| // SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- C++ -*- |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines SimpleSValBuilder, a basic implementation of SValBuilder. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/SubEngine.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| class SimpleSValBuilder : public SValBuilder { |
| protected: |
| SVal dispatchCast(SVal val, QualType castTy) override; |
| SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override; |
| SVal evalCastFromLoc(Loc val, QualType castTy) override; |
| |
| public: |
| SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context, |
| ProgramStateManager &stateMgr) |
| : SValBuilder(alloc, context, stateMgr) {} |
| ~SimpleSValBuilder() override {} |
| |
| SVal evalMinus(NonLoc val) override; |
| SVal evalComplement(NonLoc val) override; |
| SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op, |
| NonLoc lhs, NonLoc rhs, QualType resultTy) override; |
| SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op, |
| Loc lhs, Loc rhs, QualType resultTy) override; |
| SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op, |
| Loc lhs, NonLoc rhs, QualType resultTy) override; |
| |
| /// getKnownValue - evaluates a given SVal. If the SVal has only one possible |
| /// (integer) value, that value is returned. Otherwise, returns NULL. |
| const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override; |
| |
| /// Recursively descends into symbolic expressions and replaces symbols |
| /// with their known values (in the sense of the getKnownValue() method). |
| SVal simplifySVal(ProgramStateRef State, SVal V) override; |
| |
| SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op, |
| const llvm::APSInt &RHS, QualType resultTy); |
| }; |
| } // end anonymous namespace |
| |
| SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc, |
| ASTContext &context, |
| ProgramStateManager &stateMgr) { |
| return new SimpleSValBuilder(alloc, context, stateMgr); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Transfer function for Casts. |
| //===----------------------------------------------------------------------===// |
| |
| SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) { |
| assert(Val.getAs<Loc>() || Val.getAs<NonLoc>()); |
| return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy) |
| : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy); |
| } |
| |
| SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) { |
| bool isLocType = Loc::isLocType(castTy); |
| if (val.getAs<nonloc::PointerToMember>()) |
| return val; |
| |
| if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) { |
| if (isLocType) |
| return LI->getLoc(); |
| // FIXME: Correctly support promotions/truncations. |
| unsigned castSize = Context.getIntWidth(castTy); |
| if (castSize == LI->getNumBits()) |
| return val; |
| return makeLocAsInteger(LI->getLoc(), castSize); |
| } |
| |
| if (const SymExpr *se = val.getAsSymbolicExpression()) { |
| QualType T = Context.getCanonicalType(se->getType()); |
| // If types are the same or both are integers, ignore the cast. |
| // FIXME: Remove this hack when we support symbolic truncation/extension. |
| // HACK: If both castTy and T are integers, ignore the cast. This is |
| // not a permanent solution. Eventually we want to precisely handle |
| // extension/truncation of symbolic integers. This prevents us from losing |
| // precision when we assign 'x = y' and 'y' is symbolic and x and y are |
| // different integer types. |
| if (haveSameType(T, castTy)) |
| return val; |
| |
| if (!isLocType) |
| return makeNonLoc(se, T, castTy); |
| return UnknownVal(); |
| } |
| |
| // If value is a non-integer constant, produce unknown. |
| if (!val.getAs<nonloc::ConcreteInt>()) |
| return UnknownVal(); |
| |
| // Handle casts to a boolean type. |
| if (castTy->isBooleanType()) { |
| bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue(); |
| return makeTruthVal(b, castTy); |
| } |
| |
| // Only handle casts from integers to integers - if val is an integer constant |
| // being cast to a non-integer type, produce unknown. |
| if (!isLocType && !castTy->isIntegralOrEnumerationType()) |
| return UnknownVal(); |
| |
| llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue(); |
| BasicVals.getAPSIntType(castTy).apply(i); |
| |
| if (isLocType) |
| return makeIntLocVal(i); |
| else |
| return makeIntVal(i); |
| } |
| |
| SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) { |
| |
| // Casts from pointers -> pointers, just return the lval. |
| // |
| // Casts from pointers -> references, just return the lval. These |
| // can be introduced by the frontend for corner cases, e.g |
| // casting from va_list* to __builtin_va_list&. |
| // |
| if (Loc::isLocType(castTy) || castTy->isReferenceType()) |
| return val; |
| |
| // FIXME: Handle transparent unions where a value can be "transparently" |
| // lifted into a union type. |
| if (castTy->isUnionType()) |
| return UnknownVal(); |
| |
| // Casting a Loc to a bool will almost always be true, |
| // unless this is a weak function or a symbolic region. |
| if (castTy->isBooleanType()) { |
| switch (val.getSubKind()) { |
| case loc::MemRegionValKind: { |
| const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion(); |
| if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R)) |
| if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl())) |
| if (FD->isWeak()) |
| // FIXME: Currently we are using an extent symbol here, |
| // because there are no generic region address metadata |
| // symbols to use, only content metadata. |
| return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR)); |
| |
| if (const SymbolicRegion *SymR = R->getSymbolicBase()) |
| return makeNonLoc(SymR->getSymbol(), BO_NE, |
| BasicVals.getZeroWithPtrWidth(), castTy); |
| |
| // FALL-THROUGH |
| LLVM_FALLTHROUGH; |
| } |
| |
| case loc::GotoLabelKind: |
| // Labels and non-symbolic memory regions are always true. |
