message: add comments about layout
diff: @@ -77,7 +77,9 @@ class MklSoftmaxOp : public OpKernel {
  // and "ncdhw" for 5 dim tensor. Each of the symbols has the following
  // meaning: n = batch, c = channels, t = sequence length, h = height, w =
  // width, d = depth. When src tensor is MKL, layout_type here is only used
  - // for setting TF layout type of output tensor.
  + // for setting TF layout type of output tensor. When input is TF Tensor,
  + // layout here is no special sense. We use axis to define on which
  + // dimension to do softmax.
  switch (input_dims) {
  case 1:
  layout_type = memory::format::x;
  