message: Add example for TPUExtractOutsideCompilation pass.
diff: @@ -47,8 +47,32 @@ using OutsideClusterMap =
  // This pass extracts a CPU computation cluster with `_xla_outside_compilation`
  // annotation from a TPU cluster. Each outside compilation cluster is moved to
  // a parallel_execute region. The TPU cluster is also moved to a
  -// parallel_execute region.
  -// TODO(b/154363171): Add example tranformations.
  +// parallel_execute region. Communication ops between device and host are
  +// added to pass inputs/outputs to/from the outside compiled region.
  +//
  +// A simple example:
  +// "tf_device.cluster"() ( {
  +// "tf.A"()
  +// "tf.B"() {_xla_outside_compilation = "cluster1"}
  +// "tf.C"()
  +// tf_device.return
  +// }) {num_cores_per_replica = 1, topology = "", device_assignment = []}
  +//
  +// Would become the following ops (unimportant attribute, type are omitted):
  +// "tf_device.parallel_execute"() ( {
  +// "tf_device.launch"() ( {
  +// "tf.B()
  +// tf_device.return
  +// })
  +// tf_device.return
  +// }, {
  +// "tf_device.cluster"( {
  +// "tf.A"()
  +// "tf.C"()
  +// tf_device.return
  +// })
  +// tf_device.return
  +// })
  struct TPUExtractOutsideCompilation
  : public PassWrapper<TPUExtractOutsideCompilation,
  