C++ ConstantRange类代码示例

/// Annotate the Shr in (X << IVOperand) >> C as exact using the
/// information from the IV's range. Returns true if anything changed, false
/// otherwise.
bool SimplifyIndvar::strengthenRightShift(BinaryOperator *BO,
                                          Value *IVOperand) {
  using namespace llvm::PatternMatch;

  if (BO->getOpcode() == Instruction::Shl) {
    bool Changed = false;
    ConstantRange IVRange = SE->getUnsignedRange(SE->getSCEV(IVOperand));
    for (auto *U : BO->users()) {
      const APInt *C;
      if (match(U,
                m_AShr(m_Shl(m_Value(), m_Specific(IVOperand)), m_APInt(C))) ||
          match(U,
                m_LShr(m_Shl(m_Value(), m_Specific(IVOperand)), m_APInt(C)))) {
        BinaryOperator *Shr = cast<BinaryOperator>(U);
        if (!Shr->isExact() && IVRange.getUnsignedMin().uge(*C)) {
          Shr->setIsExact(true);
          Changed = true;
        }
      }
    }
    return Changed;
  }

  return false;
}

/// intersectWith - Return the range that results from the intersection of this
/// range with another range.
///
ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
  assert(getBitWidth() == CR.getBitWidth() && 
         "ConstantRange types don't agree!");
  // Handle common special cases
  if (isEmptySet() || CR.isFullSet())  
    return *this;
  if (isFullSet()  || CR.isEmptySet()) 
    return CR;

  if (!isWrappedSet()) {
    if (!CR.isWrappedSet()) {
      using namespace APIntOps;
      APInt L = umax(Lower, CR.Lower);
      APInt U = umin(Upper, CR.Upper);

      if (L.ult(U)) // If range isn't empty...
        return ConstantRange(L, U);
      else
        return ConstantRange(getBitWidth(), false);// Otherwise, empty set
    } else
      return intersect1Wrapped(CR, *this);
  } else {   // We know "this" is wrapped...
    if (!CR.isWrappedSet())
      return intersect1Wrapped(*this, CR);
    else {
      // Both ranges are wrapped...
      using namespace APIntOps;
      APInt L = umax(Lower, CR.Lower);
      APInt U = umin(Upper, CR.Upper);
      return ConstantRange(L, U);
    }
  }
  return *this;
}

// intersect1Wrapped - This helper function is used to intersect two ranges when
// it is known that LHS is wrapped and RHS isn't.
//
ConstantRange 
ConstantRange::intersect1Wrapped(const ConstantRange &LHS,
                                 const ConstantRange &RHS) {
  assert(LHS.isWrappedSet() && !RHS.isWrappedSet());

  // Check to see if we overlap on the Left side of RHS...
  //
  if (RHS.Lower.ult(LHS.Upper)) {
    // We do overlap on the left side of RHS, see if we overlap on the right of
    // RHS...
    if (RHS.Upper.ugt(LHS.Lower)) {
      // Ok, the result overlaps on both the left and right sides.  See if the
      // resultant interval will be smaller if we wrap or not...
      //
      if (LHS.getSetSize().ult(RHS.getSetSize()))
        return LHS;
      else
        return RHS;

    } else {
      // No overlap on the right, just on the left.
      return ConstantRange(RHS.Lower, LHS.Upper);
    }
  } else {
    // We don't overlap on the left side of RHS, see if we overlap on the right
    // of RHS...
    if (RHS.Upper.ugt(LHS.Lower)) {
      // Simple overlap...
      return ConstantRange(LHS.Lower, RHS.Upper);
    } else {
      // No overlap...
      return ConstantRange(LHS.getBitWidth(), false);
    }
  }
}

TEST(InterpreterTests, KBCRReduction) {
  ConstantRange CR(WIDTH, /*isFullSet=*/false);
  KnownBits KB(WIDTH);
  do {
    do {
      KnownBits CalculatedKB = KB;
      ConstantRange CalculatedCR = CR;
      improveKBCR(CalculatedKB, CalculatedCR);

