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llvm-project/clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
Valeriy Savchenko 2a09daff0f [analyzer] Generalize bitwise AND rules for ranges 
Summary:
Previously the current solver started reasoning about bitwise AND
expressions only when one of the operands is a constant.  However,
very similar logic could be applied to ranges.  This commit addresses
this shortcoming.  Additionally, it refines how we deal with negative
operands.

rdar://problem/54359410

Differential Revision: https://reviews.llvm.org/D79434
2020-05-28 18:55:49 +03:00

1106 lines
41 KiB
C++
Raw Blame History

//== RangeConstraintManager.cpp - Manage range constraints.------*- C++ -*--==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines RangeConstraintManager, a class that tracks simple
// equality and inequality constraints on symbolic values of ProgramState.
//
//===----------------------------------------------------------------------===//
#include "clang/Basic/JsonSupport.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/RangedConstraintManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableSet.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
//===----------------------------------------------------------------------===//
// RangeSet implementation
//===----------------------------------------------------------------------===//
void RangeSet::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);
}
}
}
const llvm::APSInt &RangeSet::getMinValue() const {
assert(!isEmpty());
return begin()->From();
}
const llvm::APSInt &RangeSet::getMaxValue() const {
assert(!isEmpty());
// NOTE: It's a shame that we can't implement 'getMaxValue' without scanning
// the whole tree to get to the last element.
// llvm::ImmutableSet should support decrement for 'end' iterators
// or reverse order iteration.
auto It = begin();
for (auto End = end(); std::next(It) != End; ++It) {
}
return It->To();
}
bool RangeSet::pin(llvm::APSInt &Lower, llvm::APSInt &Upper) const {
if (isEmpty()) {
// This range is already infeasible.
return false;
}
// This function has nine cases, the cartesian product of range-testing
// both the upper and lower bounds against the symbol's type.
// Each case requires a different pinning operation.
// The function returns false if the described range is entirely outside
// the range of values for the associated symbol.
APSIntType Type(getMinValue());
APSIntType::RangeTestResultKind LowerTest = Type.testInRange(Lower, true);
APSIntType::RangeTestResultKind UpperTest = Type.testInRange(Upper, true);
switch (LowerTest) {
case APSIntType::RTR_Below:
switch (UpperTest) {
case APSIntType::RTR_Below:
// The entire range is outside the symbol's set of possible values.
// If this is a conventionally-ordered range, the state is infeasible.
if (Lower <= Upper)
return false;
// However, if the range wraps around, it spans all possible values.
Lower = Type.getMinValue();
Upper = Type.getMaxValue();
break;
case APSIntType::RTR_Within:
// The range starts below what's possible but ends within it. Pin.
Lower = Type.getMinValue();
Type.apply(Upper);
break;
case APSIntType::RTR_Above:
// The range spans all possible values for the symbol. Pin.
Lower = Type.getMinValue();
Upper = Type.getMaxValue();
break;
}
break;
case APSIntType::RTR_Within:
switch (UpperTest) {
case APSIntType::RTR_Below:
// The range wraps around, but all lower values are not possible.
Type.apply(Lower);
Upper = Type.getMaxValue();
break;
case APSIntType::RTR_Within:
// The range may or may not wrap around, but both limits are valid.
Type.apply(Lower);
Type.apply(Upper);
break;
case APSIntType::RTR_Above:
// The range starts within what's possible but ends above it. Pin.
Type.apply(Lower);
Upper = Type.getMaxValue();
break;
}
break;
case APSIntType::RTR_Above:
switch (UpperTest) {
case APSIntType::RTR_Below:
// The range wraps but is outside the symbol's set of possible values.
return false;
case APSIntType::RTR_Within:
// The range starts above what's possible but ends within it (wrap).
Lower = Type.getMinValue();
Type.apply(Upper);
break;
case APSIntType::RTR_Above:
// The entire range is outside the symbol's set of possible values.
// If this is a conventionally-ordered range, the state is infeasible.
if (Lower <= Upper)
return false;
// However, if the range wraps around, it spans all possible values.
