text: //===- CodeGen/AsmPrinter/EHStreamer.cpp - Exception Directive Streamer ---===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file contains support for writing exception info into assembly files.
  //
  //===----------------------------------------------------------------------===//
  
  #include "EHStreamer.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/Twine.h"
  #include "llvm/ADT/iterator_range.h"
  #include "llvm/BinaryFormat/Dwarf.h"
  #include "llvm/CodeGen/AsmPrinter.h"
  #include "llvm/CodeGen/MachineFunction.h"
  #include "llvm/CodeGen/MachineInstr.h"
  #include "llvm/CodeGen/MachineOperand.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/Function.h"
  #include "llvm/MC/MCAsmInfo.h"
  #include "llvm/MC/MCContext.h"
  #include "llvm/MC/MCStreamer.h"
  #include "llvm/MC/MCSymbol.h"
  #include "llvm/MC/MCTargetOptions.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/LEB128.h"
  #include "llvm/Target/TargetLoweringObjectFile.h"
  #include <algorithm>
  #include <cassert>
  #include <cstdint>
  #include <vector>
  
  using namespace llvm;
  
  EHStreamer::EHStreamer(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
  
  EHStreamer::~EHStreamer() = default;
  
  /// How many leading type ids two landing pads have in common.
  unsigned EHStreamer::sharedTypeIDs(const LandingPadInfo *L,
                                     const LandingPadInfo *R) {
    const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
    unsigned LSize = LIds.size(), RSize = RIds.size();
    unsigned MinSize = LSize < RSize ? LSize : RSize;
    unsigned Count = 0;
  
    for (; Count != MinSize; ++Count)
      if (LIds[Count] != RIds[Count])
        return Count;
  
    return Count;
  }
  
  /// Compute the actions table and gather the first action index for each landing
  /// pad site.
  void EHStreamer::computeActionsTable(
      const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
      SmallVectorImpl<ActionEntry> &Actions,
      SmallVectorImpl<unsigned> &FirstActions) {
    // The action table follows the call-site table in the LSDA. The individual
    // records are of two types:
    //
    //   * Catch clause
    //   * Exception specification
    //
    // The two record kinds have the same format, with only small differences.
    // They are distinguished by the "switch value" field: Catch clauses
    // (TypeInfos) have strictly positive switch values, and exception
    // specifications (FilterIds) have strictly negative switch values. Value 0
    // indicates a catch-all clause.
    //
    // Negative type IDs index into FilterIds. Positive type IDs index into
    // TypeInfos.  The value written for a positive type ID is just the type ID
    // itself.  For a negative type ID, however, the value written is the
    // (negative) byte offset of the corresponding FilterIds entry.  The byte
    // offset is usually equal to the type ID (because the FilterIds entries are
    // written using a variable width encoding, which outputs one byte per entry
    // as long as the value written is not too large) but can differ.  This kind
    // of complication does not occur for positive type IDs because type infos are
    // output using a fixed width encoding.  FilterOffsets[i] holds the byte
    // offset corresponding to FilterIds[i].
  
    const std::vector<unsigned> &FilterIds = Asm->MF->getFilterIds();
    SmallVector<int, 16> FilterOffsets;
    FilterOffsets.reserve(FilterIds.size());
    int Offset = -1;
  
    for (std::vector<unsigned>::const_iterator
           I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
      FilterOffsets.push_back(Offset);
      Offset -= getULEB128Size(*I);
    }
  
