fix ya.make

4 files changed, 3804 insertions, 0 deletions

diff --git a/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinker.cpp b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinker.cpp
new file mode 100644
index 0000000000..d20f6dd8f3
--- /dev/null
+++ b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinker.cpp
@@ -0,0 +1,2637 @@
+//=== DWARFLinker.cpp -----------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DWARFLinker/DWARFLinker.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/CodeGen/NonRelocatableStringpool.h"
+#include "llvm/DWARFLinker/DWARFLinkerDeclContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
+#include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
+#include "llvm/DebugInfo/DWARF/DWARFDebugRangeList.h"
+#include "llvm/DebugInfo/DWARF/DWARFDie.h"
+#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
+#include "llvm/DebugInfo/DWARF/DWARFSection.h"
+#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ThreadPool.h"
+#include <vector>
+
+namespace llvm {
+
+/// Hold the input and output of the debug info size in bytes.
+struct DebugInfoSize {
+  uint64_t Input;
+  uint64_t Output;
+};
+
+/// Compute the total size of the debug info.
+static uint64_t getDebugInfoSize(DWARFContext &Dwarf) {
+  uint64_t Size = 0;
+  for (auto &Unit : Dwarf.compile_units()) {
+    Size += Unit->getLength();
+  }
+  return Size;
+}
+
+/// Similar to DWARFUnitSection::getUnitForOffset(), but returning our
+/// CompileUnit object instead.
+static CompileUnit *getUnitForOffset(const UnitListTy &Units, uint64_t Offset) {
+  auto CU = llvm::upper_bound(
+      Units, Offset, [](uint64_t LHS, const std::unique_ptr<CompileUnit> &RHS) {
+        return LHS < RHS->getOrigUnit().getNextUnitOffset();
+      });
+  return CU != Units.end() ? CU->get() : nullptr;
+}
+
+/// Resolve the DIE attribute reference that has been extracted in \p RefValue.
+/// The resulting DIE might be in another CompileUnit which is stored into \p
+/// ReferencedCU. \returns null if resolving fails for any reason.
+DWARFDie DWARFLinker::resolveDIEReference(const DWARFFile &File,
+                                          const UnitListTy &Units,
+                                          const DWARFFormValue &RefValue,
+                                          const DWARFDie &DIE,
+                                          CompileUnit *&RefCU) {
+  assert(RefValue.isFormClass(DWARFFormValue::FC_Reference));
+  uint64_t RefOffset = *RefValue.getAsReference();
+  if ((RefCU = getUnitForOffset(Units, RefOffset)))
+    if (const auto RefDie = RefCU->getOrigUnit().getDIEForOffset(RefOffset)) {
+      // In a file with broken references, an attribute might point to a NULL
+      // DIE.
+      if (!RefDie.isNULL())
+        return RefDie;
+    }
+
+  reportWarning("could not find referenced DIE", File, &DIE);
+  return DWARFDie();
+}
+
+/// \returns whether the passed \a Attr type might contain a DIE reference
+/// suitable for ODR uniquing.
+static bool isODRAttribute(uint16_t Attr) {
+  switch (Attr) {
+  default:
+    return false;
+  case dwarf::DW_AT_type:
+  case dwarf::DW_AT_containing_type:
+  case dwarf::DW_AT_specification:
+  case dwarf::DW_AT_abstract_origin:
+  case dwarf::DW_AT_import:
+    return true;
+  }
+  llvm_unreachable("Improper attribute.");
+}
+
+static bool isTypeTag(uint16_t Tag) {
+  switch (Tag) {
+  case dwarf::DW_TAG_array_type:
+  case dwarf::DW_TAG_class_type:
+  case dwarf::DW_TAG_enumeration_type:
+  case dwarf::DW_TAG_pointer_type:
+  case dwarf::DW_TAG_reference_type:
+  case dwarf::DW_TAG_string_type:
+  case dwarf::DW_TAG_structure_type:
+  case dwarf::DW_TAG_subroutine_type:
+  case dwarf::DW_TAG_typedef:
+  case dwarf::DW_TAG_union_type:
+  case dwarf::DW_TAG_ptr_to_member_type:
+  case dwarf::DW_TAG_set_type:
+  case dwarf::DW_TAG_subrange_type:
+  case dwarf::DW_TAG_base_type:
+  case dwarf::DW_TAG_const_type:
+  case dwarf::DW_TAG_constant:
+  case dwarf::DW_TAG_file_type:
+  case dwarf::DW_TAG_namelist:
+  case dwarf::DW_TAG_packed_type:
+  case dwarf::DW_TAG_volatile_type:
+  case dwarf::DW_TAG_restrict_type:
+  case dwarf::DW_TAG_atomic_type:
+  case dwarf::DW_TAG_interface_type:
+  case dwarf::DW_TAG_unspecified_type:
+  case dwarf::DW_TAG_shared_type:
+    return true;
+  default:
+    break;
+  }
+  return false;
+}
+
+AddressesMap::~AddressesMap() {}
+
+DwarfEmitter::~DwarfEmitter() {}
+
+static Optional<StringRef> StripTemplateParameters(StringRef Name) {
+  // We are looking for template parameters to strip from Name. e.g.
+  //
+  //  operator<<B>
+  //
+  // We look for > at the end but if it does not contain any < then we
+  // have something like operator>>. We check for the operator<=> case.
+  if (!Name.endswith(">") || Name.count("<") == 0 || Name.endswith("<=>"))
+    return {};
+
+  // How many < until we have the start of the template parameters.
+  size_t NumLeftAnglesToSkip = 1;
+
+  // If we have operator<=> then we need to skip its < as well.
+  NumLeftAnglesToSkip += Name.count("<=>");
+
+  size_t RightAngleCount = Name.count('>');
+  size_t LeftAngleCount = Name.count('<');
+
+  // If we have more < than > we have operator< or operator<<
+  // we to account for their < as well.
+  if (LeftAngleCount > RightAngleCount)
+    NumLeftAnglesToSkip += LeftAngleCount - RightAngleCount;
+
+  size_t StartOfTemplate = 0;
+  while (NumLeftAnglesToSkip--)
+    StartOfTemplate = Name.find('<', StartOfTemplate) + 1;
+
+  return Name.substr(0, StartOfTemplate - 1);
+}
+
+bool DWARFLinker::DIECloner::getDIENames(const DWARFDie &Die,
+                                         AttributesInfo &Info,
+                                         OffsetsStringPool &StringPool,
+                                         bool StripTemplate) {
+  // This function will be called on DIEs having low_pcs and
+  // ranges. As getting the name might be more expansive, filter out
+  // blocks directly.
+  if (Die.getTag() == dwarf::DW_TAG_lexical_block)
+    return false;
+
+  if (!Info.MangledName)
+    if (const char *MangledName = Die.getLinkageName())
+      Info.MangledName = StringPool.getEntry(MangledName);
+
+  if (!Info.Name)
+    if (const char *Name = Die.getShortName())
+      Info.Name = StringPool.getEntry(Name);
+
+  if (!Info.MangledName)
+    Info.MangledName = Info.Name;
+
+  if (StripTemplate && Info.Name && Info.MangledName != Info.Name) {
+    StringRef Name = Info.Name.getString();
+    if (Optional<StringRef> StrippedName = StripTemplateParameters(Name))
+      Info.NameWithoutTemplate = StringPool.getEntry(*StrippedName);
+  }
+
+  return Info.Name || Info.MangledName;
+}
+
+/// Resolve the relative path to a build artifact referenced by DWARF by
+/// applying DW_AT_comp_dir.
+static void resolveRelativeObjectPath(SmallVectorImpl<char> &Buf, DWARFDie CU) {
+  sys::path::append(Buf, dwarf::toString(CU.find(dwarf::DW_AT_comp_dir), ""));
+}
+
+/// Collect references to parseable Swift interfaces in imported
+/// DW_TAG_module blocks.
+static void analyzeImportedModule(
+    const DWARFDie &DIE, CompileUnit &CU,
+    swiftInterfacesMap *ParseableSwiftInterfaces,
+    std::function<void(const Twine &, const DWARFDie &)> ReportWarning) {
+  if (CU.getLanguage() != dwarf::DW_LANG_Swift)
+    return;
+
+  if (!ParseableSwiftInterfaces)
+    return;
+
+  StringRef Path = dwarf::toStringRef(DIE.find(dwarf::DW_AT_LLVM_include_path));
+  if (!Path.endswith(".swiftinterface"))
+    return;
+  // Don't track interfaces that are part of the SDK.
+  StringRef SysRoot = dwarf::toStringRef(DIE.find(dwarf::DW_AT_LLVM_sysroot));
+  if (SysRoot.empty())
+    SysRoot = CU.getSysRoot();
+  if (!SysRoot.empty() && Path.startswith(SysRoot))
+    return;
+  if (Optional<DWARFFormValue> Val = DIE.find(dwarf::DW_AT_name))
+    if (Optional<const char *> Name = Val->getAsCString()) {
+      auto &Entry = (*ParseableSwiftInterfaces)[*Name];
+      // The prepend path is applied later when copying.
+      DWARFDie CUDie = CU.getOrigUnit().getUnitDIE();
+      SmallString<128> ResolvedPath;
+      if (sys::path::is_relative(Path))
+        resolveRelativeObjectPath(ResolvedPath, CUDie);
+      sys::path::append(ResolvedPath, Path);
+      if (!Entry.empty() && Entry != ResolvedPath)
+        ReportWarning(
+            Twine("Conflicting parseable interfaces for Swift Module ") +
+                *Name + ": " + Entry + " and " + Path,
+            DIE);
+      Entry = std::string(ResolvedPath.str());
+    }
+}
+
+/// The distinct types of work performed by the work loop in
+/// analyzeContextInfo.
+enum class ContextWorklistItemType : uint8_t {
+  AnalyzeContextInfo,
+  UpdateChildPruning,
+  UpdatePruning,
+};
+
+/// This class represents an item in the work list. The type defines what kind
+/// of work needs to be performed when processing the current item. Everything
+/// but the Type and Die fields are optional based on the type.
+struct ContextWorklistItem {
+  DWARFDie Die;
+  unsigned ParentIdx;
+  union {
+    CompileUnit::DIEInfo *OtherInfo;
+    DeclContext *Context;
+  };
+  ContextWorklistItemType Type;
+  bool InImportedModule;
+
+  ContextWorklistItem(DWARFDie Die, ContextWorklistItemType T,
+                      CompileUnit::DIEInfo *OtherInfo = nullptr)
+      : Die(Die), ParentIdx(0), OtherInfo(OtherInfo), Type(T),
+        InImportedModule(false) {}
+
+  ContextWorklistItem(DWARFDie Die, DeclContext *Context, unsigned ParentIdx,
+                      bool InImportedModule)
+      : Die(Die), ParentIdx(ParentIdx), Context(Context),
+        Type(ContextWorklistItemType::AnalyzeContextInfo),
+        InImportedModule(InImportedModule) {}
+};
+
+static bool updatePruning(const DWARFDie &Die, CompileUnit &CU,
+                          uint64_t ModulesEndOffset) {
+  CompileUnit::DIEInfo &Info = CU.getInfo(Die);
+
+  // Prune this DIE if it is either a forward declaration inside a
+  // DW_TAG_module or a DW_TAG_module that contains nothing but
+  // forward declarations.
+  Info.Prune &= (Die.getTag() == dwarf::DW_TAG_module) ||
+                (isTypeTag(Die.getTag()) &&
+                 dwarf::toUnsigned(Die.find(dwarf::DW_AT_declaration), 0));
+
+  // Only prune forward declarations inside a DW_TAG_module for which a
+  // definition exists elsewhere.
+  if (ModulesEndOffset == 0)
+    Info.Prune &= Info.Ctxt && Info.Ctxt->getCanonicalDIEOffset();
+  else
+    Info.Prune &= Info.Ctxt && Info.Ctxt->getCanonicalDIEOffset() > 0 &&
+                  Info.Ctxt->getCanonicalDIEOffset() <= ModulesEndOffset;
+
+  return Info.Prune;
+}
+
+static void updateChildPruning(const DWARFDie &Die, CompileUnit &CU,
+                               CompileUnit::DIEInfo &ChildInfo) {
+  CompileUnit::DIEInfo &Info = CU.getInfo(Die);
+  Info.Prune &= ChildInfo.Prune;
+}
+
+/// Recursive helper to build the global DeclContext information and
+/// gather the child->parent relationships in the original compile unit.
+///
+/// This function uses the same work list approach as lookForDIEsToKeep.
+///
+/// \return true when this DIE and all of its children are only
+/// forward declarations to types defined in external clang modules
+/// (i.e., forward declarations that are children of a DW_TAG_module).
+static bool analyzeContextInfo(
+    const DWARFDie &DIE, unsigned ParentIdx, CompileUnit &CU,
+    DeclContext *CurrentDeclContext, DeclContextTree &Contexts,
+    uint64_t ModulesEndOffset, swiftInterfacesMap *ParseableSwiftInterfaces,
+    std::function<void(const Twine &, const DWARFDie &)> ReportWarning,
+    bool InImportedModule = false) {
+  // LIFO work list.
+  std::vector<ContextWorklistItem> Worklist;
+  Worklist.emplace_back(DIE, CurrentDeclContext, ParentIdx, InImportedModule);
+
+  while (!Worklist.empty()) {
+    ContextWorklistItem Current = Worklist.back();
+    Worklist.pop_back();
+
+    switch (Current.Type) {
+    case ContextWorklistItemType::UpdatePruning:
+      updatePruning(Current.Die, CU, ModulesEndOffset);
+      continue;
+    case ContextWorklistItemType::UpdateChildPruning:
+      updateChildPruning(Current.Die, CU, *Current.OtherInfo);
+      continue;
+    case ContextWorklistItemType::AnalyzeContextInfo:
+      break;
+    }
+
+    unsigned Idx = CU.getOrigUnit().getDIEIndex(Current.Die);
+    CompileUnit::DIEInfo &Info = CU.getInfo(Idx);
+
+    // Clang imposes an ODR on modules(!) regardless of the language:
+    //  "The module-id should consist of only a single identifier,
+    //   which provides the name of the module being defined. Each
+    //   module shall have a single definition."
+    //
+    // This does not extend to the types inside the modules:
+    //  "[I]n C, this implies that if two structs are defined in
+    //   different submodules with the same name, those two types are
+    //   distinct types (but may be compatible types if their
+    //   definitions match)."