Lower = Type.getMinValue();
Upper = Type.getMaxValue();
break;
}
break;
}
return true;
}
// 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 RangeSet::Intersect(BasicValueFactory &BV, Factory &F,
llvm::APSInt Lower, llvm::APSInt Upper) const {
PrimRangeSet newRanges = F.getEmptySet();
if (isEmpty() || !pin(Lower, Upper))
return newRanges;
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;
}
// Returns a set containing the values in the receiving set, intersected with
// the range set passed as parameter.
RangeSet RangeSet::Intersect(BasicValueFactory &BV, Factory &F,
const RangeSet &Other) const {
PrimRangeSet newRanges = F.getEmptySet();
for (iterator i = Other.begin(), e = Other.end(); i != e; ++i) {
RangeSet newPiece = Intersect(BV, F, i->From(), i->To());
for (iterator j = newPiece.begin(), ee = newPiece.end(); j != ee; ++j) {
newRanges = F.add(newRanges, *j);
}
}
return newRanges;
}
// Turn all [A, B] ranges to [-B, -A], when "-" is a C-like unary minus
// operation under the values of the type.
//
// We also handle MIN because applying unary minus to MIN does not change it.
// Example 1:
// char x = -128; // -128 is a MIN value in a range of 'char'
// char y = -x; // y: -128
// Example 2:
// unsigned char x = 0; // 0 is a MIN value in a range of 'unsigned char'
// unsigned char y = -x; // y: 0
//
// And it makes us to separate the range
// like [MIN, N] to [MIN, MIN] U [-N,MAX].
// For instance, whole range is {-128..127} and subrange is [-128,-126],
// thus [-128,-127,-126,.....] negates to [-128,.....,126,127].
//
// Negate restores disrupted ranges on bounds,
// e.g. [MIN, B] => [MIN, MIN] U [-B, MAX] => [MIN, B].
RangeSet RangeSet::Negate(BasicValueFactory &BV, Factory &F) const {
PrimRangeSet newRanges = F.getEmptySet();
if (isEmpty())
return newRanges;
const llvm::APSInt sampleValue = getMinValue();
const llvm::APSInt &MIN = BV.getMinValue(sampleValue);
const llvm::APSInt &MAX = BV.getMaxValue(sampleValue);
// Handle a special case for MIN value.
iterator i = begin();
const llvm::APSInt &from = i->From();
const llvm::APSInt &to = i->To();
if (from == MIN) {
// If [from, to] are [MIN, MAX], then just return the same [MIN, MAX].
if (to == MAX) {
newRanges = ranges;
} else {
// Add separate range for the lowest value.
newRanges = F.add(newRanges, Range(MIN, MIN));
// Skip adding the second range in case when [from, to] are [MIN, MIN].
if (to != MIN) {
newRanges = F.add(newRanges, Range(BV.getValue(-to), MAX));
}
}
// Skip the first range in the loop.
++i;
}
// Negate all other ranges.
for (iterator e = end(); i != e; ++i) {
// Negate int values.
const llvm::APSInt &newFrom = BV.getValue(-i->To());
const llvm::APSInt &newTo = BV.getValue(-i->From());
// Add a negated range.
newRanges = F.add(newRanges, Range(newFrom, newTo));
}
if (newRanges.isSingleton())
return newRanges;
// Try to find and unite next ranges:
// [MIN, MIN] & [MIN + 1, N] => [MIN, N].
iterator iter1 = newRanges.begin();
iterator iter2 = std::next(iter1);
if (iter1->To() == MIN && (iter2->From() - 1) == MIN) {
const llvm::APSInt &to = iter2->To();
// remove adjacent ranges
newRanges = F.remove(newRanges, *iter1);
newRanges = F.remove(newRanges, *newRanges.begin());
// add united range
newRanges = F.add(newRanges, Range(MIN, to));
}
return newRanges;
}
void RangeSet::print(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 << " }";
}
namespace {
/// A little component aggregating all of the reasoning we have about
/// the ranges of symbolic expressions.
///
/// Even when we don't know the exact values of the operands, we still
/// can get a pretty good estimate of the result's range.
class SymbolicRangeInferrer
: public SymExprVisitor<SymbolicRangeInferrer, RangeSet> {
public:
static RangeSet inferRange(BasicValueFactory &BV, RangeSet::Factory &F,
ProgramStateRef State, SymbolRef Sym) {
SymbolicRangeInferrer Inferrer(BV, F, State);
return Inferrer.infer(Sym);
}
RangeSet VisitSymExpr(SymbolRef Sym) {
// If we got to this function, the actual type of the symbolic
// expression is not supported for advanced inference.
