[PATCH] D125712: [SLP][X86] Improve reordering to consider alternate instruction bundles

[Vasileios Porpodas via Phabricator via llvm-commits]

vporpo added a comment.

I am not sure if there is any other pattern, but this one showed up in a regression in the eigen benchmark.
Hmm yeah fixing it in the back-end may be an option but what if we end up not vectorizing the code because of this? The alternative is a blend + add + sub which should increase the cost quite a bit. So it is probably best to teach reordering not to mess up this pattern in the first place.


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https://reviews.llvm.org/D125712