llvm-project/clang/lib/StaticAnalyzer/Core/BasicConstraintManager.cpp

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//== BasicConstraintManager.cpp - Manage basic constraints.------*- 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 BasicConstraintManager, a class that tracks simple
// equality and inequality constraints on symbolic values of ProgramState.
//
//===----------------------------------------------------------------------===//
#include "SimpleConstraintManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
namespace { class ConstNotEq {}; }
namespace { class ConstEq {}; }
typedef llvm::ImmutableMap<SymbolRef,ProgramState::IntSetTy> ConstNotEqTy;
typedef llvm::ImmutableMap<SymbolRef,const llvm::APSInt*> ConstEqTy;
static int ConstEqIndex = 0;
static int ConstNotEqIndex = 0;
namespace clang {
namespace ento {
template<>
struct ProgramStateTrait<ConstNotEq> :
public ProgramStatePartialTrait<ConstNotEqTy> {
static inline void *GDMIndex() { return &ConstNotEqIndex; }
};
template<>
struct ProgramStateTrait<ConstEq> : public ProgramStatePartialTrait<ConstEqTy> {
static inline void *GDMIndex() { return &ConstEqIndex; }
};
}
}
namespace {
// BasicConstraintManager only tracks equality and inequality constraints of
// constants and integer variables.
class BasicConstraintManager
: public SimpleConstraintManager {
ProgramState::IntSetTy::Factory ISetFactory;
public:
BasicConstraintManager(ProgramStateManager &statemgr, SubEngine &subengine)
: SimpleConstraintManager(subengine, statemgr.getBasicVals()),
ISetFactory(statemgr.getAllocator()) {}
ProgramStateRef assumeSymEquality(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment,
bool Assumption);
ProgramStateRef assumeSymNE(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
return assumeSymEquality(State, Sym, V, Adjustment, false);
}
ProgramStateRef assumeSymEQ(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
return assumeSymEquality(State, Sym, V, Adjustment, true);
}
ProgramStateRef assumeSymLT(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
ProgramStateRef assumeSymGT(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
ProgramStateRef assumeSymGE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
ProgramStateRef assumeSymLE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
ProgramStateRef AddEQ(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V);
ProgramStateRef AddNE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V);
const llvm::APSInt* getSymVal(ProgramStateRef state,
SymbolRef sym) const;
bool isNotEqual(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) const;
bool isEqual(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) const;
ProgramStateRef removeDeadBindings(ProgramStateRef state,
SymbolReaper& SymReaper);
bool performTest(llvm::APSInt SymVal, llvm::APSInt Adjustment,
BinaryOperator::Opcode Op, llvm::APSInt ComparisonVal);
void print(ProgramStateRef state,
raw_ostream &Out,
const char* nl,
const char *sep);
};
} // end anonymous namespace
ConstraintManager*
ento::CreateBasicConstraintManager(ProgramStateManager& statemgr,
SubEngine &subengine) {
return new BasicConstraintManager(statemgr, subengine);
}
// FIXME: This is a more general utility and should live somewhere else.
bool BasicConstraintManager::performTest(llvm::APSInt SymVal,
llvm::APSInt Adjustment,
BinaryOperator::Opcode Op,
llvm::APSInt ComparisonVal) {
APSIntType Type(Adjustment);
Type.apply(SymVal);
Type.apply(ComparisonVal);
SymVal += Adjustment;
assert(BinaryOperator::isComparisonOp(Op));
BasicValueFactory &BVF = getBasicVals();
const llvm::APSInt *Result = BVF.evalAPSInt(Op, SymVal, ComparisonVal);
assert(Result && "Comparisons should always have valid results.");
return Result->getBoolValue();
}
ProgramStateRef
BasicConstraintManager::assumeSymEquality(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment,
bool Assumption) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
if (AdjustmentType.testInRange(V) != APSIntType::RTR_Within)
return Assumption ? NULL : State;
// Get the symbol type.
BasicValueFactory &BVF = getBasicVals();
ASTContext &Ctx = BVF.getContext();
APSIntType SymbolType = BVF.getAPSIntType(Sym->getType(Ctx));
// First, see if the adjusted value is within range for the symbol.
llvm::APSInt Adjusted = AdjustmentType.convert(V) - Adjustment;
if (SymbolType.testInRange(Adjusted) != APSIntType::RTR_Within)
return Assumption ? NULL : State;
// Now we can do things properly in the symbol space.