// In this case, we simply backoff to the default "let's simply
// infer the range from the expression's type".
return infer(Sym->getType());
}
RangeSet VisitSymIntExpr(const SymIntExpr *Sym) {
return VisitBinaryOperator(Sym);
}
RangeSet VisitIntSymExpr(const IntSymExpr *Sym) {
return VisitBinaryOperator(Sym);
}
RangeSet VisitSymSymExpr(const SymSymExpr *Sym) {
return VisitBinaryOperator(Sym);
}
private:
SymbolicRangeInferrer(BasicValueFactory &BV, RangeSet::Factory &F,
ProgramStateRef S)
: ValueFactory(BV), RangeFactory(F), State(S) {}
/// Infer range information from the given integer constant.
///
/// It's not a real "inference", but is here for operating with
/// sub-expressions in a more polymorphic manner.
RangeSet inferAs(const llvm::APSInt &Val, QualType) {
return {RangeFactory, Val};
}
/// Infer range information from symbol in the context of the given type.
RangeSet inferAs(SymbolRef Sym, QualType DestType) {
QualType ActualType = Sym->getType();
// Check that we can reason about the symbol at all.
if (ActualType->isIntegralOrEnumerationType() ||
Loc::isLocType(ActualType)) {
return infer(Sym);
}
// Otherwise, let's simply infer from the destination type.
// We couldn't figure out nothing else about that expression.
return infer(DestType);
}
RangeSet infer(SymbolRef Sym) {
const RangeSet *AssociatedRange = State->get<ConstraintRange>(Sym);
// If Sym is a difference of symbols A - B, then maybe we have range set
// stored for B - A.
const RangeSet *RangeAssociatedWithNegatedSym =
getRangeForMinusSymbol(State, Sym);
// If we have range set stored for both A - B and B - A then calculate the
// effective range set by intersecting the range set for A - B and the
// negated range set of B - A.
if (AssociatedRange && RangeAssociatedWithNegatedSym)
return AssociatedRange->Intersect(
ValueFactory, RangeFactory,
RangeAssociatedWithNegatedSym->Negate(ValueFactory, RangeFactory));
if (AssociatedRange)
return *AssociatedRange;
if (RangeAssociatedWithNegatedSym)
return RangeAssociatedWithNegatedSym->Negate(ValueFactory, RangeFactory);
return Visit(Sym);
}
/// Infer range information solely from the type.
RangeSet infer(QualType T) {
// Lazily generate a new RangeSet representing all possible values for the
// given symbol type.
RangeSet Result(RangeFactory, ValueFactory.getMinValue(T),
ValueFactory.getMaxValue(T));
// References are known to be non-zero.
if (T->isReferenceType())
return assumeNonZero(Result, T);
return Result;
}
template <class BinarySymExprTy>
RangeSet VisitBinaryOperator(const BinarySymExprTy *Sym) {
// TODO #1: VisitBinaryOperator implementation might not make a good
// use of the inferred ranges. In this case, we might be calculating
// everything for nothing. This being said, we should introduce some
// sort of laziness mechanism here.
//
// TODO #2: We didn't go into the nested expressions before, so it
// might cause us spending much more time doing the inference.
// This can be a problem for deeply nested expressions that are
// involved in conditions and get tested continuously. We definitely
// need to address this issue and introduce some sort of caching
// in here.
QualType ResultType = Sym->getType();
return VisitBinaryOperator(inferAs(Sym->getLHS(), ResultType),
Sym->getOpcode(),
inferAs(Sym->getRHS(), ResultType), ResultType);
}
RangeSet VisitBinaryOperator(RangeSet LHS, BinaryOperator::Opcode Op,
RangeSet RHS, QualType T) {
switch (Op) {
case BO_Or:
return VisitBinaryOperator<BO_Or>(LHS, RHS, T);
case BO_And:
return VisitBinaryOperator<BO_And>(LHS, RHS, T);
default:
return infer(T);
}
}
//===----------------------------------------------------------------------===//
// Ranges and operators
//===----------------------------------------------------------------------===//
/// Return a rough approximation of the given range set.
