//   // Note: A producer is an operation that produces one of our inputs.
//   changed |= tryMergedIslandsIntoNearestProducer();
// }
//
class CoarseningAnalysis {
 public:
  // Compute the coarsening analysis over the given graph.
  explicit CoarseningAnalysis(GraphOp graph);

  // Returns a list of all of the mergable islands found in the graph.
  iterator_range<