Updated comment

Author: Mel-Chen

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1485,7 +1485,7 @@ static void transformRecipestoEVLRecipes(VPlan &Plan, VPValue &EVL) {
               })
               .Case<VPInstruction>([&](VPInstruction *VPI) -> VPRecipeBase * {
                 VPValue *LHS, *RHS;
-                // Transform predicated reduction select
+                // Transform select with a header mask condition
                 //   select(header_mask, LHS, RHS)
                 // into vector predication merge.
                 //   vp.merge(all-true, LHS, RHS, EVL)