[llvm] [VPlan] Introduce VPlan-based hasTailFolded helper. (NFC) (PR #208329)

[Florian Hahn via llvm-commits]

================
@@ -7126,6 +7125,13 @@ bool LoopVectorizationPlanner::requiresScalarEpilogue(VPlan &Plan,
   return Result;
 }
 
+bool LoopVectorizationPlanner::hasTailFolded(const VPlan &Plan) const {
----------------
fhahn wrote:

It needs to have access to LoopVectorizationCostModel for the assert, which is only visiible in this file.

https://github.com/llvm/llvm-project/pull/208329