lib/Analysis/Consumed.cpp

//===- Consumed.cpp --------------------------------------------*- C++ --*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// A intra-procedural analysis for checking consumed properties.  This is based,
// in part, on research on linear types.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/Type.h"
#include "clang/Analysis/Analyses/PostOrderCFGView.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/Analyses/Consumed.h"
#include "clang/Basic/OperatorKinds.h"
#include "clang/Basic/SourceLocation.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h"

// TODO: Correctly identify unreachable blocks when chaining boolean operators.
// TODO: Warn about unreachable code.
// TODO: Switch to using a bitmap to track unreachable blocks.
// TODO: Mark variables as Unknown going into while- or for-loops only if they
//       are referenced inside that block. (Deferred)
// TODO: Handle variable definitions, e.g. bool valid = x.isValid();
//       if (valid) ...; (Deferred)
// TODO: Add a method(s) to identify which method calls perform what state
//       transitions. (Deferred)
// TODO: Take notes on state transitions to provide better warning messages.
//       (Deferred)
// TODO: Test nested conditionals: A) Checking the same value multiple times,
//       and 2) Checking different values. (Deferred)
// TODO: Test IsFalseVisitor with values in the unknown state. (Deferred)
// TODO: Look into combining IsFalseVisitor and TestedVarsVisitor. (Deferred)

using namespace clang;
using namespace consumed;

// Key method definition
ConsumedWarningsHandlerBase::~ConsumedWarningsHandlerBase() {}

static ConsumedState invertConsumedUnconsumed(ConsumedState State) {
  switch (State) {
  case CS_Unconsumed:
    return CS_Consumed;
  case CS_Consumed:
    return CS_Unconsumed;
  case CS_None:
    return CS_None;
  case CS_Unknown:
    return CS_Unknown;
  }
  llvm_unreachable("invalid enum");
}

static bool isKnownState(ConsumedState State) {
  switch (State) {
  case CS_Unconsumed:
  case CS_Consumed:
    return true;
  case CS_None:
  case CS_Unknown:
    return false;
  }
}

static bool isTestingFunction(const FunctionDecl *FunDecl) {
  return FunDecl->hasAttr<TestsUnconsumedAttr>();
}

static StringRef stateToString(ConsumedState State) {
  switch (State) {
  case consumed::CS_None:
    return "none";
  
  case consumed::CS_Unknown:
    return "unknown";
  
  case consumed::CS_Unconsumed:
    return "unconsumed";
  
  case consumed::CS_Consumed:
    return "consumed";
  }
  llvm_unreachable("invalid enum");
}

namespace {
struct VarTestResult {
  const VarDecl *Var;
  ConsumedState TestsFor;
};
} // end anonymous::VarTestResult

namespace clang {
namespace consumed {

enum EffectiveOp {
  EO_And,
  EO_Or
};

class PropagationInfo {
  enum {
    IT_None,
    IT_State,
    IT_Test,
    IT_BinTest,
    IT_Var
  } InfoType;
  
  union {
    ConsumedState State;
    VarTestResult Test;
    const VarDecl *Var;
    struct {
      const BinaryOperator *Source;
      EffectiveOp EOp;
      VarTestResult LTest;
      VarTestResult RTest;
    } BinTest;
  };
  
public:
  PropagationInfo() : InfoType(IT_None) {}
  
  PropagationInfo(const VarTestResult &Test) : InfoType(IT_Test), Test(Test) {}
  PropagationInfo(const VarDecl *Var, ConsumedState TestsFor)
    : InfoType(IT_Test) {
    
    Test.Var      = Var;
    Test.TestsFor = TestsFor;
  }
  
  PropagationInfo(const BinaryOperator *Source, EffectiveOp EOp,
                  const VarTestResult &LTest, const VarTestResult &RTest)
    : InfoType(IT_BinTest) {
    
    BinTest.Source  = Source;
    BinTest.EOp     = EOp;
    BinTest.LTest   = LTest;
    BinTest.RTest   = RTest;
  }
  
  PropagationInfo(const BinaryOperator *Source, EffectiveOp EOp,
                  const VarDecl *LVar, ConsumedState LTestsFor,
                  const VarDecl *RVar, ConsumedState RTestsFor)
    : InfoType(IT_BinTest) {
    
    BinTest.Source         = Source;
    BinTest.EOp            = EOp;
    BinTest.LTest.Var      = LVar;
    BinTest.LTest.TestsFor = LTestsFor;
    BinTest.RTest.Var      = RVar;
    BinTest.RTest.TestsFor = RTestsFor;
  }
  