      KnownBits ExhaustiveKB = KB;
      ConstantRange ExhaustiveCR = CR;
      TestingUtil::exhaustiveKBCRReduction(ExhaustiveKB, ExhaustiveCR);

      if (KnownBitsAnalysis::isConflictingKB(CalculatedKB, ExhaustiveKB)) {
	outs() << "Unsound!! CR KB reduction for KB\n";
	outs() << "Original KB: " << KnownBitsAnalysis::knownBitsString(KB) << "\n";
	outs() << "Original CR: " << CR << "\n";
	outs() << "CalculatedKB: " << KnownBitsAnalysis::knownBitsString(CalculatedKB) << '\n';
	outs() << "ExhaustiveKB: " << KnownBitsAnalysis::knownBitsString(ExhaustiveKB) << '\n';
	ASSERT_TRUE(false);
      }

      if (!CalculatedCR.contains(ExhaustiveCR)) {
	outs() << "Unsound!! CR KB reduction for CR\n";
	outs() << "Original KB: " << KnownBitsAnalysis::knownBitsString(KB) << "\n";
	outs() << "Original CR: " << CR << "\n";
	outs() << "CalculatedCR: " << CalculatedCR << '\n';
	outs() << "ExhaustiveCR: " << ExhaustiveCR << '\n';
	ASSERT_TRUE(false);
      }

      CR = CRTesting::nextCR(CR);
    } while(!CR.isEmptySet());
  } while(KBTesting::nextKB(KB));
}

// See if we can prove that the given overflow intrinsic will not overflow.
static bool willNotOverflow(IntrinsicInst *II, LazyValueInfo *LVI) {
  using OBO = OverflowingBinaryOperator;
  auto NoWrap = [&] (Instruction::BinaryOps BinOp, unsigned NoWrapKind) {
    Value *RHS = II->getOperand(1);
    ConstantRange RRange = LVI->getConstantRange(RHS, II->getParent(), II);
    ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
        BinOp, RRange, NoWrapKind);
    // As an optimization, do not compute LRange if we do not need it.
    if (NWRegion.isEmptySet())
      return false;
    Value *LHS = II->getOperand(0);
    ConstantRange LRange = LVI->getConstantRange(LHS, II->getParent(), II);
    return NWRegion.contains(LRange);
  };
  switch (II->getIntrinsicID()) {
  default:
    break;
  case Intrinsic::uadd_with_overflow:
    return NoWrap(Instruction::Add, OBO::NoUnsignedWrap);
  case Intrinsic::sadd_with_overflow:
    return NoWrap(Instruction::Add, OBO::NoSignedWrap);
  case Intrinsic::usub_with_overflow:
    return NoWrap(Instruction::Sub, OBO::NoUnsignedWrap);
  case Intrinsic::ssub_with_overflow:
    return NoWrap(Instruction::Sub, OBO::NoSignedWrap);
  }
  return false;
}

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;
}

bool
ConstantRange::isSizeStrictlySmallerThan(const ConstantRange &Other) const {
  assert(getBitWidth() == Other.getBitWidth());
  if (isFullSet())
    return false;
  if (Other.isFullSet())
    return true;
  return (Upper - Lower).ult(Other.Upper - Other.Lower);
}

ConstantRange
ConstantRange::lshr(const ConstantRange &Amount) const {
  if (isEmptySet())
    return *this;
  
  APInt min = getUnsignedMax().lshr(Amount.getUnsignedMin());
  APInt max = getUnsignedMin().lshr(Amount.getUnsignedMax());
  return ConstantRange(min, max);
}

Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
  LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
  
  if (Result.isConstant())
    return Result.getConstant();
  if (Result.isConstantRange()) {
    ConstantRange CR = Result.getConstantRange();
    if (const APInt *SingleVal = CR.getSingleElement())
      return ConstantInt::get(V->getContext(), *SingleVal);
  }
  return 0;
}

ConstantRange
ConstantRange::lshr(const ConstantRange &Other) const {
  if (isEmptySet() || Other.isEmptySet())
    return ConstantRange(getBitWidth(), /*isFullSet=*/false);
  
