[PATCH] D102437: [LV] NFCI: Move implementation of isScalarWithPredication to LoopVectorizationLegality

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

I'd like to understand the main motivation and the reasons why it cannot be done via cost-modeling a bit better. IIUC the main problem is the case where scalable vectorization is forced by the user via pragmas or options? In the auto-vec case, the cost-model would already just skip scalable VFs in those cases as not profitable?

You mention `... we can't yet fall back on scalarization.` From that I gather you plan to add support for that in the future? If we could scalarize arbitrary instructions for scalable vectors, would we need to do the check during the legality checks? If it would be possible to scalarize, even if expensive or hard to estimate, it seems to me that the current code should work without change, right?


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  https://reviews.llvm.org/D102437/new/

https://reviews.llvm.org/D102437