///
/// For the range set:
/// { [x_0, y_0], [x_1, y_1], ... , [x_N, y_N] }
/// it will return the range [x_0, y_N].
static Range fillGaps(RangeSet Origin) {
assert(!Origin.isEmpty());
return {Origin.getMinValue(), Origin.getMaxValue()};
}
/// Try to convert given range into the given type.
///
/// It will return llvm::None only when the trivial conversion is possible.
llvm::Optional<Range> convert(const Range &Origin, APSIntType To) {
if (To.testInRange(Origin.From(), false) != APSIntType::RTR_Within ||
To.testInRange(Origin.To(), false) != APSIntType::RTR_Within) {
return llvm::None;
}
return Range(ValueFactory.Convert(To, Origin.From()),
ValueFactory.Convert(To, Origin.To()));
}
template <BinaryOperator::Opcode Op>
RangeSet VisitBinaryOperator(RangeSet LHS, RangeSet RHS, QualType T) {
// We should propagate information about unfeasbility of one of the
// operands to the resulting range.
if (LHS.isEmpty() || RHS.isEmpty()) {
return RangeFactory.getEmptySet();
}
Range CoarseLHS = fillGaps(LHS);
Range CoarseRHS = fillGaps(RHS);
APSIntType ResultType = ValueFactory.getAPSIntType(T);
// We need to convert ranges to the resulting type, so we can compare values
// and combine them in a meaningful (in terms of the given operation) way.
auto ConvertedCoarseLHS = convert(CoarseLHS, ResultType);
auto ConvertedCoarseRHS = convert(CoarseRHS, ResultType);
// It is hard to reason about ranges when conversion changes
// borders of the ranges.
if (!ConvertedCoarseLHS || !ConvertedCoarseRHS) {
return infer(T);
}
return VisitBinaryOperator<Op>(*ConvertedCoarseLHS, *ConvertedCoarseRHS, T);
}
template <BinaryOperator::Opcode Op>
RangeSet VisitBinaryOperator(Range LHS, Range RHS, QualType T) {
return infer(T);
}
/// Return a range set subtracting zero from \p Domain.
RangeSet assumeNonZero(RangeSet Domain, QualType T) {
APSIntType IntType = ValueFactory.getAPSIntType(T);
return Domain.Intersect(ValueFactory, RangeFactory,
++IntType.getZeroValue(), --IntType.getZeroValue());
}
// FIXME: Once SValBuilder supports unary minus, we should use SValBuilder to
// obtain the negated symbolic expression instead of constructing the
// symbol manually. This will allow us to support finding ranges of not
// only negated SymSymExpr-type expressions, but also of other, simpler
// expressions which we currently do not know how to negate.
const RangeSet *getRangeForMinusSymbol(ProgramStateRef State, SymbolRef Sym) {
if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(Sym)) {
if (SSE->getOpcode() == BO_Sub) {
QualType T = Sym->getType();
SymbolManager &SymMgr = State->getSymbolManager();
SymbolRef negSym =
SymMgr.getSymSymExpr(SSE->getRHS(), BO_Sub, SSE->getLHS(), T);
if (const RangeSet *negV = State->get<ConstraintRange>(negSym)) {
// Unsigned range set cannot be negated, unless it is [0, 0].
if (T->isUnsignedIntegerOrEnumerationType() ||
T->isSignedIntegerOrEnumerationType())
return negV;
}
}
}
return nullptr;
}
BasicValueFactory &ValueFactory;
RangeSet::Factory &RangeFactory;
ProgramStateRef State;
};
template <>
RangeSet SymbolicRangeInferrer::VisitBinaryOperator<BO_Or>(Range LHS, Range RHS,
QualType T) {
APSIntType ResultType = ValueFactory.getAPSIntType(T);
llvm::APSInt Zero = ResultType.getZeroValue();
bool IsLHSPositiveOrZero = LHS.From() >= Zero;
bool IsRHSPositiveOrZero = RHS.From() >= Zero;
bool IsLHSNegative = LHS.To() < Zero;
bool IsRHSNegative = RHS.To() < Zero;
// Check if both ranges have the same sign.
if ((IsLHSPositiveOrZero && IsRHSPositiveOrZero) ||
(IsLHSNegative && IsRHSNegative)) {
// The result is definitely greater or equal than any of the operands.
const llvm::APSInt &Min = std::max(LHS.From(), RHS.From());
// We estimate maximal value for positives as the maximal value for the
// given type. For negatives, we estimate it with -1 (e.g. 0x11111111).
