28448#discussion_r2615250843