Home | History | Annotate | Download | only in Core
      1 // SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- C++ -*-
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file defines SimpleSValBuilder, a basic implementation of SValBuilder.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
     15 #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"
     16 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
     17 
     18 using namespace clang;
     19 using namespace ento;
     20 
     21 namespace {
     22 class SimpleSValBuilder : public SValBuilder {
     23 protected:
     24   SVal dispatchCast(SVal val, QualType castTy) override;
     25   SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override;
     26   SVal evalCastFromLoc(Loc val, QualType castTy) override;
     27 
     28 public:
     29   SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,
     30                     ProgramStateManager &stateMgr)
     31                     : SValBuilder(alloc, context, stateMgr) {}
     32   ~SimpleSValBuilder() override {}
     33 
     34   SVal evalMinus(NonLoc val) override;
     35   SVal evalComplement(NonLoc val) override;
     36   SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op,
     37                    NonLoc lhs, NonLoc rhs, QualType resultTy) override;
     38   SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op,
     39                    Loc lhs, Loc rhs, QualType resultTy) override;
     40   SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op,
     41                    Loc lhs, NonLoc rhs, QualType resultTy) override;
     42 
     43   /// getKnownValue - evaluates a given SVal. If the SVal has only one possible
     44   ///  (integer) value, that value is returned. Otherwise, returns NULL.
     45   const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;
     46 
     47   SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,
     48                      const llvm::APSInt &RHS, QualType resultTy);
     49 };
     50 } // end anonymous namespace
     51 
     52 SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,
     53                                            ASTContext &context,
     54                                            ProgramStateManager &stateMgr) {
     55   return new SimpleSValBuilder(alloc, context, stateMgr);
     56 }
     57 
     58 //===----------------------------------------------------------------------===//
     59 // Transfer function for Casts.
     60 //===----------------------------------------------------------------------===//
     61 
     62 SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) {
     63   assert(Val.getAs<Loc>() || Val.getAs<NonLoc>());
     64   return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy)
     65                            : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy);
     66 }
     67 
     68 SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) {
     69 
     70   bool isLocType = Loc::isLocType(castTy);
     71 
     72   if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) {
     73     if (isLocType)
     74       return LI->getLoc();
     75 
     76     // FIXME: Correctly support promotions/truncations.
     77     unsigned castSize = Context.getTypeSize(castTy);
     78     if (castSize == LI->getNumBits())
     79       return val;
     80     return makeLocAsInteger(LI->getLoc(), castSize);
     81   }
     82 
     83   if (const SymExpr *se = val.getAsSymbolicExpression()) {
     84     QualType T = Context.getCanonicalType(se->getType());
     85     // If types are the same or both are integers, ignore the cast.
     86     // FIXME: Remove this hack when we support symbolic truncation/extension.
     87     // HACK: If both castTy and T are integers, ignore the cast.  This is
     88     // not a permanent solution.  Eventually we want to precisely handle
     89     // extension/truncation of symbolic integers.  This prevents us from losing
     90     // precision when we assign 'x = y' and 'y' is symbolic and x and y are
     91     // different integer types.
     92    if (haveSameType(T, castTy))
     93       return val;
     94 
     95     if (!isLocType)
     96       return makeNonLoc(se, T, castTy);
     97     return UnknownVal();
     98   }
     99 
    100   // If value is a non-integer constant, produce unknown.
    101   if (!val.getAs<nonloc::ConcreteInt>())
    102     return UnknownVal();
    103 
    104   // Handle casts to a boolean type.
    105   if (castTy->isBooleanType()) {
    106     bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue();
    107     return makeTruthVal(b, castTy);
    108   }
    109 
    110   // Only handle casts from integers to integers - if val is an integer constant
    111   // being cast to a non-integer type, produce unknown.
    112   if (!isLocType && !castTy->isIntegralOrEnumerationType())
    113     return UnknownVal();
    114 
    115   llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue();
    116   BasicVals.getAPSIntType(castTy).apply(i);
    117 
    118   if (isLocType)
    119     return makeIntLocVal(i);
    120   else
    121     return makeIntVal(i);
    122 }
    123 
    124 SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) {
    125 
    126   // Casts from pointers -> pointers, just return the lval.
