| //== RangedConstraintManager.cpp --------------------------------*- 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 RangedConstraintManager, a class that provides a |
| // range-based constraint manager interface. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/RangedConstraintManager.h" |
| |
| namespace clang { |
| |
| namespace ento { |
| |
| RangedConstraintManager::~RangedConstraintManager() {} |
| |
| ProgramStateRef RangedConstraintManager::assumeSym(ProgramStateRef State, |
| SymbolRef Sym, |
| bool Assumption) { |
| Sym = simplify(State, Sym); |
| |
| // Handle SymbolData. |
| if (isa<SymbolData>(Sym)) |
| return assumeSymUnsupported(State, Sym, Assumption); |
| |
| // Handle symbolic expression. |
| if (const SymIntExpr *SIE = dyn_cast<SymIntExpr>(Sym)) { |
| // We can only simplify expressions whose RHS is an integer. |
| |
| BinaryOperator::Opcode op = SIE->getOpcode(); |
| if (BinaryOperator::isComparisonOp(op) && op != BO_Cmp) { |
| if (!Assumption) |
| op = BinaryOperator::negateComparisonOp(op); |
| |
| return assumeSymRel(State, SIE->getLHS(), op, SIE->getRHS()); |
| } |
| |
| // Handle adjustment with non-comparison ops. |
| const llvm::APSInt &Zero = getBasicVals().getValue(0, SIE->getType()); |
| return assumeSymRel(State, SIE, (Assumption ? BO_NE : BO_EQ), Zero); |
| } |
| |
| if (const auto *SSE = dyn_cast<SymSymExpr>(Sym)) { |
| BinaryOperator::Opcode Op = SSE->getOpcode(); |
| assert(BinaryOperator::isComparisonOp(Op)); |
| |
| // We convert equality operations for pointers only. |
| if (Loc::isLocType(SSE->getLHS()->getType()) && |
| Loc::isLocType(SSE->getRHS()->getType())) { |
| // 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(); |
| 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 (BinaryOperator::isEqualityOp(Op)) { |
| SymbolManager &SymMgr = getSymbolManager(); |
| |
| QualType ExprType = SSE->getType(); |
| SymbolRef CanonicalEquality = |
| SymMgr.getSymSymExpr(SSE->getLHS(), BO_EQ, SSE->getRHS(), ExprType); |
| |
| bool WasEqual = SSE->getOpcode() == BO_EQ; |
| bool IsExpectedEqual = WasEqual == Assumption; |
| |
| const llvm::APSInt &Zero = getBasicVals().getValue(0, ExprType); |
| |
| if (IsExpectedEqual) { |
| return assumeSymNE(State, CanonicalEquality, Zero, Zero); |
| } |
| |
| return assumeSymEQ(State, CanonicalEquality, Zero, Zero); |
| } |
| } |
| |
| // If we get here, there's nothing else we can do but treat the symbol as |
| // opaque. |
| return assumeSymUnsupported(State, Sym, Assumption); |
| } |
| |
| ProgramStateRef RangedConstraintManager::assumeSymInclusiveRange( |
| ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From, |
| const llvm::APSInt &To, bool InRange) { |
| |
| Sym = simplify(State, Sym); |
| |
| // Get the type used for calculating wraparound. |
| BasicValueFactory &BVF = getBasicVals(); |
| APSIntType WraparoundType = BVF.getAPSIntType(Sym->getType()); |
| |
| llvm::APSInt Adjustment = WraparoundType.getZeroValue(); |
| SymbolRef AdjustedSym = Sym; |
| computeAdjustment(AdjustedSym, Adjustment); |
| |
| // Convert the right-hand side integer as necessary. |
| APSIntType ComparisonType = std::max(WraparoundType, APSIntType(From)); |
| llvm::APSInt ConvertedFrom = ComparisonType.convert(From); |
| llvm::APSInt ConvertedTo = ComparisonType.convert(To); |
| |
| // Prefer unsigned comparisons. |
| if (ComparisonType.getBitWidth() == WraparoundType.getBitWidth() && |
| ComparisonType.isUnsigned() && !WraparoundType.isUnsigned()) |
| Adjustment.setIsSigned(false); |
| |
| if (InRange) |
| return assumeSymWithinInclusiveRange(State, AdjustedSym, ConvertedFrom, |
| ConvertedTo, Adjustment); |
| return assumeSymOutsideInclusiveRange(State, AdjustedSym, ConvertedFrom, |
| ConvertedTo, Adjustment); |
| } |
| |
| ProgramStateRef |
| RangedConstraintManager::assumeSymUnsupported(ProgramStateRef State, |
| SymbolRef Sym, bool Assumption) { |
| Sym = simplify(State, Sym); |
| |
| BasicValueFactory &BVF = getBasicVals(); |
| QualType T = Sym->getType(); |
| |
| // Non-integer types are not supported. |
| if (!T->isIntegralOrEnumerationType()) |
| return State; |
| |
| // Reverse the operation and add directly to 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 RangedConstraintManager::assumeSymRel(ProgramStateRef State, |
| SymbolRef Sym, |
| BinaryOperator::Opcode Op, |
| const llvm::APSInt &Int) { |
| assert(BinaryOperator::isComparisonOp(Op) && |
| "Non-comparison ops should be rewritten as comparisons to zero."); |
| |
| // Simplification: translate an assume of a constraint of the form |
| // "(exp comparison_op expr) != 0" to true into an assume of |
| // "exp comparison_op expr" to true. (And similarly, an assume of the form |
| // "(exp comparison_op expr) == 0" to true into an assume of |
| // "exp comparison_op expr" to false.) |
| if (Int == 0 && (Op == BO_EQ || Op == BO_NE)) { |
| if (const BinarySymExpr *SE = dyn_cast<BinarySymExpr>(Sym)) |
| if (BinaryOperator::isComparisonOp(SE->getOpcode())) |
| return assumeSym(State, Sym, (Op == BO_NE ? true : false)); |
| } |
| |
| // Get the type used for calculating wraparound. |
| BasicValueFactory &BVF = getBasicVals(); |
| APSIntType WraparoundType = BVF.getAPSIntType(Sym->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. |
| 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 |
| } |
| |
| void RangedConstraintManager::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; |
| } |
| } |
| } |
| |
| SVal simplifyToSVal(ProgramStateRef State, SymbolRef Sym) { |
| SValBuilder &SVB = State->getStateManager().getSValBuilder(); |
| return SVB.simplifySVal(State, SVB.makeSymbolVal(Sym)); |
| } |
| |
| SymbolRef simplify(ProgramStateRef State, SymbolRef Sym) { |
| SVal SimplifiedVal = simplifyToSVal(State, Sym); |
| if (SymbolRef SimplifiedSym = SimplifiedVal.getAsSymbol()) |
| return SimplifiedSym; |
| return Sym; |
| } |
| |
| } // end of namespace ento |
| } // end of namespace clang |