  PropagationInfo(ConsumedState State) : InfoType(IT_State), State(State) {}
  PropagationInfo(const VarDecl *Var) : InfoType(IT_Var), Var(Var) {}
  
  const ConsumedState & getState() const {
    assert(InfoType == IT_State);
    return State;
  }
  
  const VarTestResult & getTest() const {
    assert(InfoType == IT_Test);
    return Test;
  }
  
  const VarTestResult & getLTest() const {
    assert(InfoType == IT_BinTest);
    return BinTest.LTest;
  }
  
  const VarTestResult & getRTest() const {
    assert(InfoType == IT_BinTest);
    return BinTest.RTest;
  }
  
  const VarDecl * getVar() const {
    assert(InfoType == IT_Var);
    return Var;
  }
  
  EffectiveOp testEffectiveOp() const {
    assert(InfoType == IT_BinTest);
    return BinTest.EOp;
  }
  
  const BinaryOperator * testSourceNode() const {
    assert(InfoType == IT_BinTest);
    return BinTest.Source;
  }
  
  bool isValid()   const { return InfoType != IT_None;     }
  bool isState()   const { return InfoType == IT_State;    }
  bool isTest()    const { return InfoType == IT_Test;     }
  bool isBinTest() const { return InfoType == IT_BinTest;  }
  bool isVar()     const { return InfoType == IT_Var;      }
  
  PropagationInfo invertTest() const {
    assert(InfoType == IT_Test || InfoType == IT_BinTest);
    
    if (InfoType == IT_Test) {
      return PropagationInfo(Test.Var, invertConsumedUnconsumed(Test.TestsFor));
    
    } else if (InfoType == IT_BinTest) {
      return PropagationInfo(BinTest.Source,
        BinTest.EOp == EO_And ? EO_Or : EO_And,
        BinTest.LTest.Var, invertConsumedUnconsumed(BinTest.LTest.TestsFor),
        BinTest.RTest.Var, invertConsumedUnconsumed(BinTest.RTest.TestsFor));
    } else {
      return PropagationInfo();
    }
  }
};

class ConsumedStmtVisitor : public ConstStmtVisitor<ConsumedStmtVisitor> {
  
  typedef llvm::DenseMap<const Stmt *, PropagationInfo> MapType;
  typedef std::pair<const Stmt *, PropagationInfo> PairType;
  typedef MapType::iterator InfoEntry;
  typedef MapType::const_iterator ConstInfoEntry;
  
  AnalysisDeclContext &AC;
  ConsumedAnalyzer &Analyzer;
  ConsumedStateMap *StateMap;
  MapType PropagationMap;
  
  void checkCallability(const PropagationInfo &PInfo,
                        const FunctionDecl *FunDecl,
                        const CallExpr *Call);
  void forwardInfo(const Stmt *From, const Stmt *To);
  void handleTestingFunctionCall(const CallExpr *Call, const VarDecl *Var);
  bool isLikeMoveAssignment(const CXXMethodDecl *MethodDecl);
  
public:

  void Visit(const Stmt *StmtNode);
  
  void VisitBinaryOperator(const BinaryOperator *BinOp);
  void VisitCallExpr(const CallExpr *Call);
  void VisitCastExpr(const CastExpr *Cast);
  void VisitCXXConstructExpr(const CXXConstructExpr *Call);
  void VisitCXXMemberCallExpr(const CXXMemberCallExpr *Call);
  void VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *Call);
  void VisitDeclRefExpr(const DeclRefExpr *DeclRef);
  void VisitDeclStmt(const DeclStmt *DelcS);
  void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *Temp);
  void VisitMemberExpr(const MemberExpr *MExpr);
  void VisitUnaryOperator(const UnaryOperator *UOp);
  void VisitVarDecl(const VarDecl *Var);

  ConsumedStmtVisitor(AnalysisDeclContext &AC, ConsumedAnalyzer &Analyzer)
      : AC(AC), Analyzer(Analyzer), StateMap(NULL) {}
  
  PropagationInfo getInfo(const Stmt *StmtNode) const {
    ConstInfoEntry Entry = PropagationMap.find(StmtNode);
    
    if (Entry != PropagationMap.end())
      return Entry->second;
    else
      return PropagationInfo();
  }
  
  void reset(ConsumedStateMap *NewStateMap) {
    StateMap = NewStateMap;
  }
};