| return makeTruthVal(true, castTy); |
| } |
| } |
| |
| if (castTy->isIntegralOrEnumerationType()) { |
| unsigned BitWidth = Context.getIntWidth(castTy); |
| |
| if (!val.getAs<loc::ConcreteInt>()) |
| return makeLocAsInteger(val, BitWidth); |
| |
| llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue(); |
| BasicVals.getAPSIntType(castTy).apply(i); |
| return makeIntVal(i); |
| } |
| |
| // All other cases: return 'UnknownVal'. This includes casting pointers |
| // to floats, which is probably badness it itself, but this is a good |
| // intermediate solution until we do something better. |
| return UnknownVal(); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Transfer function for unary operators. |
| //===----------------------------------------------------------------------===// |
| |
| SVal SimpleSValBuilder::evalMinus(NonLoc val) { |
| switch (val.getSubKind()) { |
| case nonloc::ConcreteIntKind: |
| return val.castAs<nonloc::ConcreteInt>().evalMinus(*this); |
| default: |
| return UnknownVal(); |
| } |
| } |
| |
| SVal SimpleSValBuilder::evalComplement(NonLoc X) { |
| switch (X.getSubKind()) { |
| case nonloc::ConcreteIntKind: |
| return X.castAs<nonloc::ConcreteInt>().evalComplement(*this); |
| default: |
| return UnknownVal(); |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Transfer function for binary operators. |
| //===----------------------------------------------------------------------===// |
| |
| SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS, |
| BinaryOperator::Opcode op, |
| const llvm::APSInt &RHS, |
| QualType resultTy) { |
| bool isIdempotent = false; |
| |
| // Check for a few special cases with known reductions first. |
| switch (op) { |
| default: |
| // We can't reduce this case; just treat it normally. |
| break; |
| case BO_Mul: |
| // a*0 and a*1 |
| if (RHS == 0) |
| return makeIntVal(0, resultTy); |
| else if (RHS == 1) |
| isIdempotent = true; |
| break; |
| case BO_Div: |
| // a/0 and a/1 |
| if (RHS == 0) |
| // This is also handled elsewhere. |
| return UndefinedVal(); |
| else if (RHS == 1) |
| isIdempotent = true; |
| break; |
| case BO_Rem: |
| // a%0 and a%1 |
| if (RHS == 0) |
| // This is also handled elsewhere. |
| return UndefinedVal(); |
| else if (RHS == 1) |
| return makeIntVal(0, resultTy); |
| break; |
| case BO_Add: |
| case BO_Sub: |
| case BO_Shl: |
| case BO_Shr: |
| case BO_Xor: |
| // a+0, a-0, a<<0, a>>0, a^0 |
| if (RHS == 0) |
| isIdempotent = true; |
| break; |
| case BO_And: |
| // a&0 and a&(~0) |
| if (RHS == 0) |
| return makeIntVal(0, resultTy); |
| else if (RHS.isAllOnesValue()) |
| isIdempotent = true; |
| break; |
| case BO_Or: |
| // a|0 and a|(~0) |
| if (RHS == 0) |
| isIdempotent = true; |
| else if (RHS.isAllOnesValue()) { |
| const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS); |
| return nonloc::ConcreteInt(Result); |
| } |
| break; |
| } |
| |
| // Idempotent ops (like a*1) can still change the type of an expression. |
| // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the |
| // dirty work. |
| if (isIdempotent) |
| return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy); |
| |
| // If we reach this point, the expression cannot be simplified. |
| // Make a SymbolVal for the entire expression, after converting the RHS. |
| const llvm::APSInt *ConvertedRHS = &RHS; |
| if (BinaryOperator::isComparisonOp(op)) { |
| // We're looking for a type big enough to compare the symbolic value |
| // with the given constant. |
| // FIXME: This is an approximation of Sema::UsualArithmeticConversions. |
| ASTContext &Ctx = getContext(); |
| QualType SymbolType = LHS->getType(); |
| uint64_t ValWidth = RHS.getBitWidth(); |
| uint64_t TypeWidth = Ctx.getTypeSize(SymbolType); |
| |
| if (ValWidth < TypeWidth) { |
| // If the value is too small, extend it. |
| ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); |
| } else if (ValWidth == TypeWidth) { |
| // If the value is signed but the symbol is unsigned, do the comparison |
| // in unsigned space. [C99 6.3.1.8] |
| // (For the opposite case, the value is already unsigned.) |
| if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType()) |
| ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); |
| } |
| } else |
| ConvertedRHS = &BasicVals.Convert(resultTy, RHS); |
| |
| return makeNonLoc(LHS, op, *ConvertedRHS, resultTy); |
| } |
| |
| // See if Sym is known to be a relation Rel with Bound. |
| static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym, |
| llvm::APSInt Bound, ProgramStateRef State) { |
| SValBuilder &SVB = State->getStateManager().getSValBuilder(); |
| SVal Result = |
| SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym), |
| nonloc::ConcreteInt(Bound), SVB.getConditionType()); |
| if (auto DV = Result.getAs<DefinedSVal>()) { |
| return !State->assume(*DV, false); |
| } |
| return false; |
| } |
| |
| // See if Sym is known to be within [min/4, max/4], where min and max |
| // are the bounds of the symbol's integral type. With such symbols, |
| // some manipulations can be performed without the risk of overflow. |
| // assume() doesn't cause infinite recursion because we should be dealing |
| // with simpler symbols on every recursive call. |
| static bool isWithinConstantOverflowBounds(SymbolRef Sym, |
| ProgramStateRef State) { |
| SValBuilder &SVB = State->getStateManager().getSValBuilder(); |
| BasicValueFactory &BV = SVB.getBasicValueFactory(); |
| |
| QualType T = Sym->getType(); |
| assert(T->isSignedIntegerOrEnumerationType() && |
| "This only works with signed integers!"); |
| APSIntType AT = BV.getAPSIntType(T); |
| |
| llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max; |
| return isInRelation(BO_LE, Sym, Max, State) && |
| isInRelation(BO_GE, Sym, Min, State); |
| } |
| |
| // Same for the concrete integers: see if I is within [min/4, max/4]. |
| static bool isWithinConstantOverflowBounds(llvm::APSInt I) { |
| APSIntType AT(I); |
