[llvm] [VPlan] Hook IR blocks into VPlan during skeleton creation (NFC) (PR #114292)

[via llvm-commits]

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@@ -2426,6 +2426,26 @@ InnerLoopVectorizer::getOrCreateVectorTripCount(BasicBlock *InsertBlock) {
   return VectorTripCount;
 }
 
+static void connectScalarPreheaderInVPlan(VPlan &Plan) {
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ayalz wrote:

Placed here rather than in VPlan.h/VPBlockUtils expecting it to be a temporary local scaffold? Worth documenting?

https://github.com/llvm/llvm-project/pull/114292