// TODO: When we support CallableWhenConsumed this will have to check for
//       the different attributes and change the behavior bellow. (Deferred)
void ConsumedStmtVisitor::checkCallability(const PropagationInfo &PInfo,
                                           const FunctionDecl *FunDecl,
                                           const CallExpr *Call) {
  
  if (!FunDecl->hasAttr<CallableWhenUnconsumedAttr>()) return;
  
  if (PInfo.isVar()) {
    const VarDecl *Var = PInfo.getVar();
    
    switch (StateMap->getState(Var)) {
    case CS_Consumed:
      Analyzer.WarningsHandler.warnUseWhileConsumed(
        FunDecl->getNameAsString(), Var->getNameAsString(),
        Call->getExprLoc());
      break;
    
    case CS_Unknown:
      Analyzer.WarningsHandler.warnUseInUnknownState(
        FunDecl->getNameAsString(), Var->getNameAsString(),
        Call->getExprLoc());
      break;
      
    case CS_None:
    case CS_Unconsumed:
      break;
    }
    
  } else {
    switch (PInfo.getState()) {
    case CS_Consumed:
      Analyzer.WarningsHandler.warnUseOfTempWhileConsumed(
        FunDecl->getNameAsString(), Call->getExprLoc());
      break;
    
    case CS_Unknown:
      Analyzer.WarningsHandler.warnUseOfTempInUnknownState(
        FunDecl->getNameAsString(), Call->getExprLoc());
      break;
      
    case CS_None:
    case CS_Unconsumed:
      break;
    }
  }
}

void ConsumedStmtVisitor::forwardInfo(const Stmt *From, const Stmt *To) {
  InfoEntry Entry = PropagationMap.find(From);
  
  if (Entry != PropagationMap.end())
    PropagationMap.insert(PairType(To, Entry->second));
}

void ConsumedStmtVisitor::handleTestingFunctionCall(const CallExpr *Call,
                                                    const VarDecl  *Var) {
  
  ConsumedState VarState = StateMap->getState(Var);
  
  if (VarState != CS_Unknown) {
    SourceLocation CallLoc = Call->getExprLoc();
    
    if (!CallLoc.isMacroID())
      Analyzer.WarningsHandler.warnUnnecessaryTest(Var->getNameAsString(),
        stateToString(VarState), CallLoc);
  }
  
  PropagationMap.insert(PairType(Call, PropagationInfo(Var, CS_Unconsumed)));
}

bool ConsumedStmtVisitor::isLikeMoveAssignment(
  const CXXMethodDecl *MethodDecl) {
  
  return MethodDecl->isMoveAssignmentOperator() ||
         (MethodDecl->getOverloadedOperator() == OO_Equal &&
          MethodDecl->getNumParams() == 1 &&
          MethodDecl->getParamDecl(0)->getType()->isRValueReferenceType());
}

void ConsumedStmtVisitor::Visit(const Stmt *StmtNode) {
  
  ConstStmtVisitor<ConsumedStmtVisitor>::Visit(StmtNode);
  
  for (Stmt::const_child_iterator CI = StmtNode->child_begin(),
       CE = StmtNode->child_end(); CI != CE; ++CI) {
    
    PropagationMap.erase(*CI);
  }
}

void ConsumedStmtVisitor::VisitBinaryOperator(const BinaryOperator *BinOp) {
  switch (BinOp->getOpcode()) {
  case BO_LAnd:
  case BO_LOr : {
    InfoEntry LEntry = PropagationMap.find(BinOp->getLHS()),
              REntry = PropagationMap.find(BinOp->getRHS());
    
    VarTestResult LTest, RTest;
    
    if (LEntry != PropagationMap.end() && LEntry->second.isTest()) {
      LTest = LEntry->second.getTest();
      
    } else {
      LTest.Var      = NULL;
      LTest.TestsFor = CS_None;
    }
    
    if (REntry != PropagationMap.end() && REntry->second.isTest()) {
      RTest = REntry->second.getTest();
      
    } else {
      RTest.Var      = NULL;
      RTest.TestsFor = CS_None;
    }
    
    if (!(LTest.Var == NULL && RTest.Var == NULL))
      PropagationMap.insert(PairType(BinOp, PropagationInfo(BinOp,
        static_cast<EffectiveOp>(BinOp->getOpcode() == BO_LOr), LTest, RTest)));
    
    break;
  }
    
  case BO_PtrMemD:
  case BO_PtrMemI:
    forwardInfo(BinOp->getLHS(), BinOp);
    break;
    
  default:
    break;
  }
}

void ConsumedStmtVisitor::VisitCallExpr(const CallExpr *Call) {
  if (const FunctionDecl *FunDecl =
    dyn_cast_or_null<FunctionDecl>(Call->getDirectCallee())) {
    
