C++ const_iterator::isEHFuncletEntry方法代码示例

/// Emit the language-specific data that __C_specific_handler expects.  This
/// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
/// up after faults with __try, __except, and __finally.  The typeinfo values
/// are not really RTTI data, but pointers to filter functions that return an
/// integer (1, 0, or -1) indicating how to handle the exception. For __finally
/// blocks and other cleanups, the landing pad label is zero, and the filter
/// function is actually a cleanup handler with the same prototype.  A catch-all
/// entry is modeled with a null filter function field and a non-zero landing
/// pad label.
///
/// Possible filter function return values:
///   EXCEPTION_EXECUTE_HANDLER (1):
///     Jump to the landing pad label after cleanups.
///   EXCEPTION_CONTINUE_SEARCH (0):
///     Continue searching this table or continue unwinding.
///   EXCEPTION_CONTINUE_EXECUTION (-1):
///     Resume execution at the trapping PC.
///
/// Inferred table structure:
///   struct Table {
///     int NumEntries;
///     struct Entry {
///       imagerel32 LabelStart;
///       imagerel32 LabelEnd;
///       imagerel32 FilterOrFinally;  // One means catch-all.
///       imagerel32 LabelLPad;        // Zero means __finally.
///     } Entries[NumEntries];
///   };
void WinException::emitCSpecificHandlerTable(const MachineFunction *MF) {
  auto &OS = *Asm->OutStreamer;
  MCContext &Ctx = Asm->OutContext;

  WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(MF->getFunction());
  // Use the assembler to compute the number of table entries through label
  // difference and division.
  MCSymbol *TableBegin =
      Ctx.createTempSymbol("lsda_begin", /*AlwaysAddSuffix=*/true);
  MCSymbol *TableEnd =
      Ctx.createTempSymbol("lsda_end", /*AlwaysAddSuffix=*/true);
  const MCExpr *LabelDiff = getOffset(TableEnd, TableBegin);
  const MCExpr *EntrySize = MCConstantExpr::create(16, Ctx);
  const MCExpr *EntryCount = MCBinaryExpr::createDiv(LabelDiff, EntrySize, Ctx);
  OS.EmitValue(EntryCount, 4);

  OS.EmitLabel(TableBegin);

  // Iterate over all the invoke try ranges. Unlike MSVC, LLVM currently only
  // models exceptions from invokes. LLVM also allows arbitrary reordering of
  // the code, so our tables end up looking a bit different. Rather than
  // trying to match MSVC's tables exactly, we emit a denormalized table.  For
  // each range of invokes in the same state, we emit table entries for all
  // the actions that would be taken in that state. This means our tables are
  // slightly bigger, which is OK.
  const MCSymbol *LastStartLabel = nullptr;
  int LastEHState = -1;
  // Break out before we enter into a finally funclet.
  // FIXME: We need to emit separate EH tables for cleanups.
  MachineFunction::const_iterator End = MF->end();
  MachineFunction::const_iterator Stop = std::next(MF->begin());
  while (Stop != End && !Stop->isEHFuncletEntry())
    ++Stop;
  for (const auto &StateChange :
       InvokeStateChangeIterator::range(FuncInfo, MF->begin(), Stop)) {
    // Emit all the actions for the state we just transitioned out of
    // if it was not the null state
    if (LastEHState != -1)
      emitSEHActionsForRange(FuncInfo, LastStartLabel,
                             StateChange.PreviousEndLabel, LastEHState);
    LastStartLabel = StateChange.NewStartLabel;
    LastEHState = StateChange.NewState;
  }

  OS.EmitLabel(TableEnd);
}