SymbolType.apply(Adjusted);
// Second, determine if sym == X, where X+Adjustment != V.
if (const llvm::APSInt *X = getSymVal(State, Sym)) {
bool IsFeasible = (*X == Adjusted);
return (IsFeasible == Assumption) ? State : NULL;
}
// Third, determine if we already know sym+Adjustment != V.
if (isNotEqual(State, Sym, Adjusted))
return Assumption ? NULL : State;
// If we reach here, sym is not a constant and we don't know if it is != V.
// Make the correct assumption.
if (Assumption)
return AddEQ(State, Sym, Adjusted);
else
return AddNE(State, Sym, Adjusted);
}
// The logic for these will be handled in another ConstraintManager.
// Approximate it here anyway by handling some edge cases.
ProgramStateRef
BasicConstraintManager::assumeSymLT(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
APSIntType ComparisonType(V), AdjustmentType(Adjustment);
// Is 'V' out of range above the type?
llvm::APSInt Max = AdjustmentType.getMaxValue();
if (V > ComparisonType.convert(Max)) {
// This path is trivially feasible.
return state;
}
// Is 'V' the smallest possible value, or out of range below the type?
llvm::APSInt Min = AdjustmentType.getMinValue();
if (V <= ComparisonType.convert(Min)) {
// sym cannot be any value less than 'V'. This path is infeasible.
return NULL;
}
// Reject a path if the value of sym is a constant X and !(X+Adj < V).
if (const llvm::APSInt *X = getSymVal(state, sym)) {
bool isFeasible = performTest(*X, Adjustment, BO_LT, V);
return isFeasible ? state : NULL;
}
// FIXME: For now have assuming x < y be the same as assuming sym != V;
return assumeSymNE(state, sym, V, Adjustment);
}
ProgramStateRef
BasicConstraintManager::assumeSymGT(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
APSIntType ComparisonType(V), AdjustmentType(Adjustment);
// Is 'V' the largest possible value, or out of range above the type?
llvm::APSInt Max = AdjustmentType.getMaxValue();
if (V >= ComparisonType.convert(Max)) {
// sym cannot be any value greater than 'V'. This path is infeasible.
return NULL;
}
// Is 'V' out of range below the type?
llvm::APSInt Min = AdjustmentType.getMinValue();
if (V < ComparisonType.convert(Min)) {
// This path is trivially feasible.
return state;
}
// Reject a path if the value of sym is a constant X and !(X+Adj > V).
if (const llvm::APSInt *X = getSymVal(state, sym)) {
bool isFeasible = performTest(*X, Adjustment, BO_GT, V);
return isFeasible ? state : NULL;
}
// FIXME: For now have assuming x > y be the same as assuming sym != V;
return assumeSymNE(state, sym, V, Adjustment);
}
ProgramStateRef
BasicConstraintManager::assumeSymGE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
APSIntType ComparisonType(V), AdjustmentType(Adjustment);
// Is 'V' the largest possible value, or out of range above the type?
llvm::APSInt Max = AdjustmentType.getMaxValue();
ComparisonType.apply(Max);
if (V > Max) {
// sym cannot be any value greater than 'V'. This path is infeasible.
return NULL;
} else if (V == Max) {
// If the path is feasible then as a consequence we know that
// 'sym+Adjustment == V' because there are no larger values.
// Add this constraint.
return assumeSymEQ(state, sym, V, Adjustment);
}
// Is 'V' out of range below the type?
llvm::APSInt Min = AdjustmentType.getMinValue();
if (V < ComparisonType.convert(Min)) {
// This path is trivially feasible.
return state;
}
// Reject a path if the value of sym is a constant X and !(X+Adj >= V).
if (const llvm::APSInt *X = getSymVal(state, sym)) {
bool isFeasible = performTest(*X, Adjustment, BO_GE, V);
return isFeasible ? state : NULL;
}
return state;
}
ProgramStateRef
BasicConstraintManager::assumeSymLE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
APSIntType ComparisonType(V), AdjustmentType(Adjustment);
// Is 'V' out of range above the type?
llvm::APSInt Max = AdjustmentType.getMaxValue();
if (V > ComparisonType.convert(Max)) {
// This path is trivially feasible.
return state;
}
// Is 'V' the smallest possible value, or out of range below the type?
llvm::APSInt Min = AdjustmentType.getMinValue();
ComparisonType.apply(Min);
if (V < Min) {
// sym cannot be any value less than 'V'. This path is infeasible.
return NULL;
} else if (V == Min) {
// If the path is feasible then as a consequence we know that
// 'sym+Adjustment == V' because there are no smaller values.
