[LV][NFC] Fix enums and comments in VPInstruction class

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -1299,18 +1299,10 @@ class LLVM_ABI_FOR_TEST VPInstruction : public VPRecipeWithIRFlags,
     LastActiveLane,
     // Returns a reversed vector for the operand.
     Reverse,
-
-    // The opcodes below are used for VPInstructionWithType.
-    //
-    /// Scale the first operand (vector step) by the second operand
-    /// (scalar-step).  Casts both operands to the result type if needed.
-    WideIVStep,
     /// Start vector for reductions with 3 operands: the original start value,
     /// the identity value for the reduction and an integer indicating the
     /// scaling factor.
     ReductionStartVector,
-    // Creates a step vector starting from 0 to VF with a step of 1.
-    StepVector,
     /// Extracts a single lane (first operand) from a set of vector operands.
     /// The lane specifies an index into a vector formed by combining all vector
     /// operands (all operands after the first one).
@@ -1324,15 +1316,28 @@ class LLVM_ABI_FOR_TEST VPInstruction : public VPRecipeWithIRFlags,
     /// masks (even operands -- ignoring the default value), and returns the
     /// last active value from the combined data vector using the combined mask.
     ExtractLastActive,
-
-    /// Returns the value for vscale.
-    VScale,
     /// Compute the exiting value of a wide induction after vectorization, that
     /// is the value of the last lane of the induction increment (i.e. its
     /// backedge value). Has the wide induction recipe as operand.
     ExitingIVValue,
     MaskedCond,
-    OpsEnd = MaskedCond,
+
+    // The opcodes below are used for VPInstructionWithType.
+    // NOTE: VPInstructionWithType classes are also used for:
+    // 1. All CastInst variants - see createVPInstructionsForVPBB, and other
+    //    cases where createScalarCast, createScalarZExtOrTrunc and
+    //    createScalarSExtOrTrunc are invoked.
+    // 2. Scalar load instructions - see createVPInstructionsForVPBB.
+
+    /// Scale the first operand (vector step) by the second operand
+    /// (scalar-step).  Casts both operands to the result type if needed.
+    WideIVStep,
+    // Creates a step vector starting from 0 to VF with a step of 1.
+    StepVector,
+    /// Returns the value for vscale.
+    VScale,
+
+    OpsEnd = VScale,
   };
 
   /// Returns true if this VPInstruction generates scalar values for all lanes.