[VPlan/PM] Improve comment

Author: artagnon

llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h

@@ -155,8 +155,8 @@ struct is_one {
 
 /// Match an integer 0 or a vector with all elements equal to 0.
 /// For vectors, this includes constants with undefined elements.
-/// The reason for not naming this m_Zero() is because PatternMatch::m_Zero()
-/// also matches null constants.
+/// This is different from PatternMatch::m_Zero(), which also matches null
+/// constants.
 inline int_pred_ty<is_zero_int> m_ZeroInt() {
   return int_pred_ty<is_zero_int>();
 }