Add a comment to clarify why there isn't any code in this spot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76505 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/ScalarEvolution.cpp

@@ -4324,6 +4324,8 @@ bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
     break;
   }
   case ICmpInst::ICMP_EQ:
+    // The check at the top of the function catches the case where
+    // the values are known to be equal.
     break;
   }
   return false;