//
// TODO: We basically, limit the resulting range from below, but don't do
// anything with the upper bound.
//
// For positive operands, it can be done as follows: for the upper
// bound of LHS and RHS we calculate the most significant bit set.
// Let's call it the N-th bit. Then we can estimate the maximal
// number to be 2^(N+1)-1, i.e. the number with all the bits up to
// the N-th bit set.
const llvm::APSInt &Max = IsLHSNegative
? ValueFactory.getValue(--Zero)
: ValueFactory.getMaxValue(ResultType);
return {RangeFactory, ValueFactory.getValue(Min), Max};
}
// Otherwise, let's check if at least one of the operands is negative.
if (IsLHSNegative || IsRHSNegative) {
// This means that the result is definitely negative as well.
return {RangeFactory, ValueFactory.getMinValue(ResultType),
ValueFactory.getValue(--Zero)};
}
RangeSet DefaultRange = infer(T);
// It is pretty hard to reason about operands with different signs
// (and especially with possibly different signs). We simply check if it
// can be zero. In order to conclude that the result could not be zero,
// at least one of the operands should be definitely not zero itself.
if (!LHS.Includes(Zero) || !RHS.Includes(Zero)) {
return assumeNonZero(DefaultRange, T);
}
// Nothing much else to do here.
return DefaultRange;
}
template <>
RangeSet SymbolicRangeInferrer::VisitBinaryOperator<BO_And>(Range LHS,
Range RHS,
QualType T) {
APSIntType ResultType = ValueFactory.getAPSIntType(T);
llvm::APSInt Zero = ResultType.getZeroValue();
bool IsLHSPositiveOrZero = LHS.From() >= Zero;
bool IsRHSPositiveOrZero = RHS.From() >= Zero;
bool IsLHSNegative = LHS.To() < Zero;
bool IsRHSNegative = RHS.To() < Zero;
// Check if both ranges have the same sign.
if ((IsLHSPositiveOrZero && IsRHSPositiveOrZero) ||
(IsLHSNegative && IsRHSNegative)) {
// The result is definitely less or equal than any of the operands.
const llvm::APSInt &Max = std::min(LHS.To(), RHS.To());
// We conservatively estimate lower bound to be the smallest positive
// or negative value corresponding to the sign of the operands.
const llvm::APSInt &Min = IsLHSNegative
? ValueFactory.getMinValue(ResultType)
: ValueFactory.getValue(Zero);
return {RangeFactory, Min, Max};
}
// Otherwise, let's check if at least one of the operands is positive.
if (IsLHSPositiveOrZero || IsRHSPositiveOrZero) {
// This makes result definitely positive.
//
// We can also reason about a maximal value by finding the maximal
// value of the positive operand.
const llvm::APSInt &Max = IsLHSPositiveOrZero ? LHS.To() : RHS.To();
// The minimal value on the other hand is much harder to reason about.
// The only thing we know for sure is that the result is positive.
return {RangeFactory, ValueFactory.getValue(Zero),
ValueFactory.getValue(Max)};
}
// Nothing much else to do here.
return infer(T);
}
class RangeConstraintManager : public RangedConstraintManager {
public:
RangeConstraintManager(ExprEngine *EE, SValBuilder &SVB)
: RangedConstraintManager(EE, SVB) {}
//===------------------------------------------------------------------===//
// Implementation for interface from ConstraintManager.
