path: root/lib/Core/Searcher.h

//===-- Searcher.h ----------------------------------------------*- C++ -*-===//
//
//                     The KLEE Symbolic Virtual Machine
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef KLEE_SEARCHER_H
#define KLEE_SEARCHER_H

#include "ExecutionState.h"
#include "PTree.h"
#include "klee/ADT/RNG.h"
#include "klee/System/Time.h"

#include "llvm/Support/CommandLine.h"
#include "llvm/Support/raw_ostream.h"

#include <map>
#include <queue>
#include <set>
#include <vector>

namespace llvm {
  class BasicBlock;
  class Function;
  class Instruction;
  class raw_ostream;
}

namespace klee {
  template<class T, class Comparator> class DiscretePDF;
  class ExecutionState;
  class Executor;

  class Searcher {
  public:
    virtual ~Searcher();

    virtual ExecutionState &selectState() = 0;

    virtual void update(ExecutionState *current,
                        const std::vector<ExecutionState *> &addedStates,
                        const std::vector<ExecutionState *> &removedStates) = 0;

    virtual bool empty() = 0;

    // prints name of searcher as a klee_message()
    // TODO: could probably make prettier or more flexible
    virtual void printName(llvm::raw_ostream &os) {
      os << "<unnamed searcher>\n";
    }

    // pgbovine - to be called when a searcher gets activated and
    // deactivated, say, by a higher-level searcher; most searchers
    // don't need this functionality, so don't have to override.
    virtual void activate() {}
    virtual void deactivate() {}

    // utility functions

    void addState(ExecutionState *es, ExecutionState *current = 0) {
      std::vector<ExecutionState *> tmp;
      tmp.push_back(es);
      update(current, tmp, std::vector<ExecutionState *>());
    }

    void removeState(ExecutionState *es, ExecutionState *current = 0) {
      std::vector<ExecutionState *> tmp;
      tmp.push_back(es);
      update(current, std::vector<ExecutionState *>(), tmp);
    }

    enum CoreSearchType {
      DFS,
      BFS,
      RandomState,
      RandomPath,
      NURS_CovNew,
      NURS_MD2U,
      NURS_Depth,
      NURS_RP,
      NURS_ICnt,
      NURS_CPICnt,
      NURS_QC
    };
  };

  class DFSSearcher : public Searcher {
    std::vector<ExecutionState*> states;

  public:
    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return states.empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "DFSSearcher\n";
    }
  };

  class BFSSearcher : public Searcher {
    std::deque<ExecutionState*> states;

  public:
    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return states.empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "BFSSearcher\n";
    }
  };

  class RandomSearcher : public Searcher {
    std::vector<ExecutionState*> states;
    RNG &theRNG;

  public:
    explicit RandomSearcher(RNG &rng) : theRNG{rng} {}
    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return states.empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "RandomSearcher\n";
    }
  };

  class WeightedRandomSearcher : public Searcher {
  public:
    enum WeightType {
      Depth,
      RP,
      QueryCost,
      InstCount,
      CPInstCount,
      MinDistToUncovered,
      CoveringNew
    };

  private:
    DiscretePDF<ExecutionState*, ExecutionStateIDCompare> *states;
    RNG &theRNG;
    WeightType type;
    bool updateWeights;
    
    double getWeight(ExecutionState*);

  public:
    WeightedRandomSearcher(WeightType type, RNG &rng);
    ~WeightedRandomSearcher();

    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty();
    void printName(llvm::raw_ostream &os) {
      os << "WeightedRandomSearcher::";
      switch(type) {
      case Depth              : os << "Depth\n"; return;
      case RP                 : os << "RandomPath\n"; return;
      case QueryCost          : os << "QueryCost\n"; return;
      case InstCount          : os << "InstCount\n"; return;
      case CPInstCount        : os << "CPInstCount\n"; return;
      case MinDistToUncovered : os << "MinDistToUncovered\n"; return;
      case CoveringNew        : os << "CoveringNew\n"; return;
      default                 : os << "<unknown type>\n"; return;
      }
    }
  };

  /* RandomPathSearcher performs a random walk of the PTree to
     select a state. PTree is a global data structure, however
     a searcher can sometimes only select from a subset of all states
     (depending on the update calls).

     To support this RandomPathSearcher has a subgraph view of PTree, in that it
     only
     walks the PTreeNodes that it "owns". Ownership is stored in the
     getInt method of PTreeNodePtr class (which hides it in the pointer itself).

     The current implementation of PTreeNodePtr supports only 3 instances of the
     RandomPathSearcher. This is because current PTreeNodePtr implementation
     conforms to C++ and only steals the last 3 alligment bits. This restriction
     could be relaxed  slightly by an architecture specific implementation of
     PTreeNodePtr, that also steals the top bits of the pointer.

