text: //== SymbolManager.h - Management of Symbolic Values ------------*- C++ -*--==//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file defines SymbolManager, a class that manages symbolic values
  //  created for use by ExprEngine and related classes.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
  #include "clang/Analysis/Analyses/LiveVariables.h"
  #include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
  #include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  using namespace ento;
  
  void SymExpr::anchor() { }
  
  void SymExpr::dump() const {
    dumpToStream(llvm::errs());
  }
  
  void SymIntExpr::dumpToStream(raw_ostream &os) const {
    os << '(';
    getLHS()->dumpToStream(os);
    os << ") "
       << BinaryOperator::getOpcodeStr(getOpcode()) << ' '
       << getRHS().getZExtValue();
    if (getRHS().isUnsigned())
      os << 'U';
  }
  
  void IntSymExpr::dumpToStream(raw_ostream &os) const {
    os << getLHS().getZExtValue();
    if (getLHS().isUnsigned())
      os << 'U';
    os << ' '
       << BinaryOperator::getOpcodeStr(getOpcode())
       << " (";
    getRHS()->dumpToStream(os);
    os << ')';
  }
  
  void SymSymExpr::dumpToStream(raw_ostream &os) const {
    os << '(';
    getLHS()->dumpToStream(os);
    os << ") "
       << BinaryOperator::getOpcodeStr(getOpcode())
       << " (";
    getRHS()->dumpToStream(os);
    os << ')';
  }
  
  void SymbolCast::dumpToStream(raw_ostream &os) const {
    os << '(' << ToTy.getAsString() << ") (";
    Operand->dumpToStream(os);
    os << ')';
  }
  
  void SymbolConjured::dumpToStream(raw_ostream &os) const {
    os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
  }
  
  void SymbolDerived::dumpToStream(raw_ostream &os) const {
    os << "derived_$" << getSymbolID() << '{'
       << getParentSymbol() << ',' << getRegion() << '}';
  }
  
  void SymbolExtent::dumpToStream(raw_ostream &os) const {
    os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
  }
  
  void SymbolMetadata::dumpToStream(raw_ostream &os) const {
    os << "meta_$" << getSymbolID() << '{'
       << getRegion() << ',' << T.getAsString() << '}';
  }
  
  void SymbolData::anchor() { }
  
  void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
    os << "reg_$" << getSymbolID() << "<" << R << ">";
  }
  
  bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
    return itr == X.itr;
  }
  
  bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
    return itr != X.itr;
  }
  
  SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
    itr.push_back(SE);
  }
  
  SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
    assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
    expand();
    return *this;
  }
  
  SymbolRef SymExpr::symbol_iterator::operator*() {
    assert(!itr.empty() && "attempting to dereference an 'end' iterator");
    return itr.back();
  }
  
  void SymExpr::symbol_iterator::expand() {
    const SymExpr *SE = itr.pop_back_val();
  
    switch (SE->getKind()) {
      case SymExpr::SymbolRegionValueKind:
      case SymExpr::SymbolConjuredKind:
      case SymExpr::SymbolDerivedKind:
      case SymExpr::SymbolExtentKind:
      case SymExpr::SymbolMetadataKind:
        return;
      case SymExpr::SymbolCastKind:
        itr.push_back(cast<SymbolCast>(SE)->getOperand());
        return;
      case SymExpr::SymIntExprKind:
        itr.push_back(cast<SymIntExpr>(SE)->getLHS());
        return;
      case SymExpr::IntSymExprKind:
        itr.push_back(cast<IntSymExpr>(SE)->getRHS());
        return;
      case SymExpr::SymSymExprKind: {
        const SymSymExpr *x = cast<SymSymExpr>(SE);
        itr.push_back(x->getLHS());
        itr.push_back(x->getRHS());
        return;
      }
    }
    llvm_unreachable("unhandled expansion case");
  }
  
  unsigned SymExpr::computeComplexity() const {
    unsigned R = 0;
    for (symbol_iterator I = symbol_begin(), E = symbol_end(); I != E; ++I)
      R++;
    return R;
  }
  
  const SymbolRegionValue*
  SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
    llvm::FoldingSetNodeID profile;
    SymbolRegionValue::Profile(profile, R);
    void *InsertPos;
    SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    if (!SD) {
      SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
      new (SD) SymbolRegionValue(SymbolCounter, R);
      DataSet.InsertNode(SD, InsertPos);
      ++SymbolCounter;
    }
  
    return cast<SymbolRegionValue>(SD);
  }
  
  const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
                                                     const LocationContext *LCtx,
                                                     QualType T,
                                                     unsigned Count,
                                                     const void *SymbolTag) {
    llvm::FoldingSetNodeID profile;
    SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
    void *InsertPos;
    SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    if (!SD) {
      SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
      new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
      DataSet.InsertNode(SD, InsertPos);
      ++SymbolCounter;
    }
  