    127   //
    128   // Casts from pointers -> references, just return the lval.  These
    129   //   can be introduced by the frontend for corner cases, e.g
    130   //   casting from va_list* to __builtin_va_list&.
    131   //
    132   if (Loc::isLocType(castTy) || castTy->isReferenceType())
    133     return val;
    134 
    135   // FIXME: Handle transparent unions where a value can be "transparently"
    136   //  lifted into a union type.
    137   if (castTy->isUnionType())
    138     return UnknownVal();
    139 
    140   // Casting a Loc to a bool will almost always be true,
    141   // unless this is a weak function or a symbolic region.
    142   if (castTy->isBooleanType()) {
    143     switch (val.getSubKind()) {
    144       case loc::MemRegionKind: {
    145         const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion();
    146         if (const FunctionTextRegion *FTR = dyn_cast<FunctionTextRegion>(R))
    147           if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
    148             if (FD->isWeak())
    149               // FIXME: Currently we are using an extent symbol here,
    150               // because there are no generic region address metadata
    151               // symbols to use, only content metadata.
    152               return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
    153 
    154         if (const SymbolicRegion *SymR = R->getSymbolicBase())
    155           return nonloc::SymbolVal(SymR->getSymbol());
    156 
    157         // FALL-THROUGH
    158       }
    159 
    160       case loc::GotoLabelKind:
    161         // Labels and non-symbolic memory regions are always true.
    162         return makeTruthVal(true, castTy);
    163     }
    164   }
    165 
    166   if (castTy->isIntegralOrEnumerationType()) {
    167     unsigned BitWidth = Context.getTypeSize(castTy);
    168 
    169     if (!val.getAs<loc::ConcreteInt>())
    170       return makeLocAsInteger(val, BitWidth);
    171 
    172     llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue();
    173     BasicVals.getAPSIntType(castTy).apply(i);
    174     return makeIntVal(i);
    175   }
    176 
    177   // All other cases: return 'UnknownVal'.  This includes casting pointers
    178   // to floats, which is probably badness it itself, but this is a good
    179   // intermediate solution until we do something better.
    180   return UnknownVal();
    181 }
    182 
    183 //===----------------------------------------------------------------------===//
    184 // Transfer function for unary operators.
    185 //===----------------------------------------------------------------------===//
    186 
    187 SVal SimpleSValBuilder::evalMinus(NonLoc val) {
    188   switch (val.getSubKind()) {
    189   case nonloc::ConcreteIntKind:
    190     return val.castAs<nonloc::ConcreteInt>().evalMinus(*this);
    191   default:
    192     return UnknownVal();
    193   }
    194 }
    195 
    196 SVal SimpleSValBuilder::evalComplement(NonLoc X) {
    197   switch (X.getSubKind()) {
    198   case nonloc::ConcreteIntKind:
    199     return X.castAs<nonloc::ConcreteInt>().evalComplement(*this);
    200   default:
    201     return UnknownVal();
    202   }
    203 }
    204 
    205 //===----------------------------------------------------------------------===//
    206 // Transfer function for binary operators.
    207 //===----------------------------------------------------------------------===//
    208 
    209 SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
    210                                     BinaryOperator::Opcode op,
    211                                     const llvm::APSInt &RHS,
    212                                     QualType resultTy) {
    213   bool isIdempotent = false;
    214 
    215   // Check for a few special cases with known reductions first.
    216   switch (op) {
    217   default:
    218     // We can't reduce this case; just treat it normally.
    219     break;
    220   case BO_Mul:
    221     // a*0 and a*1
    222     if (RHS == 0)
    223       return makeIntVal(0, resultTy);
    224     else if (RHS == 1)
    225       isIdempotent = true;
    226     break;
    227   case BO_Div:
    228     // a/0 and a/1
    229     if (RHS == 0)
    230       // This is also handled elsewhere.
    231       return UndefinedVal();
    232     else if (RHS == 1)
    233       isIdempotent = true;
    234     break;
    235   case BO_Rem:
    236     // a%0 and a%1
    237     if (RHS == 0)
    238       // This is also handled elsewhere.
