C++ Environment::begin方法代码示例

Environment
EnvironmentManager::RemoveDeadBindings(Environment Env, const Stmt *S,
                                       SymbolReaper &SymReaper,
                                       const GRState *ST,
                              llvm::SmallVectorImpl<const MemRegion*> &DRoots) {

  CFG &C = *Env.getAnalysisContext().getCFG();

  // We construct a new Environment object entirely, as this is cheaper than
  // individually removing all the subexpression bindings (which will greatly
  // outnumber block-level expression bindings).
  Environment NewEnv = getInitialEnvironment(&Env.getAnalysisContext());

  // Iterate over the block-expr bindings.
  for (Environment::iterator I = Env.begin(), E = Env.end();
       I != E; ++I) {

    const Stmt *BlkExpr = I.getKey();

    // Not a block-level expression?
    if (!C.isBlkExpr(BlkExpr))
      continue;

    const SVal &X = I.getData();

    if (SymReaper.isLive(S, BlkExpr)) {
      // Copy the binding to the new map.
      NewEnv.ExprBindings = F.Add(NewEnv.ExprBindings, BlkExpr, X);

      // If the block expr's value is a memory region, then mark that region.
      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
        DRoots.push_back(R);
        // Mark the super region of the RX as live.
        // e.g.: int x; char *y = (char*) &x; if (*y) ...
        // 'y' => element region. 'x' is its super region.
        // We only add one level super region for now.

        // FIXME: maybe multiple level of super regions should be added.
        if (const SubRegion *SR = dyn_cast<SubRegion>(R))
          DRoots.push_back(SR->getSuperRegion());
      }

      // Mark all symbols in the block expr's value live.
      MarkLiveCallback cb(SymReaper);
      ST->scanReachableSymbols(X, cb);
      continue;
    }

    // Otherwise the expression is dead with a couple exceptions.
    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
    // beginning of itself, but we need its UndefinedVal to determine its
    // SVal.
    if (X.isUndef() && cast<UndefinedVal>(X).getData())
      NewEnv.ExprBindings = F.Add(NewEnv.ExprBindings, BlkExpr, X);
  }

  return NewEnv;
}

// removeDeadBindings:
//  - Remove subexpression bindings.
//  - Remove dead block expression bindings.
//  - Keep live block expression bindings:
//   - Mark their reachable symbols live in SymbolReaper,
//     see ScanReachableSymbols.
//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
Environment
EnvironmentManager::removeDeadBindings(Environment Env,
                                       SymbolReaper &SymReaper,
                                       ProgramStateRef ST) {

  // We construct a new Environment object entirely, as this is cheaper than
  // individually removing all the subexpression bindings (which will greatly
  // outnumber block-level expression bindings).
  Environment NewEnv = getInitialEnvironment();

  MarkLiveCallback CB(SymReaper);
  ScanReachableSymbols RSScaner(ST, CB);

  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
             F.getTreeFactory());

  // Iterate over the block-expr bindings.
  for (Environment::iterator I = Env.begin(), E = Env.end();
       I != E; ++I) {

    const EnvironmentEntry &BlkExpr = I.getKey();
    const SVal &X = I.getData();

    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
      // Copy the binding to the new map.
      EBMapRef = EBMapRef.add(BlkExpr, X);

      // If the block expr's value is a memory region, then mark that region.
      if (Optional<loc::MemRegionVal> R = X.getAs<loc::MemRegionVal>())
        SymReaper.markLive(R->getRegion());

      // Mark all symbols in the block expr's value live.
      RSScaner.scan(X);
      continue;
    } else {
      SymExpr::symbol_iterator SI = X.symbol_begin(), SE = X.symbol_end();
      for (; SI != SE; ++SI)
        SymReaper.maybeDead(*SI);
    }
  }

  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
  return NewEnv;
}

Environment
EnvironmentManager::RemoveDeadBindings(Environment Env,
                                       SymbolReaper &SymReaper,
                                       const GRState *ST,
                              llvm::SmallVectorImpl<const MemRegion*> &DRoots) {

  CFG &C = *SymReaper.getLocationContext()->getCFG();

  // We construct a new Environment object entirely, as this is cheaper than
  // individually removing all the subexpression bindings (which will greatly
  // outnumber block-level expression bindings).
  Environment NewEnv = getInitialEnvironment();

  // Iterate over the block-expr bindings.
  for (Environment::iterator I = Env.begin(), E = Env.end();
       I != E; ++I) {

    const Stmt *BlkExpr = I.getKey();
    const SVal &X = I.getData();

    // Block-level expressions in callers are assumed always live.
    if (isBlockExprInCallers(BlkExpr, SymReaper.getLocationContext())) {
      NewEnv.ExprBindings = F.Add(NewEnv.ExprBindings, BlkExpr, X);

      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
        DRoots.push_back(R);
      }

      // Mark all symbols in the block expr's value live.
      MarkLiveCallback cb(SymReaper);
      ST->scanReachableSymbols(X, cb);
      continue;
    }

    // Not a block-level expression?
    if (!C.isBlkExpr(BlkExpr))
      continue;

    if (SymReaper.isLive(BlkExpr)) {
      // Copy the binding to the new map.
      NewEnv.ExprBindings = F.Add(NewEnv.ExprBindings, BlkExpr, X);

      // If the block expr's value is a memory region, then mark that region.
      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
        DRoots.push_back(R);
      }

      // Mark all symbols in the block expr's value live.
      MarkLiveCallback cb(SymReaper);
      ST->scanReachableSymbols(X, cb);
      continue;
    }

