lib/StaticAnalyzer/Core/SymbolManager.cpp - platform/external/clang - Git at Google

 //== 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());
 }

 static void print(raw_ostream &os, BinaryOperator::Opcode Op) {
   switch (Op) {
     default:
       llvm_unreachable("operator printing not implemented");
     case BO_Mul: os << '*'  ; break;
     case BO_Div: os << '/'  ; break;
     case BO_Rem: os << '%'  ; break;
     case BO_Add: os << '+'  ; break;
     case BO_Sub: os << '-'  ; break;
     case BO_Shl: os << "<<" ; break;
     case BO_Shr: os << ">>" ; break;
     case BO_LT:  os << "<"  ; break;
     case BO_GT:  os << '>'  ; break;
     case BO_LE:  os << "<=" ; break;
     case BO_GE:  os << ">=" ; break;
     case BO_EQ:  os << "==" ; break;
     case BO_NE:  os << "!=" ; break;
     case BO_And: os << '&'  ; break;
     case BO_Xor: os << '^'  ; break;
     case BO_Or:  os << '|'  ; break;
   }
 }

 void SymIntExpr::dumpToStream(raw_ostream &os) const {
   os << '(';
   getLHS()->dumpToStream(os);
   os << ") ";
   print(os, getOpcode());
   os << ' ' << getRHS().getZExtValue();
   if (getRHS().isUnsigned()) os << 'U';
 }

 void IntSymExpr::dumpToStream(raw_ostream &os) const {
   os << ' ' << getLHS().getZExtValue();
   if (getLHS().isUnsigned()) os << 'U';
   print(os, getOpcode());
   os << '(';
   getRHS()->dumpToStream(os);
   os << ") ";
 }

 void SymSymExpr::dumpToStream(raw_ostream &os) const {
   os << '(';
   getLHS()->dumpToStream(os);
   os << ") ";
   os << '(';
   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);
   while (!isa<SymbolData>(itr.back())) expand();
 }

 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
   assert(isa<SymbolData>(itr.back()));
   itr.pop_back();
   if (!itr.empty())
     while (!isa<SymbolData>(itr.back())) expand();
   return *this;
 }

 SymbolRef SymExpr::symbol_iterator::operator*() {
   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
   return cast<SymbolData>(itr.back());
 }

 void SymExpr::symbol_iterator::expand() {
   const SymExpr *SE = itr.back();
   itr.pop_back();

   switch (SE->getKind()) {
     case SymExpr::RegionValueKind:
     case SymExpr::ConjuredKind:
     case SymExpr::DerivedKind:
     case SymExpr::ExtentKind:
     case SymExpr::MetadataKind:
       return;
     case SymExpr::CastSymbolKind:
       itr.push_back(cast<SymbolCast>(SE)->getOperand());
       return;
     case SymExpr::SymIntKind:
       itr.push_back(cast<SymIntExpr>(SE)->getLHS());
       return;
     case SymExpr::IntSymKind:
       itr.push_back(cast<IntSymExpr>(SE)->getRHS());
       return;
     case SymExpr::SymSymKind: {
       const SymSymExpr *x = cast<SymSymExpr>(SE);
       itr.push_back(x->getLHS());
       itr.push_back(x->getRHS());
       return;
     }
   }
   llvm_unreachable("unhandled expansion case");
 }

 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::getConjuredSymbol(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(ASTContext&) const {
   return T;
 }

 QualType SymbolDerived::getType(ASTContext &Ctx) const {
   return R->getValueType();
 }

 QualType SymbolExtent::getType(ASTContext &Ctx) const {
   return Ctx.getSizeType();
 }

 QualType SymbolMetadata::getType(ASTContext&) const {
   return T;
 }

 QualType SymbolRegionValue::getType(ASTContext &C) const {
   return R->getValueType();
 }

 SymbolManager::~SymbolManager() {
   for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
        E = SymbolDependencies.end(); I != E; ++I) {
     delete I->second;
   }

 }

 bool SymbolManager::canSymbolicate(QualType T) {
   T = T.getCanonicalType();

   if (Loc::isLocType(T))
     return true;

   if (T->isIntegerType())
     return T->isScalarType();

   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 = 0;
   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 0;
   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);
 }

 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;

   return false;
 }

 bool SymbolReaper::isLive(SymbolRef sym) {
   if (TheLiving.count(sym)) {
     markDependentsLive(sym);
     return true;
   }

   if (const SymbolDerived *derived = dyn_cast<SymbolDerived>(sym)) {
     if (isLive(derived->getParentSymbol())) {
       markLive(sym);
       return true;
     }
     return false;
   }

   if (const SymbolExtent *extent = dyn_cast<SymbolExtent>(sym)) {
     if (isLiveRegion(extent->getRegion())) {
       markLive(sym);
       return true;
     }
     return false;
   }

   if (const SymbolMetadata *metadata = dyn_cast<SymbolMetadata>(sym)) {
     if (MetadataInUse.count(sym)) {
       if (isLiveRegion(metadata->getRegion())) {
         markLive(sym);
         MetadataInUse.erase(sym);
         return true;
       }
     }
     return false;
   }

   // Interogate the symbol.  It may derive from an input value to
   // the analyzed function/method.
   return isa<SymbolRegionValue>(sym);
 }

 bool
 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
   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;
   }

   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
 }

 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
   const StackFrameContext *VarContext = VR->getStackFrame();
   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();

   if (VarContext == CurrentContext) {
     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);
 }

