if (all_signatures_.insert({signature, spec}).second) return success();
    return failure();
  }

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

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

 private:

LogicalResult DeviceTarget::RegisterKernel(
    llvm::StringRef kernel, const KernelSpecs::Signature& signature,
    const ScaleFn& fn, const ScaleDecomposeFn& dfn) {
  return specs_[kernel].Add(signature, {ScaleConstraintType::CustomScale, fn});
}

namespace ph = std::placeholders;

LogicalResult DeviceTarget::RegisterKernel(
    llvm::StringRef kernel, const KernelSpecs::Signature& signature,
    const ScaleConstraintType constraint) {