| assert(!AT.isUnsigned() && |
| "This only works with signed integers!"); |
| |
| llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max; |
| return (I <= Max) && (I >= -Max); |
| } |
| |
| static std::pair<SymbolRef, llvm::APSInt> |
| decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV) { |
| if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym)) |
| if (BinaryOperator::isAdditiveOp(SymInt->getOpcode())) |
| return std::make_pair(SymInt->getLHS(), |
| (SymInt->getOpcode() == BO_Add) ? |
| (SymInt->getRHS()) : |
| (-SymInt->getRHS())); |
| |
| // Fail to decompose: "reduce" the problem to the "$x + 0" case. |
| return std::make_pair(Sym, BV.getValue(0, Sym->getType())); |
| } |
| |
| // Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the |
| // same signed integral type and no overflows occur (which should be checked |
| // by the caller). |
| static NonLoc doRearrangeUnchecked(ProgramStateRef State, |
| BinaryOperator::Opcode Op, |
| SymbolRef LSym, llvm::APSInt LInt, |
| SymbolRef RSym, llvm::APSInt RInt) { |
| SValBuilder &SVB = State->getStateManager().getSValBuilder(); |
| BasicValueFactory &BV = SVB.getBasicValueFactory(); |
| SymbolManager &SymMgr = SVB.getSymbolManager(); |
| |
| QualType SymTy = LSym->getType(); |
| assert(SymTy == RSym->getType() && |
| "Symbols are not of the same type!"); |
| assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) && |
| "Integers are not of the same type as symbols!"); |
| assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) && |
| "Integers are not of the same type as symbols!"); |
| |
| QualType ResultTy; |
| if (BinaryOperator::isComparisonOp(Op)) |
| ResultTy = SVB.getConditionType(); |
| else if (BinaryOperator::isAdditiveOp(Op)) |
| ResultTy = SymTy; |
| else |
| llvm_unreachable("Operation not suitable for unchecked rearrangement!"); |
| |
| // FIXME: Can we use assume() without getting into an infinite recursion? |
| if (LSym == RSym) |
| return SVB.evalBinOpNN(State, Op, nonloc::ConcreteInt(LInt), |
| nonloc::ConcreteInt(RInt), ResultTy) |
| .castAs<NonLoc>(); |
| |
| SymbolRef ResultSym = nullptr; |
| BinaryOperator::Opcode ResultOp; |
| llvm::APSInt ResultInt; |
| if (BinaryOperator::isComparisonOp(Op)) { |
| // Prefer comparing to a non-negative number. |
| // FIXME: Maybe it'd be better to have consistency in |
| // "$x - $y" vs. "$y - $x" because those are solver's keys. |
| if (LInt > RInt) { |
| ResultSym = SymMgr.getSymSymExpr(RSym, BO_Sub, LSym, SymTy); |
| ResultOp = BinaryOperator::reverseComparisonOp(Op); |
| ResultInt = LInt - RInt; // Opposite order! |
| } else { |
| ResultSym = SymMgr.getSymSymExpr(LSym, BO_Sub, RSym, SymTy); |
| ResultOp = Op; |
| ResultInt = RInt - LInt; // Opposite order! |
| } |
| } else { |
| ResultSym = SymMgr.getSymSymExpr(LSym, Op, RSym, SymTy); |
| ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt); |
| ResultOp = BO_Add; |
| // Bring back the cosmetic difference. |
| if (ResultInt < 0) { |
| ResultInt = -ResultInt; |
| ResultOp = BO_Sub; |
| } else if (ResultInt == 0) { |
| // Shortcut: Simplify "$x + 0" to "$x". |
| return nonloc::SymbolVal(ResultSym); |
| } |
| } |
| const llvm::APSInt &PersistentResultInt = BV.getValue(ResultInt); |
| return nonloc::SymbolVal( |
| SymMgr.getSymIntExpr(ResultSym, ResultOp, PersistentResultInt, ResultTy)); |
| } |
| |
| // Rearrange if symbol type matches the result type and if the operator is a |
| // comparison operator, both symbol and constant must be within constant |
| // overflow bounds. |
| static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op, |
| SymbolRef Sym, llvm::APSInt Int, QualType Ty) { |
| return Sym->getType() == Ty && |
| (!BinaryOperator::isComparisonOp(Op) || |
| (isWithinConstantOverflowBounds(Sym, State) && |
| isWithinConstantOverflowBounds(Int))); |
| } |
| |
| static Optional<NonLoc> tryRearrange(ProgramStateRef State, |
| BinaryOperator::Opcode Op, NonLoc Lhs, |
| NonLoc Rhs, QualType ResultTy) { |
| ProgramStateManager &StateMgr = State->getStateManager(); |
| SValBuilder &SVB = StateMgr.getSValBuilder(); |
| |
| // We expect everything to be of the same type - this type. |
| QualType SingleTy; |
| |
| auto &Opts = |
| StateMgr.getOwningEngine().getAnalysisManager().getAnalyzerOptions(); |
| |
| // FIXME: After putting complexity threshold to the symbols we can always |
| // rearrange additive operations but rearrange comparisons only if |
| // option is set. |
| if(!Opts.ShouldAggressivelySimplifyBinaryOperation) |
| return None; |
| |
| SymbolRef LSym = Lhs.getAsSymbol(); |
| if (!LSym) |
| return None; |
| |
| if (BinaryOperator::isComparisonOp(Op)) { |
| SingleTy = LSym->getType(); |
| if (ResultTy != SVB.getConditionType()) |
| return None; |
| // Initialize SingleTy later with a symbol's type. |
| } else if (BinaryOperator::isAdditiveOp(Op)) { |
| SingleTy = ResultTy; |
| if (LSym->getType() != SingleTy) |
| return None; |
| } else { |
| // Don't rearrange other operations. |
| return None; |
| } |
| |
| assert(!SingleTy.isNull() && "We should have figured out the type by now!"); |
| |
| // Rearrange signed symbolic expressions only |
| if (!SingleTy->isSignedIntegerOrEnumerationType()) |
| return None; |
| |
| SymbolRef RSym = Rhs.getAsSymbol(); |
| if (!RSym || RSym->getType() != SingleTy) |
| return None; |
| |
| BasicValueFactory &BV = State->getBasicVals(); |
| llvm::APSInt LInt, RInt; |
| std::tie(LSym, LInt) = decomposeSymbol(LSym, BV); |
| std::tie(RSym, RInt) = decomposeSymbol(RSym, BV); |
| if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) || |
| !shouldRearrange(State, Op, RSym, RInt, SingleTy)) |
| return None; |
| |
| // We know that no overflows can occur anymore. |
| return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt); |
| } |
| |
| SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state, |
| BinaryOperator::Opcode op, |
| NonLoc lhs, NonLoc rhs, |
| QualType resultTy) { |
| NonLoc InputLHS = lhs; |
| NonLoc InputRHS = rhs; |
| |