+    //
+    // We treat non-C++ modules like namespaces for this reason.
+    if (Current.Die.getTag() == dwarf::DW_TAG_module &&
+        Current.ParentIdx == 0 &&
+        dwarf::toString(Current.Die.find(dwarf::DW_AT_name), "") !=
+            CU.getClangModuleName()) {
+      Current.InImportedModule = true;
+      analyzeImportedModule(Current.Die, CU, ParseableSwiftInterfaces,
+                            ReportWarning);
+    }
+
+    Info.ParentIdx = Current.ParentIdx;
+    bool InClangModule = CU.isClangModule() || Current.InImportedModule;
+    if (CU.hasODR() || InClangModule) {
+      if (Current.Context) {
+        auto PtrInvalidPair = Contexts.getChildDeclContext(
+            *Current.Context, Current.Die, CU, InClangModule);
+        Current.Context = PtrInvalidPair.getPointer();
+        Info.Ctxt =
+            PtrInvalidPair.getInt() ? nullptr : PtrInvalidPair.getPointer();
+        if (Info.Ctxt)
+          Info.Ctxt->setDefinedInClangModule(InClangModule);
+      } else
+        Info.Ctxt = Current.Context = nullptr;
+    }
+
+    Info.Prune = Current.InImportedModule;
+    // Add children in reverse order to the worklist to effectively process
+    // them in order.
+    Worklist.emplace_back(Current.Die, ContextWorklistItemType::UpdatePruning);
+    for (auto Child : reverse(Current.Die.children())) {
+      CompileUnit::DIEInfo &ChildInfo = CU.getInfo(Child);
+      Worklist.emplace_back(
+          Current.Die, ContextWorklistItemType::UpdateChildPruning, &ChildInfo);
+      Worklist.emplace_back(Child, Current.Context, Idx,
+                            Current.InImportedModule);
+    }
+  }
+
+  return CU.getInfo(DIE).Prune;
+}
+
+static bool dieNeedsChildrenToBeMeaningful(uint32_t Tag) {
+  switch (Tag) {
+  default:
+    return false;
+  case dwarf::DW_TAG_class_type:
+  case dwarf::DW_TAG_common_block:
+  case dwarf::DW_TAG_lexical_block:
+  case dwarf::DW_TAG_structure_type:
+  case dwarf::DW_TAG_subprogram:
+  case dwarf::DW_TAG_subroutine_type:
+  case dwarf::DW_TAG_union_type:
+    return true;
+  }
+  llvm_unreachable("Invalid Tag");
+}
+
+void DWARFLinker::cleanupAuxiliarryData(LinkContext &Context) {
+  Context.clear();
+
+  for (auto I = DIEBlocks.begin(), E = DIEBlocks.end(); I != E; ++I)
+    (*I)->~DIEBlock();
+  for (auto I = DIELocs.begin(), E = DIELocs.end(); I != E; ++I)
+    (*I)->~DIELoc();
+
+  DIEBlocks.clear();
+  DIELocs.clear();
+  DIEAlloc.Reset();
+}
+
+/// Check if a variable describing DIE should be kept.
+/// \returns updated TraversalFlags.
+unsigned DWARFLinker::shouldKeepVariableDIE(AddressesMap &RelocMgr,
+                                            const DWARFDie &DIE,
+                                            CompileUnit::DIEInfo &MyInfo,
+                                            unsigned Flags) {
+  const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
+
+  // Global variables with constant value can always be kept.
+  if (!(Flags & TF_InFunctionScope) &&
+      Abbrev->findAttributeIndex(dwarf::DW_AT_const_value)) {
+    MyInfo.InDebugMap = true;
+    return Flags | TF_Keep;
+  }
+
+  // See if there is a relocation to a valid debug map entry inside
+  // this variable's location. The order is important here. We want to
+  // always check if the variable has a valid relocation, so that the
+  // DIEInfo is filled. However, we don't want a static variable in a
+  // function to force us to keep the enclosing function.
+  if (!RelocMgr.hasLiveMemoryLocation(DIE, MyInfo) ||
+      (Flags & TF_InFunctionScope))
+    return Flags;
+
+  if (Options.Verbose) {
+    outs() << "Keeping variable DIE:";
+    DIDumpOptions DumpOpts;
+    DumpOpts.ChildRecurseDepth = 0;
+    DumpOpts.Verbose = Options.Verbose;
+    DIE.dump(outs(), 8 /* Indent */, DumpOpts);
+  }
+
+  return Flags | TF_Keep;
+}
+
+/// Check if a function describing DIE should be kept.
+/// \returns updated TraversalFlags.
+unsigned DWARFLinker::shouldKeepSubprogramDIE(
+    AddressesMap &RelocMgr, RangesTy &Ranges, const DWARFDie &DIE,
+    const DWARFFile &File, CompileUnit &Unit, CompileUnit::DIEInfo &MyInfo,
+    unsigned Flags) {
+  Flags |= TF_InFunctionScope;
+
+  auto LowPc = dwarf::toAddress(DIE.find(dwarf::DW_AT_low_pc));
+  if (!LowPc)
+    return Flags;
+
+  assert(LowPc.hasValue() && "low_pc attribute is not an address.");
+  if (!RelocMgr.hasLiveAddressRange(DIE, MyInfo))
+    return Flags;
+
+  if (Options.Verbose) {
+    outs() << "Keeping subprogram DIE:";
+    DIDumpOptions DumpOpts;
+    DumpOpts.ChildRecurseDepth = 0;
+    DumpOpts.Verbose = Options.Verbose;
+    DIE.dump(outs(), 8 /* Indent */, DumpOpts);
+  }
+
+  if (DIE.getTag() == dwarf::DW_TAG_label) {
+    if (Unit.hasLabelAt(*LowPc))
+      return Flags;
+
+    DWARFUnit &OrigUnit = Unit.getOrigUnit();
+    // FIXME: dsymutil-classic compat. dsymutil-classic doesn't consider labels
+    // that don't fall into the CU's aranges. This is wrong IMO. Debug info
+    // generation bugs aside, this is really wrong in the case of labels, where
+    // a label marking the end of a function will have a PC == CU's high_pc.
+    if (dwarf::toAddress(OrigUnit.getUnitDIE().find(dwarf::DW_AT_high_pc))
+            .getValueOr(UINT64_MAX) <= LowPc)
+      return Flags;
+    Unit.addLabelLowPc(*LowPc, MyInfo.AddrAdjust);
+    return Flags | TF_Keep;
+  }
+
+  Flags |= TF_Keep;
+
+  Optional<uint64_t> HighPc = DIE.getHighPC(*LowPc);
+  if (!HighPc) {
+    reportWarning("Function without high_pc. Range will be discarded.\n", File,
+                  &DIE);
+    return Flags;
+  }
+
+  // Replace the debug map range with a more accurate one.
+  Ranges[*LowPc] = ObjFileAddressRange(*HighPc, MyInfo.AddrAdjust);
+  Unit.addFunctionRange(*LowPc, *HighPc, MyInfo.AddrAdjust);
+  return Flags;
+}
+
+/// Check if a DIE should be kept.
+/// \returns updated TraversalFlags.
+unsigned DWARFLinker::shouldKeepDIE(AddressesMap &RelocMgr, RangesTy &Ranges,
+                                    const DWARFDie &DIE, const DWARFFile &File,
+                                    CompileUnit &Unit,
+                                    CompileUnit::DIEInfo &MyInfo,
+                                    unsigned Flags) {
+  switch (DIE.getTag()) {
+  case dwarf::DW_TAG_constant:
+  case dwarf::DW_TAG_variable:
+    return shouldKeepVariableDIE(RelocMgr, DIE, MyInfo, Flags);
+  case dwarf::DW_TAG_subprogram:
+  case dwarf::DW_TAG_label:
+    return shouldKeepSubprogramDIE(RelocMgr, Ranges, DIE, File, Unit, MyInfo,
+                                   Flags);
+  case dwarf::DW_TAG_base_type:
+    // DWARF Expressions may reference basic types, but scanning them
+    // is expensive. Basic types are tiny, so just keep all of them.
+  case dwarf::DW_TAG_imported_module:
+  case dwarf::DW_TAG_imported_declaration:
+  case dwarf::DW_TAG_imported_unit:
+    // We always want to keep these.
+    return Flags | TF_Keep;
+  default:
+    break;
+  }
+
+  return Flags;
+}
+
+/// Helper that updates the completeness of the current DIE based on the
+/// completeness of one of its children. It depends on the incompleteness of
+/// the children already being computed.
+static void updateChildIncompleteness(const DWARFDie &Die, CompileUnit &CU,
+                                      CompileUnit::DIEInfo &ChildInfo) {
+  switch (Die.getTag()) {
+  case dwarf::DW_TAG_structure_type:
+  case dwarf::DW_TAG_class_type:
+    break;
+  default:
+    return;
+  }
+
+  CompileUnit::DIEInfo &MyInfo = CU.getInfo(Die);
+
+  if (ChildInfo.Incomplete || ChildInfo.Prune)
+    MyInfo.Incomplete = true;
+}
+
+/// Helper that updates the completeness of the current DIE based on the
+/// completeness of the DIEs it references. It depends on the incompleteness of
+/// the referenced DIE already being computed.
+static void updateRefIncompleteness(const DWARFDie &Die, CompileUnit &CU,
+                                    CompileUnit::DIEInfo &RefInfo) {
+  switch (Die.getTag()) {
+  case dwarf::DW_TAG_typedef:
+  case dwarf::DW_TAG_member:
+  case dwarf::DW_TAG_reference_type:
+  case dwarf::DW_TAG_ptr_to_member_type:
+  case dwarf::DW_TAG_pointer_type:
+    break;
+  default:
+    return;
+  }
+
+  CompileUnit::DIEInfo &MyInfo = CU.getInfo(Die);
+
+  if (MyInfo.Incomplete)
+    return;
+
+  if (RefInfo.Incomplete)
+    MyInfo.Incomplete = true;
+}
+
+/// Look at the children of the given DIE and decide whether they should be
+/// kept.
+void DWARFLinker::lookForChildDIEsToKeep(
+    const DWARFDie &Die, CompileUnit &CU, unsigned Flags,
+    SmallVectorImpl<WorklistItem> &Worklist) {
+  // The TF_ParentWalk flag tells us that we are currently walking up the
+  // parent chain of a required DIE, and we don't want to mark all the children
+  // of the parents as kept (consider for example a DW_TAG_namespace node in
+  // the parent chain). There are however a set of DIE types for which we want
+  // to ignore that directive and still walk their children.
+  if (dieNeedsChildrenToBeMeaningful(Die.getTag()))
+    Flags &= ~DWARFLinker::TF_ParentWalk;
+
+  // We're finished if this DIE has no children or we're walking the parent
+  // chain.
+  if (!Die.hasChildren() || (Flags & DWARFLinker::TF_ParentWalk))
+    return;
+
+  // Add children in reverse order to the worklist to effectively process them
+  // in order.
+  for (auto Child : reverse(Die.children())) {
+    // Add a worklist item before every child to calculate incompleteness right
+    // after the current child is processed.
+    CompileUnit::DIEInfo &ChildInfo = CU.getInfo(Child);
+    Worklist.emplace_back(Die, CU, WorklistItemType::UpdateChildIncompleteness,
+                          &ChildInfo);
+    Worklist.emplace_back(Child, CU, Flags);
+  }
+}
+
+/// Look at DIEs referenced by the given DIE and decide whether they should be
+/// kept. All DIEs referenced though attributes should be kept.
+void DWARFLinker::lookForRefDIEsToKeep(
+    const DWARFDie &Die, CompileUnit &CU, unsigned Flags,
+    const UnitListTy &Units, const DWARFFile &File,
+    SmallVectorImpl<WorklistItem> &Worklist) {
+  bool UseOdr = (Flags & DWARFLinker::TF_DependencyWalk)
+                    ? (Flags & DWARFLinker::TF_ODR)
+                    : CU.hasODR();
+  DWARFUnit &Unit = CU.getOrigUnit();
+  DWARFDataExtractor Data = Unit.getDebugInfoExtractor();
+  const auto *Abbrev = Die.getAbbreviationDeclarationPtr();
+  uint64_t Offset = Die.getOffset() + getULEB128Size(Abbrev->getCode());
+
+  SmallVector<std::pair<DWARFDie, CompileUnit &>, 4> ReferencedDIEs;
+  for (const auto &AttrSpec : Abbrev->attributes()) {
+    DWARFFormValue Val(AttrSpec.Form);
+    if (!Val.isFormClass(DWARFFormValue::FC_Reference) ||
+        AttrSpec.Attr == dwarf::DW_AT_sibling) {
+      DWARFFormValue::skipValue(AttrSpec.Form, Data, &Offset,
+                                Unit.getFormParams());
+      continue;
+    }
+
+    Val.extractValue(Data, &Offset, Unit.getFormParams(), &Unit);
+    CompileUnit *ReferencedCU;
+    if (auto RefDie =
+            resolveDIEReference(File, Units, Val, Die, ReferencedCU)) {
+      CompileUnit::DIEInfo &Info = ReferencedCU->getInfo(RefDie);
+      bool IsModuleRef = Info.Ctxt && Info.Ctxt->getCanonicalDIEOffset() &&
+                         Info.Ctxt->isDefinedInClangModule();
+      // If the referenced DIE has a DeclContext that has already been
+      // emitted, then do not keep the one in this CU. We'll link to
+      // the canonical DIE in cloneDieReferenceAttribute.
+      //
+      // FIXME: compatibility with dsymutil-classic. UseODR shouldn't
+      // be necessary and could be advantageously replaced by
+      // ReferencedCU->hasODR() && CU.hasODR().
+      //
+      // FIXME: compatibility with dsymutil-classic. There is no
+      // reason not to unique ref_addr references.
+      if (AttrSpec.Form != dwarf::DW_FORM_ref_addr && (UseOdr || IsModuleRef) &&
+          Info.Ctxt &&
+          Info.Ctxt != ReferencedCU->getInfo(Info.ParentIdx).Ctxt &&
+          Info.Ctxt->getCanonicalDIEOffset() && isODRAttribute(AttrSpec.Attr))
+        continue;
+
+      // Keep a module forward declaration if there is no definition.
