RFR: 8300258: C2: vectorization fails on simple ByteBuffer loop [v3]

[Roland Westrelin]

On Fri, 3 Mar 2023 15:27:06 GMT, Roland Westrelin <roland 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 ten additional commits since the last revision:
>> 
>>  - more
>>  - Merge branch 'master' into JDK-8300258
>>  - comments
>>  - extra test
>>  - more
>>  - Merge branch 'master' into JDK-8300258
>>  - review
>>  - more
>>  - fix & test
>
> I pushed some more tests than don't vectorize.

> @rwestrel : can you change the name of the Bug to reflect this? Suggestion: `C2: SuperWord alignment analysis must be based on memory slice, not velt type`

The bug database is not used only by developers that are familiar with the code. Sometimes people look for a bug matching what they observe (an error message for instance). So I'm not sure it's a good idea to change the bug synopsis that way as it's meaningless to anyone not familiar with the c2 code.

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PR: https://git.openjdk.org/jdk/pull/12440