lib/StaticAnalyzer/Core/RangedConstraintManager.cpp - llvm-project/clang - Git at Google

 //== 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();
     if (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
	//== 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();
	if (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