Example #1
DenseMap<const MachineBasicBlock *, int>
llvm::getEHScopeMembership(const MachineFunction &MF) {
  DenseMap<const MachineBasicBlock *, int> EHScopeMembership;

  // We don't have anything to do if there aren't any EH pads.
  if (!MF.hasEHScopes())
    return EHScopeMembership;

  int EntryBBNumber = MF.front().getNumber();
  bool IsSEH = isAsynchronousEHPersonality(

  const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
  SmallVector<const MachineBasicBlock *, 16> EHScopeBlocks;
  SmallVector<const MachineBasicBlock *, 16> UnreachableBlocks;
  SmallVector<const MachineBasicBlock *, 16> SEHCatchPads;
  SmallVector<std::pair<const MachineBasicBlock *, int>, 16> CatchRetSuccessors;
  for (const MachineBasicBlock &MBB : MF) {
    if (MBB.isEHScopeEntry()) {
    } else if (IsSEH && MBB.isEHPad()) {
    } else if (MBB.pred_empty()) {

    MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator();

    // CatchPads are not scopes for SEH so do not consider CatchRet to
    // transfer control to another scope.
    if (MBBI == MBB.end() || MBBI->getOpcode() != TII->getCatchReturnOpcode())

    // FIXME: SEH CatchPads are not necessarily in the parent function:
    // they could be inside a finally block.
    const MachineBasicBlock *Successor = MBBI->getOperand(0).getMBB();
    const MachineBasicBlock *SuccessorColor = MBBI->getOperand(1).getMBB();
        {Successor, IsSEH ? EntryBBNumber : SuccessorColor->getNumber()});

  // We don't have anything to do if there aren't any EH pads.
  if (EHScopeBlocks.empty())
    return EHScopeMembership;

  // Identify all the basic blocks reachable from the function entry.
  collectEHScopeMembers(EHScopeMembership, EntryBBNumber, &MF.front());
  // All blocks not part of a scope are in the parent function.
  for (const MachineBasicBlock *MBB : UnreachableBlocks)
    collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB);
  // Next, identify all the blocks inside the scopes.
  for (const MachineBasicBlock *MBB : EHScopeBlocks)
    collectEHScopeMembers(EHScopeMembership, MBB->getNumber(), MBB);
  // SEH CatchPads aren't really scopes, handle them separately.
  for (const MachineBasicBlock *MBB : SEHCatchPads)
    collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB);
  // Finally, identify all the targets of a catchret.
  for (std::pair<const MachineBasicBlock *, int> CatchRetPair :
    collectEHScopeMembers(EHScopeMembership, CatchRetPair.second,
  return EHScopeMembership;