    FirstActions.reserve(LandingPads.size());
  
    int FirstAction = 0;
    unsigned SizeActions = 0; // Total size of all action entries for a function
    const LandingPadInfo *PrevLPI = nullptr;
  
    for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
           I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
      const LandingPadInfo *LPI = *I;
      const std::vector<int> &TypeIds = LPI->TypeIds;
      unsigned NumShared = PrevLPI ? sharedTypeIDs(LPI, PrevLPI) : 0;
      unsigned SizeSiteActions = 0; // Total size of all entries for a landingpad
  
      if (NumShared < TypeIds.size()) {
        // Size of one action entry (typeid + next action)
        unsigned SizeActionEntry = 0;
        unsigned PrevAction = (unsigned)-1;
  
        if (NumShared) {
          unsigned SizePrevIds = PrevLPI->TypeIds.size();
          assert(Actions.size());
          PrevAction = Actions.size() - 1;
          SizeActionEntry = getSLEB128Size(Actions[PrevAction].NextAction) +
                            getSLEB128Size(Actions[PrevAction].ValueForTypeID);
  
          for (unsigned j = NumShared; j != SizePrevIds; ++j) {
            assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
            SizeActionEntry -= getSLEB128Size(Actions[PrevAction].ValueForTypeID);
            SizeActionEntry += -Actions[PrevAction].NextAction;
            PrevAction = Actions[PrevAction].Previous;
          }
        }
  
        // Compute the actions.
        for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
          int TypeID = TypeIds[J];
          assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
          int ValueForTypeID =
              isFilterEHSelector(TypeID) ? FilterOffsets[-1 - TypeID] : TypeID;
          unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
  
          int NextAction = SizeActionEntry ? -(SizeActionEntry + SizeTypeID) : 0;
          SizeActionEntry = SizeTypeID + getSLEB128Size(NextAction);
          SizeSiteActions += SizeActionEntry;
  
          ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
          Actions.push_back(Action);
          PrevAction = Actions.size() - 1;
        }
  
        // Record the first action of the landing pad site.
        FirstAction = SizeActions + SizeSiteActions - SizeActionEntry + 1;
      } // else identical - re-use previous FirstAction
  
      // Information used when creating the call-site table. The action record
      // field of the call site record is the offset of the first associated
      // action record, relative to the start of the actions table. This value is
      // biased by 1 (1 indicating the start of the actions table), and 0
      // indicates that there are no actions.
      FirstActions.push_back(FirstAction);
  
      // Compute this sites contribution to size.
      SizeActions += SizeSiteActions;
  
      PrevLPI = LPI;
    }
  }
  
  /// Return `true' if this is a call to a function marked `nounwind'. Return
  /// `false' otherwise.
  bool EHStreamer::callToNoUnwindFunction(const MachineInstr *MI) {
    assert(MI->isCall() && "This should be a call instruction!");
  
    bool MarkedNoUnwind = false;
    bool SawFunc = false;
  
    for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
      const MachineOperand &MO = MI->getOperand(I);
  
      if (!MO.isGlobal()) continue;
  
      const Function *F = dyn_cast<Function>(MO.getGlobal());
      if (!F) continue;
  
      if (SawFunc) {
        // Be conservative. If we have more than one function operand for this
        // call, then we can't make the assumption that it's the callee and
        // not a parameter to the call.
        //
        // FIXME: Determine if there's a way to say that `F' is the callee or
        // parameter.
        MarkedNoUnwind = false;
        break;
      }
  
      MarkedNoUnwind = F->doesNotThrow();
      SawFunc = true;
    }
  
    return MarkedNoUnwind;
  }
  
  void EHStreamer::computePadMap(
      const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
      RangeMapType &PadMap) {
    // Invokes and nounwind calls have entries in PadMap (due to being bracketed
    // by try-range labels when lowered).  Ordinary calls do not, so appropriate
    // try-ranges for them need be deduced so we can put them in the LSDA.
    for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
      const LandingPadInfo *LandingPad = LandingPads[i];
      for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
        MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
        assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
        PadRange P = { i, j };
        PadMap[BeginLabel] = P;
      }
    }
  }
  
  /// Compute the call-site table.  The entry for an invoke has a try-range
  /// containing the call, a non-zero landing pad, and an appropriate action.  The
  /// entry for an ordinary call has a try-range containing the call and zero for
  /// the landing pad and the action.  Calls marked 'nounwind' have no entry and
  /// must not be contained in the try-range of any entry - they form gaps in the
  /// table.  Entries must be ordered by try-range address.
  void EHStreamer::
  computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
                       const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
                       const SmallVectorImpl<unsigned> &FirstActions) {
    RangeMapType PadMap;
    computePadMap(LandingPads, PadMap);
  
