Address a comment.

Author: kazutakahirata

llvm/include/llvm/ADT/EquivalenceClasses.h

@@ -256,8 +256,9 @@ template <class ElemTy> class EquivalenceClasses {
       }
       if (!Next) {
         // If the current element is the last element(not leader), set the
-        // successor of the current element's predecessor to null, and set
-        // the 'Leader' field of the class leader to the predecessor element.
+        // successor of the current element's predecessor to null while
+        // preserving the leader bit, and set the 'Leader' field of the class
+        // leader to the predecessor element.
         Pre->Next = reinterpret_cast<const ECValue *>(
             static_cast<intptr_t>(Pre->isLeader()));
         Leader->Leader = Pre;