    return cast<SymbolConjured>(SD);
  }
  
  const SymbolDerived*
  SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
                                  const TypedValueRegion *R) {
  
    llvm::FoldingSetNodeID profile;
    SymbolDerived::Profile(profile, parentSymbol, R);
    void *InsertPos;
    SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    if (!SD) {
      SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
      new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
      DataSet.InsertNode(SD, InsertPos);
      ++SymbolCounter;
    }
  
    return cast<SymbolDerived>(SD);
  }
  
  const SymbolExtent*
  SymbolManager::getExtentSymbol(const SubRegion *R) {
    llvm::FoldingSetNodeID profile;
    SymbolExtent::Profile(profile, R);
    void *InsertPos;
    SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    if (!SD) {
      SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
      new (SD) SymbolExtent(SymbolCounter, R);
      DataSet.InsertNode(SD, InsertPos);
      ++SymbolCounter;
    }
  
    return cast<SymbolExtent>(SD);
  }
  
  const SymbolMetadata*
  SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
                                   unsigned Count, const void *SymbolTag) {
  
    llvm::FoldingSetNodeID profile;
    SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
    void *InsertPos;
    SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    if (!SD) {
      SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
      new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
      DataSet.InsertNode(SD, InsertPos);
      ++SymbolCounter;
    }
  
    return cast<SymbolMetadata>(SD);
  }
  
  const SymbolCast*
  SymbolManager::getCastSymbol(const SymExpr *Op,
                               QualType From, QualType To) {
    llvm::FoldingSetNodeID ID;
    SymbolCast::Profile(ID, Op, From, To);
    void *InsertPos;
    SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    if (!data) {
      data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
      new (data) SymbolCast(Op, From, To);
      DataSet.InsertNode(data, InsertPos);
    }
  
    return cast<SymbolCast>(data);
  }
  
  const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
                                                 BinaryOperator::Opcode op,
                                                 const llvm::APSInt& v,
                                                 QualType t) {
    llvm::FoldingSetNodeID ID;
    SymIntExpr::Profile(ID, lhs, op, v, t);
    void *InsertPos;
    SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
  
    if (!data) {
      data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
      new (data) SymIntExpr(lhs, op, v, t);
      DataSet.InsertNode(data, InsertPos);
    }
  
    return cast<SymIntExpr>(data);
  }
  
  const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
                                                 BinaryOperator::Opcode op,
                                                 const SymExpr *rhs,
                                                 QualType t) {
    llvm::FoldingSetNodeID ID;
    IntSymExpr::Profile(ID, lhs, op, rhs, t);
    void *InsertPos;
    SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
  
    if (!data) {
      data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
      new (data) IntSymExpr(lhs, op, rhs, t);
      DataSet.InsertNode(data, InsertPos);
    }
  
    return cast<IntSymExpr>(data);
  }
  
  const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
                                                 BinaryOperator::Opcode op,
                                                 const SymExpr *rhs,
                                                 QualType t) {
    llvm::FoldingSetNodeID ID;
    SymSymExpr::Profile(ID, lhs, op, rhs, t);
    void *InsertPos;
    SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
  
    if (!data) {
      data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
      new (data) SymSymExpr(lhs, op, rhs, t);
      DataSet.InsertNode(data, InsertPos);
    }
  
    return cast<SymSymExpr>(data);
  }
  
  QualType SymbolConjured::getType() const {
    return T;
  }
  
  QualType SymbolDerived::getType() const {
    return R->getValueType();
  }
  
  QualType SymbolExtent::getType() const {
    ASTContext &Ctx = R->getMemRegionManager()->getContext();
    return Ctx.getSizeType();
  }
  
  QualType SymbolMetadata::getType() const {
    return T;
  }
  
  QualType SymbolRegionValue::getType() const {
    return R->getValueType();
  }
  
  SymbolManager::~SymbolManager() {
    llvm::DeleteContainerSeconds(SymbolDependencies);
  }
  
  bool SymbolManager::canSymbolicate(QualType T) {
    T = T.getCanonicalType();
  
    if (Loc::isLocType(T))
      return true;
  
    if (T->isIntegralOrEnumerationType())
      return true;
  
    if (T->isRecordType() && !T->isUnionType())
      return true;
  
    return false;
  }
  
  void SymbolManager::addSymbolDependency(const SymbolRef Primary,
                                          const SymbolRef Dependent) {
    SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
    SymbolRefSmallVectorTy *dependencies = nullptr;
    if (I == SymbolDependencies.end()) {
      dependencies = new SymbolRefSmallVectorTy();
      SymbolDependencies[Primary] = dependencies;
    } else {
      dependencies = I->second;
    }
    dependencies->push_back(Dependent);
  }
  