    // Special case for the std::move function.
    // TODO: Make this more specific. (Deferred)
    if (FunDecl->getNameAsString() == "move") {
      InfoEntry Entry = PropagationMap.find(Call->getArg(0));
      
      if (Entry != PropagationMap.end()) {
        PropagationMap.insert(PairType(Call, Entry->second));
      }
      
      return;
    }
    
    unsigned Offset = Call->getNumArgs() - FunDecl->getNumParams();
    
    for (unsigned Index = Offset; Index < Call->getNumArgs(); ++Index) {
      QualType ParamType = FunDecl->getParamDecl(Index - Offset)->getType();
      
      InfoEntry Entry = PropagationMap.find(Call->getArg(Index));
      
      if (Entry == PropagationMap.end() || !Entry->second.isVar()) {
        continue;
      }
      
      PropagationInfo PInfo = Entry->second;
      
      if (ParamType->isRValueReferenceType() ||
          (ParamType->isLValueReferenceType() &&
           !cast<LValueReferenceType>(*ParamType).isSpelledAsLValue())) {
        
        StateMap->setState(PInfo.getVar(), consumed::CS_Consumed);
        
      } else if (!(ParamType.isConstQualified() ||
                   ((ParamType->isReferenceType() ||
                     ParamType->isPointerType()) &&
                    ParamType->getPointeeType().isConstQualified()))) {
        
        StateMap->setState(PInfo.getVar(), consumed::CS_Unknown);
      }
    }
  }
}

void ConsumedStmtVisitor::VisitCastExpr(const CastExpr *Cast) {
  forwardInfo(Cast->getSubExpr(), Cast);
}

void ConsumedStmtVisitor::VisitCXXConstructExpr(const CXXConstructExpr *Call) {
  CXXConstructorDecl *Constructor = Call->getConstructor();

  ASTContext &CurrContext = AC.getASTContext();
  QualType ThisType = Constructor->getThisType(CurrContext)->getPointeeType();
  
  if (Analyzer.isConsumableType(ThisType)) {
    if (Constructor->hasAttr<ConsumesAttr>() ||
        Constructor->isDefaultConstructor()) {
      
      PropagationMap.insert(PairType(Call,
        PropagationInfo(consumed::CS_Consumed)));
      
    } else if (Constructor->isMoveConstructor()) {
      
      PropagationInfo PInfo =
        PropagationMap.find(Call->getArg(0))->second;
      
      if (PInfo.isVar()) {
        const VarDecl* Var = PInfo.getVar();
        
        PropagationMap.insert(PairType(Call,
          PropagationInfo(StateMap->getState(Var))));
        
        StateMap->setState(Var, consumed::CS_Consumed);
        
      } else {
        PropagationMap.insert(PairType(Call, PInfo));
      }
        
    } else if (Constructor->isCopyConstructor()) {
      MapType::iterator Entry = PropagationMap.find(Call->getArg(0));
    
      if (Entry != PropagationMap.end())
        PropagationMap.insert(PairType(Call, Entry->second));
      
    } else {
      PropagationMap.insert(PairType(Call,
        PropagationInfo(consumed::CS_Unconsumed)));
    }
  }
}

void ConsumedStmtVisitor::VisitCXXMemberCallExpr(
  const CXXMemberCallExpr *Call) {
  
  VisitCallExpr(Call);
  
  InfoEntry Entry = PropagationMap.find(Call->getCallee()->IgnoreParens());
  
  if (Entry != PropagationMap.end()) {
    PropagationInfo PInfo = Entry->second;
    const CXXMethodDecl *MethodDecl = Call->getMethodDecl();
    
    checkCallability(PInfo, MethodDecl, Call);
    
    if (PInfo.isVar()) {
      if (isTestingFunction(MethodDecl))
        handleTestingFunctionCall(Call, PInfo.getVar());
      else if (MethodDecl->hasAttr<ConsumesAttr>())
        StateMap->setState(PInfo.getVar(), consumed::CS_Consumed);
      else if (!MethodDecl->isConst())
        StateMap->setState(PInfo.getVar(), consumed::CS_Unknown);
    }
  }
}

void ConsumedStmtVisitor::VisitCXXOperatorCallExpr(
  const CXXOperatorCallExpr *Call) {
  
  const FunctionDecl *FunDecl =
    dyn_cast_or_null<FunctionDecl>(Call->getDirectCallee());
  
  if (!FunDecl) return;
    
  if (isa<CXXMethodDecl>(FunDecl) &&
      isLikeMoveAssignment(cast<CXXMethodDecl>(FunDecl))) {
    
    InfoEntry LEntry = PropagationMap.find(Call->getArg(0));
    InfoEntry REntry = PropagationMap.find(Call->getArg(1));
    