    239       return UndefinedVal();
    240     else if (RHS == 1)
    241       return makeIntVal(0, resultTy);
    242     break;
    243   case BO_Add:
    244   case BO_Sub:
    245   case BO_Shl:
    246   case BO_Shr:
    247   case BO_Xor:
    248     // a+0, a-0, a<<0, a>>0, a^0
    249     if (RHS == 0)
    250       isIdempotent = true;
    251     break;
    252   case BO_And:
    253     // a&0 and a&(~0)
    254     if (RHS == 0)
    255       return makeIntVal(0, resultTy);
    256     else if (RHS.isAllOnesValue())
    257       isIdempotent = true;
    258     break;
    259   case BO_Or:
    260     // a|0 and a|(~0)
    261     if (RHS == 0)
    262       isIdempotent = true;
    263     else if (RHS.isAllOnesValue()) {
    264       const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS);
    265       return nonloc::ConcreteInt(Result);
    266     }
    267     break;
    268   }
    269 
    270   // Idempotent ops (like a*1) can still change the type of an expression.
    271   // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the
    272   // dirty work.
    273   if (isIdempotent)
    274       return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy);
    275 
    276   // If we reach this point, the expression cannot be simplified.
    277   // Make a SymbolVal for the entire expression, after converting the RHS.
    278   const llvm::APSInt *ConvertedRHS = &RHS;
    279   if (BinaryOperator::isComparisonOp(op)) {
    280     // We're looking for a type big enough to compare the symbolic value
    281     // with the given constant.
    282     // FIXME: This is an approximation of Sema::UsualArithmeticConversions.
    283     ASTContext &Ctx = getContext();
    284     QualType SymbolType = LHS->getType();
    285     uint64_t ValWidth = RHS.getBitWidth();
    286     uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);
    287 
    288     if (ValWidth < TypeWidth) {
    289       // If the value is too small, extend it.
    290       ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
    291     } else if (ValWidth == TypeWidth) {
    292       // If the value is signed but the symbol is unsigned, do the comparison
    293       // in unsigned space. [C99 6.3.1.8]
    294       // (For the opposite case, the value is already unsigned.)
    295       if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
    296         ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
    297     }
    298   } else
    299     ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
    300 
    301   return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);
    302 }
    303 
    304 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
    305                                   BinaryOperator::Opcode op,
    306                                   NonLoc lhs, NonLoc rhs,
    307                                   QualType resultTy)  {
    308   NonLoc InputLHS = lhs;
    309   NonLoc InputRHS = rhs;
    310 
    311   // Handle trivial case where left-side and right-side are the same.
    312   if (lhs == rhs)
    313     switch (op) {
    314       default:
    315         break;
    316       case BO_EQ:
    317       case BO_LE:
    318       case BO_GE:
    319         return makeTruthVal(true, resultTy);
    320       case BO_LT:
    321       case BO_GT:
    322       case BO_NE:
    323         return makeTruthVal(false, resultTy);
    324       case BO_Xor:
    325       case BO_Sub:
    326         if (resultTy->isIntegralOrEnumerationType())
    327           return makeIntVal(0, resultTy);
    328         return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy);
    329       case BO_Or:
    330       case BO_And:
    331         return evalCastFromNonLoc(lhs, resultTy);
    332     }
    333 
    334   while (1) {
    335     switch (lhs.getSubKind()) {
    336     default:
    337       return makeSymExprValNN(state, op, lhs, rhs, resultTy);
    338     case nonloc::LocAsIntegerKind: {
    339       Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
    340       switch (rhs.getSubKind()) {
    341         case nonloc::LocAsIntegerKind:
    342           return evalBinOpLL(state, op, lhsL,
    343                              rhs.castAs<nonloc::LocAsInteger>().getLoc(),
    344                              resultTy);
    345         case nonloc::ConcreteIntKind: {
    346           // Transform the integer into a location and compare.
    347           llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
    348           BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
    349           return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
    350         }
    351         default:
    352           switch (op) {
    353             case BO_EQ:
    354               return makeTruthVal(false, resultTy);
    355             case BO_NE:
    356               return makeTruthVal(true, resultTy);
    357             default:
    358               // This case also handles pointer arithmetic.
    359               return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
    360           }
    361       }
    362     }
    363     case nonloc::ConcreteIntKind: {
    364       llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
    365 
    366       // If we're dealing with two known constants, just perform the operation.
