C++ const_iterator::isBranch方法代码示例

void BT::runEdgeQueue(BitVector &BlockScanned) {
  while (!FlowQ.empty()) {
    CFGEdge Edge = FlowQ.front();
    FlowQ.pop();

    if (EdgeExec.count(Edge))
      return;
    EdgeExec.insert(Edge);
    ReachedBB.insert(Edge.second);

    const MachineBasicBlock &B = *MF.getBlockNumbered(Edge.second);
    MachineBasicBlock::const_iterator It = B.begin(), End = B.end();
    // Visit PHI nodes first.
    while (It != End && It->isPHI()) {
      const MachineInstr &PI = *It++;
      InstrExec.insert(&PI);
      visitPHI(PI);
    }

    // If this block has already been visited through a flow graph edge,
    // then the instructions have already been processed. Any updates to
    // the cells would now only happen through visitUsesOf...
    if (BlockScanned[Edge.second])
      return;
    BlockScanned[Edge.second] = true;

    // Visit non-branch instructions.
    while (It != End && !It->isBranch()) {
      const MachineInstr &MI = *It++;
      InstrExec.insert(&MI);
      visitNonBranch(MI);
    }
    // If block end has been reached, add the fall-through edge to the queue.
    if (It == End) {
      MachineFunction::const_iterator BIt = B.getIterator();
      MachineFunction::const_iterator Next = std::next(BIt);
      if (Next != MF.end() && B.isSuccessor(&*Next)) {
        int ThisN = B.getNumber();
        int NextN = Next->getNumber();
        FlowQ.push(CFGEdge(ThisN, NextN));
      }
    } else {
      // Handle the remaining sequence of branches. This function will update
      // the work queue.
      visitBranchesFrom(*It);
    }
  } // while (!FlowQ->empty())
}

void BT::run() {
  reset();
  assert(FlowQ.empty());

  typedef GraphTraits<const MachineFunction*> MachineFlowGraphTraits;
  const MachineBasicBlock *Entry = MachineFlowGraphTraits::getEntryNode(&MF);

  unsigned MaxBN = 0;
  for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
       I != E; ++I) {
    assert(I->getNumber() >= 0 && "Disconnected block");
    unsigned BN = I->getNumber();
    if (BN > MaxBN)
      MaxBN = BN;
  }

  // Keep track of visited blocks.
  BitVector BlockScanned(MaxBN+1);

  int EntryN = Entry->getNumber();
  // Generate a fake edge to get something to start with.
  FlowQ.push(CFGEdge(-1, EntryN));

  while (!FlowQ.empty()) {
    CFGEdge Edge = FlowQ.front();
    FlowQ.pop();

    if (EdgeExec.count(Edge))
      continue;
    EdgeExec.insert(Edge);

    const MachineBasicBlock &B = *MF.getBlockNumbered(Edge.second);
    MachineBasicBlock::const_iterator It = B.begin(), End = B.end();
    // Visit PHI nodes first.
    while (It != End && It->isPHI()) {
      const MachineInstr &PI = *It++;
      InstrExec.insert(&PI);
      visitPHI(PI);
    }

    // If this block has already been visited through a flow graph edge,
    // then the instructions have already been processed. Any updates to
    // the cells would now only happen through visitUsesOf...
    if (BlockScanned[Edge.second])
      continue;
    BlockScanned[Edge.second] = true;

    // Visit non-branch instructions.
    while (It != End && !It->isBranch()) {
      const MachineInstr &MI = *It++;
      InstrExec.insert(&MI);
      visitNonBranch(MI);
    }
    // If block end has been reached, add the fall-through edge to the queue.
    if (It == End) {
      MachineFunction::const_iterator BIt = B.getIterator();
      MachineFunction::const_iterator Next = std::next(BIt);
      if (Next != MF.end() && B.isSuccessor(&*Next)) {
        int ThisN = B.getNumber();
        int NextN = Next->getNumber();
        FlowQ.push(CFGEdge(ThisN, NextN));
      }
    } else {
      // Handle the remaining sequence of branches. This function will update
      // the work queue.
      visitBranchesFrom(*It);
    }
  } // while (!FlowQ->empty())

  if (Trace)
    print_cells(dbgs() << "Cells after propagation:\n");
}