  const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
                                                       const SymbolRef Primary) {
    SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
    if (I == SymbolDependencies.end())
      return nullptr;
    return I->second;
  }
  
  void SymbolReaper::markDependentsLive(SymbolRef sym) {
    // Do not mark dependents more then once.
    SymbolMapTy::iterator LI = TheLiving.find(sym);
    assert(LI != TheLiving.end() && "The primary symbol is not live.");
    if (LI->second == HaveMarkedDependents)
      return;
    LI->second = HaveMarkedDependents;
  
    if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
      for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
                                                  E = Deps->end(); I != E; ++I) {
        if (TheLiving.find(*I) != TheLiving.end())
          continue;
        markLive(*I);
      }
    }
  }
  
  void SymbolReaper::markLive(SymbolRef sym) {
    TheLiving[sym] = NotProcessed;
    TheDead.erase(sym);
    markDependentsLive(sym);
  }
  
  void SymbolReaper::markLive(const MemRegion *region) {
    RegionRoots.insert(region);
    markElementIndicesLive(region);
  }
  
  void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
    for (auto SR = dyn_cast<SubRegion>(region); SR;
         SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
      if (auto ER = dyn_cast<ElementRegion>(SR)) {
        SVal Idx = ER->getIndex();
        for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
          markLive(*SI);
      }
    }
  }
  
  void SymbolReaper::markInUse(SymbolRef sym) {
    if (isa<SymbolMetadata>(sym))
      MetadataInUse.insert(sym);
  }
  
  bool SymbolReaper::maybeDead(SymbolRef sym) {
    if (isLive(sym))
      return false;
  
    TheDead.insert(sym);
    return true;
  }
  
  bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
    if (RegionRoots.count(MR))
      return true;
  
    MR = MR->getBaseRegion();
  
    if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
      return isLive(SR->getSymbol());
  
    if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
      return isLive(VR, true);
  
    // FIXME: This is a gross over-approximation. What we really need is a way to
    // tell if anything still refers to this region. Unlike SymbolicRegions,
    // AllocaRegions don't have associated symbols, though, so we don't actually
    // have a way to track their liveness.
    if (isa<AllocaRegion>(MR))
      return true;
  
    if (isa<CXXThisRegion>(MR))
      return true;
  
    if (isa<MemSpaceRegion>(MR))
      return true;
  
    if (isa<CodeTextRegion>(MR))
      return true;
  
    return false;
  }
  
  bool SymbolReaper::isLive(SymbolRef sym) {
    if (TheLiving.count(sym)) {
      markDependentsLive(sym);
      return true;
    }
  
    bool KnownLive;
  
    switch (sym->getKind()) {
    case SymExpr::SymbolRegionValueKind:
      KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
      break;
    case SymExpr::SymbolConjuredKind:
      KnownLive = false;
      break;
    case SymExpr::SymbolDerivedKind:
      KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
      break;
    case SymExpr::SymbolExtentKind:
      KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
      break;
    case SymExpr::SymbolMetadataKind:
      KnownLive = MetadataInUse.count(sym) &&
                  isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
      if (KnownLive)
        MetadataInUse.erase(sym);
      break;
    case SymExpr::SymIntExprKind:
      KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
      break;
    case SymExpr::IntSymExprKind:
      KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
      break;
    case SymExpr::SymSymExprKind:
      KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
                  isLive(cast<SymSymExpr>(sym)->getRHS());
      break;
    case SymExpr::SymbolCastKind:
      KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
      break;
    }
  
    if (KnownLive)
      markLive(sym);
  
    return KnownLive;
  }
  
  bool
  SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
    if (LCtx == nullptr)
      return false;
  
    if (LCtx != ELCtx) {
      // If the reaper's location context is a parent of the expression's
      // location context, then the expression value is now "out of scope".
      if (LCtx->isParentOf(ELCtx))
        return false;
      return true;
    }
  
    // If no statement is provided, everything is this and parent contexts is live.
    if (!Loc)
      return true;
  
    return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
  }
  
  bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
    const StackFrameContext *VarContext = VR->getStackFrame();
  
    if (!VarContext)
      return true;
  
    if (!LCtx)
      return false;
    const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
  
    if (VarContext == CurrentContext) {
      // If no statement is provided, everything is live.
      if (!Loc)
        return true;
  
      if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
        return true;
  
      if (!includeStoreBindings)
        return false;
  
      unsigned &cachedQuery =
        const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
  
      if (cachedQuery) {
        return cachedQuery == 1;
      }
  
      // Query the store to see if the region occurs in any live bindings.
      if (Store store = reapedStore.getStore()) {
        bool hasRegion =
          reapedStore.getStoreManager().includedInBindings(store, VR);
        cachedQuery = hasRegion ? 1 : 2;
        return hasRegion;
      }
  
      return false;
    }
  
    return VarContext->isParentOf(CurrentContext);
  }
  