RFR: 8325064: C2 SuperWord: refactor construct_bb [v2]

[Christian Hagedorn]

On Mon, 5 Feb 2024 14:58:20 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Subtask of https://github.com/openjdk/jdk/pull/16620
>> 
>> The goal is to further disentangle different "components" in Superword.
>> 
>> In this refactoring, I disentangle the `bb`, `reduction` and `memory_slice` "components" which were all intertwined in `construct_bb`.
>> 
>> 1. Move memory slice code -> `analyze_memory_slices`.
>> 2. Remove reduction checking code -> simply use the `is_marked_reduction_loop` condition outside.
>> 3. `_data_entry`: was used for non-CFG nodes in the loop that have no input node that is also inside the loop. But that actually never happens! I removed that array, and replaced the code with verification.
>
> 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 four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8325064
>  - Merge branch 'master' into JDK-8325064
>  - small improvements
>  - 8325064

Looks good!

src/hotspot/share/opto/superword.cpp line 921:

> 919: }
> 920: 
> 921: void SuperWord::analyze_memory_slices() {

How about naming this `find_memory_slices()`? This would sound less generic than "analyze".

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17657#pullrequestreview-1863022257
PR Review Comment: https://git.openjdk.org/jdk/pull/17657#discussion_r1478389033