    // The end label of the previous invoke or nounwind try-range.
    MCSymbol *LastLabel = nullptr;
  
    // Whether there is a potentially throwing instruction (currently this means
    // an ordinary call) between the end of the previous try-range and now.
    bool SawPotentiallyThrowing = false;
  
    // Whether the last CallSite entry was for an invoke.
    bool PreviousIsInvoke = false;
  
    bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
  
    // Visit all instructions in order of address.
    for (const auto &MBB : *Asm->MF) {
      for (const auto &MI : MBB) {
        if (!MI.isEHLabel()) {
          if (MI.isCall())
            SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
          continue;
        }
  
        // End of the previous try-range?
        MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
        if (BeginLabel == LastLabel)
          SawPotentiallyThrowing = false;
  
        // Beginning of a new try-range?
        RangeMapType::const_iterator L = PadMap.find(BeginLabel);
        if (L == PadMap.end())
          // Nope, it was just some random label.
          continue;
  
        const PadRange &P = L->second;
        const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
        assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
               "Inconsistent landing pad map!");
  
        // For Dwarf exception handling (SjLj handling doesn't use this). If some
        // instruction between the previous try-range and this one may throw,
        // create a call-site entry with no landing pad for the region between the
        // try-ranges.
        if (SawPotentiallyThrowing && Asm->MAI->usesCFIForEH()) {
          CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 0 };
          CallSites.push_back(Site);
          PreviousIsInvoke = false;
        }
  
        LastLabel = LandingPad->EndLabels[P.RangeIndex];
        assert(BeginLabel && LastLabel && "Invalid landing pad!");
  
        if (!LandingPad->LandingPadLabel) {
          // Create a gap.
          PreviousIsInvoke = false;
        } else {
          // This try-range is for an invoke.
          CallSiteEntry Site = {
            BeginLabel,
            LastLabel,
            LandingPad,
            FirstActions[P.PadIndex]
          };
  
          // Try to merge with the previous call-site. SJLJ doesn't do this
          if (PreviousIsInvoke && !IsSJLJ) {
            CallSiteEntry &Prev = CallSites.back();
            if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) {
              // Extend the range of the previous entry.
              Prev.EndLabel = Site.EndLabel;
              continue;
            }
          }
  
          // Otherwise, create a new call-site.
          if (!IsSJLJ)
            CallSites.push_back(Site);
          else {
            // SjLj EH must maintain the call sites in the order assigned
            // to them by the SjLjPrepare pass.
            unsigned SiteNo = Asm->MF->getCallSiteBeginLabel(BeginLabel);
            if (CallSites.size() < SiteNo)
              CallSites.resize(SiteNo);
            CallSites[SiteNo - 1] = Site;
          }
          PreviousIsInvoke = true;
        }
      }
    }
  
    // If some instruction between the previous try-range and the end of the
    // function may throw, create a call-site entry with no landing pad for the
    // region following the try-range.
    if (SawPotentiallyThrowing && !IsSJLJ) {
      CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
      CallSites.push_back(Site);
    }
  }
  
  /// Emit landing pads and actions.
  ///
  /// The general organization of the table is complex, but the basic concepts are
  /// easy.  First there is a header which describes the location and organization
  /// of the three components that follow.
  ///
  ///  1. The landing pad site information describes the range of code covered by
  ///     the try.  In our case it's an accumulation of the ranges covered by the
  ///     invokes in the try.  There is also a reference to the landing pad that
  ///     handles the exception once processed.  Finally an index into the actions
  ///     table.
  ///  2. The action table, in our case, is composed of pairs of type IDs and next
  ///     action offset.  Starting with the action index from the landing pad
  ///     site, each type ID is checked for a match to the current exception.  If
  ///     it matches then the exception and type id are passed on to the landing
  ///     pad.  Otherwise the next action is looked up.  This chain is terminated
  ///     with a next action of zero.  If no type id is found then the frame is
  ///     unwound and handling continues.
  ///  3. Type ID table contains references to all the C++ typeinfo for all
  ///     catches in the function.  This tables is reverse indexed base 1.
  void EHStreamer::emitExceptionTable() {
    const MachineFunction *MF = Asm->MF;
    const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
    const std::vector<unsigned> &FilterIds = MF->getFilterIds();
    const std::vector<LandingPadInfo> &PadInfos = MF->getLandingPads();
  
