[PATCH] D67645: [aarch64] add def-pats for dot product

[Abderrazek Zaafrani via Phabricator via llvm-commits]

az added a comment.

There are few things missing in current work such as indexed dot product or what they call s/udot (vector, by element) in the ARM document (no need to do it now but a comment about that would help). There is also sve dot product. We need to port this code to SVE.

I agree that this work will miss many opportunities and the middle end will optimize the code in such a way that pattern matching does not work. I think that dot product need to have it own pass or subpass in the middle end. I see three places where it can be done: 1) early before the vectorizer in the same way we recognize min/max/etc., or 2) we can do it within the vectorizer as dot product is mainly a vectorization problem, or 3) we can do it post the vectorizer similar to the SIMD interleaved load/store. The third option, while not the best, has more chance of being accepted given that it less disruptive. Any tought on this as we may contribute to this effort in the future?


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https://reviews.llvm.org/D67645