// devices, and empty StringRef will be returned. Control dependencies,
// NextIteration.Source -> NextIteration.Sink token dependencies, and
// LoopCond -> Switch data dependencies are ignored.
llvm::StringRef FindDeviceFromOperands(
    Operation& op,
    const llvm::DenseMap<Value, llvm::StringRef>& value_to_device) {
  llvm::StringRef new_device;
  const bool is_switch = llvm::isa<tf_executor::SwitchOp>(op);