    367       if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
    368         llvm::APSInt RHSValue = *KnownRHSValue;
    369         if (BinaryOperator::isComparisonOp(op)) {
    370           // We're looking for a type big enough to compare the two values.
    371           // FIXME: This is not correct. char + short will result in a promotion
    372           // to int. Unfortunately we have lost types by this point.
    373           APSIntType CompareType = std::max(APSIntType(LHSValue),
    374                                             APSIntType(RHSValue));
    375           CompareType.apply(LHSValue);
    376           CompareType.apply(RHSValue);
    377         } else if (!BinaryOperator::isShiftOp(op)) {
    378           APSIntType IntType = BasicVals.getAPSIntType(resultTy);
    379           IntType.apply(LHSValue);
    380           IntType.apply(RHSValue);
    381         }
    382 
    383         const llvm::APSInt *Result =
    384           BasicVals.evalAPSInt(op, LHSValue, RHSValue);
    385         if (!Result)
    386           return UndefinedVal();
    387 
    388         return nonloc::ConcreteInt(*Result);
    389       }
    390 
    391       // Swap the left and right sides and flip the operator if doing so
    392       // allows us to better reason about the expression (this is a form
    393       // of expression canonicalization).
    394       // While we're at it, catch some special cases for non-commutative ops.
    395       switch (op) {
    396       case BO_LT:
    397       case BO_GT:
    398       case BO_LE:
    399       case BO_GE:
    400         op = BinaryOperator::reverseComparisonOp(op);
    401         // FALL-THROUGH
    402       case BO_EQ:
    403       case BO_NE:
    404       case BO_Add:
    405       case BO_Mul:
    406       case BO_And:
    407       case BO_Xor:
    408       case BO_Or:
    409         std::swap(lhs, rhs);
    410         continue;
    411       case BO_Shr:
    412         // (~0)>>a
    413         if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
    414           return evalCastFromNonLoc(lhs, resultTy);
    415         // FALL-THROUGH
    416       case BO_Shl:
    417         // 0<<a and 0>>a
    418         if (LHSValue == 0)
    419           return evalCastFromNonLoc(lhs, resultTy);
    420         return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
    421       default:
    422         return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
    423       }
    424     }
    425     case nonloc::SymbolValKind: {
    426       // We only handle LHS as simple symbols or SymIntExprs.
    427       SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
    428 
    429       // LHS is a symbolic expression.
    430       if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
    431 
    432         // Is this a logical not? (!x is represented as x == 0.)
    433         if (op == BO_EQ && rhs.isZeroConstant()) {
    434           // We know how to negate certain expressions. Simplify them here.
    435 
    436           BinaryOperator::Opcode opc = symIntExpr->getOpcode();
    437           switch (opc) {
    438           default:
    439             // We don't know how to negate this operation.
    440             // Just handle it as if it were a normal comparison to 0.
    441             break;
    442           case BO_LAnd:
    443           case BO_LOr:
    444             llvm_unreachable("Logical operators handled by branching logic.");
    445           case BO_Assign:
    446           case BO_MulAssign:
    447           case BO_DivAssign:
    448           case BO_RemAssign:
    449           case BO_AddAssign:
    450           case BO_SubAssign:
    451           case BO_ShlAssign:
    452           case BO_ShrAssign:
    453           case BO_AndAssign:
    454           case BO_XorAssign:
    455           case BO_OrAssign:
    456           case BO_Comma:
    457             llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
    458           case BO_PtrMemD:
    459           case BO_PtrMemI:
    460             llvm_unreachable("Pointer arithmetic not handled here.");
    461           case BO_LT:
    462           case BO_GT:
    463           case BO_LE:
    464           case BO_GE:
    465           case BO_EQ:
    466           case BO_NE:
    467             assert(resultTy->isBooleanType() ||
    468                    resultTy == getConditionType());
    469             assert(symIntExpr->getType()->isBooleanType() ||
    470                    getContext().hasSameUnqualifiedType(symIntExpr->getType(),
    471                                                        getConditionType()));
    472             // Negate the comparison and make a value.
