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      1 //===- InstCombineWorklist.h - Worklist for the InstCombine pass ----------===//
      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 #define DEBUG_TYPE "instcombine"
     14 #include "llvm/Instruction.h"
     15 #include "llvm/Support/Debug.h"
     16 #include "llvm/Support/Compiler.h"
     17 #include "llvm/ADT/SmallVector.h"
     18 #include "llvm/ADT/DenseMap.h"
     19 #include "llvm/Support/raw_ostream.h"
     20 
     21 namespace llvm {
     22 
     23 /// InstCombineWorklist - This is the worklist management logic for
     24 /// InstCombine.
     25 class LLVM_LIBRARY_VISIBILITY InstCombineWorklist {
     26   SmallVector<Instruction*, 256> Worklist;
     27   DenseMap<Instruction*, unsigned> WorklistMap;
     28 
     29   void operator=(const InstCombineWorklist&RHS);   // DO NOT IMPLEMENT
     30   InstCombineWorklist(const InstCombineWorklist&); // DO NOT IMPLEMENT
     31 public:
     32   InstCombineWorklist() {}
     33 
     34   bool isEmpty() const { return Worklist.empty(); }
     35 
     36   /// Add - Add the specified instruction to the worklist if it isn't already
     37   /// in it.
     38   void Add(Instruction *I) {
     39     if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
     40       DEBUG(errs() << "IC: ADD: " << *I << '\n');
     41       Worklist.push_back(I);
     42     }
     43   }
     44 
     45   void AddValue(Value *V) {
     46     if (Instruction *I = dyn_cast<Instruction>(V))
     47       Add(I);
     48   }
     49 
     50   /// AddInitialGroup - Add the specified batch of stuff in reverse order.
     51   /// which should only be done when the worklist is empty and when the group
     52   /// has no duplicates.
     53   void AddInitialGroup(Instruction *const *List, unsigned NumEntries) {
     54     assert(Worklist.empty() && "Worklist must be empty to add initial group");
     55     Worklist.reserve(NumEntries+16);
     56     WorklistMap.resize(NumEntries);
     57     DEBUG(errs() << "IC: ADDING: " << NumEntries << " instrs to worklist\n");
     58     for (; NumEntries; --NumEntries) {
     59       Instruction *I = List[NumEntries-1];
     60       WorklistMap.insert(std::make_pair(I, Worklist.size()));
     61       Worklist.push_back(I);
     62     }
     63   }
     64 
     65   // Remove - remove I from the worklist if it exists.
     66   void Remove(Instruction *I) {
     67     DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
     68     if (It == WorklistMap.end()) return; // Not in worklist.
     69 
     70     // Don't bother moving everything down, just null out the slot.
     71     Worklist[It->second] = 0;
     72 
     73     WorklistMap.erase(It);
     74   }
     75 
     76   Instruction *RemoveOne() {
     77     Instruction *I = Worklist.back();
     78     Worklist.pop_back();
     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 (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
     89          UI != UE; ++UI)
     90       Add(cast<Instruction>(*UI));
     91   }
     92 
     93 
     94   /// Zap - check that the worklist is empty and nuke the backing store for
     95   /// the map if it is large.
     96   void Zap() {
     97     assert(WorklistMap.empty() && "Worklist empty, but map not?");
     98 
     99     // Do an explicit clear, this shrinks the map if needed.
    100     WorklistMap.clear();
    101   }
    102 };
    103 
    104 } // end namespace llvm.
    105 
    106 #endif
    107