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//== RangeConstraintManager.cpp - Manage range 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 RangeConstraintManager, a class that tracks simple
// equality and inequality constraints on symbolic values of GRState.
//
//===----------------------------------------------------------------------===//
#include "SimpleConstraintManager.h"
#include "clang/Checker/PathSensitive/GRState.h"
#include "clang/Checker/PathSensitive/GRStateTrait.h"
#include "clang/Checker/PathSensitive/GRTransferFuncs.h"
#include "clang/Checker/ManagerRegistry.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableSet.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
namespace { class ConstraintRange {}; }
static int ConstraintRangeIndex = 0;
/// A Range represents the closed range [from, to]. The caller must
/// guarantee that from <= to. Note that Range is immutable, so as not
/// to subvert RangeSet's immutability.
namespace {
class Range : public std::pair<const llvm::APSInt*,
const llvm::APSInt*> {
public:
Range(const llvm::APSInt &from, const llvm::APSInt &to)
: std::pair<const llvm::APSInt*, const llvm::APSInt*>(&from, &to) {
assert(from <= to);
}
bool Includes(const llvm::APSInt &v) const {
return *first <= v && v <= *second;
}
const llvm::APSInt &From() const {
return *first;
}
const llvm::APSInt &To() const {
return *second;
}
const llvm::APSInt *getConcreteValue() const {
return &From() == &To() ? &From() : NULL;
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddPointer(&From());
ID.AddPointer(&To());
}
};
class RangeTrait : public llvm::ImutContainerInfo<Range> {
public:
// When comparing if one Range is less than another, we should compare
// the actual APSInt values instead of their pointers. This keeps the order
// consistent (instead of comparing by pointer values) and can potentially
// be used to speed up some of the operations in RangeSet.
static inline bool isLess(key_type_ref lhs, key_type_ref rhs) {
return *lhs.first < *rhs.first || (!(*rhs.first < *lhs.first) &&
*lhs.second < *rhs.second);
}
};
/// RangeSet contains a set of ranges. If the set is empty, then
/// there the value of a symbol is overly constrained and there are no
/// possible values for that symbol.
class RangeSet {
typedef llvm::ImmutableSet<Range, RangeTrait> PrimRangeSet;
PrimRangeSet ranges; // no need to make const, since it is an
// ImmutableSet - this allows default operator=
// to work.
public:
typedef PrimRangeSet::Factory Factory;
typedef PrimRangeSet::iterator iterator;
RangeSet(PrimRangeSet RS) : ranges(RS) {}
iterator begin() const { return ranges.begin(); }
iterator end() const { return ranges.end(); }
bool isEmpty() const { return ranges.isEmpty(); }
/// Construct a new RangeSet representing '{ [from, to] }'.
RangeSet(Factory &F, const llvm::APSInt &from, const llvm::APSInt &to)
: ranges(F.add(F.getEmptySet(), Range(from, to))) {}
/// Profile - Generates a hash profile of this RangeSet for use
/// by FoldingSet.
void Profile(llvm::FoldingSetNodeID &ID) const { ranges.Profile(ID); }
/// getConcreteValue - If a symbol is contrained to equal a specific integer
/// constant then this method returns that value. Otherwise, it returns
/// NULL.
const llvm::APSInt* getConcreteValue() const {
return ranges.isSingleton() ? ranges.begin()->getConcreteValue() : 0;
}
private:
void IntersectInRange(BasicValueFactory &BV, Factory &F,
const llvm::APSInt &Lower,
const llvm::APSInt &Upper,
PrimRangeSet &newRanges,
PrimRangeSet::iterator &i,
PrimRangeSet::iterator &e) const {
// There are six cases for each range R in the set:
// 1. R is entirely before the intersection range.
// 2. R is entirely after the intersection range.
// 3. R contains the entire intersection range.
// 4. R starts before the intersection range and ends in the middle.
// 5. R starts in the middle of the intersection range and ends after it.
// 6. R is entirely contained in the intersection range.