    PropagationInfo LPInfo, RPInfo;
    
    if (LEntry != PropagationMap.end() &&
        REntry != PropagationMap.end()) {
      
      LPInfo = LEntry->second;
      RPInfo = REntry->second;
      
      if (LPInfo.isVar() && RPInfo.isVar()) {
        StateMap->setState(LPInfo.getVar(),
          StateMap->getState(RPInfo.getVar()));
        
        StateMap->setState(RPInfo.getVar(), consumed::CS_Consumed);
        
        PropagationMap.insert(PairType(Call, LPInfo));
        
      } else if (LPInfo.isVar() && !RPInfo.isVar()) {
        StateMap->setState(LPInfo.getVar(), RPInfo.getState());
        
        PropagationMap.insert(PairType(Call, LPInfo));
        
      } else if (!LPInfo.isVar() && RPInfo.isVar()) {
        PropagationMap.insert(PairType(Call,
          PropagationInfo(StateMap->getState(RPInfo.getVar()))));
        
        StateMap->setState(RPInfo.getVar(), consumed::CS_Consumed);
        
      } else {
        PropagationMap.insert(PairType(Call, RPInfo));
      }
      
    } else if (LEntry != PropagationMap.end() &&
               REntry == PropagationMap.end()) {
      
      LPInfo = LEntry->second;
      
      if (LPInfo.isVar()) {
        StateMap->setState(LPInfo.getVar(), consumed::CS_Unknown);
        
        PropagationMap.insert(PairType(Call, LPInfo));
        
      } else {
        PropagationMap.insert(PairType(Call,
          PropagationInfo(consumed::CS_Unknown)));
      }
      
    } else if (LEntry == PropagationMap.end() &&
               REntry != PropagationMap.end()) {
      
      RPInfo = REntry->second;
      
      if (RPInfo.isVar()) {
        const VarDecl *Var = RPInfo.getVar();
        
        PropagationMap.insert(PairType(Call,
          PropagationInfo(StateMap->getState(Var))));
        
        StateMap->setState(Var, consumed::CS_Consumed);
        
      } else {
        PropagationMap.insert(PairType(Call, RPInfo));
      }
    }
    
  } else {
    
    VisitCallExpr(Call);
    
    InfoEntry Entry = PropagationMap.find(Call->getArg(0));
    
    if (Entry != PropagationMap.end()) {
      PropagationInfo PInfo = Entry->second;
      
      checkCallability(PInfo, FunDecl, Call);
      
      if (PInfo.isVar()) {
        if (isTestingFunction(FunDecl)) {
          handleTestingFunctionCall(Call, PInfo.getVar());
          
        } else if (FunDecl->hasAttr<ConsumesAttr>()) {
          StateMap->setState(PInfo.getVar(), consumed::CS_Consumed);
          
        } else if (const CXXMethodDecl *MethodDecl =
                     dyn_cast_or_null<CXXMethodDecl>(FunDecl)) {
          
          if (!MethodDecl->isConst())
            StateMap->setState(PInfo.getVar(), consumed::CS_Unknown);
        }
      }
    }
  }
}

void ConsumedStmtVisitor::VisitDeclRefExpr(const DeclRefExpr *DeclRef) {
  if (const VarDecl *Var = dyn_cast_or_null<VarDecl>(DeclRef->getDecl()))
    if (StateMap->getState(Var) != consumed::CS_None)
      PropagationMap.insert(PairType(DeclRef, PropagationInfo(Var)));
}

void ConsumedStmtVisitor::VisitDeclStmt(const DeclStmt *DeclS) {
  for (DeclStmt::const_decl_iterator DI = DeclS->decl_begin(),
       DE = DeclS->decl_end(); DI != DE; ++DI) {
    
    if (isa<VarDecl>(*DI)) VisitVarDecl(cast<VarDecl>(*DI));
  }
  
  if (DeclS->isSingleDecl())
    if (const VarDecl *Var = dyn_cast_or_null<VarDecl>(DeclS->getSingleDecl()))
      PropagationMap.insert(PairType(DeclS, PropagationInfo(Var)));
}

void ConsumedStmtVisitor::VisitMaterializeTemporaryExpr(
  const MaterializeTemporaryExpr *Temp) {
  
