C++ ConstantRange::getSignedMin方法代码示例

ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
                                            const ConstantRange &CR) {
  uint32_t W = CR.getBitWidth();
  switch (Pred) {
    default: assert(!"Invalid ICmp predicate to makeICmpRegion()");
    case ICmpInst::ICMP_EQ:
      return CR;
    case ICmpInst::ICMP_NE:
      if (CR.isSingleElement())
        return ConstantRange(CR.getUpper(), CR.getLower());
      return ConstantRange(W);
    case ICmpInst::ICMP_ULT:
      return ConstantRange(APInt::getMinValue(W), CR.getUnsignedMax());
    case ICmpInst::ICMP_SLT:
      return ConstantRange(APInt::getSignedMinValue(W), CR.getSignedMax());
    case ICmpInst::ICMP_ULE: {
      APInt UMax(CR.getUnsignedMax());
      if (UMax.isMaxValue())
        return ConstantRange(W);
      return ConstantRange(APInt::getMinValue(W), UMax + 1);
    }
    case ICmpInst::ICMP_SLE: {
      APInt SMax(CR.getSignedMax());
      if (SMax.isMaxSignedValue() || (SMax+1).isMaxSignedValue())
        return ConstantRange(W);
      return ConstantRange(APInt::getSignedMinValue(W), SMax + 1);
    }
    case ICmpInst::ICMP_UGT:
      return ConstantRange(CR.getUnsignedMin() + 1, APInt::getNullValue(W));
    case ICmpInst::ICMP_SGT:
      return ConstantRange(CR.getSignedMin() + 1,
                           APInt::getSignedMinValue(W));
    case ICmpInst::ICMP_UGE: {
      APInt UMin(CR.getUnsignedMin());
      if (UMin.isMinValue())
        return ConstantRange(W);
      return ConstantRange(UMin, APInt::getNullValue(W));
    }
    case ICmpInst::ICMP_SGE: {
      APInt SMin(CR.getSignedMin());
      if (SMin.isMinSignedValue())
        return ConstantRange(W);
      return ConstantRange(SMin, APInt::getSignedMinValue(W));
    }
  }
}

ConstantRange
ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
                                          const ConstantRange &Other,
                                          unsigned NoWrapKind) {
  typedef OverflowingBinaryOperator OBO;

  // Computes the intersection of CR0 and CR1.  It is different from
  // intersectWith in that the ConstantRange returned will only contain elements
  // in both CR0 and CR1 (i.e. SubsetIntersect(X, Y) is a *subset*, proper or
  // not, of both X and Y).
  auto SubsetIntersect =
      [](const ConstantRange &CR0, const ConstantRange &CR1) {
    return CR0.inverse().unionWith(CR1.inverse()).inverse();
  };

  assert(BinOp >= Instruction::BinaryOpsBegin &&
         BinOp < Instruction::BinaryOpsEnd && "Binary operators only!");

  assert((NoWrapKind == OBO::NoSignedWrap ||
          NoWrapKind == OBO::NoUnsignedWrap ||
          NoWrapKind == (OBO::NoUnsignedWrap | OBO::NoSignedWrap)) &&
         "NoWrapKind invalid!");

  unsigned BitWidth = Other.getBitWidth();
  if (BinOp != Instruction::Add)
    // Conservative answer: empty set
    return ConstantRange(BitWidth, false);

  if (auto *C = Other.getSingleElement())
    if (C->isMinValue())
      // Full set: nothing signed / unsigned wraps when added to 0.
      return ConstantRange(BitWidth);

  ConstantRange Result(BitWidth);

  if (NoWrapKind & OBO::NoUnsignedWrap)
    Result =
        SubsetIntersect(Result, ConstantRange(APInt::getNullValue(BitWidth),
                                              -Other.getUnsignedMax()));

  if (NoWrapKind & OBO::NoSignedWrap) {
    APInt SignedMin = Other.getSignedMin();
    APInt SignedMax = Other.getSignedMax();

    if (SignedMax.isStrictlyPositive())
      Result = SubsetIntersect(
          Result,
          ConstantRange(APInt::getSignedMinValue(BitWidth),
                        APInt::getSignedMinValue(BitWidth) - SignedMax));

    if (SignedMin.isNegative())
      Result = SubsetIntersect(
          Result, ConstantRange(APInt::getSignedMinValue(BitWidth) - SignedMin,
                                APInt::getSignedMinValue(BitWidth)));
  }

  return Result;
}

ConstantRange
ConstantRange::multiply(const ConstantRange &Other) const {
  // TODO: If either operand is a single element and the multiply is known to
  // be non-wrapping, round the result min and max value to the appropriate
  // multiple of that element. If wrapping is possible, at least adjust the
  // range according to the greatest power-of-two factor of the single element.

  if (isEmptySet() || Other.isEmptySet())
    return ConstantRange(getBitWidth(), /*isFullSet=*/false);

  // Multiplication is signedness-independent. However different ranges can be
  // obtained depending on how the input ranges are treated. These different
  // ranges are all conservatively correct, but one might be better than the
  // other. We calculate two ranges; one treating the inputs as unsigned
  // and the other signed, then return the smallest of these ranges.

