RFR: 8317572: C2 SuperWord: refactor/improve TraceSuperWord, replace VectorizeDebugOption with TraceAutoVectorization [v7]

[Christian Hagedorn]

On Sat, 27 Jan 2024 05:39:51 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Subtask of https://github.com/openjdk/jdk/pull/16620
>> 
>> I got approval to remove VectorizeDebugOption: [JDK-8320668](https://bugs.openjdk.org/browse/JDK-8320668)
>> 
>> I want a more general flag for AutoVectorization, that can trace different components of AutoVectorization.
>> It should be a CompileCommand, so that it can select which methods it traces for.
>> 
>> TraceSuperWord should still look similar, and select a subset of the TraceAutoVectorization components (those for SuperWord), but still apply to all classes/methods.
>> 
>> With more refactoring later in [JDK-8315361](https://bugs.openjdk.org/browse/JDK-8315361), this flag should become more usable and interpretable. Especially, the idea is that different components of the `VLoop / VLoopAnalyzer` can have tracing enabled / disabled.
>> 
>> **How to use the flag:**
>> Get "help", i.e. see all available tags:
>> `./java -Xcomp -XX:CompileCommand=TraceAutoVectorization,*::*,help --version`
>> 
>> See "rejections" (i.e. failures where we don't vectorize) and successes (using TraceNewVectors):
>> `./java -Xcomp -XX:CompileCommand=TraceAutoVectorization,*::*,SW_REJECTIONS -XX:+TraceNewVectors --version`
>> The results are currently underwhealming. I will have to track many more failures, and I will do that with the bigger refactoring, when I move around the code and require error code returning everywhere, and then I can use that error code for printing.
>
> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix missing include

Looks good, thanks for the updates!

src/hotspot/share/opto/traceAutoVectorizationTag.hpp line 26:

> 24: 
> 25: #ifndef SHARE_OPTO_TRACE_AUTO_VECTORIZATION_TAG_HPP
> 26: #define SHARE_OPTO_TRACE_AUTO_VECTORIZATION_TAG_HPP

I think for this define, you should keep `SHARE_OPTO_TRACEAUTOVECTORIZATIONTAG_HPP` to follow the convention of other files where we do not insert underlines in the filename.

-------------

Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17586#pullrequestreview-1848009572
PR Review Comment: https://git.openjdk.org/jdk/pull/17586#discussion_r1469188205