//===------------------------------------------------------------------===//
bool haveEqualConstraints(ProgramStateRef S1,
ProgramStateRef S2) const override {
return S1->get<ConstraintRange>() == S2->get<ConstraintRange>();
}
bool canReasonAbout(SVal X) const override;
ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym) override;
const llvm::APSInt *getSymVal(ProgramStateRef State,
SymbolRef Sym) const override;
ProgramStateRef removeDeadBindings(ProgramStateRef State,
SymbolReaper &SymReaper) override;
void printJson(raw_ostream &Out, ProgramStateRef State, const char *NL = "\n",
unsigned int Space = 0, bool IsDot = false) const override;
//===------------------------------------------------------------------===//
// Implementation for interface from RangedConstraintManager.
//===------------------------------------------------------------------===//
ProgramStateRef assumeSymNE(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymEQ(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymLT(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymGT(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymLE(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymGE(ProgramStateRef State, SymbolRef Sym,
const llvm::APSInt &V,
const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymWithinInclusiveRange(
ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From,
const llvm::APSInt &To, const llvm::APSInt &Adjustment) override;
ProgramStateRef assumeSymOutsideInclusiveRange(
ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From,
const llvm::APSInt &To, const llvm::APSInt &Adjustment) override;
private:
RangeSet::Factory F;
RangeSet getRange(ProgramStateRef State, SymbolRef Sym);
const RangeSet *getRangeForMinusSymbol(ProgramStateRef State, SymbolRef Sym);
RangeSet getSymLTRange(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment);
RangeSet getSymGTRange(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment);
RangeSet getSymLERange(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment);
RangeSet getSymLERange(llvm::function_ref<RangeSet()> RS,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment);
RangeSet getSymGERange(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment);
};
} // end anonymous namespace
std::unique_ptr<ConstraintManager>
ento::CreateRangeConstraintManager(ProgramStateManager &StMgr,
ExprEngine *Eng) {
return std::make_unique<RangeConstraintManager>(Eng, StMgr.getSValBuilder());
}
bool RangeConstraintManager::canReasonAbout(SVal X) const {
Optional<nonloc::SymbolVal> SymVal = X.getAs<nonloc::SymbolVal>();
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;
}
}
if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(SE)) {
// FIXME: Handle <=> here.
if (BinaryOperator::isEqualityOp(SSE->getOpcode()) ||
BinaryOperator::isRelationalOp(SSE->getOpcode())) {
// We handle Loc <> Loc comparisons, but not (yet) NonLoc <> NonLoc.
// We've recently started producing Loc <> NonLoc comparisons (that
// result from casts of one of the operands between eg. intptr_t and
// void *), but we can't reason about them yet.
if (Loc::isLocType(SSE->getLHS()->getType())) {
return Loc::isLocType(SSE->getRHS()->getType());
}
}
}
return false;
}
return true;
}
ConditionTruthVal RangeConstraintManager::checkNull(ProgramStateRef State,
SymbolRef Sym) {
const RangeSet *Ranges = State->get<ConstraintRange>(Sym);
// If we don't have any information about this symbol, it's underconstrained.
if (!Ranges)
return ConditionTruthVal();
// If we have a concrete value, see if it's zero.
if (const llvm::APSInt *Value = Ranges->getConcreteValue())
return *Value == 0;
BasicValueFactory &BV = getBasicVals();
APSIntType IntType = BV.getAPSIntType(Sym->getType());
llvm::APSInt Zero = IntType.getZeroValue();
// Check if zero is in the set of possible values.
if (Ranges->Intersect(BV, F, Zero, Zero).isEmpty())
return false;
// Zero is a possible value, but it is not the /only/ possible value.
return ConditionTruthVal();
}
const llvm::APSInt *RangeConstraintManager::getSymVal(ProgramStateRef St,
SymbolRef Sym) const {
const ConstraintRangeTy::data_type *T = St->get<ConstraintRange>(Sym);
return T ? T->getConcreteValue() : nullptr;
}
/// Scan all symbols referenced by the constraints. If the symbol is not alive
/// as marked in LSymbols, mark it as dead in DSymbols.