| // Handle trivial case where left-side and right-side are the same. |
| if (lhs == rhs) |
| switch (op) { |
| default: |
| break; |
| case BO_EQ: |
| case BO_LE: |
| case BO_GE: |
| return makeTruthVal(true, resultTy); |
| case BO_LT: |
| case BO_GT: |
| case BO_NE: |
| return makeTruthVal(false, resultTy); |
| case BO_Xor: |
| case BO_Sub: |
| if (resultTy->isIntegralOrEnumerationType()) |
| return makeIntVal(0, resultTy); |
| return evalCastFromNonLoc(makeIntVal(0, /*isUnsigned=*/false), resultTy); |
| case BO_Or: |
| case BO_And: |
| return evalCastFromNonLoc(lhs, resultTy); |
| } |
| |
| while (1) { |
| switch (lhs.getSubKind()) { |
| default: |
| return makeSymExprValNN(op, lhs, rhs, resultTy); |
| case nonloc::PointerToMemberKind: { |
| assert(rhs.getSubKind() == nonloc::PointerToMemberKind && |
| "Both SVals should have pointer-to-member-type"); |
| auto LPTM = lhs.castAs<nonloc::PointerToMember>(), |
| RPTM = rhs.castAs<nonloc::PointerToMember>(); |
| auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData(); |
| switch (op) { |
| case BO_EQ: |
| return makeTruthVal(LPTMD == RPTMD, resultTy); |
| case BO_NE: |
| return makeTruthVal(LPTMD != RPTMD, resultTy); |
| default: |
| return UnknownVal(); |
| } |
| } |
| case nonloc::LocAsIntegerKind: { |
| Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc(); |
| switch (rhs.getSubKind()) { |
| case nonloc::LocAsIntegerKind: |
| // FIXME: at the moment the implementation |
| // of modeling "pointers as integers" is not complete. |
| if (!BinaryOperator::isComparisonOp(op)) |
| return UnknownVal(); |
| return evalBinOpLL(state, op, lhsL, |
| rhs.castAs<nonloc::LocAsInteger>().getLoc(), |
| resultTy); |
| case nonloc::ConcreteIntKind: { |
| // FIXME: at the moment the implementation |
| // of modeling "pointers as integers" is not complete. |
| if (!BinaryOperator::isComparisonOp(op)) |
| return UnknownVal(); |
| // Transform the integer into a location and compare. |
| // FIXME: This only makes sense for comparisons. If we want to, say, |
| // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it, |
| // then pack it back into a LocAsInteger. |
| llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue(); |
| // If the region has a symbolic base, pay attention to the type; it |
| // might be coming from a non-default address space. For non-symbolic |
| // regions it doesn't matter that much because such comparisons would |
| // most likely evaluate to concrete false anyway. FIXME: We might |
| // still need to handle the non-comparison case. |
| if (SymbolRef lSym = lhs.getAsLocSymbol(true)) |
| BasicVals.getAPSIntType(lSym->getType()).apply(i); |
| else |
| BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i); |
| return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy); |
| } |
| default: |
| switch (op) { |
| case BO_EQ: |
| return makeTruthVal(false, resultTy); |
| case BO_NE: |
| return makeTruthVal(true, resultTy); |
| default: |
| // This case also handles pointer arithmetic. |
| return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); |
| } |
| } |
| } |
| case nonloc::ConcreteIntKind: { |
| llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue(); |
| |
| // If we're dealing with two known constants, just perform the operation. |
| if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) { |
| llvm::APSInt RHSValue = *KnownRHSValue; |
| if (BinaryOperator::isComparisonOp(op)) { |
| // We're looking for a type big enough to compare the two values. |
| // FIXME: This is not correct. char + short will result in a promotion |
| // to int. Unfortunately we have lost types by this point. |
| APSIntType CompareType = std::max(APSIntType(LHSValue), |
| APSIntType(RHSValue)); |
| CompareType.apply(LHSValue); |
| CompareType.apply(RHSValue); |
| } else if (!BinaryOperator::isShiftOp(op)) { |
| APSIntType IntType = BasicVals.getAPSIntType(resultTy); |
| IntType.apply(LHSValue); |
| IntType.apply(RHSValue); |
| } |
| |
| const llvm::APSInt *Result = |
| BasicVals.evalAPSInt(op, LHSValue, RHSValue); |
| if (!Result) |
| return UndefinedVal(); |
| |
| return nonloc::ConcreteInt(*Result); |
| } |
| |
| // Swap the left and right sides and flip the operator if doing so |
| // allows us to better reason about the expression (this is a form |
| // of expression canonicalization). |
| // While we're at it, catch some special cases for non-commutative ops. |
| switch (op) { |
| case BO_LT: |
| case BO_GT: |
| case BO_LE: |
| case BO_GE: |
| op = BinaryOperator::reverseComparisonOp(op); |
| LLVM_FALLTHROUGH; |
| case BO_EQ: |
| case BO_NE: |
| case BO_Add: |
| case BO_Mul: |
| case BO_And: |
| case BO_Xor: |
| case BO_Or: |
| std::swap(lhs, rhs); |
| continue; |
| case BO_Shr: |
| // (~0)>>a |
| if (LHSValue.isAllOnesValue() && LHSValue.isSigned()) |
| return evalCastFromNonLoc(lhs, resultTy); |
| LLVM_FALLTHROUGH; |
| case BO_Shl: |
| // 0<<a and 0>>a |
| if (LHSValue == 0) |
| return evalCastFromNonLoc(lhs, resultTy); |
| return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); |
| default: |
| return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); |
| } |
| } |
| case nonloc::SymbolValKind: { |
| // We only handle LHS as simple symbols or SymIntExprs. |
| SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol(); |
| |
| // LHS is a symbolic expression. |
| if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) { |
| |
| // Is this a logical not? (!x is represented as x == 0.) |
| if (op == BO_EQ && rhs.isZeroConstant()) { |
| // We know how to negate certain expressions. Simplify them here. |
| |
| BinaryOperator::Opcode opc = symIntExpr->getOpcode(); |
| switch (opc) { |
| default: |
| // We don't know how to negate this operation. |
| // Just handle it as if it were a normal comparison to 0. |
| break; |
| case BO_LAnd: |
| case BO_LOr: |
| llvm_unreachable("Logical operators handled by branching logic."); |
| case BO_Assign: |
| case BO_MulAssign: |
| case BO_DivAssign: |