 SymbolVisitor::~SymbolVisitor() {}
	//== 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());
	}

	static void print(raw_ostream &os, BinaryOperator::Opcode Op) {
	switch (Op) {
	default:
	llvm_unreachable("operator printing not implemented");
	case BO_Mul: os << '*' ; break;
	case BO_Div: os << '/' ; break;
	case BO_Rem: os << '%' ; break;
	case BO_Add: os << '+' ; break;
	case BO_Sub: os << '-' ; break;
	case BO_Shl: os << "<<" ; break;
	case BO_Shr: os << ">>" ; break;
	case BO_LT: os << "<" ; break;
	case BO_GT: os << '>' ; break;
	case BO_LE: os << "<=" ; break;
	case BO_GE: os << ">=" ; break;
	case BO_EQ: os << "==" ; break;
	case BO_NE: os << "!=" ; break;
	case BO_And: os << '&' ; break;
	case BO_Xor: os << '^' ; break;
	case BO_Or: os << '\|' ; break;
	}
	}

	void SymIntExpr::dumpToStream(raw_ostream &os) const {
	os << '(';
	getLHS()->dumpToStream(os);
	os << ") ";
	print(os, getOpcode());
	os << ' ' << getRHS().getZExtValue();
	if (getRHS().isUnsigned()) os << 'U';
	}

	void IntSymExpr::dumpToStream(raw_ostream &os) const {
	os << ' ' << getLHS().getZExtValue();
	if (getLHS().isUnsigned()) os << 'U';
	print(os, getOpcode());
	os << '(';
	getRHS()->dumpToStream(os);
	os << ") ";
	}

	void SymSymExpr::dumpToStream(raw_ostream &os) const {
	os << '(';
	getLHS()->dumpToStream(os);
	os << ") ";
	os << '(';
	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);
	while (!isa<SymbolData>(itr.back())) expand();
	}

	SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
	assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
	assert(isa<SymbolData>(itr.back()));
	itr.pop_back();
	if (!itr.empty())
	while (!isa<SymbolData>(itr.back())) expand();
	return *this;
	}

	SymbolRef SymExpr::symbol_iterator::operator*() {
	assert(!itr.empty() && "attempting to dereference an 'end' iterator");
	return cast<SymbolData>(itr.back());
	}

	void SymExpr::symbol_iterator::expand() {
	const SymExpr *SE = itr.back();
	itr.pop_back();

	switch (SE->getKind()) {
	case SymExpr::RegionValueKind:
	case SymExpr::ConjuredKind:
	case SymExpr::DerivedKind:
	case SymExpr::ExtentKind:
	case SymExpr::MetadataKind:
	return;
	case SymExpr::CastSymbolKind:
	itr.push_back(cast<SymbolCast>(SE)->getOperand());
	return;
	case SymExpr::SymIntKind:
	itr.push_back(cast<SymIntExpr>(SE)->getLHS());
	return;
	case SymExpr::IntSymKind:
	itr.push_back(cast<IntSymExpr>(SE)->getRHS());
	return;
	case SymExpr::SymSymKind: {
	const SymSymExpr *x = cast<SymSymExpr>(SE);
	itr.push_back(x->getLHS());
	itr.push_back(x->getRHS());
	return;
	}
	}
	llvm_unreachable("unhandled expansion case");
	}

	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::getConjuredSymbol(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(ASTContext&) const {
	return T;
	}

	QualType SymbolDerived::getType(ASTContext &Ctx) const {
	return R->getValueType();
	}

	QualType SymbolExtent::getType(ASTContext &Ctx) const {
	return Ctx.getSizeType();
	}

	QualType SymbolMetadata::getType(ASTContext&) const {
	return T;
	}

	QualType SymbolRegionValue::getType(ASTContext &C) const {
	return R->getValueType();
	}

	SymbolManager::~SymbolManager() {
	for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
	E = SymbolDependencies.end(); I != E; ++I) {
	delete I->second;
	}

	}

	bool SymbolManager::canSymbolicate(QualType T) {
	T = T.getCanonicalType();

	if (Loc::isLocType(T))
	return true;

	if (T->isIntegerType())
	return T->isScalarType();

	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 = 0;
	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 0;
	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);
	}

	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;

	return false;
	}

	bool SymbolReaper::isLive(SymbolRef sym) {
	if (TheLiving.count(sym)) {
	markDependentsLive(sym);
	return true;
	}

	if (const SymbolDerived *derived = dyn_cast<SymbolDerived>(sym)) {
	if (isLive(derived->getParentSymbol())) {
	markLive(sym);
	return true;
	}
	return false;
	}

	if (const SymbolExtent *extent = dyn_cast<SymbolExtent>(sym)) {
	if (isLiveRegion(extent->getRegion())) {
	markLive(sym);
	return true;
	}
	return false;
	}

	if (const SymbolMetadata *metadata = dyn_cast<SymbolMetadata>(sym)) {
	if (MetadataInUse.count(sym)) {
	if (isLiveRegion(metadata->getRegion())) {
	markLive(sym);
	MetadataInUse.erase(sym);
	return true;
	}
	}
	return false;
	}

	// Interogate the symbol. It may derive from an input value to
	// the analyzed function/method.
	return isa<SymbolRegionValue>(sym);
	}

	bool
	SymbolReaper::isLive(const Stmt ExprVal, const LocationContext ELCtx) const {
	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;
	}

	return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
	}

	bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
	const StackFrameContext *VarContext = VR->getStackFrame();
	const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();

	if (VarContext == CurrentContext) {
	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);
	}

	SymbolVisitor::~SymbolVisitor() {}