C++ LandingPadInst::getNextNode方法代码示例

/// Assign every distinct landingpad a unique state number for SEH. Unlike C++
/// EH, we can use this very simple algorithm while C++ EH cannot because catch
/// handlers aren't outlined and the runtime doesn't have to figure out which
/// catch handler frame to unwind to.
/// FIXME: __finally blocks are outlined, so this approach may break down there.
void WinEHStatePass::addSEHStateStores(Function &F, MachineModuleInfo &MMI) {
  WinEHFuncInfo &FuncInfo = MMI.getWinEHFuncInfo(&F);

  // Remember and return the index that we used. We save it in WinEHFuncInfo so
  // that we can lower llvm.x86.seh.recoverfp later in filter functions without
  // too much trouble.
  int RegNodeEscapeIndex = escapeRegNode(F);
  FuncInfo.EHRegNodeEscapeIndex = RegNodeEscapeIndex;

  // Iterate all the instructions and emit state number stores.
  int CurState = 0;
  SmallPtrSet<BasicBlock *, 4> ExceptBlocks;
  for (BasicBlock &BB : F) {
    for (auto I = BB.begin(), E = BB.end(); I != E; ++I) {
      if (auto *CI = dyn_cast<CallInst>(I)) {
        auto *Intrin = dyn_cast<IntrinsicInst>(CI);
        if (Intrin) {
          // Calls that "don't throw" are considered to be able to throw asynch
          // exceptions, but intrinsics cannot.
          continue;
        }
        insertStateNumberStore(RegNode, CI, -1);
      } else if (auto *II = dyn_cast<InvokeInst>(I)) {
        // Look up the state number of the landingpad this unwinds to.
        LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst();
        auto InsertionPair =
            FuncInfo.LandingPadStateMap.insert(std::make_pair(LPI, CurState));
        auto Iter = InsertionPair.first;
        int &State = Iter->second;
        bool Inserted = InsertionPair.second;
        if (Inserted) {
          // Each action consumes a state number.
          auto *EHActions = cast<IntrinsicInst>(LPI->getNextNode());
          SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
          parseEHActions(EHActions, ActionList);
          assert(!ActionList.empty());
          CurState += ActionList.size();
          State += ActionList.size() - 1;

          // Remember all the __except block targets.
          for (auto &Handler : ActionList) {
            if (auto *CH = dyn_cast<CatchHandler>(Handler.get())) {
              auto *BA = cast<BlockAddress>(CH->getHandlerBlockOrFunc());
              ExceptBlocks.insert(BA->getBasicBlock());
            }
          }
        }
        insertStateNumberStore(RegNode, II, State);
      }
    }
  }

  // Insert llvm.x86.seh.restoreframe() into each __except block.
  Function *RestoreFrame =
      Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_restoreframe);
  for (BasicBlock *ExceptBB : ExceptBlocks) {
    IRBuilder<> Builder(ExceptBB->begin());
    Builder.CreateCall(RestoreFrame, {});
  }
}

/// Assign every distinct landingpad a unique state number for SEH. Unlike C++
/// EH, we can use this very simple algorithm while C++ EH cannot because catch
/// handlers aren't outlined and the runtime doesn't have to figure out which
/// catch handler frame to unwind to.
/// FIXME: __finally blocks are outlined, so this approach may break down there.
void WinEHStatePass::addSEHStateStores(Function &F, WinEHFuncInfo &FuncInfo) {
  // Remember and return the index that we used. We save it in WinEHFuncInfo so
  // that we can lower llvm.x86.seh.recoverfp later in filter functions without
  // too much trouble.
  int RegNodeEscapeIndex = escapeRegNode(F);
  FuncInfo.EHRegNodeEscapeIndex = RegNodeEscapeIndex;

  // If this funciton uses the new EH IR, use the explicit state numbering
  // algorithm and return early.
  bool UsesLPads = false;
  for (BasicBlock &BB : F) {
    if (BB.isLandingPad()) {
      UsesLPads = true;
      break;
    }
  }
  if (!UsesLPads) {
    calculateSEHStateNumbers(&F, FuncInfo);
    addStateStoresToFunclet(RegNode, FuncInfo, F, -1);
    return;
  }
  // FIXME: Delete the rest of this code and clean things up when new EH is
  // done.

  // Iterate all the instructions and emit state number stores.
  int CurState = 0;
  SmallPtrSet<BasicBlock *, 4> ExceptBlocks;
  for (BasicBlock &BB : F) {
    for (auto I = BB.begin(), E = BB.end(); I != E; ++I) {
      if (auto *CI = dyn_cast<CallInst>(I)) {
        auto *Intrin = dyn_cast<IntrinsicInst>(CI);
        if (Intrin) {
          // Calls that "don't throw" are considered to be able to throw asynch
          // exceptions, but intrinsics cannot.
          continue;
        }
        insertStateNumberStore(RegNode, CI, -1);
      } else if (auto *II = dyn_cast<InvokeInst>(I)) {
        // Look up the state number of the landingpad this unwinds to.
        LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst();
        auto InsertionPair =
            FuncInfo.EHPadStateMap.insert(std::make_pair(LPI, CurState));
        auto Iter = InsertionPair.first;
        int &State = Iter->second;
        bool Inserted = InsertionPair.second;
        if (Inserted) {
          // Each action consumes a state number.
          auto *EHActions = cast<IntrinsicInst>(LPI->getNextNode());
          SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
          parseEHActions(EHActions, ActionList);
          assert(!ActionList.empty());
          CurState += ActionList.size();
          State += ActionList.size() - 1;

          // Remember all the __except block targets.
          for (auto &Handler : ActionList) {
            if (auto *CH = dyn_cast<CatchHandler>(Handler.get())) {
              auto *BA = cast<BlockAddress>(CH->getHandlerBlockOrFunc());
#ifndef NDEBUG
              for (BasicBlock *Pred : predecessors(BA->getBasicBlock()))
                assert(Pred->isLandingPad() &&
                       "WinEHPrepare failed to split block");
#endif
              ExceptBlocks.insert(BA->getBasicBlock());
            }
          }
        }
        insertStateNumberStore(RegNode, II, State);
      }
    }
  }

  // Insert llvm.x86.seh.restoreframe() into each __except block.
  Function *RestoreFrame =
      Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_restoreframe);
  for (BasicBlock *ExceptBB : ExceptBlocks) {
    IRBuilder<> Builder(ExceptBB->begin());
    Builder.CreateCall(RestoreFrame, {});
  }
}