diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1129,6 +1129,16 @@
 /// phis for first order recurrences, pointer inductions and reductions. The
 /// start value is the first operand of the recipe and the incoming value from
 /// the backedge is the second operand.
+///
+/// Inductions are modeled using the following sub-classes:
+///  * VPCanonicalIVPHIRecipe: Canonical scalar induction of the vector loop,
+///    starting at a specified value and stepping by 1.
+///  * VPWidenIntOrFpInductionRecipe: Generates vector values for integer and
+///    floating point inductions with arbitrary start and step values.
+///  * VPScalarIVStepsRecipe: Generates scalar values for integer and floating
+///    point inductions with arbitrary start and step values.
+///  * VPWidenPointerInductionRecipe: Generate vector and scalar values for a
+///    pointer induction.
 class VPHeaderPHIRecipe : public VPRecipeBase, public VPValue {
 protected:
   VPHeaderPHIRecipe(unsigned char VPVID, unsigned char VPDefID, PHINode *Phi,