    473             opc = BinaryOperator::negateComparisonOp(opc);
    474             return makeNonLoc(symIntExpr->getLHS(), opc,
    475                 symIntExpr->getRHS(), resultTy);
    476           }
    477         }
    478 
    479         // For now, only handle expressions whose RHS is a constant.
    480         if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
    481           // If both the LHS and the current expression are additive,
    482           // fold their constants and try again.
    483           if (BinaryOperator::isAdditiveOp(op)) {
    484             BinaryOperator::Opcode lop = symIntExpr->getOpcode();
    485             if (BinaryOperator::isAdditiveOp(lop)) {
    486               // Convert the two constants to a common type, then combine them.
    487 
    488               // resultTy may not be the best type to convert to, but it's
    489               // probably the best choice in expressions with mixed type
    490               // (such as x+1U+2LL). The rules for implicit conversions should
    491               // choose a reasonable type to preserve the expression, and will
    492               // at least match how the value is going to be used.
    493               APSIntType IntType = BasicVals.getAPSIntType(resultTy);
    494               const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
    495               const llvm::APSInt &second = IntType.convert(*RHSValue);
    496 
    497               const llvm::APSInt *newRHS;
    498               if (lop == op)
    499                 newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
    500               else
    501                 newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
    502 
    503               assert(newRHS && "Invalid operation despite common type!");
    504               rhs = nonloc::ConcreteInt(*newRHS);
    505               lhs = nonloc::SymbolVal(symIntExpr->getLHS());
    506               op = lop;
    507               continue;
    508             }
    509           }
    510 
    511           // Otherwise, make a SymIntExpr out of the expression.
    512           return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
    513         }
    514       }
    515 
    516       // Does the symbolic expression simplify to a constant?
    517       // If so, "fold" the constant by setting 'lhs' to a ConcreteInt
    518       // and try again.
    519       ConstraintManager &CMgr = state->getConstraintManager();
    520       if (const llvm::APSInt *Constant = CMgr.getSymVal(state, Sym)) {
    521         lhs = nonloc::ConcreteInt(*Constant);
    522         continue;
    523       }
    524 
    525       // Is the RHS a constant?
    526       if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
    527         return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
    528 
    529       // Give up -- this is not a symbolic expression we can handle.
    530       return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
    531     }
    532     }
    533   }
    534 }
    535 
    536 static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,
    537                                             const FieldRegion *RightFR,
    538                                             BinaryOperator::Opcode op,
    539                                             QualType resultTy,
    540                                             SimpleSValBuilder &SVB) {
    541   // Only comparisons are meaningful here!
    542   if (!BinaryOperator::isComparisonOp(op))
    543     return UnknownVal();
    544 
    545   // Next, see if the two FRs have the same super-region.
    546   // FIXME: This doesn't handle casts yet, and simply stripping the casts
    547   // doesn't help.
    548   if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
    549     return UnknownVal();
    550 
    551   const FieldDecl *LeftFD = LeftFR->getDecl();
    552   const FieldDecl *RightFD = RightFR->getDecl();
    553   const RecordDecl *RD = LeftFD->getParent();
    554 
    555   // Make sure the two FRs are from the same kind of record. Just in case!
    556   // FIXME: This is probably where inheritance would be a problem.
    557   if (RD != RightFD->getParent())
    558     return UnknownVal();
    559 
    560   // We know for sure that the two fields are not the same, since that
    561   // would have given us the same SVal.
    562   if (op == BO_EQ)
    563     return SVB.makeTruthVal(false, resultTy);
    564   if (op == BO_NE)
    565     return SVB.makeTruthVal(true, resultTy);
    566 
    567   // Iterate through the fields and see which one comes first.
    568   // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
    569   // members and the units in which bit-fields reside have addresses that
    570   // increase in the order in which they are declared."
    571   bool leftFirst = (op == BO_LT || op == BO_LE);
    572   for (const auto *I : RD->fields()) {
    573     if (I == LeftFD)
    574       return SVB.makeTruthVal(leftFirst, resultTy);
    575     if (I == RightFD)
    576       return SVB.makeTruthVal(!leftFirst, resultTy);
    577   }
    578 
    579   llvm_unreachable("Fields not found in parent record's definition");
    580 }
    581 
    582 // FIXME: all this logic will change if/when we have MemRegion::getLocation().