+      if (!(isODRAttribute(AttrSpec.Attr) && Info.Ctxt &&
+            Info.Ctxt->getCanonicalDIEOffset()))
+        Info.Prune = false;
+      ReferencedDIEs.emplace_back(RefDie, *ReferencedCU);
+    }
+  }
+
+  unsigned ODRFlag = UseOdr ? DWARFLinker::TF_ODR : 0;
+
+  // Add referenced DIEs in reverse order to the worklist to effectively
+  // process them in order.
+  for (auto &P : reverse(ReferencedDIEs)) {
+    // Add a worklist item before every child to calculate incompleteness right
+    // after the current child is processed.
+    CompileUnit::DIEInfo &Info = P.second.getInfo(P.first);
+    Worklist.emplace_back(Die, CU, WorklistItemType::UpdateRefIncompleteness,
+                          &Info);
+    Worklist.emplace_back(P.first, P.second,
+                          DWARFLinker::TF_Keep |
+                              DWARFLinker::TF_DependencyWalk | ODRFlag);
+  }
+}
+
+/// Look at the parent of the given DIE and decide whether they should be kept.
+void DWARFLinker::lookForParentDIEsToKeep(
+    unsigned AncestorIdx, CompileUnit &CU, unsigned Flags,
+    SmallVectorImpl<WorklistItem> &Worklist) {
+  // Stop if we encounter an ancestor that's already marked as kept.
+  if (CU.getInfo(AncestorIdx).Keep)
+    return;
+
+  DWARFUnit &Unit = CU.getOrigUnit();
+  DWARFDie ParentDIE = Unit.getDIEAtIndex(AncestorIdx);
+  Worklist.emplace_back(CU.getInfo(AncestorIdx).ParentIdx, CU, Flags);
+  Worklist.emplace_back(ParentDIE, CU, Flags);
+}
+
+/// Recursively walk the \p DIE tree and look for DIEs to keep. Store that
+/// information in \p CU's DIEInfo.
+///
+/// This function is the entry point of the DIE selection algorithm. It is
+/// expected to walk the DIE tree in file order and (though the mediation of
+/// its helper) call hasValidRelocation() on each DIE that might be a 'root
+/// DIE' (See DwarfLinker class comment).
+///
+/// While walking the dependencies of root DIEs, this function is also called,
+/// but during these dependency walks the file order is not respected. The
+/// TF_DependencyWalk flag tells us which kind of traversal we are currently
+/// doing.
+///
+/// The recursive algorithm is implemented iteratively as a work list because
+/// very deep recursion could exhaust the stack for large projects. The work
+/// list acts as a scheduler for different types of work that need to be
+/// performed.
+///
+/// The recursive nature of the algorithm is simulated by running the "main"
+/// algorithm (LookForDIEsToKeep) followed by either looking at more DIEs
+/// (LookForChildDIEsToKeep, LookForRefDIEsToKeep, LookForParentDIEsToKeep) or
+/// fixing up a computed property (UpdateChildIncompleteness,
+/// UpdateRefIncompleteness).
+///
+/// The return value indicates whether the DIE is incomplete.
+void DWARFLinker::lookForDIEsToKeep(AddressesMap &AddressesMap,
+                                    RangesTy &Ranges, const UnitListTy &Units,
+                                    const DWARFDie &Die, const DWARFFile &File,
+                                    CompileUnit &Cu, unsigned Flags) {
+  // LIFO work list.
+  SmallVector<WorklistItem, 4> Worklist;
+  Worklist.emplace_back(Die, Cu, Flags);
+
+  while (!Worklist.empty()) {
+    WorklistItem Current = Worklist.pop_back_val();
+
+    // Look at the worklist type to decide what kind of work to perform.
+    switch (Current.Type) {
+    case WorklistItemType::UpdateChildIncompleteness:
+      updateChildIncompleteness(Current.Die, Current.CU, *Current.OtherInfo);
+      continue;
+    case WorklistItemType::UpdateRefIncompleteness:
+      updateRefIncompleteness(Current.Die, Current.CU, *Current.OtherInfo);
+      continue;
+    case WorklistItemType::LookForChildDIEsToKeep:
+      lookForChildDIEsToKeep(Current.Die, Current.CU, Current.Flags, Worklist);
+      continue;
+    case WorklistItemType::LookForRefDIEsToKeep:
+      lookForRefDIEsToKeep(Current.Die, Current.CU, Current.Flags, Units, File,
+                           Worklist);
+      continue;
+    case WorklistItemType::LookForParentDIEsToKeep:
+      lookForParentDIEsToKeep(Current.AncestorIdx, Current.CU, Current.Flags,
+                              Worklist);
+      continue;
+    case WorklistItemType::LookForDIEsToKeep:
+      break;
+    }
+
+    unsigned Idx = Current.CU.getOrigUnit().getDIEIndex(Current.Die);
+    CompileUnit::DIEInfo &MyInfo = Current.CU.getInfo(Idx);
+
+    if (MyInfo.Prune)
+      continue;
+
+    // If the Keep flag is set, we are marking a required DIE's dependencies.
+    // If our target is already marked as kept, we're all set.
+    bool AlreadyKept = MyInfo.Keep;
+    if ((Current.Flags & TF_DependencyWalk) && AlreadyKept)
+      continue;
+
+    // We must not call shouldKeepDIE while called from keepDIEAndDependencies,
+    // because it would screw up the relocation finding logic.
+    if (!(Current.Flags & TF_DependencyWalk))
+      Current.Flags = shouldKeepDIE(AddressesMap, Ranges, Current.Die, File,
+                                    Current.CU, MyInfo, Current.Flags);
+
+    // Finish by looking for child DIEs. Because of the LIFO worklist we need
+    // to schedule that work before any subsequent items are added to the
+    // worklist.
+    Worklist.emplace_back(Current.Die, Current.CU, Current.Flags,
+                          WorklistItemType::LookForChildDIEsToKeep);
+
+    if (AlreadyKept || !(Current.Flags & TF_Keep))
+      continue;
+
+    // If it is a newly kept DIE mark it as well as all its dependencies as
+    // kept.
+    MyInfo.Keep = true;
+
+    // We're looking for incomplete types.
+    MyInfo.Incomplete =
+        Current.Die.getTag() != dwarf::DW_TAG_subprogram &&
+        Current.Die.getTag() != dwarf::DW_TAG_member &&
+        dwarf::toUnsigned(Current.Die.find(dwarf::DW_AT_declaration), 0);
+
+    // After looking at the parent chain, look for referenced DIEs. Because of
+    // the LIFO worklist we need to schedule that work before any subsequent
+    // items are added to the worklist.
+    Worklist.emplace_back(Current.Die, Current.CU, Current.Flags,
+                          WorklistItemType::LookForRefDIEsToKeep);
+
+    bool UseOdr = (Current.Flags & TF_DependencyWalk) ? (Current.Flags & TF_ODR)
+                                                      : Current.CU.hasODR();
+    unsigned ODRFlag = UseOdr ? TF_ODR : 0;
+    unsigned ParFlags = TF_ParentWalk | TF_Keep | TF_DependencyWalk | ODRFlag;
+
+    // Now schedule the parent walk.
+    Worklist.emplace_back(MyInfo.ParentIdx, Current.CU, ParFlags);
+  }
+}
+
+/// Assign an abbreviation number to \p Abbrev.
+///
+/// Our DIEs get freed after every DebugMapObject has been processed,
+/// thus the FoldingSet we use to unique DIEAbbrevs cannot refer to
+/// the instances hold by the DIEs. When we encounter an abbreviation
+/// that we don't know, we create a permanent copy of it.
+void DWARFLinker::assignAbbrev(DIEAbbrev &Abbrev) {
+  // Check the set for priors.
+  FoldingSetNodeID ID;
+  Abbrev.Profile(ID);
+  void *InsertToken;
+  DIEAbbrev *InSet = AbbreviationsSet.FindNodeOrInsertPos(ID, InsertToken);
+
+  // If it's newly added.
+  if (InSet) {
+    // Assign existing abbreviation number.
+    Abbrev.setNumber(InSet->getNumber());
+  } else {
+    // Add to abbreviation list.
+    Abbreviations.push_back(
+        std::make_unique<DIEAbbrev>(Abbrev.getTag(), Abbrev.hasChildren()));
+    for (const auto &Attr : Abbrev.getData())
+      Abbreviations.back()->AddAttribute(Attr.getAttribute(), Attr.getForm());
+    AbbreviationsSet.InsertNode(Abbreviations.back().get(), InsertToken);
+    // Assign the unique abbreviation number.
+    Abbrev.setNumber(Abbreviations.size());
+    Abbreviations.back()->setNumber(Abbreviations.size());
+  }
+}
+
+unsigned DWARFLinker::DIECloner::cloneStringAttribute(
+    DIE &Die, AttributeSpec AttrSpec, const DWARFFormValue &Val,
+    const DWARFUnit &U, OffsetsStringPool &StringPool, AttributesInfo &Info) {
+  Optional<const char *> String = Val.getAsCString();
+  if (!String)
+    return 0;
+
+  // Switch everything to out of line strings.
+  auto StringEntry = StringPool.getEntry(*String);
+
+  // Update attributes info.
+  if (AttrSpec.Attr == dwarf::DW_AT_name)
+    Info.Name = StringEntry;
+  else if (AttrSpec.Attr == dwarf::DW_AT_MIPS_linkage_name ||
+           AttrSpec.Attr == dwarf::DW_AT_linkage_name)
+    Info.MangledName = StringEntry;
+
+  Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr), dwarf::DW_FORM_strp,
+               DIEInteger(StringEntry.getOffset()));
+
+  return 4;
+}
+
+unsigned DWARFLinker::DIECloner::cloneDieReferenceAttribute(
+    DIE &Die, const DWARFDie &InputDIE, AttributeSpec AttrSpec,
+    unsigned AttrSize, const DWARFFormValue &Val, const DWARFFile &File,
+    CompileUnit &Unit) {
+  const DWARFUnit &U = Unit.getOrigUnit();
+  uint64_t Ref = *Val.getAsReference();
+
+  DIE *NewRefDie = nullptr;
+  CompileUnit *RefUnit = nullptr;
+  DeclContext *Ctxt = nullptr;
+
+  DWARFDie RefDie =
+      Linker.resolveDIEReference(File, CompileUnits, Val, InputDIE, RefUnit);
+
+  // If the referenced DIE is not found,  drop the attribute.
+  if (!RefDie || AttrSpec.Attr == dwarf::DW_AT_sibling)
+    return 0;
+
+  CompileUnit::DIEInfo &RefInfo = RefUnit->getInfo(RefDie);
+
+  // If we already have emitted an equivalent DeclContext, just point
+  // at it.
+  if (isODRAttribute(AttrSpec.Attr)) {
+    Ctxt = RefInfo.Ctxt;
+    if (Ctxt && Ctxt->getCanonicalDIEOffset()) {
+      DIEInteger Attr(Ctxt->getCanonicalDIEOffset());
+      Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                   dwarf::DW_FORM_ref_addr, Attr);
+      return U.getRefAddrByteSize();
+    }
+  }
+
+  if (!RefInfo.Clone) {
+    assert(Ref > InputDIE.getOffset());
+    // We haven't cloned this DIE yet. Just create an empty one and
+    // store it. It'll get really cloned when we process it.
+    RefInfo.Clone = DIE::get(DIEAlloc, dwarf::Tag(RefDie.getTag()));
+  }
+  NewRefDie = RefInfo.Clone;
+
+  if (AttrSpec.Form == dwarf::DW_FORM_ref_addr ||
+      (Unit.hasODR() && isODRAttribute(AttrSpec.Attr))) {
+    // We cannot currently rely on a DIEEntry to emit ref_addr
+    // references, because the implementation calls back to DwarfDebug
+    // to find the unit offset. (We don't have a DwarfDebug)
+    // FIXME: we should be able to design DIEEntry reliance on
+    // DwarfDebug away.
+    uint64_t Attr;
+    if (Ref < InputDIE.getOffset()) {
+      // We must have already cloned that DIE.
+      uint32_t NewRefOffset =
+          RefUnit->getStartOffset() + NewRefDie->getOffset();
+      Attr = NewRefOffset;
+      Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                   dwarf::DW_FORM_ref_addr, DIEInteger(Attr));
+    } else {
+      // A forward reference. Note and fixup later.
+      Attr = 0xBADDEF;
+      Unit.noteForwardReference(
+          NewRefDie, RefUnit, Ctxt,
+          Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                       dwarf::DW_FORM_ref_addr, DIEInteger(Attr)));
+    }
+    return U.getRefAddrByteSize();
+  }
+
+  Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+               dwarf::Form(AttrSpec.Form), DIEEntry(*NewRefDie));
+
+  return AttrSize;
+}
+
+void DWARFLinker::DIECloner::cloneExpression(
+    DataExtractor &Data, DWARFExpression Expression, const DWARFFile &File,
+    CompileUnit &Unit, SmallVectorImpl<uint8_t> &OutputBuffer) {
+  using Encoding = DWARFExpression::Operation::Encoding;
+
+  uint64_t OpOffset = 0;
+  for (auto &Op : Expression) {
+    auto Description = Op.getDescription();
+    // DW_OP_const_type is variable-length and has 3
+    // operands. DWARFExpression thus far only supports 2.
+    auto Op0 = Description.Op[0];
+    auto Op1 = Description.Op[1];
+    if ((Op0 == Encoding::BaseTypeRef && Op1 != Encoding::SizeNA) ||
+        (Op1 == Encoding::BaseTypeRef && Op0 != Encoding::Size1))
+      Linker.reportWarning("Unsupported DW_OP encoding.", File);
+
+    if ((Op0 == Encoding::BaseTypeRef && Op1 == Encoding::SizeNA) ||
+        (Op1 == Encoding::BaseTypeRef && Op0 == Encoding::Size1)) {
+      // This code assumes that the other non-typeref operand fits into 1 byte.
+      assert(OpOffset < Op.getEndOffset());
+      uint32_t ULEBsize = Op.getEndOffset() - OpOffset - 1;
+      assert(ULEBsize <= 16);
+
+      // Copy over the operation.
+      OutputBuffer.push_back(Op.getCode());
+      uint64_t RefOffset;
+      if (Op1 == Encoding::SizeNA) {
+        RefOffset = Op.getRawOperand(0);
+      } else {
+        OutputBuffer.push_back(Op.getRawOperand(0));
+        RefOffset = Op.getRawOperand(1);
+      }
+      uint32_t Offset = 0;
+      // Look up the base type. For DW_OP_convert, the operand may be 0 to
+      // instead indicate the generic type. The same holds for
+      // DW_OP_reinterpret, which is currently not supported.
