C++ SmallPtrSetImpl::end方法代码示例

void checkEraseAndIterators(SmallPtrSetImpl<int*> &S) {
  int buf[3];

  S.insert(&buf[0]);
  S.insert(&buf[1]);
  S.insert(&buf[2]);

  // Iterators must still be valid after erase() calls;
  auto B = S.begin();
  auto M = std::next(B);
  auto E = S.end();
  EXPECT_TRUE(*B == &buf[0] || *B == &buf[1] || *B == &buf[2]);
  EXPECT_TRUE(*M == &buf[0] || *M == &buf[1] || *M == &buf[2]);
  EXPECT_TRUE(*B != *M);
  int *Removable = *std::next(M);
  // No iterator points to Removable now.
  EXPECT_TRUE(Removable == &buf[0] || Removable == &buf[1] ||
              Removable == &buf[2]);
  EXPECT_TRUE(Removable != *B && Removable != *M);

  S.erase(Removable);

  // B,M,E iterators should still be valid
  EXPECT_EQ(B, S.begin());
  EXPECT_EQ(M, std::next(B));
  EXPECT_EQ(E, S.end());
  EXPECT_EQ(std::next(M), E);
}

// Breadth-first walk of the use-def graph; determine the set of nodes
// we care about and eagerly determine if some of them are poisonous.
void Float2IntPass::walkBackwards(const SmallPtrSetImpl<Instruction*> &Roots) {
  std::deque<Instruction*> Worklist(Roots.begin(), Roots.end());
  while (!Worklist.empty()) {
    Instruction *I = Worklist.back();
    Worklist.pop_back();

    if (SeenInsts.find(I) != SeenInsts.end())
      // Seen already.
      continue;

    switch (I->getOpcode()) {
      // FIXME: Handle select and phi nodes.
    default:
      // Path terminated uncleanly.
      seen(I, badRange());
      break;

    case Instruction::UIToFP:
    case Instruction::SIToFP: {
      // Path terminated cleanly - use the type of the integer input to seed
      // the analysis.
      unsigned BW = I->getOperand(0)->getType()->getPrimitiveSizeInBits();
      auto Input = ConstantRange(BW, true);
      auto CastOp = (Instruction::CastOps)I->getOpcode();
      seen(I, validateRange(Input.castOp(CastOp, MaxIntegerBW+1)));
      continue;
    }

    case Instruction::FAdd:
    case Instruction::FSub:
    case Instruction::FMul:
    case Instruction::FPToUI:
    case Instruction::FPToSI:
    case Instruction::FCmp:
      seen(I, unknownRange());
      break;
    }

    for (Value *O : I->operands()) {
      if (Instruction *OI = dyn_cast<Instruction>(O)) {
        // Unify def-use chains if they interfere.
        ECs.unionSets(I, OI);
        if (SeenInsts.find(I)->second != badRange())
          Worklist.push_back(OI);
      } else if (!isa<ConstantFP>(O)) {
        // Not an instruction or ConstantFP? we can't do anything.
        seen(I, badRange());
      }
    }
  }
}

/// Return a set of basic blocks to insert sinked instructions.
///
/// The returned set of basic blocks (BBsToSinkInto) should satisfy:
///
/// * Inside the loop \p L
/// * For each UseBB in \p UseBBs, there is at least one BB in BBsToSinkInto
///   that domintates the UseBB
/// * Has minimum total frequency that is no greater than preheader frequency
///
/// The purpose of the function is to find the optimal sinking points to
/// minimize execution cost, which is defined as "sum of frequency of
/// BBsToSinkInto".
/// As a result, the returned BBsToSinkInto needs to have minimum total
/// frequency.
/// Additionally, if the total frequency of BBsToSinkInto exceeds preheader
/// frequency, the optimal solution is not sinking (return empty set).
///
/// \p ColdLoopBBs is used to help find the optimal sinking locations.
/// It stores a list of BBs that is:
///
/// * Inside the loop \p L
/// * Has a frequency no larger than the loop's preheader
/// * Sorted by BB frequency
///
/// The complexity of the function is O(UseBBs.size() * ColdLoopBBs.size()).
/// To avoid expensive computation, we cap the maximum UseBBs.size() in its
/// caller.
static SmallPtrSet<BasicBlock *, 2>
findBBsToSinkInto(const Loop &L, const SmallPtrSetImpl<BasicBlock *> &UseBBs,
                  const SmallVectorImpl<BasicBlock *> &ColdLoopBBs,
                  DominatorTree &DT, BlockFrequencyInfo &BFI) {
  SmallPtrSet<BasicBlock *, 2> BBsToSinkInto;
  if (UseBBs.size() == 0)
    return BBsToSinkInto;

  BBsToSinkInto.insert(UseBBs.begin(), UseBBs.end());
  SmallPtrSet<BasicBlock *, 2> BBsDominatedByColdestBB;

  // For every iteration:
  //   * Pick the ColdestBB from ColdLoopBBs
  //   * Find the set BBsDominatedByColdestBB that satisfy:
  //     - BBsDominatedByColdestBB is a subset of BBsToSinkInto
  //     - Every BB in BBsDominatedByColdestBB is dominated by ColdestBB
  //   * If Freq(ColdestBB) < Freq(BBsDominatedByColdestBB), remove
  //     BBsDominatedByColdestBB from BBsToSinkInto, add ColdestBB to
  //     BBsToSinkInto
  for (BasicBlock *ColdestBB : ColdLoopBBs) {
    BBsDominatedByColdestBB.clear();
    for (BasicBlock *SinkedBB : BBsToSinkInto)
      if (DT.dominates(ColdestBB, SinkedBB))
        BBsDominatedByColdestBB.insert(SinkedBB);
    if (BBsDominatedByColdestBB.size() == 0)
      continue;
    if (adjustedSumFreq(BBsDominatedByColdestBB, BFI) >
        BFI.getBlockFreq(ColdestBB)) {
      for (BasicBlock *DominatedBB : BBsDominatedByColdestBB) {
        BBsToSinkInto.erase(DominatedBB);
      }
      BBsToSinkInto.insert(ColdestBB);
    }
  }

  // If the total frequency of BBsToSinkInto is larger than preheader frequency,
  // do not sink.
  if (adjustedSumFreq(BBsToSinkInto, BFI) >
      BFI.getBlockFreq(L.getLoopPreheader()))
    BBsToSinkInto.clear();
  return BBsToSinkInto;
}