C++ ConstantInt::getContext方法代码示例

void StraightLineStrengthReduce::factorArrayIndex(Value *ArrayIdx,
                                                  const SCEV *Base,
                                                  uint64_t ElementSize,
                                                  GetElementPtrInst *GEP) {
  // At least, ArrayIdx = ArrayIdx *nsw 1.
  allocateCandidatesAndFindBasisForGEP(
      Base, ConstantInt::get(cast<IntegerType>(ArrayIdx->getType()), 1),
      ArrayIdx, ElementSize, GEP);
  Value *LHS = nullptr;
  ConstantInt *RHS = nullptr;
  // One alternative is matching the SCEV of ArrayIdx instead of ArrayIdx
  // itself. This would allow us to handle the shl case for free. However,
  // matching SCEVs has two issues:
  //
  // 1. this would complicate rewriting because the rewriting procedure
  // would have to translate SCEVs back to IR instructions. This translation
  // is difficult when LHS is further evaluated to a composite SCEV.
  //
  // 2. ScalarEvolution is designed to be control-flow oblivious. It tends
  // to strip nsw/nuw flags which are critical for SLSR to trace into
  // sext'ed multiplication.
  if (match(ArrayIdx, m_NSWMul(m_Value(LHS), m_ConstantInt(RHS)))) {
    // SLSR is currently unsafe if i * S may overflow.
    // GEP = Base + sext(LHS *nsw RHS) * ElementSize
    allocateCandidatesAndFindBasisForGEP(Base, RHS, LHS, ElementSize, GEP);
  } else if (match(ArrayIdx, m_NSWShl(m_Value(LHS), m_ConstantInt(RHS)))) {
    // GEP = Base + sext(LHS <<nsw RHS) * ElementSize
    //     = Base + sext(LHS *nsw (1 << RHS)) * ElementSize
    APInt One(RHS->getBitWidth(), 1);
    ConstantInt *PowerOf2 =
        ConstantInt::get(RHS->getContext(), One << RHS->getValue());
    allocateCandidatesAndFindBasisForGEP(Base, PowerOf2, LHS, ElementSize, GEP);
  }
}

void StraightLineStrengthReduce::allocateCandidatesAndFindBasisForAdd(
    Value *LHS, Value *RHS, Instruction *I) {
  Value *S = nullptr;
  ConstantInt *Idx = nullptr;
  if (match(RHS, m_Mul(m_Value(S), m_ConstantInt(Idx)))) {
    // I = LHS + RHS = LHS + Idx * S
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), Idx, S, I);
  } else if (match(RHS, m_Shl(m_Value(S), m_ConstantInt(Idx)))) {
    // I = LHS + RHS = LHS + (S << Idx) = LHS + S * (1 << Idx)
    APInt One(Idx->getBitWidth(), 1);
    Idx = ConstantInt::get(Idx->getContext(), One << Idx->getValue());
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), Idx, S, I);
  } else {
    // At least, I = LHS + 1 * RHS
    ConstantInt *One = ConstantInt::get(cast<IntegerType>(I->getType()), 1);
    allocateCandidatesAndFindBasis(Candidate::Add, SE->getSCEV(LHS), One, RHS,
                                   I);
  }
}

// switchConvert - Convert the switch statement into a binary lookup of
// the case values. The function recursively builds this tree.
// LowerBound and UpperBound are used to keep track of the bounds for Val
// that have already been checked by a block emitted by one of the previous
// calls to switchConvert in the call stack.
BasicBlock *
LowerSwitch::switchConvert(CaseItr Begin, CaseItr End, ConstantInt *LowerBound,
                           ConstantInt *UpperBound, Value *Val,
                           BasicBlock *Predecessor, BasicBlock *OrigBlock,
                           BasicBlock *Default,
                           const std::vector<IntRange> &UnreachableRanges) {
  unsigned Size = End - Begin;

  if (Size == 1) {
    // Check if the Case Range is perfectly squeezed in between
    // already checked Upper and Lower bounds. If it is then we can avoid
    // emitting the code that checks if the value actually falls in the range
    // because the bounds already tell us so.
    if (Begin->Low == LowerBound && Begin->High == UpperBound) {
      unsigned NumMergedCases = 0;
      if (LowerBound && UpperBound)
        NumMergedCases =
            UpperBound->getSExtValue() - LowerBound->getSExtValue();
      fixPhis(Begin->BB, OrigBlock, Predecessor, NumMergedCases);
      return Begin->BB;
    }
    return newLeafBlock(*Begin, Val, OrigBlock, Default);
  }

  unsigned Mid = Size / 2;
  std::vector<CaseRange> LHS(Begin, Begin + Mid);
  DEBUG(dbgs() << "LHS: " << LHS << "\n");
  std::vector<CaseRange> RHS(Begin + Mid, End);
  DEBUG(dbgs() << "RHS: " << RHS << "\n");

  CaseRange &Pivot = *(Begin + Mid);
  DEBUG(dbgs() << "Pivot ==> "
               << Pivot.Low->getValue()
               << " -" << Pivot.High->getValue() << "\n");

  // NewLowerBound here should never be the integer minimal value.
  // This is because it is computed from a case range that is never
  // the smallest, so there is always a case range that has at least
  // a smaller value.
  ConstantInt *NewLowerBound = Pivot.Low;

  // Because NewLowerBound is never the smallest representable integer
  // it is safe here to subtract one.
  ConstantInt *NewUpperBound = ConstantInt::get(NewLowerBound->getContext(),
                                                NewLowerBound->getValue() - 1);

  if (!UnreachableRanges.empty()) {
    // Check if the gap between LHS's highest and NewLowerBound is unreachable.
    int64_t GapLow = LHS.back().High->getSExtValue() + 1;
    int64_t GapHigh = NewLowerBound->getSExtValue() - 1;
    IntRange Gap = { GapLow, GapHigh };
    if (GapHigh >= GapLow && IsInRanges(Gap, UnreachableRanges))
      NewUpperBound = LHS.back().High;
  }

  DEBUG(dbgs() << "LHS Bounds ==> ";
        if (LowerBound) {
          dbgs() << LowerBound->getSExtValue();
        } else {
          dbgs() << "NONE";
        }
        dbgs() << " - " << NewUpperBound->getSExtValue() << "\n";
        dbgs() << "RHS Bounds ==> ";
        dbgs() << NewLowerBound->getSExtValue() << " - ";
        if (UpperBound) {
          dbgs() << UpperBound->getSExtValue() << "\n";
        } else {
          dbgs() << "NONE\n";
        });