  APInt max = getUnsignedMax().lshr(Other.getUnsignedMin());
  APInt min = getUnsignedMin().lshr(Other.getUnsignedMax());
  if (min == max + 1)
    return ConstantRange(getBitWidth(), /*isFullSet=*/true);

  return ConstantRange(min, max + 1);
}

ConstantRange
ConstantRange::smin(const ConstantRange &Other) const {
  // X smin Y is: range(smin(X_smin, Y_smin),
  //                    smin(X_smax, Y_smax))
  if (isEmptySet() || Other.isEmptySet())
    return ConstantRange(getBitWidth(), /*isFullSet=*/false);
  APInt NewL = APIntOps::smin(getSignedMin(), Other.getSignedMin());
  APInt NewU = APIntOps::smin(getSignedMax(), Other.getSignedMax()) + 1;
  if (NewU == NewL)
    return ConstantRange(getBitWidth(), /*isFullSet=*/true);
  return ConstantRange(std::move(NewL), std::move(NewU));
}

static bool processAdd(BinaryOperator *AddOp, LazyValueInfo *LVI) {
  typedef OverflowingBinaryOperator OBO;

  if (DontProcessAdds)
    return false;

  if (AddOp->getType()->isVectorTy() || hasLocalDefs(AddOp))
    return false;

  bool NSW = AddOp->hasNoSignedWrap();
  bool NUW = AddOp->hasNoUnsignedWrap();
  if (NSW && NUW)
    return false;

  BasicBlock *BB = AddOp->getParent();

  Value *LHS = AddOp->getOperand(0);
  Value *RHS = AddOp->getOperand(1);

  ConstantRange LRange = LVI->getConstantRange(LHS, BB, AddOp);

  // Initialize RRange only if we need it. If we know that guaranteed no wrap
  // range for the given LHS range is empty don't spend time calculating the
  // range for the RHS.
  Optional<ConstantRange> RRange;
  auto LazyRRange = [&] () {
      if (!RRange)
        RRange = LVI->getConstantRange(RHS, BB, AddOp);
      return RRange.getValue();
  };

  bool Changed = false;
  if (!NUW) {
    ConstantRange NUWRange =
            LRange.makeGuaranteedNoWrapRegion(BinaryOperator::Add, LRange,
                                              OBO::NoUnsignedWrap);
    if (!NUWRange.isEmptySet()) {
      bool NewNUW = NUWRange.contains(LazyRRange());
      AddOp->setHasNoUnsignedWrap(NewNUW);
      Changed |= NewNUW;
    }
  }
  if (!NSW) {
    ConstantRange NSWRange =
            LRange.makeGuaranteedNoWrapRegion(BinaryOperator::Add, LRange,
                                              OBO::NoSignedWrap);
    if (!NSWRange.isEmptySet()) {
      bool NewNSW = NSWRange.contains(LazyRRange());
      AddOp->setHasNoSignedWrap(NewNSW);
      Changed |= NewNSW;
    }
  }

  return Changed;
}

Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB,
                                     Instruction *CxtI) {
  LVILatticeVal Result =
      getCache(PImpl, AC, DL, DT).getValueInBlock(V, BB, CxtI);

  if (Result.isConstant())
    return Result.getConstant();
  if (Result.isConstantRange()) {
    ConstantRange CR = Result.getConstantRange();
    if (const APInt *SingleVal = CR.getSingleElement())
      return ConstantInt::get(V->getContext(), *SingleVal);
  }
  return nullptr;
}

static bool tryMergeRange(SmallVectorImpl<Value *> &EndPoints, ConstantInt *Low,
                          ConstantInt *High) {
  ConstantRange NewRange(Low->getValue(), High->getValue());
  unsigned Size = EndPoints.size();
  APInt LB = cast<ConstantInt>(EndPoints[Size - 2])->getValue();
  APInt LE = cast<ConstantInt>(EndPoints[Size - 1])->getValue();
  ConstantRange LastRange(LB, LE);
  if (canBeMerged(NewRange, LastRange)) {
    ConstantRange Union = LastRange.unionWith(NewRange);
    Type *Ty = High->getType();
    EndPoints[Size - 2] = ConstantInt::get(Ty, Union.getLower());
    EndPoints[Size - 1] = ConstantInt::get(Ty, Union.getUpper());
    return true;
  }
  return false;
}

/// Determine whether the specified value is known to be a
/// constant on the specified edge. Return null if not.
Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
                                           BasicBlock *ToBB,
                                           Instruction *CxtI) {
  const DataLayout &DL = FromBB->getModule()->getDataLayout();
  LVILatticeVal Result =
      getCache(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);

  if (Result.isConstant())
    return Result.getConstant();
  if (Result.isConstantRange()) {
    ConstantRange CR = Result.getConstantRange();
    if (const APInt *SingleVal = CR.getSingleElement())
      return ConstantInt::get(V->getContext(), *SingleVal);
  }
  return nullptr;
}