    // Sort the landing pads in order of their type ids.  This is used to fold
    // duplicate actions.
    SmallVector<const LandingPadInfo *, 64> LandingPads;
    LandingPads.reserve(PadInfos.size());
  
    for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
      LandingPads.push_back(&PadInfos[i]);
  
    // Order landing pads lexicographically by type id.
    llvm::sort(LandingPads, [](const LandingPadInfo *L, const LandingPadInfo *R) {
      return L->TypeIds < R->TypeIds;
    });
  
    // Compute the actions table and gather the first action index for each
    // landing pad site.
    SmallVector<ActionEntry, 32> Actions;
    SmallVector<unsigned, 64> FirstActions;
    computeActionsTable(LandingPads, Actions, FirstActions);
  
    // Compute the call-site table.
    SmallVector<CallSiteEntry, 64> CallSites;
    computeCallSiteTable(CallSites, LandingPads, FirstActions);
  
    bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
    unsigned CallSiteEncoding =
        IsSJLJ ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_uleb128;
    bool HaveTTData = !TypeInfos.empty() || !FilterIds.empty();
  
    // Type infos.
    MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
    unsigned TTypeEncoding;
  
    if (!HaveTTData) {
      // If there is no TypeInfo, then we just explicitly say that we're omitting
      // that bit.
      TTypeEncoding = dwarf::DW_EH_PE_omit;
    } else {
      // Okay, we have actual filters or typeinfos to emit.  As such, we need to
      // pick a type encoding for them.  We're about to emit a list of pointers to
      // typeinfo objects at the end of the LSDA.  However, unless we're in static
      // mode, this reference will require a relocation by the dynamic linker.
      //
      // Because of this, we have a couple of options:
      //
      //   1) If we are in -static mode, we can always use an absolute reference
      //      from the LSDA, because the static linker will resolve it.
      //
      //   2) Otherwise, if the LSDA section is writable, we can output the direct
      //      reference to the typeinfo and allow the dynamic linker to relocate
      //      it.  Since it is in a writable section, the dynamic linker won't
      //      have a problem.
      //
      //   3) Finally, if we're in PIC mode and the LDSA section isn't writable,
      //      we need to use some form of indirection.  For example, on Darwin,
      //      we can output a statically-relocatable reference to a dyld stub. The
      //      offset to the stub is constant, but the contents are in a section
      //      that is updated by the dynamic linker.  This is easy enough, but we
      //      need to tell the personality function of the unwinder to indirect
      //      through the dyld stub.
      //
      // FIXME: When (3) is actually implemented, we'll have to emit the stubs
      // somewhere.  This predicate should be moved to a shared location that is
      // in target-independent code.
      //
      TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
    }
  
    // Begin the exception table.
    // Sometimes we want not to emit the data into separate section (e.g. ARM
    // EHABI). In this case LSDASection will be NULL.
    if (LSDASection)
      Asm->OutStreamer->SwitchSection(LSDASection);
    Asm->EmitAlignment(2);
  
    // Emit the LSDA.
    MCSymbol *GCCETSym =
      Asm->OutContext.getOrCreateSymbol(Twine("GCC_except_table")+
                                        Twine(Asm->getFunctionNumber()));
    Asm->OutStreamer->EmitLabel(GCCETSym);
    Asm->OutStreamer->EmitLabel(Asm->getCurExceptionSym());
  
    // Emit the LSDA header.
    Asm->EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
    Asm->EmitEncodingByte(TTypeEncoding, "@TType");
  