     The ownership bits are maintained in the update method.
  */
  class RandomPathSearcher : public Searcher {
    PTree &processTree;
    RNG &theRNG;

    // Unique bitmask of this searcher
    const uint8_t idBitMask;

  public:
    RandomPathSearcher(PTree &processTree, RNG &rng);
    ~RandomPathSearcher();

    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty();
    void printName(llvm::raw_ostream &os) {
      os << "RandomPathSearcher\n";
    }
  };


  extern llvm::cl::opt<bool> UseIncompleteMerge;
  class MergeHandler;
  class MergingSearcher : public Searcher {
    friend class MergeHandler;

    private:

    Searcher *baseSearcher;

    /// States that have been paused by the 'pauseState' function
    std::vector<ExecutionState*> pausedStates;

    public:
    MergingSearcher(Searcher *baseSearcher);
    ~MergingSearcher();

    /// ExecutionStates currently paused from scheduling because they are
    /// waiting to be merged in a klee_close_merge instruction
    std::set<ExecutionState *> inCloseMerge;

    /// Keeps track of all currently ongoing merges.
    /// An ongoing merge is a set of states (stored in a MergeHandler object)
    /// which branched from a single state which ran into a klee_open_merge(),
    /// and not all states in the set have reached the corresponding
    /// klee_close_merge() yet.
    std::vector<MergeHandler *> mergeGroups;

    /// Remove state from the searcher chain, while keeping it in the executor.
    /// This is used here to 'freeze' a state while it is waiting for other
    /// states in its merge group to reach the same instruction.
    void pauseState(ExecutionState &state){
      assert(std::find(pausedStates.begin(), pausedStates.end(), &state) == pausedStates.end());
      pausedStates.push_back(&state);
      baseSearcher->removeState(&state);
    }

    /// Continue a paused state
    void continueState(ExecutionState &state){
      auto it = std::find(pausedStates.begin(), pausedStates.end(), &state);
      assert( it != pausedStates.end());
      pausedStates.erase(it);
      baseSearcher->addState(&state);
    }

    ExecutionState &selectState();

    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates) {
      // We have to check if the current execution state was just deleted, as to
      // not confuse the nurs searchers
      if (std::find(pausedStates.begin(), pausedStates.end(), current) ==
          pausedStates.end()) {
        baseSearcher->update(current, addedStates, removedStates);
      }
    }

    bool empty() { return baseSearcher->empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "MergingSearcher\n";
    }
  };

  class BatchingSearcher : public Searcher {
    Searcher *baseSearcher;
    time::Span timeBudget;
    unsigned instructionBudget;

    ExecutionState *lastState;
    time::Point lastStartTime;
    unsigned lastStartInstructions;

  public:
    BatchingSearcher(Searcher *baseSearcher, 
                     time::Span _timeBudget,
                     unsigned _instructionBudget);
    ~BatchingSearcher();

    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return baseSearcher->empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "<BatchingSearcher> timeBudget: " << timeBudget
         << ", instructionBudget: " << instructionBudget
         << ", baseSearcher:\n";
      baseSearcher->printName(os);
      os << "</BatchingSearcher>\n";
    }
  };

  class IterativeDeepeningTimeSearcher : public Searcher {
    Searcher *baseSearcher;
    time::Point startTime;
    time::Span time;
    std::set<ExecutionState*> pausedStates;

  public:
    IterativeDeepeningTimeSearcher(Searcher *baseSearcher);
    ~IterativeDeepeningTimeSearcher();

    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return baseSearcher->empty() && pausedStates.empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "IterativeDeepeningTimeSearcher\n";
    }
  };

  class InterleavedSearcher : public Searcher {
    typedef std::vector<Searcher*> searchers_ty;

    searchers_ty searchers;
    unsigned index;

  public:
    explicit InterleavedSearcher(const searchers_ty &_searchers);
    ~InterleavedSearcher();

    ExecutionState &selectState();
    void update(ExecutionState *current,
                const std::vector<ExecutionState *> &addedStates,
                const std::vector<ExecutionState *> &removedStates);
    bool empty() { return searchers[0]->empty(); }
    void printName(llvm::raw_ostream &os) {
      os << "<InterleavedSearcher> containing "
         << searchers.size() << " searchers:\n";
      for (searchers_ty::iterator it = searchers.begin(), ie = searchers.end();
           it != ie; ++it)
        (*it)->printName(os);
      os << "</InterleavedSearcher>\n";
    }
  };

}

#endif /* KLEE_SEARCHER_H */