    583 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
    584                                   BinaryOperator::Opcode op,
    585                                   Loc lhs, Loc rhs,
    586                                   QualType resultTy) {
    587   // Only comparisons and subtractions are valid operations on two pointers.
    588   // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
    589   // However, if a pointer is casted to an integer, evalBinOpNN may end up
    590   // calling this function with another operation (PR7527). We don't attempt to
    591   // model this for now, but it could be useful, particularly when the
    592   // "location" is actually an integer value that's been passed through a void*.
    593   if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
    594     return UnknownVal();
    595 
    596   // Special cases for when both sides are identical.
    597   if (lhs == rhs) {
    598     switch (op) {
    599     default:
    600       llvm_unreachable("Unimplemented operation for two identical values");
    601     case BO_Sub:
    602       return makeZeroVal(resultTy);
    603     case BO_EQ:
    604     case BO_LE:
    605     case BO_GE:
    606       return makeTruthVal(true, resultTy);
    607     case BO_NE:
    608     case BO_LT:
    609     case BO_GT:
    610       return makeTruthVal(false, resultTy);
    611     }
    612   }
    613 
    614   switch (lhs.getSubKind()) {
    615   default:
    616     llvm_unreachable("Ordering not implemented for this Loc.");
    617 
    618   case loc::GotoLabelKind:
    619     // The only thing we know about labels is that they're non-null.
    620     if (rhs.isZeroConstant()) {
    621       switch (op) {
    622       default:
    623         break;
    624       case BO_Sub:
    625         return evalCastFromLoc(lhs, resultTy);
    626       case BO_EQ:
    627       case BO_LE:
    628       case BO_LT:
    629         return makeTruthVal(false, resultTy);
    630       case BO_NE:
    631       case BO_GT:
    632       case BO_GE:
    633         return makeTruthVal(true, resultTy);
    634       }
    635     }
    636     // There may be two labels for the same location, and a function region may
    637     // have the same address as a label at the start of the function (depending
    638     // on the ABI).
    639     // FIXME: we can probably do a comparison against other MemRegions, though.
    640     // FIXME: is there a way to tell if two labels refer to the same location?
    641     return UnknownVal();
    642 
    643   case loc::ConcreteIntKind: {
    644     // If one of the operands is a symbol and the other is a constant,
    645     // build an expression for use by the constraint manager.
    646     if (SymbolRef rSym = rhs.getAsLocSymbol()) {
    647       // We can only build expressions with symbols on the left,
    648       // so we need a reversible operator.
    649       if (!BinaryOperator::isComparisonOp(op))
    650         return UnknownVal();
    651 
    652       const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
    653       op = BinaryOperator::reverseComparisonOp(op);
    654       return makeNonLoc(rSym, op, lVal, resultTy);
    655     }
    656 
    657     // If both operands are constants, just perform the operation.
    658     if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
    659       SVal ResultVal =
    660           lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
    661       if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
    662         return evalCastFromNonLoc(*Result, resultTy);
    663 
    664       assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
    665       return UnknownVal();
    666     }
    667 
    668     // Special case comparisons against NULL.
    669     // This must come after the test if the RHS is a symbol, which is used to
    670     // build constraints. The address of any non-symbolic region is guaranteed
    671     // to be non-NULL, as is any label.
    672     assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
    673     if (lhs.isZeroConstant()) {
    674       switch (op) {
    675       default:
    676         break;
    677       case BO_EQ:
    678       case BO_GT:
    679       case BO_GE:
    680         return makeTruthVal(false, resultTy);
    681       case BO_NE:
    682       case BO_LT:
    683       case BO_LE:
    684         return makeTruthVal(true, resultTy);
    685       }
    686     }
    687 
    688     // Comparing an arbitrary integer to a region or label address is
    689     // completely unknowable.
    690     return UnknownVal();
    691   }
    692   case loc::MemRegionKind: {
    693     if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
    694       // If one of the operands is a symbol and the other is a constant,
    695       // build an expression for use by the constraint manager.
    696       if (SymbolRef lSym = lhs.getAsLocSymbol(true))
    697         return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
    698 
    699       // Special case comparisons to NULL.
    700       // This must come after the test if the LHS is a symbol, which is used to
    701       // build constraints. The address of any non-symbolic region is guaranteed
    702       // to be non-NULL.