// Add this constraint.
return assumeSymEQ(state, sym, V, Adjustment);
}
// Reject a path if the value of sym is a constant X and !(X+Adj >= V).
if (const llvm::APSInt *X = getSymVal(state, sym)) {
bool isFeasible = performTest(*X, Adjustment, BO_LE, V);
return isFeasible ? state : NULL;
}
return state;
}
ProgramStateRef BasicConstraintManager::AddEQ(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) {
// Now that we have an actual value, we can throw out the NE-set.
// Create a new state with the old bindings replaced.
state = state->remove<ConstNotEq>(sym);
return state->set<ConstEq>(sym, &getBasicVals().getValue(V));
}
ProgramStateRef BasicConstraintManager::AddNE(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) {
// First, retrieve the NE-set associated with the given symbol.
ConstNotEqTy::data_type* T = state->get<ConstNotEq>(sym);
ProgramState::IntSetTy S = T ? *T : ISetFactory.getEmptySet();
// Now add V to the NE set.
S = ISetFactory.add(S, &getBasicVals().getValue(V));
// Create a new state with the old binding replaced.
return state->set<ConstNotEq>(sym, S);
}
const llvm::APSInt* BasicConstraintManager::getSymVal(ProgramStateRef state,
SymbolRef sym) const {
const ConstEqTy::data_type* T = state->get<ConstEq>(sym);
return T ? *T : NULL;
}
bool BasicConstraintManager::isNotEqual(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) const {
// Retrieve the NE-set associated with the given symbol.
const ConstNotEqTy::data_type* T = state->get<ConstNotEq>(sym);
// See if V is present in the NE-set.
return T ? T->contains(&getBasicVals().getValue(V)) : false;
}
bool BasicConstraintManager::isEqual(ProgramStateRef state,
SymbolRef sym,
const llvm::APSInt& V) const {
// Retrieve the EQ-set associated with the given symbol.
const ConstEqTy::data_type* T = state->get<ConstEq>(sym);
// See if V is present in the EQ-set.
return T ? **T == V : false;
}
2008-11-27 10:39:34 +08:00
/// Scan all symbols referenced by the constraints. If the symbol is not alive
/// as marked in LSymbols, mark it as dead in DSymbols.
ProgramStateRef
BasicConstraintManager::removeDeadBindings(ProgramStateRef state,
SymbolReaper& SymReaper) {
ConstEqTy CE = state->get<ConstEq>();
ConstEqTy::Factory& CEFactory = state->get_context<ConstEq>();
for (ConstEqTy::iterator I = CE.begin(), E = CE.end(); I!=E; ++I) {
SymbolRef sym = I.getKey();
if (SymReaper.maybeDead(sym))
CE = CEFactory.remove(CE, sym);
}
state = state->set<ConstEq>(CE);
ConstNotEqTy CNE = state->get<ConstNotEq>();
ConstNotEqTy::Factory& CNEFactory = state->get_context<ConstNotEq>();
for (ConstNotEqTy::iterator I = CNE.begin(), E = CNE.end(); I != E; ++I) {
SymbolRef sym = I.getKey();
if (SymReaper.maybeDead(sym))
CNE = CNEFactory.remove(CNE, sym);
}
return state->set<ConstNotEq>(CNE);
}
void BasicConstraintManager::print(ProgramStateRef state,
raw_ostream &Out,
const char* nl, const char *sep) {
// Print equality constraints.
ConstEqTy CE = state->get<ConstEq>();
if (!CE.isEmpty()) {
Out << nl << sep << "'==' constraints:";
for (ConstEqTy::iterator I = CE.begin(), E = CE.end(); I!=E; ++I)
Out << nl << " $" << I.getKey() << " : " << *I.getData();
}
// Print != constraints.
ConstNotEqTy CNE = state->get<ConstNotEq>();
if (!CNE.isEmpty()) {
Out << nl << sep << "'!=' constraints:";
for (ConstNotEqTy::iterator I = CNE.begin(), EI = CNE.end(); I!=EI; ++I) {
Out << nl << " $" << I.getKey() << " : ";
bool isFirst = true;
ProgramState::IntSetTy::iterator J = I.getData().begin(),
EJ = I.getData().end();
for ( ; J != EJ; ++J) {
if (isFirst) isFirst = false;
else Out << ", ";
Out << (*J)->getSExtValue(); // Hack: should print to raw_ostream.
}
}
}
}