[llvm] [VPlan] Document current status. (PR #85689)

[Florian Hahn via llvm-commits]

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@@ -19,6 +19,49 @@ candidates. It serves for both optimizing candidates including estimating their
 cost reliably, and for performing their final translation into IR. This
 facilitates dealing with multiple vectorization candidates.
 
+Current Status
+==============
+VPlan is currently used to drive code-generation in LoopVectorize. VPlans are
+constructed after all cost-based and most legality-related decisions have been
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fhahn wrote:

Costs are computed first, when building a VPlan they are used to make decision (what to widen, what to scalarize and so on). After building the VPlans, the best VF is chosen using the legacy cost model, but that may soon change.

https://github.com/llvm/llvm-project/pull/85689