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

339 lines
12 KiB
C++

//== 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 GRState.
//
//===----------------------------------------------------------------------===//
#include "SimpleConstraintManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/GRState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/GRStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/TransferFuncs.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
namespace { class ConstNotEq {}; }
namespace { class ConstEq {}; }
typedef llvm::ImmutableMap<SymbolRef,GRState::IntSetTy> ConstNotEqTy;
typedef llvm::ImmutableMap<SymbolRef,const llvm::APSInt*> ConstEqTy;
static int ConstEqIndex = 0;
static int ConstNotEqIndex = 0;
namespace clang {
namespace ento {
template<>
struct GRStateTrait<ConstNotEq> : public GRStatePartialTrait<ConstNotEqTy> {
static inline void* GDMIndex() { return &ConstNotEqIndex; }
};
template<>
struct GRStateTrait<ConstEq> : public GRStatePartialTrait<ConstEqTy> {
static inline void* GDMIndex() { return &ConstEqIndex; }
};
}
}
namespace {
// BasicConstraintManager only tracks equality and inequality constraints of
// constants and integer variables.
class BasicConstraintManager
: public SimpleConstraintManager {
GRState::IntSetTy::Factory ISetFactory;
public:
BasicConstraintManager(GRStateManager &statemgr, SubEngine &subengine)
: SimpleConstraintManager(subengine),
ISetFactory(statemgr.getAllocator()) {}
const GRState *assumeSymNE(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState *assumeSymEQ(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState *assumeSymLT(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState *assumeSymGT(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState *assumeSymGE(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState *assumeSymLE(const GRState* state, SymbolRef sym,
const llvm::APSInt& V,
const llvm::APSInt& Adjustment);
const GRState* AddEQ(const GRState* state, SymbolRef sym, const llvm::APSInt& V);
const GRState* AddNE(const GRState* state, SymbolRef sym, const llvm::APSInt& V);
const llvm::APSInt* getSymVal(const GRState* state, SymbolRef sym) const;
bool isNotEqual(const GRState* state, SymbolRef sym, const llvm::APSInt& V)
const;
bool isEqual(const GRState* state, SymbolRef sym, const llvm::APSInt& V)
const;
const GRState* removeDeadBindings(const GRState* state, SymbolReaper& SymReaper);
void print(const GRState* state, llvm::raw_ostream& Out,
const char* nl, const char *sep);
};
} // end anonymous namespace
ConstraintManager* ento::CreateBasicConstraintManager(GRStateManager& statemgr,
SubEngine &subengine) {
return new BasicConstraintManager(statemgr, subengine);
}
const GRState*
BasicConstraintManager::assumeSymNE(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
// First, determine if sym == X, where X+Adjustment != V.
llvm::APSInt Adjusted = V-Adjustment;
if (const llvm::APSInt* X = getSymVal(state, sym)) {
bool isFeasible = (*X != Adjusted);
return isFeasible ? state : NULL;
}
// Second, determine if sym+Adjustment != V.
if (isNotEqual(state, sym, Adjusted))
return state;
// If we reach here, sym is not a constant and we don't know if it is != V.
// Make that assumption.
return AddNE(state, sym, Adjusted);
}
const GRState*
BasicConstraintManager::assumeSymEQ(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
// First, determine if sym == X, where X+Adjustment != V.
llvm::APSInt Adjusted = V-Adjustment;
if (const llvm::APSInt* X = getSymVal(state, sym)) {
bool isFeasible = (*X == Adjusted);
return isFeasible ? state : NULL;
}
// Second, determine if sym+Adjustment != V.
if (isNotEqual(state, sym, Adjusted))
return NULL;
// If we reach here, sym is not a constant and we don't know if it is == V.
// Make that assumption.
return AddEQ(state, sym, Adjusted);
}
// The logic for these will be handled in another ConstraintManager.
const GRState*
BasicConstraintManager::assumeSymLT(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
// Is 'V' the smallest possible value?
if (V == llvm::APSInt::getMinValue(V.getBitWidth(), V.isUnsigned())) {
// sym cannot be any value less than 'V'. This path is infeasible.
return NULL;
}
// FIXME: For now have assuming x < y be the same as assuming sym != V;
return assumeSymNE(state, sym, V, Adjustment);
}
const GRState*
BasicConstraintManager::assumeSymGT(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) {
// Is 'V' the largest possible value?
if (V == llvm::APSInt::getMaxValue(V.getBitWidth(), V.isUnsigned())) {
// sym cannot be any value greater than 'V'. This path is infeasible.
return NULL;
}
// FIXME: For now have assuming x > y be the same as assuming sym != V;
return assumeSymNE(state, sym, V, Adjustment);
}
const GRState*
BasicConstraintManager::assumeSymGE(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &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 = (*X >= V-Adjustment);
return isFeasible ? state : NULL;
}
// Sym is not a constant, but it is worth looking to see if V is the
// maximum integer value.
if (V == llvm::APSInt::getMaxValue(V.getBitWidth(), V.isUnsigned())) {
llvm::APSInt Adjusted = V-Adjustment;
// If we know that sym != V (after adjustment), then this condition
// is infeasible since there is no other value greater than V.
bool isFeasible = !isNotEqual(state, sym, Adjusted);
// If the path is still feasible then as a consequence we know that
// 'sym+Adjustment == V' because there are no larger values.
// Add this constraint.
return isFeasible ? AddEQ(state, sym, Adjusted) : NULL;
}
return state;
}
const GRState*
BasicConstraintManager::assumeSymLE(const GRState *state, SymbolRef sym,
const llvm::APSInt &V,
const llvm::APSInt &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 = (*X <= V-Adjustment);
return isFeasible ? state : NULL;
}
// Sym is not a constant, but it is worth looking to see if V is the
// minimum integer value.
if (V == llvm::APSInt::getMinValue(V.getBitWidth(), V.isUnsigned())) {
llvm::APSInt Adjusted = V-Adjustment;
// If we know that sym != V (after adjustment), then this condition
// is infeasible since there is no other value less than V.
bool isFeasible = !isNotEqual(state, sym, Adjusted);
// If the path is still feasible then as a consequence we know that
// 'sym+Adjustment == V' because there are no smaller values.
// Add this constraint.
return isFeasible ? AddEQ(state, sym, Adjusted) : NULL;
}
return state;
}
const GRState* BasicConstraintManager::AddEQ(const GRState* state, SymbolRef sym,
const llvm::APSInt& V) {
// Create a new state with the old binding replaced.
return state->set<ConstEq>(sym, &state->getBasicVals().getValue(V));
}
const GRState* BasicConstraintManager::AddNE(const GRState* 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);
GRState::IntSetTy S = T ? *T : ISetFactory.getEmptySet();
// Now add V to the NE set.
S = ISetFactory.add(S, &state->getBasicVals().getValue(V));
// Create a new state with the old binding replaced.
return state->set<ConstNotEq>(sym, S);
}
const llvm::APSInt* BasicConstraintManager::getSymVal(const GRState* state,
SymbolRef sym) const {
const ConstEqTy::data_type* T = state->get<ConstEq>(sym);
return T ? *T : NULL;
}
bool BasicConstraintManager::isNotEqual(const GRState* 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(&state->getBasicVals().getValue(V)) : false;
}
bool BasicConstraintManager::isEqual(const GRState* 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;
}
/// Scan all symbols referenced by the constraints. If the symbol is not alive
/// as marked in LSymbols, mark it as dead in DSymbols.
const GRState*
BasicConstraintManager::removeDeadBindings(const GRState* 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(const GRState* state, llvm::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;
GRState::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.
}
}
}
}