[PATCH] D109296: [LV] Improve inclusivity of vectorization

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

Shouldn't this be taking the trip count into account somehow? Generating 7 times the scalar loop in run-time checks seems okay if you have thousands of iterations, but would be bad for a cold loop with a few iterations. After a quick look at D75981 <https://reviews.llvm.org/D75981> that variant does look at the TC. From the patch description, it's not entirely clear to me why a fixed factor of the scalar loop cost is preferable.

(Though as a comment on D75981 <https://reviews.llvm.org/D75981>, it uses getSmallBestKnownTC, which may return getSmallConstantMaxTripCount, which I believe will commonly just be INT_MAX for loops that are finite but have unknown trip count, so it may be drastically overestimating the TC for loops without exact trip count or profile data.)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109296/new/

https://reviews.llvm.org/D109296