auto succ = use.getOwner();
      successors.push_back(succ);
    }
  }
  return successors;
}
// Gets the predecessors of an op wrapped in tf_executor.island.
llvm::SmallVector<Operation*> GetPredecessors(Operation* op) {
  llvm::SmallVector<Operation*> predecessors;
  for (auto operand : op->getOperands()) {
    if (Operation* pred = operand.getDefiningOp()) {
      pred->walk([&](mlir::Operation* opinexecutor) {

    }

    // If we're in an inner block, the we have to find all ops that branch
    // to that block, and trace through them.
    llvm::DenseSet<BlockArgument> options;
    for (Block *block : blockArg.getOwner()->getPredecessors()) {
      if (!block->empty()) {
        Operation *back = &block->back();
        if (BranchOpInterface branchOp = dyn_cast<BranchOpInterface>(back)) {
          for (int i = 0; i < branchOp->getNumSuccessors(); i++) {