RFR: 8327978: C2 SuperWord: Fix compilation time regression in dependency graph traversal after JDK-8325651 [v3]

[Emanuel Peter]

On Thu, 4 Apr 2024 11:25:37 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Emanuel Peter 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 seven additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8327978-dependency-graph-comp-time-regression
>>  - For Vladimir: check is_Store first
>>  - Load / Store precedence
>>  - add some comments and asserts
>>  - ensure Load/Store order
>>  - Merge branch 'master' into JDK-8327978-dependency-graph-comp-time-regression
>>  - 8327978
>
> Good catch! Could such a long-running/compiling test also be added as jtreg test which fails due to a timeout without this patch and passes with the patch?

@chhagedorn I added a regression test as you requested. It results in timeout before the patch, and passes with plenty of time to spare with the patch.
I also did the code change you requested.

> src/hotspot/share/opto/vectorization.cpp line 324:
> 
>> 322:         }
>> 323:       }
>> 324:     }
> 
> This is identical to the loop above. Could this code be shared (e.g. `find_max_pred_depth()`)?

Good idea!

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PR Comment: https://git.openjdk.org/jdk/pull/18532#issuecomment-2037130738
PR Review Comment: https://git.openjdk.org/jdk/pull/18532#discussion_r1551620700