+      if (RefOffset > 0 || Op.getCode() != dwarf::DW_OP_convert) {
+        auto RefDie = Unit.getOrigUnit().getDIEForOffset(RefOffset);
+        CompileUnit::DIEInfo &Info = Unit.getInfo(RefDie);
+        if (DIE *Clone = Info.Clone)
+          Offset = Clone->getOffset();
+        else
+          Linker.reportWarning(
+              "base type ref doesn't point to DW_TAG_base_type.", File);
+      }
+      uint8_t ULEB[16];
+      unsigned RealSize = encodeULEB128(Offset, ULEB, ULEBsize);
+      if (RealSize > ULEBsize) {
+        // Emit the generic type as a fallback.
+        RealSize = encodeULEB128(0, ULEB, ULEBsize);
+        Linker.reportWarning("base type ref doesn't fit.", File);
+      }
+      assert(RealSize == ULEBsize && "padding failed");
+      ArrayRef<uint8_t> ULEBbytes(ULEB, ULEBsize);
+      OutputBuffer.append(ULEBbytes.begin(), ULEBbytes.end());
+    } else {
+      // Copy over everything else unmodified.
+      StringRef Bytes = Data.getData().slice(OpOffset, Op.getEndOffset());
+      OutputBuffer.append(Bytes.begin(), Bytes.end());
+    }
+    OpOffset = Op.getEndOffset();
+  }
+}
+
+unsigned DWARFLinker::DIECloner::cloneBlockAttribute(
+    DIE &Die, const DWARFFile &File, CompileUnit &Unit, AttributeSpec AttrSpec,
+    const DWARFFormValue &Val, unsigned AttrSize, bool IsLittleEndian) {
+  DIEValueList *Attr;
+  DIEValue Value;
+  DIELoc *Loc = nullptr;
+  DIEBlock *Block = nullptr;
+  if (AttrSpec.Form == dwarf::DW_FORM_exprloc) {
+    Loc = new (DIEAlloc) DIELoc;
+    Linker.DIELocs.push_back(Loc);
+  } else {
+    Block = new (DIEAlloc) DIEBlock;
+    Linker.DIEBlocks.push_back(Block);
+  }
+  Attr = Loc ? static_cast<DIEValueList *>(Loc)
+             : static_cast<DIEValueList *>(Block);
+
+  if (Loc)
+    Value = DIEValue(dwarf::Attribute(AttrSpec.Attr),
+                     dwarf::Form(AttrSpec.Form), Loc);
+  else
+    Value = DIEValue(dwarf::Attribute(AttrSpec.Attr),
+                     dwarf::Form(AttrSpec.Form), Block);
+
+  // If the block is a DWARF Expression, clone it into the temporary
+  // buffer using cloneExpression(), otherwise copy the data directly.
+  SmallVector<uint8_t, 32> Buffer;
+  ArrayRef<uint8_t> Bytes = *Val.getAsBlock();
+  if (DWARFAttribute::mayHaveLocationDescription(AttrSpec.Attr) &&
+      (Val.isFormClass(DWARFFormValue::FC_Block) ||
+       Val.isFormClass(DWARFFormValue::FC_Exprloc))) {
+    DWARFUnit &OrigUnit = Unit.getOrigUnit();
+    DataExtractor Data(StringRef((const char *)Bytes.data(), Bytes.size()),
+                       IsLittleEndian, OrigUnit.getAddressByteSize());
+    DWARFExpression Expr(Data, OrigUnit.getAddressByteSize(),
+                         OrigUnit.getFormParams().Format);
+    cloneExpression(Data, Expr, File, Unit, Buffer);
+    Bytes = Buffer;
+  }
+  for (auto Byte : Bytes)
+    Attr->addValue(DIEAlloc, static_cast<dwarf::Attribute>(0),
+                   dwarf::DW_FORM_data1, DIEInteger(Byte));
+
+  // FIXME: If DIEBlock and DIELoc just reuses the Size field of
+  // the DIE class, this "if" could be replaced by
+  // Attr->setSize(Bytes.size()).
+  if (Loc)
+    Loc->setSize(Bytes.size());
+  else
+    Block->setSize(Bytes.size());
+
+  Die.addValue(DIEAlloc, Value);
+  return AttrSize;
+}
+
+unsigned DWARFLinker::DIECloner::cloneAddressAttribute(
+    DIE &Die, AttributeSpec AttrSpec, const DWARFFormValue &Val,
+    const CompileUnit &Unit, AttributesInfo &Info) {
+  dwarf::Form Form = AttrSpec.Form;
+  uint64_t Addr = *Val.getAsAddress();
+
+  if (LLVM_UNLIKELY(Linker.Options.Update)) {
+    if (AttrSpec.Attr == dwarf::DW_AT_low_pc)
+      Info.HasLowPc = true;
+    Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                 dwarf::Form(AttrSpec.Form), DIEInteger(Addr));
+    return Unit.getOrigUnit().getAddressByteSize();
+  }
+
+  if (AttrSpec.Attr == dwarf::DW_AT_low_pc) {
+    if (Die.getTag() == dwarf::DW_TAG_inlined_subroutine ||
+        Die.getTag() == dwarf::DW_TAG_lexical_block)
+      // The low_pc of a block or inline subroutine might get
+      // relocated because it happens to match the low_pc of the
+      // enclosing subprogram. To prevent issues with that, always use
+      // the low_pc from the input DIE if relocations have been applied.
+      Addr = (Info.OrigLowPc != std::numeric_limits<uint64_t>::max()
+                  ? Info.OrigLowPc
+                  : Addr) +
+             Info.PCOffset;
+    else if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
+      Addr = Unit.getLowPc();
+      if (Addr == std::numeric_limits<uint64_t>::max())
+        return 0;
+    }
+    Info.HasLowPc = true;
+  } else if (AttrSpec.Attr == dwarf::DW_AT_high_pc) {
+    if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
+      if (uint64_t HighPc = Unit.getHighPc())
+        Addr = HighPc;
+      else
+        return 0;
+    } else
+      // If we have a high_pc recorded for the input DIE, use
+      // it. Otherwise (when no relocations where applied) just use the
+      // one we just decoded.
+      Addr = (Info.OrigHighPc ? Info.OrigHighPc : Addr) + Info.PCOffset;
+  } else if (AttrSpec.Attr == dwarf::DW_AT_call_return_pc) {
+    // Relocate a return PC address within a call site entry.
+    if (Die.getTag() == dwarf::DW_TAG_call_site)
+      Addr = (Info.OrigCallReturnPc ? Info.OrigCallReturnPc : Addr) +
+             Info.PCOffset;
+  } else if (AttrSpec.Attr == dwarf::DW_AT_call_pc) {
+    // Relocate the address of a branch instruction within a call site entry.
+    if (Die.getTag() == dwarf::DW_TAG_call_site)
+      Addr = (Info.OrigCallPc ? Info.OrigCallPc : Addr) + Info.PCOffset;
+  }
+
+  // If this is an indexed address emit the relocated address.
+  if (Form == dwarf::DW_FORM_addrx) {
+    if (llvm::Expected<uint64_t> RelocAddr =
+            ObjFile.Addresses->relocateIndexedAddr(Addr)) {
+      Addr = *RelocAddr;
+      Form = dwarf::DW_FORM_addr;
+    } else {
+      Linker.reportWarning(toString(RelocAddr.takeError()), ObjFile);
+    }
+  }
+
+  Die.addValue(DIEAlloc, static_cast<dwarf::Attribute>(AttrSpec.Attr),
+               static_cast<dwarf::Form>(Form), DIEInteger(Addr));
+  return Unit.getOrigUnit().getAddressByteSize();
+}
+
+unsigned DWARFLinker::DIECloner::cloneScalarAttribute(
+    DIE &Die, const DWARFDie &InputDIE, const DWARFFile &File,
+    CompileUnit &Unit, AttributeSpec AttrSpec, const DWARFFormValue &Val,
+    unsigned AttrSize, AttributesInfo &Info) {
+  uint64_t Value;
+
+  if (LLVM_UNLIKELY(Linker.Options.Update)) {
+    if (auto OptionalValue = Val.getAsUnsignedConstant())
+      Value = *OptionalValue;
+    else if (auto OptionalValue = Val.getAsSignedConstant())
+      Value = *OptionalValue;
+    else if (auto OptionalValue = Val.getAsSectionOffset())
+      Value = *OptionalValue;
+    else {
+      Linker.reportWarning(
+          "Unsupported scalar attribute form. Dropping attribute.", File,
+          &InputDIE);
+      return 0;
+    }
+    if (AttrSpec.Attr == dwarf::DW_AT_declaration && Value)
+      Info.IsDeclaration = true;
+    Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                 dwarf::Form(AttrSpec.Form), DIEInteger(Value));
+    return AttrSize;
+  }
+
+  if (AttrSpec.Attr == dwarf::DW_AT_high_pc &&
+      Die.getTag() == dwarf::DW_TAG_compile_unit) {
+    if (Unit.getLowPc() == -1ULL)
+      return 0;
+    // Dwarf >= 4 high_pc is an size, not an address.
+    Value = Unit.getHighPc() - Unit.getLowPc();
+  } else if (AttrSpec.Form == dwarf::DW_FORM_sec_offset)
+    Value = *Val.getAsSectionOffset();
+  else if (AttrSpec.Form == dwarf::DW_FORM_sdata)
+    Value = *Val.getAsSignedConstant();
+  else if (auto OptionalValue = Val.getAsUnsignedConstant())
+    Value = *OptionalValue;
+  else {
+    Linker.reportWarning(
+        "Unsupported scalar attribute form. Dropping attribute.", File,
+        &InputDIE);
+    return 0;
+  }
+  PatchLocation Patch =
+      Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                   dwarf::Form(AttrSpec.Form), DIEInteger(Value));
+  if (AttrSpec.Attr == dwarf::DW_AT_ranges) {
+    Unit.noteRangeAttribute(Die, Patch);
+    Info.HasRanges = true;
+  }
+
+  // A more generic way to check for location attributes would be
+  // nice, but it's very unlikely that any other attribute needs a
+  // location list.
+  // FIXME: use DWARFAttribute::mayHaveLocationDescription().
+  else if (AttrSpec.Attr == dwarf::DW_AT_location ||
+           AttrSpec.Attr == dwarf::DW_AT_frame_base) {
+    Unit.noteLocationAttribute(Patch, Info.PCOffset);
+  } else if (AttrSpec.Attr == dwarf::DW_AT_declaration && Value)
+    Info.IsDeclaration = true;
+
+  return AttrSize;
+}
+
+/// Clone \p InputDIE's attribute described by \p AttrSpec with
+/// value \p Val, and add it to \p Die.
+/// \returns the size of the cloned attribute.
+unsigned DWARFLinker::DIECloner::cloneAttribute(
+    DIE &Die, const DWARFDie &InputDIE, const DWARFFile &File,
+    CompileUnit &Unit, OffsetsStringPool &StringPool, const DWARFFormValue &Val,
+    const AttributeSpec AttrSpec, unsigned AttrSize, AttributesInfo &Info,
+    bool IsLittleEndian) {
+  const DWARFUnit &U = Unit.getOrigUnit();
+
+  switch (AttrSpec.Form) {
+  case dwarf::DW_FORM_strp:
+  case dwarf::DW_FORM_string:
+  case dwarf::DW_FORM_strx:
+  case dwarf::DW_FORM_strx1:
+  case dwarf::DW_FORM_strx2:
+  case dwarf::DW_FORM_strx3:
+  case dwarf::DW_FORM_strx4:
+    return cloneStringAttribute(Die, AttrSpec, Val, U, StringPool, Info);
+  case dwarf::DW_FORM_ref_addr:
+  case dwarf::DW_FORM_ref1:
+  case dwarf::DW_FORM_ref2:
+  case dwarf::DW_FORM_ref4:
+  case dwarf::DW_FORM_ref8:
+    return cloneDieReferenceAttribute(Die, InputDIE, AttrSpec, AttrSize, Val,
+                                      File, Unit);
+  case dwarf::DW_FORM_block:
+  case dwarf::DW_FORM_block1:
+  case dwarf::DW_FORM_block2:
+  case dwarf::DW_FORM_block4:
+  case dwarf::DW_FORM_exprloc:
+    return cloneBlockAttribute(Die, File, Unit, AttrSpec, Val, AttrSize,
+                               IsLittleEndian);
+  case dwarf::DW_FORM_addr:
+  case dwarf::DW_FORM_addrx:
+    return cloneAddressAttribute(Die, AttrSpec, Val, Unit, Info);
+  case dwarf::DW_FORM_data1:
+  case dwarf::DW_FORM_data2:
+  case dwarf::DW_FORM_data4:
+  case dwarf::DW_FORM_data8:
+  case dwarf::DW_FORM_udata:
+  case dwarf::DW_FORM_sdata:
+  case dwarf::DW_FORM_sec_offset:
+  case dwarf::DW_FORM_flag:
+  case dwarf::DW_FORM_flag_present:
+    return cloneScalarAttribute(Die, InputDIE, File, Unit, AttrSpec, Val,
+                                AttrSize, Info);
+  default:
+    Linker.reportWarning("Unsupported attribute form " +
+                             dwarf::FormEncodingString(AttrSpec.Form) +
+                             " in cloneAttribute. Dropping.",
+                         File, &InputDIE);
+  }
+
+  return 0;
+}
+
+static bool isObjCSelector(StringRef Name) {
+  return Name.size() > 2 && (Name[0] == '-' || Name[0] == '+') &&
+         (Name[1] == '[');
+}
+
+void DWARFLinker::DIECloner::addObjCAccelerator(CompileUnit &Unit,
+                                                const DIE *Die,
+                                                DwarfStringPoolEntryRef Name,
+                                                OffsetsStringPool &StringPool,
+                                                bool SkipPubSection) {
+  assert(isObjCSelector(Name.getString()) && "not an objc selector");
+  // Objective C method or class function.
+  // "- [Class(Category) selector :withArg ...]"
+  StringRef ClassNameStart(Name.getString().drop_front(2));
+  size_t FirstSpace = ClassNameStart.find(' ');
+  if (FirstSpace == StringRef::npos)
+    return;
+
+  StringRef SelectorStart(ClassNameStart.data() + FirstSpace + 1);
+  if (!SelectorStart.size())
+    return;
+
+  StringRef Selector(SelectorStart.data(), SelectorStart.size() - 1);
+  Unit.addNameAccelerator(Die, StringPool.getEntry(Selector), SkipPubSection);
+
+  // Add an entry for the class name that points to this
+  // method/class function.