  InfoEntry Entry = PropagationMap.find(Temp->GetTemporaryExpr());
  
  if (Entry != PropagationMap.end())
    PropagationMap.insert(PairType(Temp, Entry->second));
}

void ConsumedStmtVisitor::VisitMemberExpr(const MemberExpr *MExpr) {
  forwardInfo(MExpr->getBase(), MExpr);
}

void ConsumedStmtVisitor::VisitUnaryOperator(const UnaryOperator *UOp) {
  InfoEntry Entry = PropagationMap.find(UOp->getSubExpr()->IgnoreParens());
  if (Entry == PropagationMap.end()) return;
  
  switch (UOp->getOpcode()) {
  case UO_AddrOf:
    PropagationMap.insert(PairType(UOp, Entry->second));
    break;
  
  case UO_LNot:
    if (Entry->second.isTest() || Entry->second.isBinTest())
      PropagationMap.insert(PairType(UOp, Entry->second.invertTest()));
    break;
  
  default:
    break;
  }
}

void ConsumedStmtVisitor::VisitVarDecl(const VarDecl *Var) {
  if (Analyzer.isConsumableType(Var->getType())) {
    PropagationInfo PInfo =
      PropagationMap.find(Var->getInit())->second;
    
    StateMap->setState(Var, PInfo.isVar() ?
      StateMap->getState(PInfo.getVar()) : PInfo.getState());
  }
}
}} // end clang::consumed::ConsumedStmtVisitor

namespace clang {
namespace consumed {

void splitVarStateForIf(const IfStmt * IfNode, const VarTestResult &Test,
                        ConsumedStateMap *ThenStates,
                        ConsumedStateMap *ElseStates) {

  ConsumedState VarState = ThenStates->getState(Test.Var);
  
  if (VarState == CS_Unknown) {
    ThenStates->setState(Test.Var, Test.TestsFor);
    if (ElseStates)
      ElseStates->setState(Test.Var, invertConsumedUnconsumed(Test.TestsFor));
  
  } else if (VarState == invertConsumedUnconsumed(Test.TestsFor)) {
    ThenStates->markUnreachable();
    
  } else if (VarState == Test.TestsFor && ElseStates) {
    ElseStates->markUnreachable();
  }
}

void splitVarStateForIfBinOp(const PropagationInfo &PInfo,
  ConsumedStateMap *ThenStates, ConsumedStateMap *ElseStates) {
  
  const VarTestResult &LTest = PInfo.getLTest(),
                      &RTest = PInfo.getRTest();
  
  ConsumedState LState = LTest.Var ? ThenStates->getState(LTest.Var) : CS_None,
                RState = RTest.Var ? ThenStates->getState(RTest.Var) : CS_None;
  
  if (LTest.Var) {
    if (PInfo.testEffectiveOp() == EO_And) {
      if (LState == CS_Unknown) {
        ThenStates->setState(LTest.Var, LTest.TestsFor);
        
      } else if (LState == invertConsumedUnconsumed(LTest.TestsFor)) {
        ThenStates->markUnreachable();
        
      } else if (LState == LTest.TestsFor && isKnownState(RState)) {
        if (RState == RTest.TestsFor) {
          if (ElseStates)
            ElseStates->markUnreachable();
        } else {
          ThenStates->markUnreachable();
        }
      }
      
    } else {
      if (LState == CS_Unknown && ElseStates) {
        ElseStates->setState(LTest.Var,
                             invertConsumedUnconsumed(LTest.TestsFor));
      
      } else if (LState == LTest.TestsFor && ElseStates) {
        ElseStates->markUnreachable();
        
      } else if (LState == invertConsumedUnconsumed(LTest.TestsFor) &&
                 isKnownState(RState)) {
        
        if (RState == RTest.TestsFor) {
          if (ElseStates)
            ElseStates->markUnreachable();
        } else {
          ThenStates->markUnreachable();
        }
      }
    }
  }
  
  if (RTest.Var) {
    if (PInfo.testEffectiveOp() == EO_And) {
      if (RState == CS_Unknown)
        ThenStates->setState(RTest.Var, RTest.TestsFor);
      else if (RState == invertConsumedUnconsumed(RTest.TestsFor))
        ThenStates->markUnreachable();
      
    } else if (ElseStates) {
      if (RState == CS_Unknown)
        ElseStates->setState(RTest.Var,
                             invertConsumedUnconsumed(RTest.TestsFor));
      else if (RState == RTest.TestsFor)
        ElseStates->markUnreachable();
    }
  }
}

void ConsumedBlockInfo::addInfo(const CFGBlock *Block,
                                ConsumedStateMap *StateMap,
                                bool &AlreadyOwned) {
  
  if (VisitedBlocks.alreadySet(Block)) return;
  
  ConsumedStateMap *Entry = StateMapsArray[Block->getBlockID()];
    
  if (Entry) {
    Entry->intersect(StateMap);
    
  } else if (AlreadyOwned) {
    StateMapsArray[Block->getBlockID()] = new ConsumedStateMap(*StateMap);
    
