// guaranteed to dominate all live-in values. On the other hand, it is still
// possible that live-out values don't dominate the region. For example:
//
// ```
// %0 = "tf.OpA"()
// %1 = "tf.OpB"(%0)
// %2 = "tf.OpC"(%0)
// ```
//
// Assuming `tf.OpA` and `tf.OpC` are clustered together, the region will be
// inserted right after `tf.OpC`. The live-out `%0`, however, is used by

//
// tf_executor.island wraps "tf.OpA"
// tf_executor.island {
//  "tf_device.replicate" {n = 2} {
//    "tf.OpB"
//    "tf_device.parallel_execute"() ({
//      "tf.OpC"
//    }, {
//      "tf.OpD"
//    })
//  }
//
// The above IR will be flattened after `ReplicateToIslandPass` and
// `ParallelExecuteToIslandsPass` as follows:
//
// tf_executor.island wraps "tf.OpA"

    %handle0, %handle0_control = tf_executor.island wraps "tf.SomeOp"() : () -> !tf_res
    %handle1, %handle1_control = tf_executor.island wraps "tf.SomeOp"() : () -> !tf_res
    %control_A = tf_executor.island wraps "tf.OpA"() : () -> ()
    %while_out:2, %while_control = tf_executor.island(%control_A) wraps "tf.While"(
            %handle0, %handle1) {
        body = @body, cond = @cond, is_stateless = false