+  StringRef ClassName(ClassNameStart.data(), FirstSpace);
+  Unit.addObjCAccelerator(Die, StringPool.getEntry(ClassName), SkipPubSection);
+
+  if (ClassName[ClassName.size() - 1] == ')') {
+    size_t OpenParens = ClassName.find('(');
+    if (OpenParens != StringRef::npos) {
+      StringRef ClassNameNoCategory(ClassName.data(), OpenParens);
+      Unit.addObjCAccelerator(Die, StringPool.getEntry(ClassNameNoCategory),
+                              SkipPubSection);
+
+      std::string MethodNameNoCategory(Name.getString().data(), OpenParens + 2);
+      // FIXME: The missing space here may be a bug, but
+      //        dsymutil-classic also does it this way.
+      MethodNameNoCategory.append(std::string(SelectorStart));
+      Unit.addNameAccelerator(Die, StringPool.getEntry(MethodNameNoCategory),
+                              SkipPubSection);
+    }
+  }
+}
+
+static bool
+shouldSkipAttribute(DWARFAbbreviationDeclaration::AttributeSpec AttrSpec,
+                    uint16_t Tag, bool InDebugMap, bool SkipPC,
+                    bool InFunctionScope) {
+  switch (AttrSpec.Attr) {
+  default:
+    return false;
+  case dwarf::DW_AT_low_pc:
+  case dwarf::DW_AT_high_pc:
+  case dwarf::DW_AT_ranges:
+    return SkipPC;
+  case dwarf::DW_AT_str_offsets_base:
+    // FIXME: Use the string offset table with Dwarf 5.
+    return true;
+  case dwarf::DW_AT_location:
+  case dwarf::DW_AT_frame_base:
+    // FIXME: for some reason dsymutil-classic keeps the location attributes
+    // when they are of block type (i.e. not location lists). This is totally
+    // wrong for globals where we will keep a wrong address. It is mostly
+    // harmless for locals, but there is no point in keeping these anyway when
+    // the function wasn't linked.
+    return (SkipPC || (!InFunctionScope && Tag == dwarf::DW_TAG_variable &&
+                       !InDebugMap)) &&
+           !DWARFFormValue(AttrSpec.Form).isFormClass(DWARFFormValue::FC_Block);
+  }
+}
+
+DIE *DWARFLinker::DIECloner::cloneDIE(const DWARFDie &InputDIE,
+                                      const DWARFFile &File, CompileUnit &Unit,
+                                      OffsetsStringPool &StringPool,
+                                      int64_t PCOffset, uint32_t OutOffset,
+                                      unsigned Flags, bool IsLittleEndian,
+                                      DIE *Die) {
+  DWARFUnit &U = Unit.getOrigUnit();
+  unsigned Idx = U.getDIEIndex(InputDIE);
+  CompileUnit::DIEInfo &Info = Unit.getInfo(Idx);
+
+  // Should the DIE appear in the output?
+  if (!Unit.getInfo(Idx).Keep)
+    return nullptr;
+
+  uint64_t Offset = InputDIE.getOffset();
+  assert(!(Die && Info.Clone) && "Can't supply a DIE and a cloned DIE");
+  if (!Die) {
+    // The DIE might have been already created by a forward reference
+    // (see cloneDieReferenceAttribute()).
+    if (!Info.Clone)
+      Info.Clone = DIE::get(DIEAlloc, dwarf::Tag(InputDIE.getTag()));
+    Die = Info.Clone;
+  }
+
+  assert(Die->getTag() == InputDIE.getTag());
+  Die->setOffset(OutOffset);
+  if ((Unit.hasODR() || Unit.isClangModule()) && !Info.Incomplete &&
+      Die->getTag() != dwarf::DW_TAG_namespace && Info.Ctxt &&
+      Info.Ctxt != Unit.getInfo(Info.ParentIdx).Ctxt &&
+      !Info.Ctxt->getCanonicalDIEOffset()) {
+    // We are about to emit a DIE that is the root of its own valid
+    // DeclContext tree. Make the current offset the canonical offset
+    // for this context.
+    Info.Ctxt->setCanonicalDIEOffset(OutOffset + Unit.getStartOffset());
+  }
+
+  // Extract and clone every attribute.
+  DWARFDataExtractor Data = U.getDebugInfoExtractor();
+  // Point to the next DIE (generally there is always at least a NULL
+  // entry after the current one). If this is a lone
+  // DW_TAG_compile_unit without any children, point to the next unit.
+  uint64_t NextOffset = (Idx + 1 < U.getNumDIEs())
+                            ? U.getDIEAtIndex(Idx + 1).getOffset()
+                            : U.getNextUnitOffset();
+  AttributesInfo AttrInfo;
+
+  // We could copy the data only if we need to apply a relocation to it. After
+  // testing, it seems there is no performance downside to doing the copy
+  // unconditionally, and it makes the code simpler.
+  SmallString<40> DIECopy(Data.getData().substr(Offset, NextOffset - Offset));
+  Data =
+      DWARFDataExtractor(DIECopy, Data.isLittleEndian(), Data.getAddressSize());
+
+  // Modify the copy with relocated addresses.
+  if (ObjFile.Addresses->areRelocationsResolved() &&
+      ObjFile.Addresses->applyValidRelocs(DIECopy, Offset,
+                                          Data.isLittleEndian())) {
+    // If we applied relocations, we store the value of high_pc that was
+    // potentially stored in the input DIE. If high_pc is an address
+    // (Dwarf version == 2), then it might have been relocated to a
+    // totally unrelated value (because the end address in the object
+    // file might be start address of another function which got moved
+    // independently by the linker). The computation of the actual
+    // high_pc value is done in cloneAddressAttribute().
+    AttrInfo.OrigHighPc =
+        dwarf::toAddress(InputDIE.find(dwarf::DW_AT_high_pc), 0);
+    // Also store the low_pc. It might get relocated in an
+    // inline_subprogram that happens at the beginning of its
+    // inlining function.
+    AttrInfo.OrigLowPc = dwarf::toAddress(InputDIE.find(dwarf::DW_AT_low_pc),
+                                          std::numeric_limits<uint64_t>::max());
+    AttrInfo.OrigCallReturnPc =
+        dwarf::toAddress(InputDIE.find(dwarf::DW_AT_call_return_pc), 0);
+    AttrInfo.OrigCallPc =
+        dwarf::toAddress(InputDIE.find(dwarf::DW_AT_call_pc), 0);
+  }
+
+  // Reset the Offset to 0 as we will be working on the local copy of
+  // the data.
+  Offset = 0;
+
+  const auto *Abbrev = InputDIE.getAbbreviationDeclarationPtr();
+  Offset += getULEB128Size(Abbrev->getCode());
+
+  // We are entering a subprogram. Get and propagate the PCOffset.
+  if (Die->getTag() == dwarf::DW_TAG_subprogram)
+    PCOffset = Info.AddrAdjust;
+  AttrInfo.PCOffset = PCOffset;
+
+  if (Abbrev->getTag() == dwarf::DW_TAG_subprogram) {
+    Flags |= TF_InFunctionScope;
+    if (!Info.InDebugMap && LLVM_LIKELY(!Update))
+      Flags |= TF_SkipPC;
+  }
+
+  bool Copied = false;
+  for (const auto &AttrSpec : Abbrev->attributes()) {
+    if (LLVM_LIKELY(!Update) &&
+        shouldSkipAttribute(AttrSpec, Die->getTag(), Info.InDebugMap,
+                            Flags & TF_SkipPC, Flags & TF_InFunctionScope)) {
+      DWARFFormValue::skipValue(AttrSpec.Form, Data, &Offset,
+                                U.getFormParams());
+      // FIXME: dsymutil-classic keeps the old abbreviation around
+      // even if it's not used. We can remove this (and the copyAbbrev
+      // helper) as soon as bit-for-bit compatibility is not a goal anymore.
+      if (!Copied) {
+        copyAbbrev(*InputDIE.getAbbreviationDeclarationPtr(), Unit.hasODR());
+        Copied = true;
+      }
+      continue;
+    }
+
+    DWARFFormValue Val(AttrSpec.Form);
+    uint64_t AttrSize = Offset;
+    Val.extractValue(Data, &Offset, U.getFormParams(), &U);
+    AttrSize = Offset - AttrSize;
+
+    OutOffset += cloneAttribute(*Die, InputDIE, File, Unit, StringPool, Val,
+                                AttrSpec, AttrSize, AttrInfo, IsLittleEndian);
+  }
+
+  // Look for accelerator entries.
+  uint16_t Tag = InputDIE.getTag();
+  // FIXME: This is slightly wrong. An inline_subroutine without a
+  // low_pc, but with AT_ranges might be interesting to get into the
+  // accelerator tables too. For now stick with dsymutil's behavior.
+  if ((Info.InDebugMap || AttrInfo.HasLowPc || AttrInfo.HasRanges) &&
+      Tag != dwarf::DW_TAG_compile_unit &&
+      getDIENames(InputDIE, AttrInfo, StringPool,
+                  Tag != dwarf::DW_TAG_inlined_subroutine)) {
+    if (AttrInfo.MangledName && AttrInfo.MangledName != AttrInfo.Name)
+      Unit.addNameAccelerator(Die, AttrInfo.MangledName,
+                              Tag == dwarf::DW_TAG_inlined_subroutine);
+    if (AttrInfo.Name) {
+      if (AttrInfo.NameWithoutTemplate)
+        Unit.addNameAccelerator(Die, AttrInfo.NameWithoutTemplate,
+                                /* SkipPubSection */ true);
+      Unit.addNameAccelerator(Die, AttrInfo.Name,
+                              Tag == dwarf::DW_TAG_inlined_subroutine);
+    }
+    if (AttrInfo.Name && isObjCSelector(AttrInfo.Name.getString()))
+      addObjCAccelerator(Unit, Die, AttrInfo.Name, StringPool,
+                         /* SkipPubSection =*/true);
+
+  } else if (Tag == dwarf::DW_TAG_namespace) {
+    if (!AttrInfo.Name)
+      AttrInfo.Name = StringPool.getEntry("(anonymous namespace)");
+    Unit.addNamespaceAccelerator(Die, AttrInfo.Name);
+  } else if (isTypeTag(Tag) && !AttrInfo.IsDeclaration &&
+             getDIENames(InputDIE, AttrInfo, StringPool) && AttrInfo.Name &&
+             AttrInfo.Name.getString()[0]) {
+    uint32_t Hash = hashFullyQualifiedName(InputDIE, Unit, File);
+    uint64_t RuntimeLang =
+        dwarf::toUnsigned(InputDIE.find(dwarf::DW_AT_APPLE_runtime_class))
+            .getValueOr(0);
+    bool ObjCClassIsImplementation =
+        (RuntimeLang == dwarf::DW_LANG_ObjC ||
+         RuntimeLang == dwarf::DW_LANG_ObjC_plus_plus) &&
+        dwarf::toUnsigned(InputDIE.find(dwarf::DW_AT_APPLE_objc_complete_type))
+            .getValueOr(0);
+    Unit.addTypeAccelerator(Die, AttrInfo.Name, ObjCClassIsImplementation,
+                            Hash);
+  }
+
+  // Determine whether there are any children that we want to keep.
+  bool HasChildren = false;
+  for (auto Child : InputDIE.children()) {
+    unsigned Idx = U.getDIEIndex(Child);
+    if (Unit.getInfo(Idx).Keep) {
+      HasChildren = true;
+      break;
+    }
+  }
+
+  DIEAbbrev NewAbbrev = Die->generateAbbrev();
+  if (HasChildren)
+    NewAbbrev.setChildrenFlag(dwarf::DW_CHILDREN_yes);
+  // Assign a permanent abbrev number
+  Linker.assignAbbrev(NewAbbrev);
+  Die->setAbbrevNumber(NewAbbrev.getNumber());
+
+  // Add the size of the abbreviation number to the output offset.
+  OutOffset += getULEB128Size(Die->getAbbrevNumber());
+
+  if (!HasChildren) {
+    // Update our size.
+    Die->setSize(OutOffset - Die->getOffset());
+    return Die;
+  }
+
+  // Recursively clone children.
+  for (auto Child : InputDIE.children()) {
+    if (DIE *Clone = cloneDIE(Child, File, Unit, StringPool, PCOffset,
+                              OutOffset, Flags, IsLittleEndian)) {
+      Die->addChild(Clone);
+      OutOffset = Clone->getOffset() + Clone->getSize();
+    }
+  }
+
+  // Account for the end of children marker.
+  OutOffset += sizeof(int8_t);
+  // Update our size.
+  Die->setSize(OutOffset - Die->getOffset());
+  return Die;
+}
+
+/// Patch the input object file relevant debug_ranges entries
+/// and emit them in the output file. Update the relevant attributes
+/// to point at the new entries.
+void DWARFLinker::patchRangesForUnit(const CompileUnit &Unit,
+                                     DWARFContext &OrigDwarf,
+                                     const DWARFFile &File) const {
+  DWARFDebugRangeList RangeList;
+  const auto &FunctionRanges = Unit.getFunctionRanges();
+  unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
+  DWARFDataExtractor RangeExtractor(OrigDwarf.getDWARFObj(),
+                                    OrigDwarf.getDWARFObj().getRangesSection(),
+                                    OrigDwarf.isLittleEndian(), AddressSize);
+  auto InvalidRange = FunctionRanges.end(), CurrRange = InvalidRange;
+  DWARFUnit &OrigUnit = Unit.getOrigUnit();
+  auto OrigUnitDie = OrigUnit.getUnitDIE(false);
+  uint64_t OrigLowPc =
+      dwarf::toAddress(OrigUnitDie.find(dwarf::DW_AT_low_pc), -1ULL);
+  // Ranges addresses are based on the unit's low_pc. Compute the
+  // offset we need to apply to adapt to the new unit's low_pc.