  } else {
    StateMapsArray[Block->getBlockID()] = StateMap;
    AlreadyOwned = true;
  }
}

void ConsumedBlockInfo::addInfo(const CFGBlock *Block,
                                ConsumedStateMap *StateMap) {
  
  if (VisitedBlocks.alreadySet(Block)) {
    delete StateMap;
    return;
  }
  
  ConsumedStateMap *Entry = StateMapsArray[Block->getBlockID()];
    
  if (Entry) {
    Entry->intersect(StateMap);
    delete StateMap;
    
  } else {
    StateMapsArray[Block->getBlockID()] = StateMap;
  }
}

ConsumedStateMap* ConsumedBlockInfo::getInfo(const CFGBlock *Block) {
  return StateMapsArray[Block->getBlockID()];
}

void ConsumedBlockInfo::markVisited(const CFGBlock *Block) {
  VisitedBlocks.insert(Block);
}

ConsumedState ConsumedStateMap::getState(const VarDecl *Var) {
  MapType::const_iterator Entry = Map.find(Var);
  
  if (Entry != Map.end()) {
    return Entry->second;
    
  } else {
    return CS_None;
  }
}

void ConsumedStateMap::intersect(const ConsumedStateMap *Other) {
  ConsumedState LocalState;
  
  if (this->From && this->From == Other->From && !Other->Reachable) {
    this->markUnreachable();
    return;
  }
  
  for (MapType::const_iterator DMI = Other->Map.begin(),
       DME = Other->Map.end(); DMI != DME; ++DMI) {
    
    LocalState = this->getState(DMI->first);
    
    if (LocalState == CS_None)
      continue;
    
    if (LocalState != DMI->second)
       Map[DMI->first] = CS_Unknown;
  }
}

void ConsumedStateMap::markUnreachable() {
  this->Reachable = false;
  Map.clear();
}

void ConsumedStateMap::makeUnknown() {
  for (MapType::const_iterator DMI = Map.begin(), DME = Map.end(); DMI != DME;
       ++DMI) {
    
    Map[DMI->first] = CS_Unknown;
  }
}

void ConsumedStateMap::setState(const VarDecl *Var, ConsumedState State) {
  Map[Var] = State;
}

void ConsumedStateMap::remove(const VarDecl *Var) {
  Map.erase(Var);
}

bool ConsumedAnalyzer::isConsumableType(QualType Type) {
  const CXXRecordDecl *RD =
    dyn_cast_or_null<CXXRecordDecl>(Type->getAsCXXRecordDecl());
  
  if (!RD) return false;
  
  std::pair<CacheMapType::iterator, bool> Entry =
    ConsumableTypeCache.insert(std::make_pair(RD, false));
  
  if (Entry.second)
    Entry.first->second = hasConsumableAttributes(RD);
  
  return Entry.first->second;
}

// TODO: Walk the base classes to see if any of them are unique types.
//       (Deferred)
bool ConsumedAnalyzer::hasConsumableAttributes(const CXXRecordDecl *RD) {
  for (CXXRecordDecl::method_iterator MI = RD->method_begin(),
       ME = RD->method_end(); MI != ME; ++MI) {
    
    for (Decl::attr_iterator AI = (*MI)->attr_begin(), AE = (*MI)->attr_end();
         AI != AE; ++AI) {
      
      switch ((*AI)->getKind()) {
      case attr::CallableWhenUnconsumed:
      case attr::TestsUnconsumed:
        return true;
      
      default:
        break;
      }
    }
  }
  
  return false;
}

bool ConsumedAnalyzer::splitState(const CFGBlock *CurrBlock,
                                  const ConsumedStmtVisitor &Visitor) {
  
  ConsumedStateMap *FalseStates = new ConsumedStateMap(*CurrStates);
  PropagationInfo PInfo;
  
  if (const IfStmt *IfNode =
    dyn_cast_or_null<IfStmt>(CurrBlock->getTerminator().getStmt())) {
    
    bool HasElse = IfNode->getElse() != NULL;
    const Stmt *Cond = IfNode->getCond();
    
    PInfo = Visitor.getInfo(Cond);
    if (!PInfo.isValid() && isa<BinaryOperator>(Cond))
      PInfo = Visitor.getInfo(cast<BinaryOperator>(Cond)->getRHS());
    
    if (PInfo.isTest()) {
      CurrStates->setSource(Cond);
      FalseStates->setSource(Cond);
      
      splitVarStateForIf(IfNode, PInfo.getTest(), CurrStates,
                         HasElse ? FalseStates : NULL);
      
    } else if (PInfo.isBinTest()) {
      CurrStates->setSource(PInfo.testSourceNode());
      FalseStates->setSource(PInfo.testSourceNode());
      
      splitVarStateForIfBinOp(PInfo, CurrStates, HasElse ? FalseStates : NULL);
      
