message: Remove some unnecessary code in clustering pass and reword comments.
diff: @@ -321,10 +321,6 @@ static void ClusterOpsInTheBlock(
  members.emplace_back(members.size(), &op, first_user);
  }
  - // Operations that are candidates for clustering.
  - llvm::DenseSet<Operation *> member_ops;
  - for (auto &member : members) member_ops.insert(member.op);
  -
  // Mapping from the member operation to the id.
  llvm::DenseMap<Operation *, unsigned> member_ids;
  for (auto kv : llvm::enumerate(members))
  @@ -354,13 +350,14 @@ static void ClusterOpsInTheBlock(
  for (Operation *user : users) {
  // Skip users that are past the first cluster result user in the block,
  - // because after clustering we'll violate dominance property (the cluster
  - // operation will be defined after the first user in the block).
  + // because otherwise after clustering we would violate dominance property
  + // (the cluster operation would be defined after the first user in the
  + // block).
  unsigned root = FindRoot(members, member_id);
  Operation *first_cluster_user = members[root].first_user;
  if (first_cluster_user->isBeforeInBlock(user)) continue;
  - Union(members, member_ids.lookup(member.op), member_ids.lookup(user));
  + Union(members, member_id, member_ids.lookup(user));
  }
  }
  