}
    callees.push_back(callee);
  }
  return success();
}

bool HasSingleBlock(func::FuncOp func) {
  return func->getNumRegions() == 1 && func.getBody().hasOneBlock();
}

  // Check if the island has only one block thats contain two ops, including
  // one resource op and one Yield op.
  auto island_op = llvm::dyn_cast_or_null<IslandOp>(op);
  if (!island_op || !island_op.getBody().hasOneBlock()) return nullptr;
  auto& island_block = island_op.getBody().front();
  if (++island_block.begin() != --island_block.end()) return nullptr;

  Operation* resource_op = &island_block.front();