| case BO_RemAssign: |
| case BO_AddAssign: |
| case BO_SubAssign: |
| case BO_ShlAssign: |
| case BO_ShrAssign: |
| case BO_AndAssign: |
| case BO_XorAssign: |
| case BO_OrAssign: |
| case BO_Comma: |
| llvm_unreachable("'=' and ',' operators handled by ExprEngine."); |
| case BO_PtrMemD: |
| case BO_PtrMemI: |
| llvm_unreachable("Pointer arithmetic not handled here."); |
| case BO_LT: |
| case BO_GT: |
| case BO_LE: |
| case BO_GE: |
| case BO_EQ: |
| case BO_NE: |
| assert(resultTy->isBooleanType() || |
| resultTy == getConditionType()); |
| assert(symIntExpr->getType()->isBooleanType() || |
| getContext().hasSameUnqualifiedType(symIntExpr->getType(), |
| getConditionType())); |
| // Negate the comparison and make a value. |
| opc = BinaryOperator::negateComparisonOp(opc); |
| return makeNonLoc(symIntExpr->getLHS(), opc, |
| symIntExpr->getRHS(), resultTy); |
| } |
| } |
| |
| // For now, only handle expressions whose RHS is a constant. |
| if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) { |
| // If both the LHS and the current expression are additive, |
| // fold their constants and try again. |
| if (BinaryOperator::isAdditiveOp(op)) { |
| BinaryOperator::Opcode lop = symIntExpr->getOpcode(); |
| if (BinaryOperator::isAdditiveOp(lop)) { |
| // Convert the two constants to a common type, then combine them. |
| |
| // resultTy may not be the best type to convert to, but it's |
| // probably the best choice in expressions with mixed type |
| // (such as x+1U+2LL). The rules for implicit conversions should |
| // choose a reasonable type to preserve the expression, and will |
| // at least match how the value is going to be used. |
| APSIntType IntType = BasicVals.getAPSIntType(resultTy); |
| const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS()); |
| const llvm::APSInt &second = IntType.convert(*RHSValue); |
| |
| const llvm::APSInt *newRHS; |
| if (lop == op) |
| newRHS = BasicVals.evalAPSInt(BO_Add, first, second); |
| else |
| newRHS = BasicVals.evalAPSInt(BO_Sub, first, second); |
| |
| assert(newRHS && "Invalid operation despite common type!"); |
| rhs = nonloc::ConcreteInt(*newRHS); |
| lhs = nonloc::SymbolVal(symIntExpr->getLHS()); |
| op = lop; |
| continue; |
| } |
| } |
| |
| // Otherwise, make a SymIntExpr out of the expression. |
| return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy); |
| } |
| } |
| |
| // Does the symbolic expression simplify to a constant? |
| // If so, "fold" the constant by setting 'lhs' to a ConcreteInt |
| // and try again. |
| SVal simplifiedLhs = simplifySVal(state, lhs); |
| if (simplifiedLhs != lhs) |
| if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) { |
| lhs = *simplifiedLhsAsNonLoc; |
| continue; |
| } |
| |
| // Is the RHS a constant? |
| if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) |
| return MakeSymIntVal(Sym, op, *RHSValue, resultTy); |
| |
| if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy)) |
| return *V; |
| |
| // Give up -- this is not a symbolic expression we can handle. |
| return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); |
| } |
| } |
| } |
| } |
| |
| static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR, |
| const FieldRegion *RightFR, |
| BinaryOperator::Opcode op, |
| QualType resultTy, |
| SimpleSValBuilder &SVB) { |
| // Only comparisons are meaningful here! |
| if (!BinaryOperator::isComparisonOp(op)) |
| return UnknownVal(); |
| |
| // Next, see if the two FRs have the same super-region. |
| // FIXME: This doesn't handle casts yet, and simply stripping the casts |
| // doesn't help. |
| if (LeftFR->getSuperRegion() != RightFR->getSuperRegion()) |
| return UnknownVal(); |
| |
| const FieldDecl *LeftFD = LeftFR->getDecl(); |
| const FieldDecl *RightFD = RightFR->getDecl(); |
| const RecordDecl *RD = LeftFD->getParent(); |
| |
| // Make sure the two FRs are from the same kind of record. Just in case! |
| // FIXME: This is probably where inheritance would be a problem. |
| if (RD != RightFD->getParent()) |
| return UnknownVal(); |
| |
| // We know for sure that the two fields are not the same, since that |
| // would have given us the same SVal. |
| if (op == BO_EQ) |
| return SVB.makeTruthVal(false, resultTy); |
| if (op == BO_NE) |
| return SVB.makeTruthVal(true, resultTy); |
| |
| // Iterate through the fields and see which one comes first. |
| // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field |
| // members and the units in which bit-fields reside have addresses that |
| // increase in the order in which they are declared." |
| bool leftFirst = (op == BO_LT || op == BO_LE); |
| for (const auto *I : RD->fields()) { |
| if (I == LeftFD) |
| return SVB.makeTruthVal(leftFirst, resultTy); |
| if (I == RightFD) |
| return SVB.makeTruthVal(!leftFirst, resultTy); |
| } |
| |
| llvm_unreachable("Fields not found in parent record's definition"); |
| } |
| |
| // FIXME: all this logic will change if/when we have MemRegion::getLocation(). |
| SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state, |
| BinaryOperator::Opcode op, |
| Loc lhs, Loc rhs, |
| QualType resultTy) { |
| // Only comparisons and subtractions are valid operations on two pointers. |
| // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15]. |
| // However, if a pointer is casted to an integer, evalBinOpNN may end up |
| // calling this function with another operation (PR7527). We don't attempt to |
| // model this for now, but it could be useful, particularly when the |
| // "location" is actually an integer value that's been passed through a void*. |
| if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub)) |
| return UnknownVal(); |
| |
| // Special cases for when both sides are identical. |
| if (lhs == rhs) { |
| switch (op) { |
| default: |
| llvm_unreachable("Unimplemented operation for two identical values"); |
| case BO_Sub: |
| return makeZeroVal(resultTy); |
| case BO_EQ: |
| case BO_LE: |
| case BO_GE: |
| return makeTruthVal(true, resultTy); |