+  int64_t UnitPcOffset = 0;
+  if (OrigLowPc != -1ULL)
+    UnitPcOffset = int64_t(OrigLowPc) - Unit.getLowPc();
+
+  for (const auto &RangeAttribute : Unit.getRangesAttributes()) {
+    uint64_t Offset = RangeAttribute.get();
+    RangeAttribute.set(TheDwarfEmitter->getRangesSectionSize());
+    if (Error E = RangeList.extract(RangeExtractor, &Offset)) {
+      llvm::consumeError(std::move(E));
+      reportWarning("invalid range list ignored.", File);
+      RangeList.clear();
+    }
+    const auto &Entries = RangeList.getEntries();
+    if (!Entries.empty()) {
+      const DWARFDebugRangeList::RangeListEntry &First = Entries.front();
+
+      if (CurrRange == InvalidRange ||
+          First.StartAddress + OrigLowPc < CurrRange.start() ||
+          First.StartAddress + OrigLowPc >= CurrRange.stop()) {
+        CurrRange = FunctionRanges.find(First.StartAddress + OrigLowPc);
+        if (CurrRange == InvalidRange ||
+            CurrRange.start() > First.StartAddress + OrigLowPc) {
+          reportWarning("no mapping for range.", File);
+          continue;
+        }
+      }
+    }
+
+    TheDwarfEmitter->emitRangesEntries(UnitPcOffset, OrigLowPc, CurrRange,
+                                       Entries, AddressSize);
+  }
+}
+
+/// Generate the debug_aranges entries for \p Unit and if the
+/// unit has a DW_AT_ranges attribute, also emit the debug_ranges
+/// contribution for this attribute.
+/// FIXME: this could actually be done right in patchRangesForUnit,
+/// but for the sake of initial bit-for-bit compatibility with legacy
+/// dsymutil, we have to do it in a delayed pass.
+void DWARFLinker::generateUnitRanges(CompileUnit &Unit) const {
+  auto Attr = Unit.getUnitRangesAttribute();
+  if (Attr)
+    Attr->set(TheDwarfEmitter->getRangesSectionSize());
+  TheDwarfEmitter->emitUnitRangesEntries(Unit, static_cast<bool>(Attr));
+}
+
+/// Insert the new line info sequence \p Seq into the current
+/// set of already linked line info \p Rows.
+static void insertLineSequence(std::vector<DWARFDebugLine::Row> &Seq,
+                               std::vector<DWARFDebugLine::Row> &Rows) {
+  if (Seq.empty())
+    return;
+
+  if (!Rows.empty() && Rows.back().Address < Seq.front().Address) {
+    llvm::append_range(Rows, Seq);
+    Seq.clear();
+    return;
+  }
+
+  object::SectionedAddress Front = Seq.front().Address;
+  auto InsertPoint = partition_point(
+      Rows, [=](const DWARFDebugLine::Row &O) { return O.Address < Front; });
+
+  // FIXME: this only removes the unneeded end_sequence if the
+  // sequences have been inserted in order. Using a global sort like
+  // described in patchLineTableForUnit() and delaying the end_sequene
+  // elimination to emitLineTableForUnit() we can get rid of all of them.
+  if (InsertPoint != Rows.end() && InsertPoint->Address == Front &&
+      InsertPoint->EndSequence) {
+    *InsertPoint = Seq.front();
+    Rows.insert(InsertPoint + 1, Seq.begin() + 1, Seq.end());
+  } else {
+    Rows.insert(InsertPoint, Seq.begin(), Seq.end());
+  }
+
+  Seq.clear();
+}
+
+static void patchStmtList(DIE &Die, DIEInteger Offset) {
+  for (auto &V : Die.values())
+    if (V.getAttribute() == dwarf::DW_AT_stmt_list) {
+      V = DIEValue(V.getAttribute(), V.getForm(), Offset);
+      return;
+    }
+
+  llvm_unreachable("Didn't find DW_AT_stmt_list in cloned DIE!");
+}
+
+/// Extract the line table for \p Unit from \p OrigDwarf, and
+/// recreate a relocated version of these for the address ranges that
+/// are present in the binary.
+void DWARFLinker::patchLineTableForUnit(CompileUnit &Unit,
+                                        DWARFContext &OrigDwarf,
+                                        const DWARFFile &File) {
+  DWARFDie CUDie = Unit.getOrigUnit().getUnitDIE();
+  auto StmtList = dwarf::toSectionOffset(CUDie.find(dwarf::DW_AT_stmt_list));
+  if (!StmtList)
+    return;
+
+  // Update the cloned DW_AT_stmt_list with the correct debug_line offset.
+  if (auto *OutputDIE = Unit.getOutputUnitDIE())
+    patchStmtList(*OutputDIE,
+                  DIEInteger(TheDwarfEmitter->getLineSectionSize()));
+
+  RangesTy &Ranges = File.Addresses->getValidAddressRanges();
+
+  // Parse the original line info for the unit.
+  DWARFDebugLine::LineTable LineTable;
+  uint64_t StmtOffset = *StmtList;
+  DWARFDataExtractor LineExtractor(
+      OrigDwarf.getDWARFObj(), OrigDwarf.getDWARFObj().getLineSection(),
+      OrigDwarf.isLittleEndian(), Unit.getOrigUnit().getAddressByteSize());
+  if (needToTranslateStrings())
+    return TheDwarfEmitter->translateLineTable(LineExtractor, StmtOffset);
+
+  if (Error Err =
+          LineTable.parse(LineExtractor, &StmtOffset, OrigDwarf,
+                          &Unit.getOrigUnit(), OrigDwarf.getWarningHandler()))
+    OrigDwarf.getWarningHandler()(std::move(Err));
+
+  // This vector is the output line table.
+  std::vector<DWARFDebugLine::Row> NewRows;
+  NewRows.reserve(LineTable.Rows.size());
+
+  // Current sequence of rows being extracted, before being inserted
+  // in NewRows.
+  std::vector<DWARFDebugLine::Row> Seq;
+  const auto &FunctionRanges = Unit.getFunctionRanges();
+  auto InvalidRange = FunctionRanges.end(), CurrRange = InvalidRange;
+
+  // FIXME: This logic is meant to generate exactly the same output as
+  // Darwin's classic dsymutil. There is a nicer way to implement this
+  // by simply putting all the relocated line info in NewRows and simply
+  // sorting NewRows before passing it to emitLineTableForUnit. This
+  // should be correct as sequences for a function should stay
+  // together in the sorted output. There are a few corner cases that
+  // look suspicious though, and that required to implement the logic
+  // this way. Revisit that once initial validation is finished.
+
+  // Iterate over the object file line info and extract the sequences
+  // that correspond to linked functions.
+  for (auto &Row : LineTable.Rows) {
+    // Check whether we stepped out of the range. The range is
+    // half-open, but consider accept the end address of the range if
+    // it is marked as end_sequence in the input (because in that
+    // case, the relocation offset is accurate and that entry won't
+    // serve as the start of another function).
+    if (CurrRange == InvalidRange || Row.Address.Address < CurrRange.start() ||
+        Row.Address.Address > CurrRange.stop() ||
+        (Row.Address.Address == CurrRange.stop() && !Row.EndSequence)) {
+      // We just stepped out of a known range. Insert a end_sequence
+      // corresponding to the end of the range.
+      uint64_t StopAddress = CurrRange != InvalidRange
+                                 ? CurrRange.stop() + CurrRange.value()
+                                 : -1ULL;
+      CurrRange = FunctionRanges.find(Row.Address.Address);
+      bool CurrRangeValid =
+          CurrRange != InvalidRange && CurrRange.start() <= Row.Address.Address;
+      if (!CurrRangeValid) {
+        CurrRange = InvalidRange;
+        if (StopAddress != -1ULL) {
+          // Try harder by looking in the Address ranges map.
+          // There are corner cases where this finds a
+          // valid entry. It's unclear if this is right or wrong, but
+          // for now do as dsymutil.
+          // FIXME: Understand exactly what cases this addresses and
+          // potentially remove it along with the Ranges map.
+          auto Range = Ranges.lower_bound(Row.Address.Address);
+          if (Range != Ranges.begin() && Range != Ranges.end())
+            --Range;
+
+          if (Range != Ranges.end() && Range->first <= Row.Address.Address &&
+              Range->second.HighPC >= Row.Address.Address) {
+            StopAddress = Row.Address.Address + Range->second.Offset;
+          }
+        }
+      }
+      if (StopAddress != -1ULL && !Seq.empty()) {
+        // Insert end sequence row with the computed end address, but
+        // the same line as the previous one.
+        auto NextLine = Seq.back();
+        NextLine.Address.Address = StopAddress;
+        NextLine.EndSequence = 1;
+        NextLine.PrologueEnd = 0;
+        NextLine.BasicBlock = 0;
+        NextLine.EpilogueBegin = 0;
+        Seq.push_back(NextLine);
+        insertLineSequence(Seq, NewRows);
+      }
+
+      if (!CurrRangeValid)
+        continue;
+    }
+
+    // Ignore empty sequences.
+    if (Row.EndSequence && Seq.empty())
+      continue;
+
+    // Relocate row address and add it to the current sequence.
+    Row.Address.Address += CurrRange.value();
+    Seq.emplace_back(Row);
+
+    if (Row.EndSequence)
+      insertLineSequence(Seq, NewRows);
+  }
+
+  // Finished extracting, now emit the line tables.
+  // FIXME: LLVM hard-codes its prologue values. We just copy the
+  // prologue over and that works because we act as both producer and
+  // consumer. It would be nicer to have a real configurable line
+  // table emitter.
+  if (LineTable.Prologue.getVersion() < 2 ||
+      LineTable.Prologue.getVersion() > 5 ||
+      LineTable.Prologue.DefaultIsStmt != DWARF2_LINE_DEFAULT_IS_STMT ||
+      LineTable.Prologue.OpcodeBase > 13)
+    reportWarning("line table parameters mismatch. Cannot emit.", File);
+  else {
+    uint32_t PrologueEnd = *StmtList + 10 + LineTable.Prologue.PrologueLength;
+    // DWARF v5 has an extra 2 bytes of information before the header_length
+    // field.
+    if (LineTable.Prologue.getVersion() == 5)
+      PrologueEnd += 2;
+    StringRef LineData = OrigDwarf.getDWARFObj().getLineSection().Data;
+    MCDwarfLineTableParams Params;
+    Params.DWARF2LineOpcodeBase = LineTable.Prologue.OpcodeBase;
+    Params.DWARF2LineBase = LineTable.Prologue.LineBase;
+    Params.DWARF2LineRange = LineTable.Prologue.LineRange;
+    TheDwarfEmitter->emitLineTableForUnit(
+        Params, LineData.slice(*StmtList + 4, PrologueEnd),
+        LineTable.Prologue.MinInstLength, NewRows,
+        Unit.getOrigUnit().getAddressByteSize());
+  }
+}
+
+void DWARFLinker::emitAcceleratorEntriesForUnit(CompileUnit &Unit) {
+  switch (Options.TheAccelTableKind) {
+  case AccelTableKind::Apple:
+    emitAppleAcceleratorEntriesForUnit(Unit);
+    break;
+  case AccelTableKind::Dwarf:
+    emitDwarfAcceleratorEntriesForUnit(Unit);
+    break;
+  case AccelTableKind::Default:
+    llvm_unreachable("The default must be updated to a concrete value.");
+    break;
+  }
+}
+
+void DWARFLinker::emitAppleAcceleratorEntriesForUnit(CompileUnit &Unit) {
+  // Add namespaces.
+  for (const auto &Namespace : Unit.getNamespaces())
+    AppleNamespaces.addName(Namespace.Name,
+                            Namespace.Die->getOffset() + Unit.getStartOffset());
+
+  /// Add names.
+  TheDwarfEmitter->emitPubNamesForUnit(Unit);
+  for (const auto &Pubname : Unit.getPubnames())
+    AppleNames.addName(Pubname.Name,
+                       Pubname.Die->getOffset() + Unit.getStartOffset());
+
+  /// Add types.
+  TheDwarfEmitter->emitPubTypesForUnit(Unit);
+  for (const auto &Pubtype : Unit.getPubtypes())
+    AppleTypes.addName(
+        Pubtype.Name, Pubtype.Die->getOffset() + Unit.getStartOffset(),
+        Pubtype.Die->getTag(),
+        Pubtype.ObjcClassImplementation ? dwarf::DW_FLAG_type_implementation
+                                        : 0,
+        Pubtype.QualifiedNameHash);
+
+  /// Add ObjC names.
+  for (const auto &ObjC : Unit.getObjC())
+    AppleObjc.addName(ObjC.Name, ObjC.Die->getOffset() + Unit.getStartOffset());
+}
+
+void DWARFLinker::emitDwarfAcceleratorEntriesForUnit(CompileUnit &Unit) {
+  for (const auto &Namespace : Unit.getNamespaces())
+    DebugNames.addName(Namespace.Name, Namespace.Die->getOffset(),
+                       Namespace.Die->getTag(), Unit.getUniqueID());
+  for (const auto &Pubname : Unit.getPubnames())
+    DebugNames.addName(Pubname.Name, Pubname.Die->getOffset(),
+                       Pubname.Die->getTag(), Unit.getUniqueID());
+  for (const auto &Pubtype : Unit.getPubtypes())
+    DebugNames.addName(Pubtype.Name, Pubtype.Die->getOffset(),
+                       Pubtype.Die->getTag(), Unit.getUniqueID());
+}
+
+/// Read the frame info stored in the object, and emit the
+/// patched frame descriptions for the resulting file.
+///
+/// This is actually pretty easy as the data of the CIEs and FDEs can
+/// be considered as black boxes and moved as is. The only thing to do
+/// is to patch the addresses in the headers.
+void DWARFLinker::patchFrameInfoForObject(const DWARFFile &File,
+                                          RangesTy &Ranges,
+                                          DWARFContext &OrigDwarf,
+                                          unsigned AddrSize) {
+  StringRef FrameData = OrigDwarf.getDWARFObj().getFrameSection().Data;
+  if (FrameData.empty())
+    return;
+
+  DataExtractor Data(FrameData, OrigDwarf.isLittleEndian(), 0);
+  uint64_t InputOffset = 0;
+
+  // Store the data of the CIEs defined in this object, keyed by their
+  // offsets.
+  DenseMap<uint64_t, StringRef> LocalCIES;
+
+  while (Data.isValidOffset(InputOffset)) {
+    uint64_t EntryOffset = InputOffset;
+    uint32_t InitialLength = Data.getU32(&InputOffset);
+    if (InitialLength == 0xFFFFFFFF)
+      return reportWarning("Dwarf64 bits no supported", File);
+
+    uint32_t CIEId = Data.getU32(&InputOffset);
+    if (CIEId == 0xFFFFFFFF) {
+      // This is a CIE, store it.
