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      1 //===- llvm/ADT/ilist_node_base.h - Intrusive List Node Base -----*- 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_ADT_ILIST_NODE_BASE_H
     10 #define LLVM_ADT_ILIST_NODE_BASE_H
     11 
     12 #include "llvm/ADT/PointerIntPair.h"
     13 
     14 namespace llvm {
     15 
     16 /// Base class for ilist nodes.
     17 ///
     18 /// Optionally tracks whether this node is the sentinel.
     19 template <bool EnableSentinelTracking> class ilist_node_base;
     20 
     21 template <> class ilist_node_base<false> {
     22   ilist_node_base *Prev = nullptr;
     23   ilist_node_base *Next = nullptr;
     24 
     25 public:
     26   void setPrev(ilist_node_base *Prev) { this->Prev = Prev; }
     27   void setNext(ilist_node_base *Next) { this->Next = Next; }
     28   ilist_node_base *getPrev() const { return Prev; }
     29   ilist_node_base *getNext() const { return Next; }
     30 
     31   bool isKnownSentinel() const { return false; }
     32   void initializeSentinel() {}
     33 };
     34 
     35 template <> class ilist_node_base<true> {
     36   PointerIntPair<ilist_node_base *, 1> PrevAndSentinel;
     37   ilist_node_base *Next = nullptr;
     38 
     39 public:
     40   void setPrev(ilist_node_base *Prev) { PrevAndSentinel.setPointer(Prev); }
     41   void setNext(ilist_node_base *Next) { this->Next = Next; }
     42   ilist_node_base *getPrev() const { return PrevAndSentinel.getPointer(); }
     43   ilist_node_base *getNext() const { return Next; }
     44 
     45   bool isSentinel() const { return PrevAndSentinel.getInt(); }
     46   bool isKnownSentinel() const { return isSentinel(); }
     47   void initializeSentinel() { PrevAndSentinel.setInt(true); }
     48 };
     49 
     50 } // end namespace llvm
     51 
     52 #endif // LLVM_ADT_ILIST_NODE_BASE_H
     53