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> {
    static inline Signature getEmptyKey() { return {}; }
    static inline Signature getTombstoneKey() { return {nullptr}; }
    static unsigned getHashValue(Signature val) {