//== 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/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
namespace clang {
namespace ento {
SimpleConstraintManager::~SimpleConstraintManager() {}
bool SimpleConstraintManager::canReasonAbout(SVal X) const {
nonloc::SymbolVal *SymVal = dyn_cast<nonloc::SymbolVal>(&X);
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;
}
}
return false;
}
return true;
}
ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state,
DefinedSVal Cond,
bool Assumption) {
if (isa<NonLoc>(Cond))
return assume(state, cast<NonLoc>(Cond), Assumption);
else
return assume(state, cast<Loc>(Cond), Assumption);
}
ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, Loc cond,
bool assumption) {
state = assumeAux(state, cond, assumption);
return SU.processAssume(state, cond, assumption);
}
ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state,
Loc Cond, bool Assumption) {
BasicValueFactory &BasicVals = state->getBasicVals();
switch (Cond.getSubKind()) {
default:
assert (false && "'Assume' not implemented for this Loc.");
return state;
case loc::MemRegionKind: {
// FIXME: Should this go into the storemanager?
const MemRegion *R = cast<loc::MemRegionVal>(Cond).getRegion();
const SubRegion *SubR = dyn_cast<SubRegion>(R);
while (SubR) {
// FIXME: now we only find the first symbolic region.
if (const SymbolicRegion *SymR = dyn_cast<SymbolicRegion>(SubR)) {
const llvm::APSInt &zero = BasicVals.getZeroWithPtrWidth();
if (Assumption)
return assumeSymNE(state, SymR->getSymbol(), zero, zero);
else
return assumeSymEQ(state, SymR->getSymbol(), zero, zero);
}
SubR = dyn_cast<SubRegion>(SubR->getSuperRegion());
}
// FALL-THROUGH.
}
case loc::GotoLabelKind:
return Assumption ? state : NULL;
case loc::ConcreteIntKind: {
bool b = cast<loc::ConcreteInt>(Cond).getValue() != 0;
bool isFeasible = b ? Assumption : !Assumption;
return isFeasible ? state : NULL;
}
} // end switch
}
ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state,
NonLoc cond,
bool assumption) {
state = assumeAux(state, cond, assumption);
return SU.processAssume(state, cond, assumption);
}
static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) {
// FIXME: This should probably be part of BinaryOperator, since this isn't
// the only place it's used. (This code was copied from SimpleSValBuilder.cpp.)
switch (op) {
default:
llvm_unreachable("Invalid opcode.");
case BO_LT: return BO_GE;
case BO_GT: return BO_LE;
case BO_LE: return BO_GT;
case BO_GE: return BO_LT;
case BO_EQ: return BO_NE;
case BO_NE: return BO_EQ;
}
}
ProgramStateRef SimpleConstraintManager::assumeAuxForSymbol(
ProgramStateRef State,
SymbolRef Sym,
bool Assumption) {
QualType T = State->getSymbolManager().getType(Sym);
const llvm::APSInt &zero = State->getBasicVals().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);
}
BasicValueFactory &BasicVals = state->getBasicVals();
SymbolManager &SymMgr = state->getSymbolManager();
switch (Cond.getSubKind()) {
default:
llvm_unreachable("'Assume' not implemented for this NonLoc");
case nonloc::SymbolValKind: {
nonloc::SymbolVal& SV = cast<nonloc::SymbolVal>(Cond);
SymbolRef sym = SV.getSymbol();
assert(sym);
// Handle SymbolData.
if (!SV.isExpression()) {
return assumeAuxForSymbol(state, sym, Assumption);
// Handle symbolic expression.
} else {
// We can only simplify expressions whose RHS is an integer.
const SymIntExpr *SE = dyn_cast<SymIntExpr>(sym);
if (!SE)
return assumeAuxForSymbol(state, sym, Assumption);
BinaryOperator::Opcode op = SE->getOpcode();
// Implicitly compare non-comparison expressions to 0.
if (!BinaryOperator::isComparisonOp(op)) {
QualType T = SymMgr.getType(SE);
const llvm::APSInt &zero = BasicVals.getValue(0, T);
op = (Assumption ? BO_NE : BO_EQ);
return assumeSymRel(state, SE, op, zero);
}
// From here on out, op is the real comparison we'll be testing.
if (!Assumption)
op = NegateComparison(op);
return assumeSymRel(state, SE->getLHS(), op, SE->getRHS());
}
}
case nonloc::ConcreteIntKind: {
bool b = cast<nonloc::ConcreteInt>(Cond).getValue() != 0;
bool isFeasible = b ? Assumption : !Assumption;
return isFeasible ? state : NULL;
}
case nonloc::LocAsIntegerKind:
return assumeAux(state, cast<nonloc::LocAsInteger>(Cond).getLoc(),
Assumption);
} // end switch
}
static llvm::APSInt computeAdjustment(const SymExpr *LHS,
SymbolRef &Sym) {
llvm::APSInt DefaultAdjustment;
DefaultAdjustment = 0;
// First check if the LHS is a simple symbol reference.
if (isa<SymbolData>(LHS))
return DefaultAdjustment;
// Next, see if it's a "($sym+constant1)" expression.
const SymIntExpr *SE = dyn_cast<SymIntExpr>(LHS);
// We cannot simplify "($sym1+$sym2)".
if (!SE)
return DefaultAdjustment;
// Get the constant out of the expression "($sym+constant1)" or
// "<expr>+constant1".
Sym = SE->getLHS();
switch (SE->getOpcode()) {
case BO_Add:
return SE->getRHS();
case BO_Sub:
return -SE->getRHS();
default:
// We cannot simplify non-additive operators.
return DefaultAdjustment;
}
}
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.");
// 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 = computeAdjustment(LHS, Sym);
// FIXME: This next section is a hack. It silently converts the integers to
// be of the same type as the symbol, which is not always correct. Really the
// comparisons should be performed using the Int's type, then mapped back to
// the symbol's range of values.
ProgramStateManager &StateMgr = state->getStateManager();
ASTContext &Ctx = StateMgr.getContext();
QualType T = Sym->getType(Ctx);
assert(T->isIntegerType() || Loc::isLocType(T));
unsigned bitwidth = Ctx.getTypeSize(T);
bool isSymUnsigned
= T->isUnsignedIntegerOrEnumerationType() || Loc::isLocType(T);
// Convert the adjustment.
Adjustment.setIsUnsigned(isSymUnsigned);
Adjustment = Adjustment.extOrTrunc(bitwidth);
// Convert the right-hand side integer.
llvm::APSInt ConvertedInt(Int, isSymUnsigned);
ConvertedInt = ConvertedInt.extOrTrunc(bitwidth);
switch (op) {
default:
// No logic yet for other operators. assume the constraint is feasible.
return state;
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