| case BO_NE: |
| case BO_LT: |
| case BO_GT: |
| return makeTruthVal(false, resultTy); |
| } |
| } |
| |
| switch (lhs.getSubKind()) { |
| default: |
| llvm_unreachable("Ordering not implemented for this Loc."); |
| |
| case loc::GotoLabelKind: |
| // The only thing we know about labels is that they're non-null. |
| if (rhs.isZeroConstant()) { |
| switch (op) { |
| default: |
| break; |
| case BO_Sub: |
| return evalCastFromLoc(lhs, resultTy); |
| case BO_EQ: |
| case BO_LE: |
| case BO_LT: |
| return makeTruthVal(false, resultTy); |
| case BO_NE: |
| case BO_GT: |
| case BO_GE: |
| return makeTruthVal(true, resultTy); |
| } |
| } |
| // There may be two labels for the same location, and a function region may |
| // have the same address as a label at the start of the function (depending |
| // on the ABI). |
| // FIXME: we can probably do a comparison against other MemRegions, though. |
| // FIXME: is there a way to tell if two labels refer to the same location? |
| return UnknownVal(); |
| |
| case loc::ConcreteIntKind: { |
| // If one of the operands is a symbol and the other is a constant, |
| // build an expression for use by the constraint manager. |
| if (SymbolRef rSym = rhs.getAsLocSymbol()) { |
| // We can only build expressions with symbols on the left, |
| // so we need a reversible operator. |
| if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp) |
| return UnknownVal(); |
| |
| const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue(); |
| op = BinaryOperator::reverseComparisonOp(op); |
| return makeNonLoc(rSym, op, lVal, resultTy); |
| } |
| |
| // If both operands are constants, just perform the operation. |
| if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { |
| SVal ResultVal = |
| lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt); |
| if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>()) |
| return evalCastFromNonLoc(*Result, resultTy); |
| |
| assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs"); |
| return UnknownVal(); |
| } |
| |
| // Special case comparisons against NULL. |
| // This must come after the test if the RHS is a symbol, which is used to |
| // build constraints. The address of any non-symbolic region is guaranteed |
| // to be non-NULL, as is any label. |
| assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>()); |
| if (lhs.isZeroConstant()) { |
| switch (op) { |
| default: |
| break; |
| case BO_EQ: |
| case BO_GT: |
| case BO_GE: |
| return makeTruthVal(false, resultTy); |
| case BO_NE: |
| case BO_LT: |
| case BO_LE: |
| return makeTruthVal(true, resultTy); |
| } |
| } |
| |
| // Comparing an arbitrary integer to a region or label address is |
| // completely unknowable. |
| return UnknownVal(); |
| } |
| case loc::MemRegionValKind: { |
| if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { |
| // If one of the operands is a symbol and the other is a constant, |
| // build an expression for use by the constraint manager. |
| if (SymbolRef lSym = lhs.getAsLocSymbol(true)) { |
| if (BinaryOperator::isComparisonOp(op)) |
| return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy); |
| return UnknownVal(); |
| } |
| // Special case comparisons to NULL. |
| // This must come after the test if the LHS is a symbol, which is used to |
| // build constraints. The address of any non-symbolic region is guaranteed |
| // to be non-NULL. |
| if (rInt->isZeroConstant()) { |
| if (op == BO_Sub) |
| return evalCastFromLoc(lhs, resultTy); |
| |
| if (BinaryOperator::isComparisonOp(op)) { |
| QualType boolType = getContext().BoolTy; |
| NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>(); |
| NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>(); |
| return evalBinOpNN(state, op, l, r, resultTy); |
| } |
| } |
| |
| // Comparing a region to an arbitrary integer is completely unknowable. |
| return UnknownVal(); |
| } |
| |
| // Get both values as regions, if possible. |
| const MemRegion *LeftMR = lhs.getAsRegion(); |
| assert(LeftMR && "MemRegionValKind SVal doesn't have a region!"); |
| |
| const MemRegion *RightMR = rhs.getAsRegion(); |
| if (!RightMR) |
| // The RHS is probably a label, which in theory could address a region. |
| // FIXME: we can probably make a more useful statement about non-code |
| // regions, though. |
| return UnknownVal(); |
| |
| const MemRegion *LeftBase = LeftMR->getBaseRegion(); |
| const MemRegion *RightBase = RightMR->getBaseRegion(); |
| const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace(); |
| const MemSpaceRegion *RightMS = RightBase->getMemorySpace(); |
| const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion(); |
| |
| // If the two regions are from different known memory spaces they cannot be |
| // equal. Also, assume that no symbolic region (whose memory space is |
| // unknown) is on the stack. |
| if (LeftMS != RightMS && |
| ((LeftMS != UnknownMS && RightMS != UnknownMS) || |
| (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) { |
| switch (op) { |
| default: |
| return UnknownVal(); |
| case BO_EQ: |
| return makeTruthVal(false, resultTy); |
| case BO_NE: |
| return makeTruthVal(true, resultTy); |
| } |
| } |
| |
| // If both values wrap regions, see if they're from different base regions. |
| // Note, heap base symbolic regions are assumed to not alias with |
| // each other; for example, we assume that malloc returns different address |
| // on each invocation. |
| // FIXME: ObjC object pointers always reside on the heap, but currently |
| // we treat their memory space as unknown, because symbolic pointers |
| // to ObjC objects may alias. There should be a way to construct |
| // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker |
| // guesses memory space for ObjC object pointers manually instead of |
| // relying on us. |
| if (LeftBase != RightBase && |
| ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) || |
| (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){ |
