message: Added comment to all-reduce simplifier.
diff: @@ -34,6 +34,9 @@ StatusOr<bool> AllReduceSimplifier::Run(HloModule* module) {
  for (HloInstruction* inst : computation->MakeInstructionPostOrder()) {
  if (!inst->shape().IsArray()) {
  // We currently do not change tuple-shaped all-reduce.
  + // Until XLA will support Token fed AllReduce(), the PyTorch client code
  + // uses a fake data token (constant) which relies on this pass to not
  + // optimize out (being fed within a tuple input).
  continue;
  }
  if (inst->IsCrossReplicaAllReduce() &&
  