    MCSymbol *TTBaseLabel = nullptr;
    if (HaveTTData) {
      // N.B.: There is a dependency loop between the size of the TTBase uleb128
      // here and the amount of padding before the aligned type table. The
      // assembler must sometimes pad this uleb128 or insert extra padding before
      // the type table. See PR35809 or GNU as bug 4029.
      MCSymbol *TTBaseRefLabel = Asm->createTempSymbol("ttbaseref");
      TTBaseLabel = Asm->createTempSymbol("ttbase");
      Asm->EmitLabelDifferenceAsULEB128(TTBaseLabel, TTBaseRefLabel);
      Asm->OutStreamer->EmitLabel(TTBaseRefLabel);
    }
  
    bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
  
    // Emit the landing pad call site table.
    MCSymbol *CstBeginLabel = Asm->createTempSymbol("cst_begin");
    MCSymbol *CstEndLabel = Asm->createTempSymbol("cst_end");
    Asm->EmitEncodingByte(CallSiteEncoding, "Call site");
    Asm->EmitLabelDifferenceAsULEB128(CstEndLabel, CstBeginLabel);
    Asm->OutStreamer->EmitLabel(CstBeginLabel);
  
    // SjLj Exception handling
    if (IsSJLJ) {
      unsigned idx = 0;
      for (SmallVectorImpl<CallSiteEntry>::const_iterator
           I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
        const CallSiteEntry &S = *I;
  
        // Index of the call site entry.
        if (VerboseAsm) {
          Asm->OutStreamer->AddComment(">> Call Site " + Twine(idx) + " <<");
          Asm->OutStreamer->AddComment("  On exception at call site "+Twine(idx));
        }
        Asm->EmitULEB128(idx);
  
        // Offset of the first associated action record, relative to the start of
        // the action table. This value is biased by 1 (1 indicates the start of
        // the action table), and 0 indicates that there are no actions.
        if (VerboseAsm) {
          if (S.Action == 0)
            Asm->OutStreamer->AddComment("  Action: cleanup");
          else
            Asm->OutStreamer->AddComment("  Action: " +
                                         Twine((S.Action - 1) / 2 + 1));
        }
        Asm->EmitULEB128(S.Action);
      }
    } else {
      // Itanium LSDA exception handling
  
      // The call-site table is a list of all call sites that may throw an
      // exception (including C++ 'throw' statements) in the procedure
      // fragment. It immediately follows the LSDA header. Each entry indicates,
      // for a given call, the first corresponding action record and corresponding
      // landing pad.
      //
      // The table begins with the number of bytes, stored as an LEB128
      // compressed, unsigned integer. The records immediately follow the record
      // count. They are sorted in increasing call-site address. Each record
      // indicates:
      //
      //   * The position of the call-site.
      //   * The position of the landing pad.
      //   * The first action record for that call site.
      //
      // A missing entry in the call-site table indicates that a call is not
      // supposed to throw.
  
      unsigned Entry = 0;
      for (SmallVectorImpl<CallSiteEntry>::const_iterator
           I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
        const CallSiteEntry &S = *I;
  
        MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
  
        MCSymbol *BeginLabel = S.BeginLabel;
        if (!BeginLabel)
          BeginLabel = EHFuncBeginSym;
        MCSymbol *EndLabel = S.EndLabel;
        if (!EndLabel)
          EndLabel = Asm->getFunctionEnd();
  
        // Offset of the call site relative to the start of the procedure.
        if (VerboseAsm)
          Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + " <<");
        Asm->EmitLabelDifferenceAsULEB128(BeginLabel, EHFuncBeginSym);
        if (VerboseAsm)
          Asm->OutStreamer->AddComment(Twine("  Call between ") +
                                       BeginLabel->getName() + " and " +
                                       EndLabel->getName());
        Asm->EmitLabelDifferenceAsULEB128(EndLabel, BeginLabel);
  
