RFR: 8302652: [SuperWord] Reduction should happen after loop, when possible

[Jatin Bhateja]

On Thu, 30 Mar 2023 11:41:48 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> Where exactly would you put it? We need a location during LoopOpts, so that we have the ctrl information. I previously suggested in `split_if`, but @vnkozlov seemed not very excited. Additionally, I have not seen any case where VectorAPI could make use of it. I gave it a quick look, so maybe you can find something.

May I know the penalty which you see if we do this as a separate pass towards the end of _PhaseIdealLoop::build_and_optimize_, where we can iterate over __ltree_root_ and for each counted loop marked as a vector loop we can do this processing for all the reduction nodes part of loop body.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13056#discussion_r1157004962