[PATCH] D53865: [LoopVectorizer] Improve computation of scalarization overhead.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

> Are you proposing some kind of search over instruction sequences with some limited lookahead?

Yes, something like this.

> I suspect that an algorithm that makes these decisions would benefit from knowing which instructions the target *must* scalarize

I think you would just start with instructions where the cost model says that VectorOperationCost > ScalarOperationCost*VF.  It doesn't really matter why it's expensive.  (I guess at some point, we might want to model which execution units are used by a vector instruction, but I think you'd want a different interface for that.)


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https://reviews.llvm.org/D53865