  // Unsigned range first.
  APInt this_min = getUnsignedMin().zext(getBitWidth() * 2);
  APInt this_max = getUnsignedMax().zext(getBitWidth() * 2);
  APInt Other_min = Other.getUnsignedMin().zext(getBitWidth() * 2);
  APInt Other_max = Other.getUnsignedMax().zext(getBitWidth() * 2);

  ConstantRange Result_zext = ConstantRange(this_min * Other_min,
                                            this_max * Other_max + 1);
  ConstantRange UR = Result_zext.truncate(getBitWidth());

  // If the unsigned range doesn't wrap, and isn't negative then it's a range
  // from one positive number to another which is as good as we can generate.
  // In this case, skip the extra work of generating signed ranges which aren't
  // going to be better than this range.
  if (!UR.isWrappedSet() &&
      (UR.getUpper().isNonNegative() || UR.getUpper().isMinSignedValue()))
    return UR;

  // Now the signed range. Because we could be dealing with negative numbers
  // here, the lower bound is the smallest of the cartesian product of the
  // lower and upper ranges; for example:
  //   [-1,4) * [-2,3) = min(-1*-2, -1*2, 3*-2, 3*2) = -6.
  // Similarly for the upper bound, swapping min for max.

  this_min = getSignedMin().sext(getBitWidth() * 2);
  this_max = getSignedMax().sext(getBitWidth() * 2);
  Other_min = Other.getSignedMin().sext(getBitWidth() * 2);
  Other_max = Other.getSignedMax().sext(getBitWidth() * 2);
  
  auto L = {this_min * Other_min, this_min * Other_max,
            this_max * Other_min, this_max * Other_max};
  auto Compare = [](const APInt &A, const APInt &B) { return A.slt(B); };
  ConstantRange Result_sext(std::min(L, Compare), std::max(L, Compare) + 1);
  ConstantRange SR = Result_sext.truncate(getBitWidth());

  return UR.isSizeStrictlySmallerThan(SR) ? UR : SR;
}

ConstantRange ConstantRange::makeAllowedICmpRegion(CmpInst::Predicate Pred,
                                                   const ConstantRange &CR) {
  if (CR.isEmptySet())
    return CR;

  uint32_t W = CR.getBitWidth();
  switch (Pred) {
  default:
    llvm_unreachable("Invalid ICmp predicate to makeAllowedICmpRegion()");
    case CmpInst::ICMP_EQ:
      return CR;
    case CmpInst::ICMP_NE:
      if (CR.isSingleElement())
        return ConstantRange(CR.getUpper(), CR.getLower());
      return ConstantRange(W);
    case CmpInst::ICMP_ULT: {
      APInt UMax(CR.getUnsignedMax());
      if (UMax.isMinValue())
        return ConstantRange(W, /* empty */ false);
      return ConstantRange(APInt::getMinValue(W), UMax);
    }
    case CmpInst::ICMP_SLT: {
      APInt SMax(CR.getSignedMax());
      if (SMax.isMinSignedValue())
        return ConstantRange(W, /* empty */ false);
      return ConstantRange(APInt::getSignedMinValue(W), SMax);
    }
    case CmpInst::ICMP_ULE: {
      APInt UMax(CR.getUnsignedMax());
      if (UMax.isMaxValue())
        return ConstantRange(W);
      return ConstantRange(APInt::getMinValue(W), UMax + 1);
    }
    case CmpInst::ICMP_SLE: {
      APInt SMax(CR.getSignedMax());
      if (SMax.isMaxSignedValue())
        return ConstantRange(W);
      return ConstantRange(APInt::getSignedMinValue(W), SMax + 1);
    }
    case CmpInst::ICMP_UGT: {
      APInt UMin(CR.getUnsignedMin());
      if (UMin.isMaxValue())
        return ConstantRange(W, /* empty */ false);
      return ConstantRange(UMin + 1, APInt::getNullValue(W));
    }
    case CmpInst::ICMP_SGT: {
      APInt SMin(CR.getSignedMin());
      if (SMin.isMaxSignedValue())
        return ConstantRange(W, /* empty */ false);
      return ConstantRange(SMin + 1, APInt::getSignedMinValue(W));
    }
    case CmpInst::ICMP_UGE: {
      APInt UMin(CR.getUnsignedMin());
      if (UMin.isMinValue())
        return ConstantRange(W);
      return ConstantRange(UMin, APInt::getNullValue(W));
    }
    case CmpInst::ICMP_SGE: {
      APInt SMin(CR.getSignedMin());
      if (SMin.isMinSignedValue())
        return ConstantRange(W);
      return ConstantRange(SMin, APInt::getSignedMinValue(W));
    }
  }
}