[PATCH] D131028: [AArch64] Fix cost model for FADD vector reduction

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

It was worse on every CPU I tried it on. I did take some time last week looking at if we could adjust the cost of fma, but it looked like it had issues in itself and I wasn't even sure it would fix the problems with SLP vectorization.

>From the results I have, it looks like this patch causes more problems than it solves, and the stated reason for doing it (Matrix dotproduct lowering) seems niche compared to the amount of SLP vectorization this will enable. If there are known issues in the SLP vectorizer, in my opinion it would make sense to address those first. Maybe we won't get anywhere and we will end up having to enable this as-is, but it seems prudent to try.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D131028/new/

https://reviews.llvm.org/D131028