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

[via llvm-commits]

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@@ -3986,12 +3978,14 @@ class VPlan {
   }
 
   /// \return The block corresponding to the original preheader.
-  VPBasicBlock *getPreheader() { return Preheader; }
-  const VPBasicBlock *getPreheader() const { return Preheader; }
+  VPBasicBlock *getPreheader() { return Entry; }
+  const VPBasicBlock *getPreheader() const { return Entry; }
 
   /// Clone the current VPlan, update all VPValues of the new VPlan and cloned
   /// recipes to refer to the clones, and return it.
   VPlan *duplicate();
+
+  VPBasicBlock *getScalarPreheader();
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ayalz wrote:

Better document and place above next to getVectorLoopRegion().

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