// can be merged but not 2nd IfRegion and 2nd IfRegion should be moved after
// newly merged IfRegion.

// CHECK-LABEL: func @same_predicate_3_ifregions_reorder
func.func @same_predicate_3_ifregions_reorder() {
  // CHECK:      tf_device.cluster
  // CHECK:        "tf.IfRegion"
  // CHECK:          "tf.A"
  // CHECK:          "tf.G"
  // CHECK-NEXT    "tf.IfRegion"
  // CHECK:          "tf.E"

  // CHECK: %[[IF:.*]]:2 = "tf.IfRegion"(%[[ARG0]])
  %0 = "tf.VarHandleOp"() {container = "c", shared_name = "v"} : () -> tensor<*x!tf_type.resource<tensor<4xf32>>>
  %1 = "tf.VarHandleOp"() {container = "c", shared_name = "v2"} : () -> tensor<*x!tf_type.resource<tensor<4xf32>>>
  %2 = "tf_device.cluster"() ({
    %3:2 = "tf.IfRegion"(%arg0) ({
          // CHECK-NEXT: %[[CONST:.*]] = "tf.Const"()

  // CHECK: "tf.IfRegion"(%[[PRED]]) <{is_stateless = false}> ({
  %case_op = "tf.IfRegion"(%arg0) <{is_stateless = false}> ({
      // CHECK: %[[TA_VAL:.*]] = "tf.ReadVariableOp"(%[[TA_BUFFER]])
      // CHECK: "tf.Slice"(%[[TA_VAL]]
      // CHECK-NOT: tf.TensorArrayReadV3

their `mlir_module` string attribute.
### `-tf-merge-control-flow`

_Merges IfRegion ops together with a common predicate._

This pass merges IfRegion ops together if they have the same predicate and it
is safe to do so (there are no intermediate dependencies, they are in the
same block, etc).

For example:

```mlir
"tf.IfRegion"(%0) ( {
  %2 = "tf.A"() : () -> (tensor<f32>)
  "tf.Yield"() : () -> ()

  std::string retvals_communication_key =
      llvm::formatv("host_compute_channel_{0}_retvals",
                    (communication_key_index))
          .str();

  // Use a unique name when sending just the IfRegion predicate.  This is
  // for readable and to match the key in the TF2XLA bridge.
  if (clustered_ops.size() == 1 && llvm::isa<mlir::TF::IfRegionOp>(op) &&
      external_operands.size() == 1) {
    args_communication_key =

    types of inputs must match the signature of the operation that contains the
    region.
  }];

  let arguments = (ins Variadic<AnyType>);
}

def TF_IfRegionOp : TF_Op<"IfRegion",
      [SingleBlockImplicitTerminator<"YieldOp">, NoRegionArguments,
       DeclareOpInterfaceMethods<RegionBranchOpInterface, [
           "areTypesCompatible",
           "getEntrySuccessorOperands",