+      StringRef CIEData = FrameData.substr(EntryOffset, InitialLength + 4);
+      LocalCIES[EntryOffset] = CIEData;
+      // The -4 is to account for the CIEId we just read.
+      InputOffset += InitialLength - 4;
+      continue;
+    }
+
+    uint32_t Loc = Data.getUnsigned(&InputOffset, AddrSize);
+
+    // Some compilers seem to emit frame info that doesn't start at
+    // the function entry point, thus we can't just lookup the address
+    // in the debug map. Use the AddressInfo's range map to see if the FDE
+    // describes something that we can relocate.
+    auto Range = Ranges.upper_bound(Loc);
+    if (Range != Ranges.begin())
+      --Range;
+    if (Range == Ranges.end() || Range->first > Loc ||
+        Range->second.HighPC <= Loc) {
+      // The +4 is to account for the size of the InitialLength field itself.
+      InputOffset = EntryOffset + InitialLength + 4;
+      continue;
+    }
+
+    // This is an FDE, and we have a mapping.
+    // Have we already emitted a corresponding CIE?
+    StringRef CIEData = LocalCIES[CIEId];
+    if (CIEData.empty())
+      return reportWarning("Inconsistent debug_frame content. Dropping.", File);
+
+    // Look if we already emitted a CIE that corresponds to the
+    // referenced one (the CIE data is the key of that lookup).
+    auto IteratorInserted = EmittedCIEs.insert(
+        std::make_pair(CIEData, TheDwarfEmitter->getFrameSectionSize()));
+    // If there is no CIE yet for this ID, emit it.
+    if (IteratorInserted.second ||
+        // FIXME: dsymutil-classic only caches the last used CIE for
+        // reuse. Mimic that behavior for now. Just removing that
+        // second half of the condition and the LastCIEOffset variable
+        // makes the code DTRT.
+        LastCIEOffset != IteratorInserted.first->getValue()) {
+      LastCIEOffset = TheDwarfEmitter->getFrameSectionSize();
+      IteratorInserted.first->getValue() = LastCIEOffset;
+      TheDwarfEmitter->emitCIE(CIEData);
+    }
+
+    // Emit the FDE with updated address and CIE pointer.
+    // (4 + AddrSize) is the size of the CIEId + initial_location
+    // fields that will get reconstructed by emitFDE().
+    unsigned FDERemainingBytes = InitialLength - (4 + AddrSize);
+    TheDwarfEmitter->emitFDE(IteratorInserted.first->getValue(), AddrSize,
+                             Loc + Range->second.Offset,
+                             FrameData.substr(InputOffset, FDERemainingBytes));
+    InputOffset += FDERemainingBytes;
+  }
+}
+
+void DWARFLinker::DIECloner::copyAbbrev(
+    const DWARFAbbreviationDeclaration &Abbrev, bool HasODR) {
+  DIEAbbrev Copy(dwarf::Tag(Abbrev.getTag()),
+                 dwarf::Form(Abbrev.hasChildren()));
+
+  for (const auto &Attr : Abbrev.attributes()) {
+    uint16_t Form = Attr.Form;
+    if (HasODR && isODRAttribute(Attr.Attr))
+      Form = dwarf::DW_FORM_ref_addr;
+    Copy.AddAttribute(dwarf::Attribute(Attr.Attr), dwarf::Form(Form));
+  }
+
+  Linker.assignAbbrev(Copy);
+}
+
+uint32_t DWARFLinker::DIECloner::hashFullyQualifiedName(DWARFDie DIE,
+                                                        CompileUnit &U,
+                                                        const DWARFFile &File,
+                                                        int ChildRecurseDepth) {
+  const char *Name = nullptr;
+  DWARFUnit *OrigUnit = &U.getOrigUnit();
+  CompileUnit *CU = &U;
+  Optional<DWARFFormValue> Ref;
+
+  while (1) {
+    if (const char *CurrentName = DIE.getName(DINameKind::ShortName))
+      Name = CurrentName;
+
+    if (!(Ref = DIE.find(dwarf::DW_AT_specification)) &&
+        !(Ref = DIE.find(dwarf::DW_AT_abstract_origin)))
+      break;
+
+    if (!Ref->isFormClass(DWARFFormValue::FC_Reference))
+      break;
+
+    CompileUnit *RefCU;
+    if (auto RefDIE =
+            Linker.resolveDIEReference(File, CompileUnits, *Ref, DIE, RefCU)) {
+      CU = RefCU;
+      OrigUnit = &RefCU->getOrigUnit();
+      DIE = RefDIE;
+    }
+  }
+
+  unsigned Idx = OrigUnit->getDIEIndex(DIE);
+  if (!Name && DIE.getTag() == dwarf::DW_TAG_namespace)
+    Name = "(anonymous namespace)";
+
+  if (CU->getInfo(Idx).ParentIdx == 0 ||
+      // FIXME: dsymutil-classic compatibility. Ignore modules.
+      CU->getOrigUnit().getDIEAtIndex(CU->getInfo(Idx).ParentIdx).getTag() ==
+          dwarf::DW_TAG_module)
+    return djbHash(Name ? Name : "", djbHash(ChildRecurseDepth ? "" : "::"));
+
+  DWARFDie Die = OrigUnit->getDIEAtIndex(CU->getInfo(Idx).ParentIdx);
+  return djbHash(
+      (Name ? Name : ""),
+      djbHash((Name ? "::" : ""),
+              hashFullyQualifiedName(Die, *CU, File, ++ChildRecurseDepth)));
+}
+
+static uint64_t getDwoId(const DWARFDie &CUDie, const DWARFUnit &Unit) {
+  auto DwoId = dwarf::toUnsigned(
+      CUDie.find({dwarf::DW_AT_dwo_id, dwarf::DW_AT_GNU_dwo_id}));
+  if (DwoId)
+    return *DwoId;
+  return 0;
+}
+
+static std::string remapPath(StringRef Path,
+                             const objectPrefixMap &ObjectPrefixMap) {
+  if (ObjectPrefixMap.empty())
+    return Path.str();
+
+  SmallString<256> p = Path;
+  for (const auto &Entry : ObjectPrefixMap)
+    if (llvm::sys::path::replace_path_prefix(p, Entry.first, Entry.second))
+      break;
+  return p.str().str();
+}
+
+bool DWARFLinker::registerModuleReference(DWARFDie CUDie, const DWARFUnit &Unit,
+                                          const DWARFFile &File,
+                                          OffsetsStringPool &StringPool,
+                                          DeclContextTree &ODRContexts,
+                                          uint64_t ModulesEndOffset,
+                                          unsigned &UnitID, bool IsLittleEndian,
+                                          unsigned Indent, bool Quiet) {
+  std::string PCMfile = dwarf::toString(
+      CUDie.find({dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}), "");
+  if (PCMfile.empty())
+    return false;
+  if (Options.ObjectPrefixMap)
+    PCMfile = remapPath(PCMfile, *Options.ObjectPrefixMap);
+
+  // Clang module DWARF skeleton CUs abuse this for the path to the module.
+  uint64_t DwoId = getDwoId(CUDie, Unit);
+
+  std::string Name = dwarf::toString(CUDie.find(dwarf::DW_AT_name), "");
+  if (Name.empty()) {
+    if (!Quiet)
+      reportWarning("Anonymous module skeleton CU for " + PCMfile, File);
+    return true;
+  }
+
+  if (!Quiet && Options.Verbose) {
+    outs().indent(Indent);
+    outs() << "Found clang module reference " << PCMfile;
+  }
+
+  auto Cached = ClangModules.find(PCMfile);
+  if (Cached != ClangModules.end()) {
+    // FIXME: Until PR27449 (https://llvm.org/bugs/show_bug.cgi?id=27449) is
+    // fixed in clang, only warn about DWO_id mismatches in verbose mode.
+    // ASTFileSignatures will change randomly when a module is rebuilt.
+    if (!Quiet && Options.Verbose && (Cached->second != DwoId))
+      reportWarning(Twine("hash mismatch: this object file was built against a "
+                          "different version of the module ") +
+                        PCMfile,
+                    File);
+    if (!Quiet && Options.Verbose)
+      outs() << " [cached].\n";
+    return true;
+  }
+  if (!Quiet && Options.Verbose)
+    outs() << " ...\n";
+
+  // Cyclic dependencies are disallowed by Clang, but we still
+  // shouldn't run into an infinite loop, so mark it as processed now.
+  ClangModules.insert({PCMfile, DwoId});
+
+  if (Error E = loadClangModule(CUDie, PCMfile, Name, DwoId, File, StringPool,
+                                ODRContexts, ModulesEndOffset, UnitID,
+                                IsLittleEndian, Indent + 2, Quiet)) {
+    consumeError(std::move(E));
+    return false;
+  }
+  return true;
+}
+
+Error DWARFLinker::loadClangModule(
+    DWARFDie CUDie, StringRef Filename, StringRef ModuleName, uint64_t DwoId,
+    const DWARFFile &File, OffsetsStringPool &StringPool,
+    DeclContextTree &ODRContexts, uint64_t ModulesEndOffset, unsigned &UnitID,
+    bool IsLittleEndian, unsigned Indent, bool Quiet) {
+  /// Using a SmallString<0> because loadClangModule() is recursive.
+  SmallString<0> Path(Options.PrependPath);
+  if (sys::path::is_relative(Filename))
+    resolveRelativeObjectPath(Path, CUDie);
+  sys::path::append(Path, Filename);
+  // Don't use the cached binary holder because we have no thread-safety
+  // guarantee and the lifetime is limited.
+
+  if (Options.ObjFileLoader == nullptr)
+    return Error::success();
+
+  auto ErrOrObj = Options.ObjFileLoader(File.FileName, Path);
+  if (!ErrOrObj)
+    return Error::success();
+
+  std::unique_ptr<CompileUnit> Unit;
+
+  for (const auto &CU : ErrOrObj->Dwarf->compile_units()) {
+    updateDwarfVersion(CU->getVersion());
+    // Recursively get all modules imported by this one.
+    auto CUDie = CU->getUnitDIE(false);
+    if (!CUDie)
+      continue;
+    if (!registerModuleReference(CUDie, *CU, File, StringPool, ODRContexts,
+                                 ModulesEndOffset, UnitID, IsLittleEndian,
+                                 Indent, Quiet)) {
+      if (Unit) {
+        std::string Err =
+            (Filename +
+             ": Clang modules are expected to have exactly 1 compile unit.\n")
+                .str();
+        reportError(Err, File);
+        return make_error<StringError>(Err, inconvertibleErrorCode());
+      }
+      // FIXME: Until PR27449 (https://llvm.org/bugs/show_bug.cgi?id=27449) is
+      // fixed in clang, only warn about DWO_id mismatches in verbose mode.
+      // ASTFileSignatures will change randomly when a module is rebuilt.
+      uint64_t PCMDwoId = getDwoId(CUDie, *CU);
+      if (PCMDwoId != DwoId) {
+        if (!Quiet && Options.Verbose)
+          reportWarning(
+              Twine("hash mismatch: this object file was built against a "
+                    "different version of the module ") +
+                  Filename,
+              File);
+        // Update the cache entry with the DwoId of the module loaded from disk.
+        ClangModules[Filename] = PCMDwoId;
+      }
+
+      // Add this module.
+      Unit = std::make_unique<CompileUnit>(*CU, UnitID++, !Options.NoODR,
+                                           ModuleName);
+      Unit->setHasInterestingContent();
+      analyzeContextInfo(CUDie, 0, *Unit, &ODRContexts.getRoot(), ODRContexts,
+                         ModulesEndOffset, Options.ParseableSwiftInterfaces,
+                         [&](const Twine &Warning, const DWARFDie &DIE) {
+                           reportWarning(Warning, File, &DIE);
+                         });
+      // Keep everything.
+      Unit->markEverythingAsKept();
+    }
+  }
+  if (!Unit->getOrigUnit().getUnitDIE().hasChildren())
+    return Error::success();
+  if (!Quiet && Options.Verbose) {
+    outs().indent(Indent);
+    outs() << "cloning .debug_info from " << Filename << "\n";
+  }
+
+  UnitListTy CompileUnits;
+  CompileUnits.push_back(std::move(Unit));
+  assert(TheDwarfEmitter);
+  DIECloner(*this, TheDwarfEmitter, *ErrOrObj, DIEAlloc, CompileUnits,
+            Options.Update)
+      .cloneAllCompileUnits(*(ErrOrObj->Dwarf), File, StringPool,
+                            IsLittleEndian);
+  return Error::success();
+}
+
+uint64_t DWARFLinker::DIECloner::cloneAllCompileUnits(
+    DWARFContext &DwarfContext, const DWARFFile &File,
+    OffsetsStringPool &StringPool, bool IsLittleEndian) {
+  uint64_t OutputDebugInfoSize =
+      Linker.Options.NoOutput ? 0 : Emitter->getDebugInfoSectionSize();
+  const uint64_t StartOutputDebugInfoSize = OutputDebugInfoSize;
+
+  for (auto &CurrentUnit : CompileUnits) {
+    const uint16_t DwarfVersion = CurrentUnit->getOrigUnit().getVersion();
+    const uint32_t UnitHeaderSize = DwarfVersion >= 5 ? 12 : 11;
+    auto InputDIE = CurrentUnit->getOrigUnit().getUnitDIE();
+    CurrentUnit->setStartOffset(OutputDebugInfoSize);
+    if (!InputDIE) {
+      OutputDebugInfoSize = CurrentUnit->computeNextUnitOffset(DwarfVersion);
+      continue;
+    }
+    if (CurrentUnit->getInfo(0).Keep) {
+      // Clone the InputDIE into your Unit DIE in our compile unit since it
+      // already has a DIE inside of it.