| switch (op) { |
| default: |
| return UnknownVal(); |
| case BO_EQ: |
| return makeTruthVal(false, resultTy); |
| case BO_NE: |
| return makeTruthVal(true, resultTy); |
| } |
| } |
| |
| // Handle special cases for when both regions are element regions. |
| const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR); |
| const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR); |
| if (RightER && LeftER) { |
| // Next, see if the two ERs have the same super-region and matching types. |
| // FIXME: This should do something useful even if the types don't match, |
| // though if both indexes are constant the RegionRawOffset path will |
| // give the correct answer. |
| if (LeftER->getSuperRegion() == RightER->getSuperRegion() && |
| LeftER->getElementType() == RightER->getElementType()) { |
| // Get the left index and cast it to the correct type. |
| // If the index is unknown or undefined, bail out here. |
| SVal LeftIndexVal = LeftER->getIndex(); |
| Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>(); |
| if (!LeftIndex) |
| return UnknownVal(); |
| LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy); |
| LeftIndex = LeftIndexVal.getAs<NonLoc>(); |
| if (!LeftIndex) |
| return UnknownVal(); |
| |
| // Do the same for the right index. |
| SVal RightIndexVal = RightER->getIndex(); |
| Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>(); |
| if (!RightIndex) |
| return UnknownVal(); |
| RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy); |
| RightIndex = RightIndexVal.getAs<NonLoc>(); |
| if (!RightIndex) |
| return UnknownVal(); |
| |
| // Actually perform the operation. |
| // evalBinOpNN expects the two indexes to already be the right type. |
| return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy); |
| } |
| } |
| |
| // Special handling of the FieldRegions, even with symbolic offsets. |
| const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR); |
| const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR); |
| if (RightFR && LeftFR) { |
| SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy, |
| *this); |
| if (!R.isUnknown()) |
| return R; |
| } |
| |
| // Compare the regions using the raw offsets. |
| RegionOffset LeftOffset = LeftMR->getAsOffset(); |
| RegionOffset RightOffset = RightMR->getAsOffset(); |
| |
| if (LeftOffset.getRegion() != nullptr && |
| LeftOffset.getRegion() == RightOffset.getRegion() && |
| !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) { |
| int64_t left = LeftOffset.getOffset(); |
| int64_t right = RightOffset.getOffset(); |
| |
| switch (op) { |
| default: |
| return UnknownVal(); |
| case BO_LT: |
| return makeTruthVal(left < right, resultTy); |
| case BO_GT: |
| return makeTruthVal(left > right, resultTy); |
| case BO_LE: |
| return makeTruthVal(left <= right, resultTy); |
| case BO_GE: |
| return makeTruthVal(left >= right, resultTy); |
| case BO_EQ: |
| return makeTruthVal(left == right, resultTy); |
| case BO_NE: |
| return makeTruthVal(left != right, resultTy); |
| } |
| } |
| |
| // At this point we're not going to get a good answer, but we can try |
| // conjuring an expression instead. |
| SymbolRef LHSSym = lhs.getAsLocSymbol(); |
| SymbolRef RHSSym = rhs.getAsLocSymbol(); |
| if (LHSSym && RHSSym) |
| return makeNonLoc(LHSSym, op, RHSSym, resultTy); |
| |
| // If we get here, we have no way of comparing the regions. |
| return UnknownVal(); |
| } |
| } |
| } |
| |
| SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state, |
| BinaryOperator::Opcode op, |
| Loc lhs, NonLoc rhs, QualType resultTy) { |
| if (op >= BO_PtrMemD && op <= BO_PtrMemI) { |
| if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) { |
| if (PTMSV->isNullMemberPointer()) |
| return UndefinedVal(); |
| if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) { |
| SVal Result = lhs; |
| |
| for (const auto &I : *PTMSV) |
| Result = StateMgr.getStoreManager().evalDerivedToBase( |
| Result, I->getType(),I->isVirtual()); |
| return state->getLValue(FD, Result); |
| } |
| } |
| |
| return rhs; |
| } |
| |
| assert(!BinaryOperator::isComparisonOp(op) && |
| "arguments to comparison ops must be of the same type"); |
| |
| // Special case: rhs is a zero constant. |
| if (rhs.isZeroConstant()) |
| return lhs; |
| |
| // Perserve the null pointer so that it can be found by the DerefChecker. |
| if (lhs.isZeroConstant()) |
| return lhs; |
| |
| // We are dealing with pointer arithmetic. |
| |
| // Handle pointer arithmetic on constant values. |
| if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) { |
| if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) { |
| const llvm::APSInt &leftI = lhsInt->getValue(); |
| assert(leftI.isUnsigned()); |
| llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true); |
| |
| // Convert the bitwidth of rightI. This should deal with overflow |
| // since we are dealing with concrete values. |
| rightI = rightI.extOrTrunc(leftI.getBitWidth()); |
| |
| // Offset the increment by the pointer size. |
| llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true); |
| QualType pointeeType = resultTy->getPointeeType(); |
| Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity(); |
| rightI *= Multiplicand; |
| |
| // Compute the adjusted pointer. |
| switch (op) { |
| case BO_Add: |
| rightI = leftI + rightI; |
| break; |
| case BO_Sub: |
| rightI = leftI - rightI; |
| break; |
| default: |
| llvm_unreachable("Invalid pointer arithmetic operation"); |
| } |
| return loc::ConcreteInt(getBasicValueFactory().getValue(rightI)); |
| } |
| } |
| |
| // Handle cases where 'lhs' is a region. |
| if (const MemRegion *region = lhs.getAsRegion()) { |
| rhs = convertToArrayIndex(rhs).castAs<NonLoc>(); |
| SVal index = UnknownVal(); |
| const SubRegion *superR = nullptr; |
| // We need to know the type of the pointer in order to add an integer to it. |
| // Depending on the type, different amount of bytes is added. |
| QualType elementType; |
| |
