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