    703       if (rInt->isZeroConstant()) {
    704         if (op == BO_Sub)
    705           return evalCastFromLoc(lhs, resultTy);
    706 
    707         if (BinaryOperator::isComparisonOp(op)) {
    708           QualType boolType = getContext().BoolTy;
    709           NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
    710           NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
    711           return evalBinOpNN(state, op, l, r, resultTy);
    712         }
    713       }
    714 
    715       // Comparing a region to an arbitrary integer is completely unknowable.
    716       return UnknownVal();
    717     }
    718 
    719     // Get both values as regions, if possible.
    720     const MemRegion *LeftMR = lhs.getAsRegion();
    721     assert(LeftMR && "MemRegionKind SVal doesn't have a region!");
    722 
    723     const MemRegion *RightMR = rhs.getAsRegion();
    724     if (!RightMR)
    725       // The RHS is probably a label, which in theory could address a region.
    726       // FIXME: we can probably make a more useful statement about non-code
    727       // regions, though.
    728       return UnknownVal();
    729 
    730     const MemRegion *LeftBase = LeftMR->getBaseRegion();
    731     const MemRegion *RightBase = RightMR->getBaseRegion();
    732     const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
    733     const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
    734     const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
    735 
    736     // If the two regions are from different known memory spaces they cannot be
    737     // equal. Also, assume that no symbolic region (whose memory space is
    738     // unknown) is on the stack.
    739     if (LeftMS != RightMS &&
    740         ((LeftMS != UnknownMS && RightMS != UnknownMS) ||
    741          (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
    742       switch (op) {
    743       default:
    744         return UnknownVal();
    745       case BO_EQ:
    746         return makeTruthVal(false, resultTy);
    747       case BO_NE:
    748         return makeTruthVal(true, resultTy);
    749       }
    750     }
    751 
    752     // If both values wrap regions, see if they're from different base regions.
    753     // Note, heap base symbolic regions are assumed to not alias with
    754     // each other; for example, we assume that malloc returns different address
    755     // on each invocation.
    756     if (LeftBase != RightBase &&
    757         ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
    758          (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
    759       switch (op) {
    760       default:
    761         return UnknownVal();
    762       case BO_EQ:
    763         return makeTruthVal(false, resultTy);
    764       case BO_NE:
    765         return makeTruthVal(true, resultTy);
    766       }
    767     }
    768 
    769     // Handle special cases for when both regions are element regions.
    770     const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
    771     const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
    772     if (RightER && LeftER) {
    773       // Next, see if the two ERs have the same super-region and matching types.
    774       // FIXME: This should do something useful even if the types don't match,
    775       // though if both indexes are constant the RegionRawOffset path will
    776       // give the correct answer.
    777       if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
    778           LeftER->getElementType() == RightER->getElementType()) {
    779         // Get the left index and cast it to the correct type.
    780         // If the index is unknown or undefined, bail out here.
    781         SVal LeftIndexVal = LeftER->getIndex();
    782         Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
    783         if (!LeftIndex)
    784           return UnknownVal();
    785         LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
    786         LeftIndex = LeftIndexVal.getAs<NonLoc>();
    787         if (!LeftIndex)
    788           return UnknownVal();
    789 
    790         // Do the same for the right index.
    791         SVal RightIndexVal = RightER->getIndex();
    792         Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
    793         if (!RightIndex)
    794           return UnknownVal();
    795         RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
    796         RightIndex = RightIndexVal.getAs<NonLoc>();
    797         if (!RightIndex)
    798           return UnknownVal();
    799 
    800         // Actually perform the operation.
    801         // evalBinOpNN expects the two indexes to already be the right type.
    802         return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
    803       }
    804     }
    805 
    806     // Special handling of the FieldRegions, even with symbolic offsets.
    807     const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
    808     const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
    809     if (RightFR && LeftFR) {
    810       SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
    811                                                *this);
    812       if (!R.isUnknown())
    813         return R;
    814     }
    815 
    816     // Compare the regions using the raw offsets.
