message: Condintional Simplifier: Return early before creating any instruction.
  The newly created instruction can activate DCE and then trigger HloFixPass, which creates long compilation time.
diff: @@ -144,6 +144,15 @@ StatusOr<bool> TryRemoveConditional(HloInstruction* conditional) {
  << conditional->ToShortString();
  return false;
  }
  +
  + bool branch_empty =
  + ComputationIsEmptyWithArrayRoot(conditional->branch_computation(0)) ||
  + ComputationIsEmptyWithArrayRoot(conditional->branch_computation(1));
  + // Empty branch is faster to execute than select.
  + if (branch_empty) {
  + return false;
  + }
  +
  HloInstruction* true_call_op = create_call(0);
  HloInstruction* false_call_op = create_call(1);
  auto condition_broadcast = [&](const Shape& shape) {
  @@ -160,13 +169,6 @@ StatusOr<bool> TryRemoveConditional(HloInstruction* conditional) {
  hlo->shape().tuple_shapes(i), hlo, i));
  };
  - bool branch_empty =
  - ComputationIsEmptyWithArrayRoot(conditional->branch_computation(0)) ||
  - ComputationIsEmptyWithArrayRoot(conditional->branch_computation(1));
  - // Empty branch is faster to execute than select.
  - if (branch_empty) {
  - return false;
  - }
  std::function<HloInstruction*(HloInstruction*, HloInstruction*)> select =
  [&](HloInstruction* t, HloInstruction* f) {
  if (f->shape().IsToken()) {
  