| //== SimpleConstraintManager.cpp --------------------------------*- C++ -*--==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines SimpleConstraintManager, a class that holds code shared |
| // between BasicConstraintManager and RangeConstraintManager. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "SimpleConstraintManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" |
| |
| namespace clang { |
| |
| namespace ento { |
| |
| SimpleConstraintManager::~SimpleConstraintManager() {} |
| |
| bool SimpleConstraintManager::canReasonAbout(SVal X) const { |
| Optional<nonloc::SymbolVal> SymVal = X.getAs<nonloc::SymbolVal>(); |
| if (SymVal && SymVal->isExpression()) { |
| const SymExpr *SE = SymVal->getSymbol(); |
| |
| if (const SymIntExpr *SIE = dyn_cast<SymIntExpr>(SE)) { |
| switch (SIE->getOpcode()) { |
| // We don't reason yet about bitwise-constraints on symbolic values. |
| case BO_And: |
| case BO_Or: |
| case BO_Xor: |
| return false; |
| // We don't reason yet about these arithmetic constraints on |
| // symbolic values. |
| case BO_Mul: |
| case BO_Div: |
| case BO_Rem: |
| case BO_Shl: |
| case BO_Shr: |
| return false; |
| // All other cases. |
| default: |
| return true; |
| } |
| } |
| |
| if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(SE)) { |
| if (BinaryOperator::isComparisonOp(SSE->getOpcode())) { |
| // We handle Loc <> Loc comparisons, but not (yet) NonLoc <> NonLoc. |
| if (Loc::isLocType(SSE->getLHS()->getType())) { |
| assert(Loc::isLocType(SSE->getRHS()->getType())); |
| return true; |
| } |
| } |
| } |
| |
| return false; |
| } |
| |
| return true; |
| } |
| |
| ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, |
| DefinedSVal Cond, |
| bool Assumption) { |
| // If we have a Loc value, cast it to a bool NonLoc first. |
| if (Optional<Loc> LV = Cond.getAs<Loc>()) { |
| SValBuilder &SVB = state->getStateManager().getSValBuilder(); |
| QualType T; |
| const MemRegion *MR = LV->getAsRegion(); |
| if (const TypedRegion *TR = dyn_cast_or_null<TypedRegion>(MR)) |
| T = TR->getLocationType(); |
| else |
| T = SVB.getContext().VoidPtrTy; |
| |
| Cond = SVB.evalCast(*LV, SVB.getContext().BoolTy, T).castAs<DefinedSVal>(); |
| } |
| |
| return assume(state, Cond.castAs<NonLoc>(), Assumption); |
| } |
| |
| ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, |
| NonLoc cond, |
| bool assumption) { |
| state = assumeAux(state, cond, assumption); |
| if (NotifyAssumeClients && SU) |
| return SU->processAssume(state, cond, assumption); |
| return state; |
| } |
| |
| |
| ProgramStateRef |
| SimpleConstraintManager::assumeAuxForSymbol(ProgramStateRef State, |
| SymbolRef Sym, bool Assumption) { |
| BasicValueFactory &BVF = getBasicVals(); |
| QualType T = Sym->getType(); |
| |
| // None of the constraint solvers currently support non-integer types. |
| if (!T->isIntegralOrEnumerationType()) |
| return State; |
| |
| const llvm::APSInt &zero = BVF.getValue(0, T); |
| if (Assumption) |
| return assumeSymNE(State, Sym, zero, zero); |
| else |
| return assumeSymEQ(State, Sym, zero, zero); |
| } |
| |
| ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state, |
| NonLoc Cond, |
| bool Assumption) { |
| |
| // We cannot reason about SymSymExprs, and can only reason about some |
| // SymIntExprs. |
| if (!canReasonAbout(Cond)) { |
| // Just add the constraint to the expression without trying to simplify. |
| SymbolRef sym = Cond.getAsSymExpr(); |
| return assumeAuxForSymbol(state, sym, Assumption); |
| } |
| |
| switch (Cond.getSubKind()) { |
| default: |
| llvm_unreachable("'Assume' not implemented for this NonLoc"); |
| |
| case nonloc::SymbolValKind: { |
| nonloc::SymbolVal SV = Cond.castAs<nonloc::SymbolVal>(); |
| SymbolRef sym = SV.getSymbol(); |
| assert(sym); |
| |
| // Handle SymbolData. |
| if (!SV.isExpression()) { |
| return assumeAuxForSymbol(state, sym, Assumption); |
| |
| // Handle symbolic expression. |
| } else if (const SymIntExpr *SE = dyn_cast<SymIntExpr>(sym)) { |
| // We can only simplify expressions whose RHS is an integer. |
| |
| BinaryOperator::Opcode op = SE->getOpcode(); |
| if (BinaryOperator::isComparisonOp(op)) { |
| if (!Assumption) |
| op = BinaryOperator::negateComparisonOp(op); |
| |
| return assumeSymRel(state, SE->getLHS(), op, SE->getRHS()); |
| } |
| |
| } else if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(sym)) { |
| // Translate "a != b" to "(b - a) != 0". |
