const ScaleConstraintType constraint) {
  if (failed(specs_[kernel].Add(signature, {constraint, {}}))) return failure();
  switch (constraint) {
    case ScaleConstraintType::OutputInputSameScale:
      specs_[kernel].WithImpl(std::bind(&DeviceTarget::DecomposeSameScale,
                                        ph::_1, ph::_2, ph::_3, ph::_4));
      return success();
    default:
      return failure();
  }
}

                             const ScaleFn& fn) {
    (void)Add(signature, {ScaleConstraintType::CustomScale, fn});
    return *this;
  }

  KernelSpecs& WithImpl(const ScaleDecomposeFn& dfn) {
    decompose_fn_ = dfn;
    return *this;
  }

 private:
  // The signature is pattern match based.
  struct SignatureInfo : public llvm::DenseMapInfo<Signature> {