ProgramStateRef
RangeConstraintManager::removeDeadBindings(ProgramStateRef State,
SymbolReaper &SymReaper) {
bool Changed = false;
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.isDead(Sym)) {
Changed = true;
CR = CRFactory.remove(CR, Sym);
}
}
return Changed ? State->set<ConstraintRange>(CR) : State;
}
RangeSet RangeConstraintManager::getRange(ProgramStateRef State,
SymbolRef Sym) {
return SymbolicRangeInferrer::inferRange(getBasicVals(), F, State, Sym);
}
// FIXME: Once SValBuilder supports unary minus, we should use SValBuilder to
// obtain the negated symbolic expression instead of constructing the
// symbol manually. This will allow us to support finding ranges of not
// only negated SymSymExpr-type expressions, but also of other, simpler
// expressions which we currently do not know how to negate.
const RangeSet*
RangeConstraintManager::getRangeForMinusSymbol(ProgramStateRef State,
SymbolRef Sym) {
if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(Sym)) {
if (SSE->getOpcode() == BO_Sub) {
QualType T = Sym->getType();
SymbolManager &SymMgr = State->getSymbolManager();
SymbolRef negSym = SymMgr.getSymSymExpr(SSE->getRHS(), BO_Sub,
SSE->getLHS(), T);
if (const RangeSet *negV = State->get<ConstraintRange>(negSym)) {
if (T->isUnsignedIntegerOrEnumerationType() ||
T->isSignedIntegerOrEnumerationType())
return negV;
}
}
}
return nullptr;
}
//===------------------------------------------------------------------------===
// assumeSymX methods: protected 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.
ProgramStateRef
RangeConstraintManager::assumeSymNE(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
if (AdjustmentType.testInRange(Int, true) != APSIntType::RTR_Within)
return St;
llvm::APSInt Lower = AdjustmentType.convert(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(St, Sym).Intersect(getBasicVals(), F, Upper, Lower);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
ProgramStateRef
RangeConstraintManager::assumeSymEQ(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
if (AdjustmentType.testInRange(Int, true) != APSIntType::RTR_Within)
return nullptr;
// [Int-Adjustment, Int-Adjustment]
llvm::APSInt AdjInt = AdjustmentType.convert(Int) - Adjustment;
RangeSet New = getRange(St, Sym).Intersect(getBasicVals(), F, AdjInt, AdjInt);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
RangeSet RangeConstraintManager::getSymLTRange(ProgramStateRef St,
SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
switch (AdjustmentType.testInRange(Int, true)) {
case APSIntType::RTR_Below:
return F.getEmptySet();
case APSIntType::RTR_Within:
break;
case APSIntType::RTR_Above:
return getRange(St, Sym);
}
// Special case for Int == Min. This is always false.
llvm::APSInt ComparisonVal = AdjustmentType.convert(Int);
llvm::APSInt Min = AdjustmentType.getMinValue();
if (ComparisonVal == Min)
return F.getEmptySet();
llvm::APSInt Lower = Min - Adjustment;
llvm::APSInt Upper = ComparisonVal - Adjustment;
--Upper;
return getRange(St, Sym).Intersect(getBasicVals(), F, Lower, Upper);
}
ProgramStateRef
RangeConstraintManager::assumeSymLT(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
RangeSet New = getSymLTRange(St, Sym, Int, Adjustment);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
RangeSet RangeConstraintManager::getSymGTRange(ProgramStateRef St,
SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
switch (AdjustmentType.testInRange(Int, true)) {
case APSIntType::RTR_Below:
return getRange(St, Sym);
case APSIntType::RTR_Within:
break;
case APSIntType::RTR_Above:
return F.getEmptySet();
}
// Special case for Int == Max. This is always false.
llvm::APSInt ComparisonVal = AdjustmentType.convert(Int);
llvm::APSInt Max = AdjustmentType.getMaxValue();
if (ComparisonVal == Max)
return F.getEmptySet();
llvm::APSInt Lower = ComparisonVal - Adjustment;
llvm::APSInt Upper = Max - Adjustment;
++Lower;
return getRange(St, Sym).Intersect(getBasicVals(), F, Lower, Upper);
}
ProgramStateRef
RangeConstraintManager::assumeSymGT(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
RangeSet New = getSymGTRange(St, Sym, Int, Adjustment);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
RangeSet RangeConstraintManager::getSymGERange(ProgramStateRef St,
SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
switch (AdjustmentType.testInRange(Int, true)) {
case APSIntType::RTR_Below:
return getRange(St, Sym);
case APSIntType::RTR_Within:
break;
case APSIntType::RTR_Above:
return F.getEmptySet();
}
// Special case for Int == Min. This is always feasible.