| // We invert the order of the operands as a heuristic for how loop |
| // conditions are usually written ("begin != end") as compared to length |
| // calculations ("end - begin"). The more correct thing to do would be to |
| // canonicalize "a - b" and "b - a", which would allow us to treat |
| // "a != b" and "b != a" the same. |
| SymbolManager &SymMgr = getSymbolManager(); |
| BinaryOperator::Opcode Op = SSE->getOpcode(); |
| assert(BinaryOperator::isComparisonOp(Op)); |
| |
| // For now, we only support comparing pointers. |
| assert(Loc::isLocType(SSE->getLHS()->getType())); |
| assert(Loc::isLocType(SSE->getRHS()->getType())); |
| QualType DiffTy = SymMgr.getContext().getPointerDiffType(); |
| SymbolRef Subtraction = SymMgr.getSymSymExpr(SSE->getRHS(), BO_Sub, |
| SSE->getLHS(), DiffTy); |
| |
| const llvm::APSInt &Zero = getBasicVals().getValue(0, DiffTy); |
| Op = BinaryOperator::reverseComparisonOp(Op); |
| if (!Assumption) |
| Op = BinaryOperator::negateComparisonOp(Op); |
| return assumeSymRel(state, Subtraction, Op, Zero); |
| } |
| |
| // If we get here, there's nothing else we can do but treat the symbol as |
| // opaque. |
| return assumeAuxForSymbol(state, sym, Assumption); |
| } |
| |
| case nonloc::ConcreteIntKind: { |
| bool b = Cond.castAs<nonloc::ConcreteInt>().getValue() != 0; |
| bool isFeasible = b ? Assumption : !Assumption; |
| return isFeasible ? state : NULL; |
| } |
| |
| case nonloc::LocAsIntegerKind: |
| return assume(state, Cond.castAs<nonloc::LocAsInteger>().getLoc(), |
| Assumption); |
| } // end switch |
| } |
| |
| static void computeAdjustment(SymbolRef &Sym, llvm::APSInt &Adjustment) { |
| // Is it a "($sym+constant1)" expression? |
| if (const SymIntExpr *SE = dyn_cast<SymIntExpr>(Sym)) { |
| BinaryOperator::Opcode Op = SE->getOpcode(); |
| if (Op == BO_Add || Op == BO_Sub) { |
| Sym = SE->getLHS(); |
| Adjustment = APSIntType(Adjustment).convert(SE->getRHS()); |
| |
| // Don't forget to negate the adjustment if it's being subtracted. |
| // This should happen /after/ promotion, in case the value being |
| // subtracted is, say, CHAR_MIN, and the promoted type is 'int'. |
| if (Op == BO_Sub) |
| Adjustment = -Adjustment; |
| } |
| } |
| } |
| |
| ProgramStateRef SimpleConstraintManager::assumeSymRel(ProgramStateRef state, |
| const SymExpr *LHS, |
| BinaryOperator::Opcode op, |
| const llvm::APSInt& Int) { |
| assert(BinaryOperator::isComparisonOp(op) && |
| "Non-comparison ops should be rewritten as comparisons to zero."); |
| |
| // Get the type used for calculating wraparound. |
| BasicValueFactory &BVF = getBasicVals(); |
| APSIntType WraparoundType = BVF.getAPSIntType(LHS->getType()); |
| |
| // We only handle simple comparisons of the form "$sym == constant" |
| // or "($sym+constant1) == constant2". |
| // The adjustment is "constant1" in the above expression. It's used to |
| // "slide" the solution range around for modular arithmetic. For example, |
| // x < 4 has the solution [0, 3]. x+2 < 4 has the solution [0-2, 3-2], which |
| // in modular arithmetic is [0, 1] U [UINT_MAX-1, UINT_MAX]. It's up to |
| // the subclasses of SimpleConstraintManager to handle the adjustment. |
| SymbolRef Sym = LHS; |
| llvm::APSInt Adjustment = WraparoundType.getZeroValue(); |
| computeAdjustment(Sym, Adjustment); |
| |
| // Convert the right-hand side integer as necessary. |
| APSIntType ComparisonType = std::max(WraparoundType, APSIntType(Int)); |
| llvm::APSInt ConvertedInt = ComparisonType.convert(Int); |
| |
| // Prefer unsigned comparisons. |
| if (ComparisonType.getBitWidth() == WraparoundType.getBitWidth() && |
| ComparisonType.isUnsigned() && !WraparoundType.isUnsigned()) |
| Adjustment.setIsSigned(false); |
| |
| switch (op) { |
| default: |
| llvm_unreachable("invalid operation not caught by assertion above"); |
| |
| case BO_EQ: |
| return assumeSymEQ(state, Sym, ConvertedInt, Adjustment); |
| |
| case BO_NE: |
| return assumeSymNE(state, Sym, ConvertedInt, Adjustment); |
| |
| case BO_GT: |
| return assumeSymGT(state, Sym, ConvertedInt, Adjustment); |
| |
| case BO_GE: |
| return assumeSymGE(state, Sym, ConvertedInt, Adjustment); |
| |
| case BO_LT: |
| return assumeSymLT(state, Sym, ConvertedInt, Adjustment); |
| |
| case BO_LE: |
| return assumeSymLE(state, Sym, ConvertedInt, Adjustment); |
| } // end switch |
| } |
| |
| } // end of namespace ento |
| |
| } // end of namespace clang |