// These correspond to each of the conditions below.
for (/* i = begin(), e = end() */; i != e; ++i) {
if (i->To() < Lower) {
continue;
}
if (i->From() > Upper) {
break;
}
if (i->Includes(Lower)) {
if (i->Includes(Upper)) {
newRanges = F.add(newRanges, Range(BV.getValue(Lower),
BV.getValue(Upper)));
break;
} else
newRanges = F.add(newRanges, Range(BV.getValue(Lower), i->To()));
} else {
if (i->Includes(Upper)) {
newRanges = F.add(newRanges, Range(i->From(), BV.getValue(Upper)));
break;
} else
newRanges = F.add(newRanges, *i);
}
}
}
public:
// Returns a set containing the values in the receiving set, intersected with
// the closed range [Lower, Upper]. Unlike the Range type, this range uses
// modular arithmetic, corresponding to the common treatment of C integer
// overflow. Thus, if the Lower bound is greater than the Upper bound, the
// range is taken to wrap around. This is equivalent to taking the
// intersection with the two ranges [Min, Upper] and [Lower, Max],
// or, alternatively, /removing/ all integers between Upper and Lower.
RangeSet Intersect(BasicValueFactory &BV, Factory &F,
const llvm::APSInt &Lower,
const llvm::APSInt &Upper) const {
PrimRangeSet newRanges = F.getEmptySet();
PrimRangeSet::iterator i = begin(), e = end();
if (Lower <= Upper)
IntersectInRange(BV, F, Lower, Upper, newRanges, i, e);
else {
// The order of the next two statements is important!
// IntersectInRange() does not reset the iteration state for i and e.
// Therefore, the lower range most be handled first.
IntersectInRange(BV, F, BV.getMinValue(Upper), Upper, newRanges, i, e);
IntersectInRange(BV, F, Lower, BV.getMaxValue(Lower), newRanges, i, e);
}
return newRanges;
}
void print(llvm::raw_ostream &os) const {
bool isFirst = true;
os << "{ ";
for (iterator i = begin(), e = end(); i != e; ++i) {
if (isFirst)
isFirst = false;
else
os << ", ";
os << '[' << i->From().toString(10) << ", " << i->To().toString(10)
<< ']';
}
os << " }";
}
bool operator==(const RangeSet &other) const {
return ranges == other.ranges;
}
};
} // end anonymous namespace
typedef llvm::ImmutableMap<SymbolRef,RangeSet> ConstraintRangeTy;
namespace clang {
template<>
struct GRStateTrait<ConstraintRange>
: public GRStatePartialTrait<ConstraintRangeTy> {
static inline void* GDMIndex() { return &ConstraintRangeIndex; }
};
}
namespace {
class RangeConstraintManager : public SimpleConstraintManager{
RangeSet GetRange(const GRState *state, SymbolRef sym);
public:
RangeConstraintManager(GRSubEngine &subengine)
: SimpleConstraintManager(subengine) {}
const GRState* AssumeSymNE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const GRState* AssumeSymEQ(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const GRState* AssumeSymLT(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const GRState* AssumeSymGT(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const GRState* AssumeSymGE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const GRState* AssumeSymLE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment);
const llvm::APSInt* getSymVal(const GRState* St, SymbolRef sym) const;
// FIXME: Refactor into SimpleConstraintManager?
bool isEqual(const GRState* St, SymbolRef sym, const llvm::APSInt& V) const {
const llvm::APSInt *i = getSymVal(St, sym);
return i ? *i == V : false;
}
const GRState* RemoveDeadBindings(const GRState* St, SymbolReaper& SymReaper);
void print(const GRState* St, llvm::raw_ostream& Out,
const char* nl, const char *sep);
private:
RangeSet::Factory F;
};
} // end anonymous namespace
ConstraintManager* clang::CreateRangeConstraintManager(GRStateManager&,
GRSubEngine &subeng) {
return new RangeConstraintManager(subeng);
}
const llvm::APSInt* RangeConstraintManager::getSymVal(const GRState* St,
SymbolRef sym) const {
const ConstraintRangeTy::data_type *T = St->get<ConstraintRange>(sym);
return T ? T->getConcreteValue() : NULL;
}
/// 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*
RangeConstraintManager::RemoveDeadBindings(const GRState* state,
SymbolReaper& SymReaper) {
ConstraintRangeTy CR = state->get<ConstraintRange>();
ConstraintRangeTy::Factory& CRFactory = state->get_context<ConstraintRange>();
for (ConstraintRangeTy::iterator I = CR.begin(), E = CR.end(); I != E; ++I) {
SymbolRef sym = I.getKey();
if (SymReaper.maybeDead(sym))
CR = CRFactory.remove(CR, sym);
}
return state->set<ConstraintRange>(CR);
}
RangeSet
RangeConstraintManager::GetRange(const GRState *state, SymbolRef sym) {
if (ConstraintRangeTy::data_type* V = state->get<ConstraintRange>(sym))
return *V;
// Lazily generate a new RangeSet representing all possible values for the
// given symbol type.