    } else {
      delete FalseStates;
      return false;
    }
    
  } else if (const BinaryOperator *BinOp =
    dyn_cast_or_null<BinaryOperator>(CurrBlock->getTerminator().getStmt())) {
    
    PInfo = Visitor.getInfo(BinOp->getLHS());
    if (!PInfo.isTest()) {
      if ((BinOp = dyn_cast_or_null<BinaryOperator>(BinOp->getLHS()))) {
        PInfo = Visitor.getInfo(BinOp->getRHS());
        
        if (!PInfo.isTest()) {
          delete FalseStates;
          return false;
        }
        
      } else {
        delete FalseStates;
        return false;
      }
    }
    
    CurrStates->setSource(BinOp);
    FalseStates->setSource(BinOp);
    
    const VarTestResult &Test = PInfo.getTest();
    ConsumedState VarState = CurrStates->getState(Test.Var);
    
    if (BinOp->getOpcode() == BO_LAnd) {
      if (VarState == CS_Unknown)
        CurrStates->setState(Test.Var, Test.TestsFor);
      else if (VarState == invertConsumedUnconsumed(Test.TestsFor))
        CurrStates->markUnreachable();
      
    } else if (BinOp->getOpcode() == BO_LOr) {
      if (VarState == CS_Unknown)
        FalseStates->setState(Test.Var,
                              invertConsumedUnconsumed(Test.TestsFor));
      else if (VarState == Test.TestsFor)
        FalseStates->markUnreachable();
    }
    
  } else {
    delete FalseStates;
    return false;
  }
  
  CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin();
  
  if (*SI)
    BlockInfo.addInfo(*SI, CurrStates);
  else
    delete CurrStates;
    
  if (*++SI)
    BlockInfo.addInfo(*SI, FalseStates);
  else
    delete FalseStates;
  
  CurrStates = NULL;
  return true;
}

void ConsumedAnalyzer::run(AnalysisDeclContext &AC) {
  const FunctionDecl *D = dyn_cast_or_null<FunctionDecl>(AC.getDecl());
  
  if (!D) return;
  
  BlockInfo = ConsumedBlockInfo(AC.getCFG());
  
  PostOrderCFGView *SortedGraph = AC.getAnalysis<PostOrderCFGView>();
  
  CurrStates = new ConsumedStateMap();
  ConsumedStmtVisitor Visitor(AC, *this);
  
  // Visit all of the function's basic blocks.
  for (PostOrderCFGView::iterator I = SortedGraph->begin(),
       E = SortedGraph->end(); I != E; ++I) {
    
    const CFGBlock *CurrBlock = *I;
    BlockInfo.markVisited(CurrBlock);
    
    if (CurrStates == NULL)
      CurrStates = BlockInfo.getInfo(CurrBlock);
    
    if (!CurrStates) {
      continue;
      
    } else if (!CurrStates->isReachable()) {
      delete CurrStates;
      CurrStates = NULL;
      continue;
    }
    
    Visitor.reset(CurrStates);
    
    // Visit all of the basic block's statements.
    for (CFGBlock::const_iterator BI = CurrBlock->begin(),
         BE = CurrBlock->end(); BI != BE; ++BI) {
      
      switch (BI->getKind()) {
      case CFGElement::Statement:
        Visitor.Visit(BI->castAs<CFGStmt>().getStmt());
        break;
      case CFGElement::AutomaticObjectDtor:
        CurrStates->remove(BI->castAs<CFGAutomaticObjDtor>().getVarDecl());
      default:
        break;
      }
    }
    
    // TODO: Handle other forms of branching with precision, including while-
    //       and for-loops. (Deferred)
    if (!splitState(CurrBlock, Visitor)) {
      CurrStates->setSource(NULL);
      
      if (CurrBlock->succ_size() > 1) {
        CurrStates->makeUnknown();
        
        bool OwnershipTaken = false;
        
        for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
             SE = CurrBlock->succ_end(); SI != SE; ++SI) {
          
          if (*SI) BlockInfo.addInfo(*SI, CurrStates, OwnershipTaken);
        }
        
        if (!OwnershipTaken)
          delete CurrStates;
        
        CurrStates = NULL;
        
      } else if (CurrBlock->succ_size() == 1 &&
                 (*CurrBlock->succ_begin())->pred_size() > 1) {
        
        BlockInfo.addInfo(*CurrBlock->succ_begin(), CurrStates);
        CurrStates = NULL;
      }
    }
  } // End of block iterator.
  
  // Delete the last existing state map.
  delete CurrStates;
  
  WarningsHandler.emitDiagnostics();
}
}} // end namespace clang::consumed