//== 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_Cmp236k
) {

      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_NE170
 : 
BO_EQ170
), 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())982
) {

        // 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()12.5k
 && 
!WraparoundType.isUnsigned()350
)

    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 && 
(177k
Op == BO_EQ177k
 || 
Op == BO_NE92.6k
)) {

    if (const BinarySymExpr *SE = dyn_cast<BinarySymExpr>(Sym))

      if (BinaryOperator::isComparisonOp(SE->getOpcode()))

        return assumeSym(State, Sym, (Op == BO_NE ? 
true106
 : 
false106
));

  }

  // 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()234k
 && 
!WraparoundType.isUnsigned()132k
)

    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_Sub40.1k
) {

      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