    817     RegionOffset LeftOffset = LeftMR->getAsOffset();
    818     RegionOffset RightOffset = RightMR->getAsOffset();
    819 
    820     if (LeftOffset.getRegion() != nullptr &&
    821         LeftOffset.getRegion() == RightOffset.getRegion() &&
    822         !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
    823       int64_t left = LeftOffset.getOffset();
    824       int64_t right = RightOffset.getOffset();
    825 
    826       switch (op) {
    827         default:
    828           return UnknownVal();
    829         case BO_LT:
    830           return makeTruthVal(left < right, resultTy);
    831         case BO_GT:
    832           return makeTruthVal(left > right, resultTy);
    833         case BO_LE:
    834           return makeTruthVal(left <= right, resultTy);
    835         case BO_GE:
    836           return makeTruthVal(left >= right, resultTy);
    837         case BO_EQ:
    838           return makeTruthVal(left == right, resultTy);
    839         case BO_NE:
    840           return makeTruthVal(left != right, resultTy);
    841       }
    842     }
    843 
    844     // At this point we're not going to get a good answer, but we can try
    845     // conjuring an expression instead.
    846     SymbolRef LHSSym = lhs.getAsLocSymbol();
    847     SymbolRef RHSSym = rhs.getAsLocSymbol();
    848     if (LHSSym && RHSSym)
    849       return makeNonLoc(LHSSym, op, RHSSym, resultTy);
    850 
    851     // If we get here, we have no way of comparing the regions.
    852     return UnknownVal();
    853   }
    854   }
    855 }
    856 
    857 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
    858                                   BinaryOperator::Opcode op,
    859                                   Loc lhs, NonLoc rhs, QualType resultTy) {
    860   assert(!BinaryOperator::isComparisonOp(op) &&
    861          "arguments to comparison ops must be of the same type");
    862 
    863   // Special case: rhs is a zero constant.
    864   if (rhs.isZeroConstant())
    865     return lhs;
    866 
    867   // We are dealing with pointer arithmetic.
    868 
    869   // Handle pointer arithmetic on constant values.
    870   if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) {
    871     if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
    872       const llvm::APSInt &leftI = lhsInt->getValue();
    873       assert(leftI.isUnsigned());
    874       llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
    875 
    876       // Convert the bitwidth of rightI.  This should deal with overflow
    877       // since we are dealing with concrete values.
    878       rightI = rightI.extOrTrunc(leftI.getBitWidth());
    879 
    880       // Offset the increment by the pointer size.
    881       llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
    882       rightI *= Multiplicand;
    883 
    884       // Compute the adjusted pointer.
    885       switch (op) {
    886         case BO_Add:
    887           rightI = leftI + rightI;
    888           break;
    889         case BO_Sub:
    890           rightI = leftI - rightI;
    891           break;
    892         default:
    893           llvm_unreachable("Invalid pointer arithmetic operation");
    894       }
    895       return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
    896     }
    897   }
    898 
    899   // Handle cases where 'lhs' is a region.
    900   if (const MemRegion *region = lhs.getAsRegion()) {
    901     rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
    902     SVal index = UnknownVal();
    903     const MemRegion *superR = nullptr;
    904     QualType elementType;
    905 
    906     if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
    907       assert(op == BO_Add || op == BO_Sub);
    908       index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
    909                           getArrayIndexType());
    910       superR = elemReg->getSuperRegion();
    911       elementType = elemReg->getElementType();
    912     }
    913     else if (isa<SubRegion>(region)) {
    914       assert(op == BO_Add || op == BO_Sub);
    915       index = (op == BO_Add) ? rhs : evalMinus(rhs);
    916       superR = region;
    917       if (resultTy->isAnyPointerType())
    918         elementType = resultTy->getPointeeType();
    919     }
    920 
    921     if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
    922       return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
    923                                                        superR, getContext()));
    924     }
    925   }
    926   return UnknownVal();
    927 }
    928 
    929 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
    930                                                    SVal V) {
    931   if (V.isUnknownOrUndef())
    932     return nullptr;
    933 
    934   if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())
    935     return &X->getValue();
    936 
    937   if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())
    938     return &X->getValue();
    939 
    940   if (SymbolRef Sym = V.getAsSymbol())
    941     return state->getConstraintManager().getSymVal(state, Sym);
    942 
    943   // FIXME: Add support for SymExprs.
    944   return nullptr;
    945 }
    946