RFR: 8325589: C2 SuperWord refactoring: create VLoopAnalyzer with Submodules [v3]

[Christian Hagedorn]

On Tue, 13 Feb 2024 16:26:25 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Subtask of https://github.com/openjdk/jdk/pull/16620
>> 
>> **Goals**:
>> - **modularity**: SuperWord is a nasty large class, and it is difficult to know what impacts what.
>> - **code reuse**: In the future, we may want to reuse some components of SuperWord in other Vectorizers. For example the post-loop-vectorizer ([JDK-8308994](https://bugs.openjdk.org/browse/JDK-8308994)).
>> 
>> Hence, I pull some parts out of SuperWord, and put them in a new class `VLoopAnalyzer`, with submodules:
>> 
>> VLoopAnalyzer
>>   VLoopReductions
>>   VLoopMemorySlices
>>   VLoopBody
>>   VLoopTypes
>> 
>> 
>> **Future Work**
>> In my draft for https://github.com/openjdk/jdk/pull/16620, I also created a submodule `VLoopDependenceGraph`.
>> But that is also a lot of code change.
>> I decided to do this in a separate RFE, to keep this patch here reasonably short.
>> 
>> I also left many functions in `superword.cpp`, even though their classes are in `vectorization.hpp`.
>> I think it is easier to review them in their old palces, with minor changes, for now.
>> In a future RFE, I can then cleanly copy them, without any changes to them.
>
> Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains eight commits:
> 
>  - manual merge
>  - move _loop_or_ctrl from ResouceArena, bc ResourceMark in SuperWord::dependence_graph
>  - remove some comments
>  - VLoopTypes
>  - VLoopBody
>  - VLoopMemorySlices
>  - VLoopReductions
>  - 8325589

src/hotspot/share/opto/superword.hpp line 235:

> 233:   CountedLoopNode* cl()                 const { return vloop().cl(); }
> 234:   PhiNode* iv()                         const { return vloop().iv(); }
> 235:   int iv_stride()                       const { return cl()->stride_con(); }

Could these also be field? You access these quite a lot but only inside this class and they seem to be constant.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17800#discussion_r1489671760