[PATCH] D96025: [LoopVectorize] Return both fixed and scalable Max VF from computeMaxVF.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen created this revision.
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This patch introduces a new class, `OptionalVFCandidates`, that holds
the possible maximum vectorization factors that have been computed. The
algorithm guarantees there is always at least one maximum VF (in worst
case ElementCount::getFixed(1) for scalarization), but may have both a
fixed MaxVF and a scalable MaxVF.

This patch is intended to be a non-functional change for now,
because LoopVectorizationPlanner::plan doesn't actually use the
scalable MaxVF yet to automatically pick a scalable VPlan
(at least not beyond the UserVF if that's given).

This patch is a preparatory patch with the ultimate goal of making
`computeMaxVF()` return both a max fixed VF and a max scalable VF,
so that `selectVectorizationFactor()` can pick the most cost-effective
vectorization factor.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D96025

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

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