[llvm] [VPlan] Implement interleaving as VPlan-to-VPlan transform. (PR #95842)

[Florian Hahn via llvm-commits]

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@@ -1330,6 +1332,9 @@ class VPInstruction : public VPRecipeWithIRFlags {
   /// Returns true if this VPInstruction produces a scalar value from a vector,
   /// e.g. by performing a reduction or extracting a lane.
   bool isVectorToScalar() const;
+
+  /// Return the interleave count from the VPInstruction's last argument.
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fhahn wrote:

It is the interleave count. It could be part of the region, but it is also needed for instructions outside the region (`CalculateTripCountMinusVF`)

https://github.com/llvm/llvm-project/pull/95842