[PATCH] D29727: [SLP] Fix for PR31690: Allow using of extra values in horizontal reductions.

[Michael Kuperstein via Phabricator via llvm-commits]

mkuper added a comment.

So, I understand you decided to vectorize the failing case, instead of bailing on it?
I'm not sure this is a good idea. I'm pretty sure I can craft a test-case where this will retain all of the scalar computation, in addition to performing the scalar one (e.g. have all of %x1 - %x4 as extra arguments).  If I understand this code correctly, the cost model will not get adjusted for this, so you'll end up vectorizing cases you really don't want to vectorize, just so you can perform the vector reduction.

Why do you prefer not to bail?


https://reviews.llvm.org/D29727