C++ BasicValueFactory::getMinValue方法代码示例

// Turn all [A, B] ranges to [-B, -A]. Ranges [MIN, B] are turned to range set
// [MIN, MIN] U [-B, MAX], when MIN and MAX are the minimal and the maximal
// signed values of the type.
RangeSet RangeSet::Negate(BasicValueFactory &BV, Factory &F) const {
  PrimRangeSet newRanges = F.getEmptySet();

  for (iterator i = begin(), e = end(); i != e; ++i) {
    const llvm::APSInt &from = i->From(), &to = i->To();
    const llvm::APSInt &newTo = (from.isMinSignedValue() ?
                                 BV.getMaxValue(from) :
                                 BV.getValue(- from));
    if (to.isMaxSignedValue() && !newRanges.isEmpty() &&
        newRanges.begin()->From().isMinSignedValue()) {
      assert(newRanges.begin()->To().isMinSignedValue() &&
             "Ranges should not overlap");
      assert(!from.isMinSignedValue() && "Ranges should not overlap");
      const llvm::APSInt &newFrom = newRanges.begin()->From();
      newRanges =
        F.add(F.remove(newRanges, *newRanges.begin()), Range(newFrom, newTo));
    } else if (!to.isMinSignedValue()) {
      const llvm::APSInt &newFrom = BV.getValue(- to);
      newRanges = F.add(newRanges, Range(newFrom, newTo));
    }
    if (from.isMinSignedValue()) {
      newRanges = F.add(newRanges, Range(BV.getMinValue(from),
                                         BV.getMinValue(from)));
    }
  }

  return newRanges;
}

/// Apply implicit constraints for bitwise OR- and AND-.
/// For unsigned types, bitwise OR with a constant always returns
/// a value greater-or-equal than the constant, and bitwise AND
/// returns a value less-or-equal then the constant.
///
/// Pattern matches the expression \p Sym against those rule,
/// and applies the required constraints.
/// \p Input Previously established expression range set
static RangeSet applyBitwiseConstraints(
    BasicValueFactory &BV,
    RangeSet::Factory &F,
    RangeSet Input,
    const SymIntExpr* SIE) {
  QualType T = SIE->getType();
  bool IsUnsigned = T->isUnsignedIntegerType();
  const llvm::APSInt &RHS = SIE->getRHS();
  const llvm::APSInt &Zero = BV.getAPSIntType(T).getZeroValue();
  BinaryOperator::Opcode Operator = SIE->getOpcode();

  // For unsigned types, the output of bitwise-or is bigger-or-equal than RHS.
  if (Operator == BO_Or && IsUnsigned)
    return Input.Intersect(BV, F, RHS, BV.getMaxValue(T));

  // Bitwise-or with a non-zero constant is always non-zero.
  if (Operator == BO_Or && RHS != Zero)
    return assumeNonZero(BV, F, SIE, Input);

  // For unsigned types, or positive RHS,
  // bitwise-and output is always smaller-or-equal than RHS (assuming two's
  // complement representation of signed types).
  if (Operator == BO_And && (IsUnsigned || RHS >= Zero))
    return Input.Intersect(BV, F, BV.getMinValue(T), RHS);

  return Input;
}

// 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 {
  if (!pin(Lower, Upper))
    return F.getEmptySet();

  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;
}