        // Offset of the landing pad relative to the start of the procedure.
        if (!S.LPad) {
          if (VerboseAsm)
            Asm->OutStreamer->AddComment("    has no landing pad");
          Asm->EmitULEB128(0);
        } else {
          if (VerboseAsm)
            Asm->OutStreamer->AddComment(Twine("    jumps to ") +
                                         S.LPad->LandingPadLabel->getName());
          Asm->EmitLabelDifferenceAsULEB128(S.LPad->LandingPadLabel,
                                            EHFuncBeginSym);
        }
  
        // Offset of the first associated action record, relative to the start of
        // the action table. This value is biased by 1 (1 indicates the start of
        // the action table), and 0 indicates that there are no actions.
        if (VerboseAsm) {
          if (S.Action == 0)
            Asm->OutStreamer->AddComment("  On action: cleanup");
          else
            Asm->OutStreamer->AddComment("  On action: " +
                                         Twine((S.Action - 1) / 2 + 1));
        }
        Asm->EmitULEB128(S.Action);
      }
    }
    Asm->OutStreamer->EmitLabel(CstEndLabel);
  
    // Emit the Action Table.
    int Entry = 0;
    for (SmallVectorImpl<ActionEntry>::const_iterator
           I = Actions.begin(), E = Actions.end(); I != E; ++I) {
      const ActionEntry &Action = *I;
  
      if (VerboseAsm) {
        // Emit comments that decode the action table.
        Asm->OutStreamer->AddComment(">> Action Record " + Twine(++Entry) + " <<");
      }
  
      // Type Filter
      //
      //   Used by the runtime to match the type of the thrown exception to the
      //   type of the catch clauses or the types in the exception specification.
      if (VerboseAsm) {
        if (Action.ValueForTypeID > 0)
          Asm->OutStreamer->AddComment("  Catch TypeInfo " +
                                       Twine(Action.ValueForTypeID));
        else if (Action.ValueForTypeID < 0)
          Asm->OutStreamer->AddComment("  Filter TypeInfo " +
                                       Twine(Action.ValueForTypeID));
        else
          Asm->OutStreamer->AddComment("  Cleanup");
      }
      Asm->EmitSLEB128(Action.ValueForTypeID);
  
      // Action Record
      //
      //   Self-relative signed displacement in bytes of the next action record,
      //   or 0 if there is no next action record.
      if (VerboseAsm) {
        if (Action.NextAction == 0) {
          Asm->OutStreamer->AddComment("  No further actions");
        } else {
          unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
          Asm->OutStreamer->AddComment("  Continue to action "+Twine(NextAction));
        }
      }
      Asm->EmitSLEB128(Action.NextAction);
    }
  
    if (HaveTTData) {
      Asm->EmitAlignment(2);
      emitTypeInfos(TTypeEncoding, TTBaseLabel);
    }
  
    Asm->EmitAlignment(2);
  }
  
  void EHStreamer::emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) {
    const MachineFunction *MF = Asm->MF;
    const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
    const std::vector<unsigned> &FilterIds = MF->getFilterIds();
  
    bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
  
    int Entry = 0;
    // Emit the Catch TypeInfos.
    if (VerboseAsm && !TypeInfos.empty()) {
      Asm->OutStreamer->AddComment(">> Catch TypeInfos <<");
      Asm->OutStreamer->AddBlankLine();
      Entry = TypeInfos.size();
    }
  
    for (const GlobalValue *GV : make_range(TypeInfos.rbegin(),
                                            TypeInfos.rend())) {
      if (VerboseAsm)
        Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
      Asm->EmitTTypeReference(GV, TTypeEncoding);
    }
  
    Asm->OutStreamer->EmitLabel(TTBaseLabel);
  
    // Emit the Exception Specifications.
    if (VerboseAsm && !FilterIds.empty()) {
      Asm->OutStreamer->AddComment(">> Filter TypeInfos <<");
      Asm->OutStreamer->AddBlankLine();
      Entry = 0;
    }
    for (std::vector<unsigned>::const_iterator
           I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
      unsigned TypeID = *I;
      if (VerboseAsm) {
        --Entry;
        if (isFilterEHSelector(TypeID))
          Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry));
      }
  
      Asm->EmitULEB128(TypeID);
    }
  }
  