QualType T = state->getSymbolManager().getType(sym);
BasicValueFactory& BV = state->getBasicVals();
return RangeSet(F, BV.getMinValue(T), BV.getMaxValue(T));
}
//===------------------------------------------------------------------------===
// AssumeSymX methods: public interface for RangeConstraintManager.
//===------------------------------------------------------------------------===/
// The syntax for ranges below is mathematical, using [x, y] for closed ranges
// and (x, y) for open ranges. These ranges are modular, corresponding with
// a common treatment of C integer overflow. This means that these methods
// do not have to worry about overflow; RangeSet::Intersect can handle such a
// "wraparound" range.
// As an example, the range [UINT_MAX-1, 3) contains five values: UINT_MAX-1,
// UINT_MAX, 0, 1, and 2.
const GRState*
RangeConstraintManager::AssumeSymNE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
BasicValueFactory &BV = state->getBasicVals();
llvm::APSInt Lower = Int-Adjustment;
llvm::APSInt Upper = Lower;
--Lower;
++Upper;
// [Int-Adjustment+1, Int-Adjustment-1]
// Notice that the lower bound is greater than the upper bound.
RangeSet New = GetRange(state, sym).Intersect(BV, F, Upper, Lower);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
const GRState*
RangeConstraintManager::AssumeSymEQ(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
// [Int-Adjustment, Int-Adjustment]
BasicValueFactory &BV = state->getBasicVals();
llvm::APSInt AdjInt = Int-Adjustment;
RangeSet New = GetRange(state, sym).Intersect(BV, F, AdjInt, AdjInt);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
const GRState*
RangeConstraintManager::AssumeSymLT(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
BasicValueFactory &BV = state->getBasicVals();
QualType T = state->getSymbolManager().getType(sym);
const llvm::APSInt &Min = BV.getMinValue(T);
// Special case for Int == Min. This is always false.
if (Int == Min)
return NULL;
llvm::APSInt Lower = Min-Adjustment;
llvm::APSInt Upper = Int-Adjustment;
--Upper;
RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
const GRState*
RangeConstraintManager::AssumeSymGT(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
BasicValueFactory &BV = state->getBasicVals();
QualType T = state->getSymbolManager().getType(sym);
const llvm::APSInt &Max = BV.getMaxValue(T);
// Special case for Int == Max. This is always false.
if (Int == Max)
return NULL;
llvm::APSInt Lower = Int-Adjustment;
llvm::APSInt Upper = Max-Adjustment;
++Lower;
RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
const GRState*
RangeConstraintManager::AssumeSymGE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
BasicValueFactory &BV = state->getBasicVals();
QualType T = state->getSymbolManager().getType(sym);
const llvm::APSInt &Min = BV.getMinValue(T);
// Special case for Int == Min. This is always feasible.
if (Int == Min)
return state;
const llvm::APSInt &Max = BV.getMaxValue(T);
llvm::APSInt Lower = Int-Adjustment;
llvm::APSInt Upper = Max-Adjustment;
RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
const GRState*
RangeConstraintManager::AssumeSymLE(const GRState* state, SymbolRef sym,
const llvm::APSInt& Int,
const llvm::APSInt& Adjustment) {
BasicValueFactory &BV = state->getBasicVals();
QualType T = state->getSymbolManager().getType(sym);
const llvm::APSInt &Max = BV.getMaxValue(T);
// Special case for Int == Max. This is always feasible.
if (Int == Max)
return state;
const llvm::APSInt &Min = BV.getMinValue(T);
llvm::APSInt Lower = Min-Adjustment;
llvm::APSInt Upper = Int-Adjustment;
RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
}
//===------------------------------------------------------------------------===
// Pretty-printing.
//===------------------------------------------------------------------------===/
void RangeConstraintManager::print(const GRState* St, llvm::raw_ostream& Out,
const char* nl, const char *sep) {
ConstraintRangeTy Ranges = St->get<ConstraintRange>();
if (Ranges.isEmpty())
return;
Out << nl << sep << "ranges of symbol values:";
for (ConstraintRangeTy::iterator I=Ranges.begin(), E=Ranges.end(); I!=E; ++I){
Out << nl << ' ' << I.getKey() << " : ";
I.getData().print(Out);
}
}