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      1 //===- InstCombineWorklist.h - Worklist for InstCombine pass ----*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #ifndef INSTCOMBINE_WORKLIST_H
     11 #define INSTCOMBINE_WORKLIST_H
     12 
     13 #include "llvm/ADT/DenseMap.h"
     14 #include "llvm/ADT/SmallVector.h"
     15 #include "llvm/IR/Instruction.h"
     16 #include "llvm/Support/Compiler.h"
     17 #include "llvm/Support/Debug.h"
     18 #include "llvm/Support/raw_ostream.h"
     19 
     20 #define DEBUG_TYPE "instcombine"
     21 
     22 namespace llvm {
     23 
     24 /// InstCombineWorklist - This is the worklist management logic for
     25 /// InstCombine.
     26 class LLVM_LIBRARY_VISIBILITY InstCombineWorklist {
     27   SmallVector<Instruction*, 256> Worklist;
     28   DenseMap<Instruction*, unsigned> WorklistMap;
     29 
     30   void operator=(const InstCombineWorklist&RHS) LLVM_DELETED_FUNCTION;
     31   InstCombineWorklist(const InstCombineWorklist&) LLVM_DELETED_FUNCTION;
     32 public:
     33   InstCombineWorklist() {}
     34 
     35   bool isEmpty() const { return Worklist.empty(); }
     36 
     37   /// Add - Add the specified instruction to the worklist if it isn't already
     38   /// in it.
     39   void Add(Instruction *I) {
     40     if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
     41       DEBUG(dbgs() << "IC: ADD: " << *I << '\n');
     42       Worklist.push_back(I);
     43     }
     44   }
     45 
     46   void AddValue(Value *V) {
     47     if (Instruction *I = dyn_cast<Instruction>(V))
     48       Add(I);
     49   }
     50 
     51   /// AddInitialGroup - Add the specified batch of stuff in reverse order.
     52   /// which should only be done when the worklist is empty and when the group
     53   /// has no duplicates.
     54   void AddInitialGroup(Instruction *const *List, unsigned NumEntries) {
     55     assert(Worklist.empty() && "Worklist must be empty to add initial group");
     56     Worklist.reserve(NumEntries+16);
     57     WorklistMap.resize(NumEntries);
     58     DEBUG(dbgs() << "IC: ADDING: " << NumEntries << " instrs to worklist\n");
     59     for (unsigned Idx = 0; NumEntries; --NumEntries) {
     60       Instruction *I = List[NumEntries-1];
     61       WorklistMap.insert(std::make_pair(I, Idx++));
     62       Worklist.push_back(I);
     63     }
     64   }
     65 
     66   // Remove - remove I from the worklist if it exists.
     67   void Remove(Instruction *I) {
     68     DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
     69     if (It == WorklistMap.end()) return; // Not in worklist.
     70 
     71     // Don't bother moving everything down, just null out the slot.
     72     Worklist[It->second] = nullptr;
     73 
     74     WorklistMap.erase(It);
     75   }
     76 
     77   Instruction *RemoveOne() {
     78     Instruction *I = Worklist.pop_back_val();
     79     WorklistMap.erase(I);
     80     return I;
     81   }
     82 
     83   /// AddUsersToWorkList - When an instruction is simplified, add all users of
     84   /// the instruction to the work lists because they might get more simplified
     85   /// now.
     86   ///
     87   void AddUsersToWorkList(Instruction &I) {
     88     for (User *U : I.users())
     89       Add(cast<Instruction>(U));
     90   }
     91 
     92 
     93   /// Zap - check that the worklist is empty and nuke the backing store for
     94   /// the map if it is large.
     95   void Zap() {
     96     assert(WorklistMap.empty() && "Worklist empty, but map not?");
     97 
     98     // Do an explicit clear, this shrinks the map if needed.
     99     WorklistMap.clear();
    100   }
    101 };
    102 
    103 } // end namespace llvm.
    104 
    105 #undef DEBUG_TYPE
    106 
    107 #endif
    108