    // Otherwise the expression is dead with a couple exceptions.
    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
    // beginning of itself, but we need its UndefinedVal to determine its
    // SVal.
    if (X.isUndef() && cast<UndefinedVal>(X).getData())
      NewEnv.ExprBindings = F.Add(NewEnv.ExprBindings, BlkExpr, X);
  }

  return NewEnv;
}

// removeDeadBindings:
//  - Remove subexpression bindings.
//  - Remove dead block expression bindings.
//  - Keep live block expression bindings:
//   - Mark their reachable symbols live in SymbolReaper,
//     see ScanReachableSymbols.
//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
Environment
EnvironmentManager::removeDeadBindings(Environment Env,
                                       SymbolReaper &SymReaper,
                                       const ProgramState *ST) {

  // We construct a new Environment object entirely, as this is cheaper than
  // individually removing all the subexpression bindings (which will greatly
  // outnumber block-level expression bindings).
  Environment NewEnv = getInitialEnvironment();
  
  SmallVector<std::pair<EnvironmentEntry, SVal>, 10> deferredLocations;

  MarkLiveCallback CB(SymReaper);
  ScanReachableSymbols RSScaner(ST, CB);

  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
             F.getTreeFactory());

  // Iterate over the block-expr bindings.
  for (Environment::iterator I = Env.begin(), E = Env.end();
       I != E; ++I) {

    const EnvironmentEntry &BlkExpr = I.getKey();
    // For recorded locations (used when evaluating loads and stores), we
    // consider them live only when their associated normal expression is
    // also live.
    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
    // still have an entry in the map.
    if (IsLocation(BlkExpr)) {
      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
      continue;
    }
    const SVal &X = I.getData();

    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
      // Copy the binding to the new map.
      EBMapRef = EBMapRef.add(BlkExpr, X);

      // If the block expr's value is a memory region, then mark that region.
      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
        SymReaper.markLive(R);
      }

      // Mark all symbols in the block expr's value live.
      RSScaner.scan(X);
      continue;
    }

    // Otherwise the expression is dead with a couple exceptions.
    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
    // beginning of itself, but we need its UndefinedVal to determine its
    // SVal.
    if (X.isUndef() && cast<UndefinedVal>(X).getData())
      EBMapRef = EBMapRef.add(BlkExpr, X);
  }
  
  // Go through he deferred locations and add them to the new environment if
  // the correspond Stmt* is in the map as well.
  for (SmallVectorImpl<std::pair<EnvironmentEntry, SVal> >::iterator
      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
    const EnvironmentEntry &En = I->first;
    const Stmt *S = (Stmt*) (((uintptr_t) En.getStmt()) & (uintptr_t) ~0x1);
    if (EBMapRef.lookup(EnvironmentEntry(S, En.getLocationContext())))
      EBMapRef = EBMapRef.add(En, I->second);
  }

  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
  return NewEnv;
}

// removeDeadBindings:
//  - Remove subexpression bindings.
//  - Remove dead block expression bindings.
//  - Keep live block expression bindings:
//   - Mark their reachable symbols live in SymbolReaper,
//     see ScanReachableSymbols.
//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
Environment
EnvironmentManager::removeDeadBindings(Environment Env,
                                       SymbolReaper &SymReaper,
                                       const GRState *ST,
                              llvm::SmallVectorImpl<const MemRegion*> &DRoots) {

  CFG &C = *SymReaper.getLocationContext()->getCFG();

  // We construct a new Environment object entirely, as this is cheaper than
  // individually removing all the subexpression bindings (which will greatly
  // outnumber block-level expression bindings).
  Environment NewEnv = getInitialEnvironment();
  
  llvm::SmallVector<std::pair<const Stmt*, SVal>, 10> deferredLocations;

  // Iterate over the block-expr bindings.
  for (Environment::iterator I = Env.begin(), E = Env.end();
       I != E; ++I) {

    const Stmt *BlkExpr = I.getKey();
    
    // For recorded locations (used when evaluating loads and stores), we
    // consider them live only when their associated normal expression is
    // also live.
    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
    // still have an entry in the map.
    if (IsLocation(BlkExpr)) {
      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
      continue;
    }
    
    const SVal &X = I.getData();

    // Block-level expressions in callers are assumed always live.
    if (isBlockExprInCallers(BlkExpr, SymReaper.getLocationContext())) {
      NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);

      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
        DRoots.push_back(R);
      }

      // Mark all symbols in the block expr's value live.
      MarkLiveCallback cb(SymReaper);
      ST->scanReachableSymbols(X, cb);
      continue;
    }

    // Not a block-level expression?
    if (!C.isBlkExpr(BlkExpr))
      continue;

    if (SymReaper.isLive(BlkExpr)) {
      // Copy the binding to the new map.
      NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);

      // If the block expr's value is a memory region, then mark that region.
      if (isa<loc::MemRegionVal>(X)) {
        const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
        DRoots.push_back(R);
      }

      // Mark all symbols in the block expr's value live.
      MarkLiveCallback cb(SymReaper);
      ST->scanReachableSymbols(X, cb);
      continue;
    }

    // Otherwise the expression is dead with a couple exceptions.
    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
    // beginning of itself, but we need its UndefinedVal to determine its
    // SVal.
    if (X.isUndef() && cast<UndefinedVal>(X).getData())
      NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);
  }
  
  // Go through he deferred locations and add them to the new environment if
  // the correspond Stmt* is in the map as well.
  for (llvm::SmallVectorImpl<std::pair<const Stmt*, SVal> >::iterator
      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
    const Stmt *S = (Stmt*) (((uintptr_t) I->first) & (uintptr_t) ~0x1);
    if (NewEnv.ExprBindings.lookup(S))
      NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, I->first, I->second);
  }

  return NewEnv;
}