text: //===- InstCombineWorklist.h - Worklist for InstCombine pass ----*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_SEAHORN_TRANSFORMS_INSTCOMBINE_INSTCOMBINEWORKLIST_H
  #define LLVM_SEAHORN_TRANSFORMS_INSTCOMBINE_INSTCOMBINEWORKLIST_H
  
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/raw_ostream.h"
  
  #define DEBUG_TYPE "sea-instcombine"
  
  namespace llvm_seahorn {
    
  /// InstCombineWorklist - This is the worklist management logic for
  /// InstCombine.
  class InstCombineWorklist {
    llvm::SmallVector<llvm::Instruction*, 256> Worklist;
    llvm::DenseMap<llvm::Instruction*, unsigned> WorklistMap;
  
  public:
    InstCombineWorklist() = default;
  
    InstCombineWorklist(InstCombineWorklist &&) = default;
    InstCombineWorklist &operator=(InstCombineWorklist &&) = default;
  
    bool isEmpty() const { return Worklist.empty(); }
  
    /// Add - Add the specified instruction to the worklist if it isn't already
    /// in it.
    void Add(llvm::Instruction *I) {
      if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
        DEBUG(llvm::dbgs() << "IC: ADD: " << *I << '\n');
        Worklist.push_back(I);
      }
    }
  
    void AddValue(llvm::Value *V) {
      if (llvm::Instruction *I = llvm::dyn_cast<llvm::Instruction>(V))
        Add(I);
    }
  
    /// AddInitialGroup - Add the specified batch of stuff in reverse order.
    /// which should only be done when the worklist is empty and when the group
    /// has no duplicates.
    void AddInitialGroup(llvm::ArrayRef<llvm::Instruction *> List) {
      assert(Worklist.empty() && "Worklist must be empty to add initial group");
      Worklist.reserve(List.size()+16);
      WorklistMap.reserve(List.size());
      DEBUG(llvm::dbgs() << "IC: ADDING: " << List.size() << " instrs to worklist\n");
      unsigned Idx = 0;
      for (llvm::Instruction *I : reverse(List)) {
        WorklistMap.insert(std::make_pair(I, Idx++));
        Worklist.push_back(I);
      }
    }
  
    // Remove - remove I from the worklist if it exists.
    void Remove(llvm::Instruction *I) {
      llvm::DenseMap<llvm::Instruction*, unsigned>::iterator It = WorklistMap.find(I);
      if (It == WorklistMap.end()) return; // Not in worklist.
  
      // Don't bother moving everything down, just null out the slot.
      Worklist[It->second] = nullptr;
  
      WorklistMap.erase(It);
    }
  
    llvm::Instruction *RemoveOne() {
      llvm::Instruction *I = Worklist.pop_back_val();
      WorklistMap.erase(I);
      return I;
    }
  
    /// AddUsersToWorkList - When an instruction is simplified, add all users of
    /// the instruction to the work lists because they might get more simplified
    /// now.
    ///
    void AddUsersToWorkList(llvm::Instruction &I) {
      for (llvm::User *U : I.users())
        Add(llvm::cast<llvm::Instruction>(U));
    }
  
  
    /// Zap - check that the worklist is empty and nuke the backing store for
    /// the map if it is large.
    void Zap() {
      assert(WorklistMap.empty() && "Worklist empty, but map not?");
  
      // Do an explicit clear, this shrinks the map if needed.
      WorklistMap.clear();
    }
  };
  
  } // end namespace llvm_seahorn
  
  #undef DEBUG_TYPE
  
  #endif
  