| if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) { |
| assert(op == BO_Add || op == BO_Sub); |
| index = evalBinOpNN(state, op, elemReg->getIndex(), rhs, |
| getArrayIndexType()); |
| superR = cast<SubRegion>(elemReg->getSuperRegion()); |
| elementType = elemReg->getElementType(); |
| } |
| else if (isa<SubRegion>(region)) { |
| assert(op == BO_Add || op == BO_Sub); |
| index = (op == BO_Add) ? rhs : evalMinus(rhs); |
| superR = cast<SubRegion>(region); |
| // TODO: Is this actually reliable? Maybe improving our MemRegion |
| // hierarchy to provide typed regions for all non-void pointers would be |
| // better. For instance, we cannot extend this towards LocAsInteger |
| // operations, where result type of the expression is integer. |
| if (resultTy->isAnyPointerType()) |
| elementType = resultTy->getPointeeType(); |
| } |
| |
| // Represent arithmetic on void pointers as arithmetic on char pointers. |
| // It is fine when a TypedValueRegion of char value type represents |
| // a void pointer. Note that arithmetic on void pointers is a GCC extension. |
| if (elementType->isVoidType()) |
| elementType = getContext().CharTy; |
| |
| if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) { |
| return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV, |
| superR, getContext())); |
| } |
| } |
| return UnknownVal(); |
| } |
| |
| const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state, |
| SVal V) { |
| V = simplifySVal(state, V); |
| if (V.isUnknownOrUndef()) |
| return nullptr; |
| |
| if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>()) |
| return &X->getValue(); |
| |
| if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>()) |
| return &X->getValue(); |
| |
| if (SymbolRef Sym = V.getAsSymbol()) |
| return state->getConstraintManager().getSymVal(state, Sym); |
| |
| // FIXME: Add support for SymExprs. |
| return nullptr; |
| } |
| |
| SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) { |
| // For now, this function tries to constant-fold symbols inside a |
| // nonloc::SymbolVal, and does nothing else. More simplifications should |
| // be possible, such as constant-folding an index in an ElementRegion. |
| |
| class Simplifier : public FullSValVisitor<Simplifier, SVal> { |
| ProgramStateRef State; |
| SValBuilder &SVB; |
| |
| // Cache results for the lifetime of the Simplifier. Results change every |
| // time new constraints are added to the program state, which is the whole |
| // point of simplifying, and for that very reason it's pointless to maintain |
| // the same cache for the duration of the whole analysis. |
| llvm::DenseMap<SymbolRef, SVal> Cached; |
| |
| static bool isUnchanged(SymbolRef Sym, SVal Val) { |
| return Sym == Val.getAsSymbol(); |
| } |
| |
| SVal cache(SymbolRef Sym, SVal V) { |
| Cached[Sym] = V; |
| return V; |
| } |
| |
| SVal skip(SymbolRef Sym) { |
| return cache(Sym, SVB.makeSymbolVal(Sym)); |
| } |
| |
| public: |
| Simplifier(ProgramStateRef State) |
| : State(State), SVB(State->getStateManager().getSValBuilder()) {} |
| |
| SVal VisitSymbolData(const SymbolData *S) { |
| // No cache here. |
| if (const llvm::APSInt *I = |
| SVB.getKnownValue(State, SVB.makeSymbolVal(S))) |
| return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I) |
| : (SVal)SVB.makeIntVal(*I); |
| return SVB.makeSymbolVal(S); |
| } |
| |
| // TODO: Support SymbolCast. Support IntSymExpr when/if we actually |
| // start producing them. |
| |
| SVal VisitSymIntExpr(const SymIntExpr *S) { |
| auto I = Cached.find(S); |
| if (I != Cached.end()) |
| return I->second; |
| |
| SVal LHS = Visit(S->getLHS()); |
| if (isUnchanged(S->getLHS(), LHS)) |
| return skip(S); |
| |
| SVal RHS; |
| // By looking at the APSInt in the right-hand side of S, we cannot |
| // figure out if it should be treated as a Loc or as a NonLoc. |
| // So make our guess by recalling that we cannot multiply pointers |
| // or compare a pointer to an integer. |
| if (Loc::isLocType(S->getLHS()->getType()) && |
| BinaryOperator::isComparisonOp(S->getOpcode())) { |
| // The usual conversion of $sym to &SymRegion{$sym}, as they have |
| // the same meaning for Loc-type symbols, but the latter form |
| // is preferred in SVal computations for being Loc itself. |
| if (SymbolRef Sym = LHS.getAsSymbol()) { |
| assert(Loc::isLocType(Sym->getType())); |
| LHS = SVB.makeLoc(Sym); |
| } |
| RHS = SVB.makeIntLocVal(S->getRHS()); |
| } else { |
| RHS = SVB.makeIntVal(S->getRHS()); |
| } |
| |
| return cache( |
| S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType())); |
| } |
| |
| SVal VisitSymSymExpr(const SymSymExpr *S) { |
| auto I = Cached.find(S); |
| if (I != Cached.end()) |
| return I->second; |
| |
| // For now don't try to simplify mixed Loc/NonLoc expressions |
| // because they often appear from LocAsInteger operations |
| // and we don't know how to combine a LocAsInteger |
| // with a concrete value. |
| if (Loc::isLocType(S->getLHS()->getType()) != |
| Loc::isLocType(S->getRHS()->getType())) |
| return skip(S); |
| |
| SVal LHS = Visit(S->getLHS()); |
| SVal RHS = Visit(S->getRHS()); |
| if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS)) |
| return skip(S); |
| |
| return cache( |
| S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType())); |
| } |
| |
| SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); } |
| |
| SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); } |
| |
| SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) { |
| // Simplification is much more costly than computing complexity. |
| // For high complexity, it may be not worth it. |
| return Visit(V.getSymbol()); |
| } |
| |
| SVal VisitSVal(SVal V) { return V; } |
| }; |
| |
| // A crude way of preventing this function from calling itself from evalBinOp. |
| static bool isReentering = false; |
| if (isReentering) |
| return V; |
| |
| isReentering = true; |
| SVal SimplifiedV = Simplifier(State).Visit(V); |
| isReentering = false; |
| |
| return SimplifiedV; |
| } |
