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

[Michael Maitland 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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michaelmaitland wrote:

> VPlans are constructed after all cost-based ... decisions have been taken

It is my understanding that we build VPlans and then we determine the cost of each VPlan we have built to find the best VPlan. I haven't had a chance to work in LV for a few months now so I am not so familiar with recent changes. Did we move away from this, or are you describing a different kind of cost decisions?

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