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

Thu Sep 19 08:05:09 PDT 2019

SjoerdMeijer added a comment.

> Instruction selection and vectorizers are orthogonal.

Well, okay, sure..... but depending on what tricks the vectoriser does, its output can be different, and the input to instruction selection be different, triggering different instruction selection patterns.

> I don't think that isel work would become obsolete with a vectorizer emitting dot builtins:
>  there will be need to recognize the dot instructions in code that has not been processed by the vectorizers.

So, if the vectoriser for example emits dot product instructions, these patterns won't trigger and then it's say dead code if you see what I mean, but please correct me if I am wrong.

But at the same time, as I also said before, if this helps a few cases now, I don't see what's wrong with a nice little bit of pattern matching.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67645/new/

https://reviews.llvm.org/D67645