llvm::APSInt ComparisonVal = AdjustmentType.convert(Int);
llvm::APSInt Min = AdjustmentType.getMinValue();
if (ComparisonVal == Min)
return getRange(St, Sym);
llvm::APSInt Max = AdjustmentType.getMaxValue();
llvm::APSInt Lower = ComparisonVal - Adjustment;
llvm::APSInt Upper = Max - Adjustment;
return getRange(St, Sym).Intersect(getBasicVals(), F, Lower, Upper);
}
ProgramStateRef
RangeConstraintManager::assumeSymGE(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
RangeSet New = getSymGERange(St, Sym, Int, Adjustment);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
RangeSet RangeConstraintManager::getSymLERange(
llvm::function_ref<RangeSet()> RS,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
// Before we do any real work, see if the value can even show up.
APSIntType AdjustmentType(Adjustment);
switch (AdjustmentType.testInRange(Int, true)) {
case APSIntType::RTR_Below:
return F.getEmptySet();
case APSIntType::RTR_Within:
break;
case APSIntType::RTR_Above:
return RS();
}
// Special case for Int == Max. This is always feasible.
llvm::APSInt ComparisonVal = AdjustmentType.convert(Int);
llvm::APSInt Max = AdjustmentType.getMaxValue();
if (ComparisonVal == Max)
return RS();
llvm::APSInt Min = AdjustmentType.getMinValue();
llvm::APSInt Lower = Min - Adjustment;
llvm::APSInt Upper = ComparisonVal - Adjustment;
return RS().Intersect(getBasicVals(), F, Lower, Upper);
}
RangeSet RangeConstraintManager::getSymLERange(ProgramStateRef St,
SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
return getSymLERange([&] { return getRange(St, Sym); }, Int, Adjustment);
}
ProgramStateRef
RangeConstraintManager::assumeSymLE(ProgramStateRef St, SymbolRef Sym,
const llvm::APSInt &Int,
const llvm::APSInt &Adjustment) {
RangeSet New = getSymLERange(St, Sym, Int, Adjustment);
return New.isEmpty() ? nullptr : St->set<ConstraintRange>(Sym, New);
}
ProgramStateRef RangeConstraintManager::assumeSymWithinInclusiveRange(
ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From,
const llvm::APSInt &To, const llvm::APSInt &Adjustment) {
RangeSet New = getSymGERange(State, Sym, From, Adjustment);
if (New.isEmpty())
return nullptr;
RangeSet Out = getSymLERange([&] { return New; }, To, Adjustment);
return Out.isEmpty() ? nullptr : State->set<ConstraintRange>(Sym, Out);
}
ProgramStateRef RangeConstraintManager::assumeSymOutsideInclusiveRange(
ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From,
const llvm::APSInt &To, const llvm::APSInt &Adjustment) {
RangeSet RangeLT = getSymLTRange(State, Sym, From, Adjustment);
RangeSet RangeGT = getSymGTRange(State, Sym, To, Adjustment);
RangeSet New(RangeLT.addRange(F, RangeGT));
return New.isEmpty() ? nullptr : State->set<ConstraintRange>(Sym, New);
}
//===----------------------------------------------------------------------===//
// Pretty-printing.
//===----------------------------------------------------------------------===//
void RangeConstraintManager::printJson(raw_ostream &Out, ProgramStateRef State,
const char *NL, unsigned int Space,
bool IsDot) const {
ConstraintRangeTy Constraints = State->get<ConstraintRange>();
Indent(Out, Space, IsDot) << "\"constraints\": ";
if (Constraints.isEmpty()) {
Out << "null," << NL;
return;
}
++Space;
Out << '[' << NL;
for (ConstraintRangeTy::iterator I = Constraints.begin();
I != Constraints.end(); ++I) {
Indent(Out, Space, IsDot)
<< "{ \"symbol\": \"" << I.getKey() << "\", \"range\": \"";
I.getData().print(Out);
Out << "\" }";
if (std::next(I) != Constraints.end())
Out << ',';
Out << NL;
}
--Space;
Indent(Out, Space, IsDot) << "]," << NL;
}
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