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      1 //===- DerivedUser.h - Base for non-IR Users --------------------*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_IR_DERIVEDUSER_H
     10 #define LLVM_IR_DERIVEDUSER_H
     11 
     12 #include "llvm/IR/User.h"
     13 
     14 namespace llvm {
     15 
     16 class Type;
     17 class Use;
     18 
     19 /// Extension point for the Value hierarchy. All classes outside of lib/IR
     20 /// that wish to inherit from User should instead inherit from DerivedUser
     21 /// instead. Inheriting from this class is discouraged.
     22 ///
     23 /// Generally speaking, Value is the base of a closed class hierarchy
     24 /// that can't be extended by code outside of lib/IR. This class creates a
     25 /// loophole that allows classes outside of lib/IR to extend User to leverage
     26 /// its use/def list machinery.
     27 class DerivedUser : public User {
     28 protected:
     29   using  DeleteValueTy = void (*)(DerivedUser *);
     30 
     31 private:
     32   friend class Value;
     33 
     34   DeleteValueTy DeleteValue;
     35 
     36 public:
     37   DerivedUser(Type *Ty, unsigned VK, Use *U, unsigned NumOps,
     38               DeleteValueTy DeleteValue)
     39       : User(Ty, VK, U, NumOps), DeleteValue(DeleteValue) {}
     40 };
     41 
     42 } // end namespace llvm
     43 
     44 #endif // LLVM_IR_DERIVEDUSER_H
     45