Function CastGrad

tensorflow/cc/gradients/math_grad.cc:1170–1188

}

Status CastGrad(const Scope& scope, const Operation& op,
                const std::vector<Output>& grad_inputs,
                std::vector<Output>* grad_outputs) {
  if (op.num_inputs() != 1) {
    return errors::InvalidArgument("Cast requires 2 arguments");
  }
  if (grad_inputs.size() != 1) {
    return errors::InvalidArgument("Cast grad requires 1 grad input");
  }

  auto src_type = op.input_type(0);
  auto dst_type = grad_inputs[0].type();
  if (IsFloatingPointDtype(src_type) && IsFloatingPointDtype(dst_type)) {
    grad_outputs->push_back(Cast(scope, grad_inputs[0], src_type));
  } else {
    grad_outputs->push_back(NoGradient());
  }
  return scope.status();
}
REGISTER_GRADIENT_OP("Cast", CastGrad);

Status SelectGrad(const Scope& scope, const Operation& op,