auto x_shape = Shape(scope, x);
  auto output_shape = Shape(scope, op.output(0));

  // Reduce away broadcasted leading dims.
  auto reduce_x = internal::BroadcastGradientArgs(scope, x_shape, output_shape);
  auto gx_sum =
      ReduceSum(scope, gx, /*axis=*/reduce_x.r0, ReduceSum::KeepDims(true));
  auto gx_sum_reshape = Reshape(scope, gx_sum, x_shape);

  auto gy = SelectV2(scope, c, zeros, grad_inputs[0]);