C++ MCSectionData类代码示例

void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
                                       const MCSubtargetInfo &STI) {
  // @LOCALMOD-BEGIN
  if (getAssembler().isBundlingEnabled() &&
      getAssembler().getBackend().CustomExpandInst(Inst, *this)) {
    return;
  }
  // @LOCALMOD-END

  MCStreamer::EmitInstruction(Inst, STI);

  MCSectionData *SD = getCurrentSectionData();
  SD->setHasInstructions(true);

  // Now that a machine instruction has been assembled into this section, make
  // a line entry for any .loc directive that has been seen.
  MCLineEntry::Make(this, getCurrentSection().first);

  // If this instruction doesn't need relaxation, just emit it as data.
  MCAssembler &Assembler = getAssembler();
  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
    EmitInstToData(Inst, STI);
    return;
  }

  // Otherwise, relax and emit it as data if either:
  // - The RelaxAll flag was passed
  // - Bundling is enabled and this instruction is inside a bundle-locked
  //   group. We want to emit all such instructions into the same data
  //   fragment.
  if (Assembler.getRelaxAll() ||
      (Assembler.isBundlingEnabled() && SD->isBundleLocked())) {
    MCInst Relaxed;
    getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
      getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
    EmitInstToData(Relaxed, STI);
    return;
  }

  // Otherwise emit to a separate fragment.
  EmitInstToFragment(Inst, STI);
}

void MCELFStreamer::ChangeSection(const MCSection *Section,
                                  const MCExpr *Subsection) {
  MCSectionData *CurSection = getCurrentSectionData();
  if (CurSection && CurSection->isBundleLocked())
    report_fatal_error("Unterminated .bundle_lock when changing a section");

  MCAssembler &Asm = getAssembler();
  auto *SectionELF = static_cast<const MCSectionELF *>(Section);
  const MCSymbol *Grp = SectionELF->getGroup();
  if (Grp)
    Asm.getOrCreateSymbolData(*Grp);

  this->MCObjectStreamer::ChangeSection(Section, Subsection);
  MCSymbol *SectionSymbol = getContext().getOrCreateSectionSymbol(*SectionELF);
  if (SectionSymbol->isUndefined()) {
    EmitLabel(SectionSymbol);
    MCELF::SetType(Asm.getSymbolData(*SectionSymbol), ELF::STT_SECTION);
  }
}

void MCObjectStreamer::EmitInstruction(const MCInst &Inst) {
  // Scan for values.
  for (unsigned i = Inst.getNumOperands(); i--; )
    if (Inst.getOperand(i).isExpr())
      AddValueSymbols(Inst.getOperand(i).getExpr());

  MCSectionData *SD = getCurrentSectionData();
  SD->setHasInstructions(true);

  // Now that a machine instruction has been assembled into this section, make
  // a line entry for any .loc directive that has been seen.
  MCLineEntry::Make(this, getCurrentSection().first);

  // If this instruction doesn't need relaxation, just emit it as data.
  MCAssembler &Assembler = getAssembler();
  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
    EmitInstToData(Inst);
    return;
  }

  // Otherwise, relax and emit it as data if either:
  // - The RelaxAll flag was passed
  // - Bundling is enabled and this instruction is inside a bundle-locked
  //   group. We want to emit all such instructions into the same data
  //   fragment.
  if (Assembler.getRelaxAll() ||
      (Assembler.isBundlingEnabled() && SD->isBundleLocked())) {
    MCInst Relaxed;
    getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
      getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
    EmitInstToData(Relaxed);
    return;
  }

  // Otherwise emit to a separate fragment.
  EmitInstToFragment(Inst);
}

void MCELFStreamer::EmitInstToData(const MCInst &Inst,
                                   const MCSubtargetInfo &STI) {
  MCAssembler &Assembler = getAssembler();
  SmallVector<MCFixup, 4> Fixups;
  SmallString<256> Code;
  raw_svector_ostream VecOS(Code);
  Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups, STI);
  VecOS.flush();

  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
    fixSymbolsInTLSFixups(Fixups[i].getValue());

  // There are several possibilities here:
  //
  // If bundling is disabled, append the encoded instruction to the current data
  // fragment (or create a new such fragment if the current fragment is not a
  // data fragment).
  //
  // If bundling is enabled:
  // - If we're not in a bundle-locked group, emit the instruction into a
  //   fragment of its own. If there are no fixups registered for the
  //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
  //   MCDataFragment.
  // - If we're in a bundle-locked group, append the instruction to the current
  //   data fragment because we want all the instructions in a group to get into
  //   the same fragment. Be careful not to do that for the first instruction in
  //   the group, though.
  MCDataFragment *DF;

  if (Assembler.isBundlingEnabled()) {
    MCSectionData *SD = getCurrentSectionData();
    if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
      // If we are bundle-locked, we re-use the current fragment.
      // The bundle-locking directive ensures this is a new data fragment.
      DF = cast<MCDataFragment>(getCurrentFragment());
    else if (!SD->isBundleLocked() && Fixups.size() == 0) {
      // Optimize memory usage by emitting the instruction to a
      // MCCompactEncodedInstFragment when not in a bundle-locked group and
      // there are no fixups registered.
      MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
      insert(CEIF);
      CEIF->getContents().append(Code.begin(), Code.end());
      return;
    } else {
      DF = new MCDataFragment();
      insert(DF);
    }
    if (SD->getBundleLockState() == MCSectionData::BundleLockedAlignToEnd) {
      // If this fragment is for a group marked "align_to_end", set a flag
      // in the fragment. This can happen after the fragment has already been
      // created if there are nested bundle_align groups and an inner one
      // is the one marked align_to_end.
      DF->setAlignToBundleEnd(true);
    }

    // We're now emitting an instruction in a bundle group, so this flag has
    // to be turned off.
    SD->setBundleGroupBeforeFirstInst(false);
  } else {
    DF = getOrCreateDataFragment();
  }

  // Add the fixups and data.
  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
    DF->getFixups().push_back(Fixups[i]);
  }
  DF->setHasInstructions(true);
  DF->getContents().append(Code.begin(), Code.end());
}