+      CurrentUnit->createOutputDIE();
+      cloneDIE(InputDIE, File, *CurrentUnit, StringPool, 0 /* PC offset */,
+               UnitHeaderSize, 0, IsLittleEndian,
+               CurrentUnit->getOutputUnitDIE());
+    }
+
+    OutputDebugInfoSize = CurrentUnit->computeNextUnitOffset(DwarfVersion);
+
+    if (!Linker.Options.NoOutput) {
+      assert(Emitter);
+
+      if (LLVM_LIKELY(!Linker.Options.Update) ||
+          Linker.needToTranslateStrings())
+        Linker.patchLineTableForUnit(*CurrentUnit, DwarfContext, File);
+
+      Linker.emitAcceleratorEntriesForUnit(*CurrentUnit);
+
+      if (LLVM_UNLIKELY(Linker.Options.Update))
+        continue;
+
+      Linker.patchRangesForUnit(*CurrentUnit, DwarfContext, File);
+      auto ProcessExpr = [&](StringRef Bytes,
+                             SmallVectorImpl<uint8_t> &Buffer) {
+        DWARFUnit &OrigUnit = CurrentUnit->getOrigUnit();
+        DataExtractor Data(Bytes, IsLittleEndian,
+                           OrigUnit.getAddressByteSize());
+        cloneExpression(Data,
+                        DWARFExpression(Data, OrigUnit.getAddressByteSize(),
+                                        OrigUnit.getFormParams().Format),
+                        File, *CurrentUnit, Buffer);
+      };
+      Emitter->emitLocationsForUnit(*CurrentUnit, DwarfContext, ProcessExpr);
+    }
+  }
+
+  if (!Linker.Options.NoOutput) {
+    assert(Emitter);
+    // Emit all the compile unit's debug information.
+    for (auto &CurrentUnit : CompileUnits) {
+      if (LLVM_LIKELY(!Linker.Options.Update))
+        Linker.generateUnitRanges(*CurrentUnit);
+
+      CurrentUnit->fixupForwardReferences();
+
+      if (!CurrentUnit->getOutputUnitDIE())
+        continue;
+
+      unsigned DwarfVersion = CurrentUnit->getOrigUnit().getVersion();
+
+      assert(Emitter->getDebugInfoSectionSize() ==
+             CurrentUnit->getStartOffset());
+      Emitter->emitCompileUnitHeader(*CurrentUnit, DwarfVersion);
+      Emitter->emitDIE(*CurrentUnit->getOutputUnitDIE());
+      assert(Emitter->getDebugInfoSectionSize() ==
+             CurrentUnit->computeNextUnitOffset(DwarfVersion));
+    }
+  }
+
+  return OutputDebugInfoSize - StartOutputDebugInfoSize;
+}
+
+void DWARFLinker::updateAccelKind(DWARFContext &Dwarf) {
+  if (Options.TheAccelTableKind != AccelTableKind::Default)
+    return;
+
+  auto &DwarfObj = Dwarf.getDWARFObj();
+
+  if (!AtLeastOneDwarfAccelTable &&
+      (!DwarfObj.getAppleNamesSection().Data.empty() ||
+       !DwarfObj.getAppleTypesSection().Data.empty() ||
+       !DwarfObj.getAppleNamespacesSection().Data.empty() ||
+       !DwarfObj.getAppleObjCSection().Data.empty())) {
+    AtLeastOneAppleAccelTable = true;
+  }
+
+  if (!AtLeastOneDwarfAccelTable && !DwarfObj.getNamesSection().Data.empty()) {
+    AtLeastOneDwarfAccelTable = true;
+  }
+}
+
+bool DWARFLinker::emitPaperTrailWarnings(const DWARFFile &File,
+                                         OffsetsStringPool &StringPool) {
+
+  if (File.Warnings.empty())
+    return false;
+
+  DIE *CUDie = DIE::get(DIEAlloc, dwarf::DW_TAG_compile_unit);
+  CUDie->setOffset(11);
+  StringRef Producer;
+  StringRef WarningHeader;
+
+  switch (DwarfLinkerClientID) {
+  case DwarfLinkerClient::Dsymutil:
+    Producer = StringPool.internString("dsymutil");
+    WarningHeader = "dsymutil_warning";
+    break;
+
+  default:
+    Producer = StringPool.internString("dwarfopt");
+    WarningHeader = "dwarfopt_warning";
+    break;
+  }
+
+  StringRef FileName = StringPool.internString(File.FileName);
+  CUDie->addValue(DIEAlloc, dwarf::DW_AT_producer, dwarf::DW_FORM_strp,
+                  DIEInteger(StringPool.getStringOffset(Producer)));
+  DIEBlock *String = new (DIEAlloc) DIEBlock();
+  DIEBlocks.push_back(String);
+  for (auto &C : FileName)
+    String->addValue(DIEAlloc, dwarf::Attribute(0), dwarf::DW_FORM_data1,
+                     DIEInteger(C));
+  String->addValue(DIEAlloc, dwarf::Attribute(0), dwarf::DW_FORM_data1,
+                   DIEInteger(0));
+
+  CUDie->addValue(DIEAlloc, dwarf::DW_AT_name, dwarf::DW_FORM_string, String);
+  for (const auto &Warning : File.Warnings) {
+    DIE &ConstDie = CUDie->addChild(DIE::get(DIEAlloc, dwarf::DW_TAG_constant));
+    ConstDie.addValue(DIEAlloc, dwarf::DW_AT_name, dwarf::DW_FORM_strp,
+                      DIEInteger(StringPool.getStringOffset(WarningHeader)));
+    ConstDie.addValue(DIEAlloc, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag,
+                      DIEInteger(1));
+    ConstDie.addValue(DIEAlloc, dwarf::DW_AT_const_value, dwarf::DW_FORM_strp,
+                      DIEInteger(StringPool.getStringOffset(Warning)));
+  }
+  unsigned Size = 4 /* FORM_strp */ + FileName.size() + 1 +
+                  File.Warnings.size() * (4 + 1 + 4) + 1 /* End of children */;
+  DIEAbbrev Abbrev = CUDie->generateAbbrev();
+  assignAbbrev(Abbrev);
+  CUDie->setAbbrevNumber(Abbrev.getNumber());
+  Size += getULEB128Size(Abbrev.getNumber());
+  // Abbreviation ordering needed for classic compatibility.
+  for (auto &Child : CUDie->children()) {
+    Abbrev = Child.generateAbbrev();
+    assignAbbrev(Abbrev);
+    Child.setAbbrevNumber(Abbrev.getNumber());
+    Size += getULEB128Size(Abbrev.getNumber());
+  }
+  CUDie->setSize(Size);
+  TheDwarfEmitter->emitPaperTrailWarningsDie(*CUDie);
+
+  return true;
+}
+
+void DWARFLinker::copyInvariantDebugSection(DWARFContext &Dwarf) {
+  if (!needToTranslateStrings())
+    TheDwarfEmitter->emitSectionContents(
+        Dwarf.getDWARFObj().getLineSection().Data, "debug_line");
+  TheDwarfEmitter->emitSectionContents(Dwarf.getDWARFObj().getLocSection().Data,
+                                       "debug_loc");
+  TheDwarfEmitter->emitSectionContents(
+      Dwarf.getDWARFObj().getRangesSection().Data, "debug_ranges");
+  TheDwarfEmitter->emitSectionContents(
+      Dwarf.getDWARFObj().getFrameSection().Data, "debug_frame");
+  TheDwarfEmitter->emitSectionContents(Dwarf.getDWARFObj().getArangesSection(),
+                                       "debug_aranges");
+}
+
+void DWARFLinker::addObjectFile(DWARFFile &File) {
+  ObjectContexts.emplace_back(LinkContext(File));
+
+  if (ObjectContexts.back().File.Dwarf)
+    updateAccelKind(*ObjectContexts.back().File.Dwarf);
+}
+
+bool DWARFLinker::link() {
+  assert(Options.NoOutput || TheDwarfEmitter);
+
+  // A unique ID that identifies each compile unit.
+  unsigned UnitID = 0;
+
+  // First populate the data structure we need for each iteration of the
+  // parallel loop.
+  unsigned NumObjects = ObjectContexts.size();
+
+  // This Dwarf string pool which is used for emission. It must be used
+  // serially as the order of calling getStringOffset matters for
+  // reproducibility.
+  OffsetsStringPool OffsetsStringPool(StringsTranslator, true);
+
+  // ODR Contexts for the optimize.
+  DeclContextTree ODRContexts;
+
+  // If we haven't decided on an accelerator table kind yet, we base ourselves
+  // on the DWARF we have seen so far. At this point we haven't pulled in debug
+  // information from modules yet, so it is technically possible that they
+  // would affect the decision. However, as they're built with the same
+  // compiler and flags, it is safe to assume that they will follow the
+  // decision made here.
+  if (Options.TheAccelTableKind == AccelTableKind::Default) {
+    if (AtLeastOneDwarfAccelTable && !AtLeastOneAppleAccelTable)
+      Options.TheAccelTableKind = AccelTableKind::Dwarf;
+    else
+      Options.TheAccelTableKind = AccelTableKind::Apple;
+  }
+
+  for (LinkContext &OptContext : ObjectContexts) {
+    if (Options.Verbose) {
+      if (DwarfLinkerClientID == DwarfLinkerClient::Dsymutil)
+        outs() << "DEBUG MAP OBJECT: " << OptContext.File.FileName << "\n";
+      else
+        outs() << "OBJECT FILE: " << OptContext.File.FileName << "\n";
+    }
+
+    if (emitPaperTrailWarnings(OptContext.File, OffsetsStringPool))
+      continue;
+
+    if (!OptContext.File.Dwarf)
+      continue;
+    // Look for relocations that correspond to address map entries.
+
+    // there was findvalidrelocations previously ... probably we need to gather
+    // info here
+    if (LLVM_LIKELY(!Options.Update) &&
+        !OptContext.File.Addresses->hasValidRelocs()) {
+      if (Options.Verbose)
+        outs() << "No valid relocations found. Skipping.\n";
+
+      // Set "Skip" flag as a signal to other loops that we should not
+      // process this iteration.
+      OptContext.Skip = true;
+      continue;
+    }
+
+    // Setup access to the debug info.
+    if (!OptContext.File.Dwarf)
+      continue;
+
+    // In a first phase, just read in the debug info and load all clang modules.
+    OptContext.CompileUnits.reserve(
+        OptContext.File.Dwarf->getNumCompileUnits());
+
+    for (const auto &CU : OptContext.File.Dwarf->compile_units()) {
+      updateDwarfVersion(CU->getVersion());
+      auto CUDie = CU->getUnitDIE(false);
+      if (Options.Verbose) {
+        outs() << "Input compilation unit:";
+        DIDumpOptions DumpOpts;
+        DumpOpts.ChildRecurseDepth = 0;
+        DumpOpts.Verbose = Options.Verbose;
+        CUDie.dump(outs(), 0, DumpOpts);
+      }
+      if (CUDie && !LLVM_UNLIKELY(Options.Update))
+        registerModuleReference(CUDie, *CU, OptContext.File, OffsetsStringPool,
+                                ODRContexts, 0, UnitID,
+                                OptContext.File.Dwarf->isLittleEndian());
+    }
+  }
+
+  // If we haven't seen any CUs, pick an arbitrary valid Dwarf version anyway.
+  if (MaxDwarfVersion == 0)
+    MaxDwarfVersion = 3;
+
+  // At this point we know how much data we have emitted. We use this value to
+  // compare canonical DIE offsets in analyzeContextInfo to see if a definition
+  // is already emitted, without being affected by canonical die offsets set
+  // later. This prevents undeterminism when analyze and clone execute
+  // concurrently, as clone set the canonical DIE offset and analyze reads it.
+  const uint64_t ModulesEndOffset =
+      Options.NoOutput ? 0 : TheDwarfEmitter->getDebugInfoSectionSize();
+
+  // These variables manage the list of processed object files.
+  // The mutex and condition variable are to ensure that this is thread safe.
+  std::mutex ProcessedFilesMutex;
+  std::condition_variable ProcessedFilesConditionVariable;
+  BitVector ProcessedFiles(NumObjects, false);
+
+  //  Analyzing the context info is particularly expensive so it is executed in
+  //  parallel with emitting the previous compile unit.
+  auto AnalyzeLambda = [&](size_t I) {
+    auto &Context = ObjectContexts[I];
+
+    if (Context.Skip || !Context.File.Dwarf)
+      return;
+
+    for (const auto &CU : Context.File.Dwarf->compile_units()) {
+      updateDwarfVersion(CU->getVersion());
+      // The !registerModuleReference() condition effectively skips
+      // over fully resolved skeleton units. This second pass of
+      // registerModuleReferences doesn't do any new work, but it
+      // will collect top-level errors, which are suppressed. Module
+      // warnings were already displayed in the first iteration.
+      bool Quiet = true;
+      auto CUDie = CU->getUnitDIE(false);
+      if (!CUDie || LLVM_UNLIKELY(Options.Update) ||
+          !registerModuleReference(CUDie, *CU, Context.File, OffsetsStringPool,
+                                   ODRContexts, ModulesEndOffset, UnitID,
+                                   Quiet)) {
+        Context.CompileUnits.push_back(std::make_unique<CompileUnit>(
+            *CU, UnitID++, !Options.NoODR && !Options.Update, ""));
+      }
+    }
+
+    // Now build the DIE parent links that we will use during the next phase.
+    for (auto &CurrentUnit : Context.CompileUnits) {
+      auto CUDie = CurrentUnit->getOrigUnit().getUnitDIE();
+      if (!CUDie)
+        continue;
+      analyzeContextInfo(CurrentUnit->getOrigUnit().getUnitDIE(), 0,
+                         *CurrentUnit, &ODRContexts.getRoot(), ODRContexts,
+                         ModulesEndOffset, Options.ParseableSwiftInterfaces,
+                         [&](const Twine &Warning, const DWARFDie &DIE) {
+                           reportWarning(Warning, Context.File, &DIE);
+                         });
+    }
+  };
+
+  // For each object file map how many bytes were emitted.
+  StringMap<DebugInfoSize> SizeByObject;
+
+  // And then the remaining work in serial again.
+  // Note, although this loop runs in serial, it can run in parallel with
+  // the analyzeContextInfo loop so long as we process files with indices >=
+  // than those processed by analyzeContextInfo.
+  auto CloneLambda = [&](size_t I) {
+    auto &OptContext = ObjectContexts[I];
+    if (OptContext.Skip || !OptContext.File.Dwarf)
+      return;
+
+    // Then mark all the DIEs that need to be present in the generated output
+    // and collect some information about them.
+    // Note that this loop can not be merged with the previous one because
+    // cross-cu references require the ParentIdx to be setup for every CU in
+    // the object file before calling this.
+    if (LLVM_UNLIKELY(Options.Update)) {
+      for (auto &CurrentUnit : OptContext.CompileUnits)
+        CurrentUnit->markEverythingAsKept();
+      copyInvariantDebugSection(*OptContext.File.Dwarf);
+    } else {
+      for (auto &CurrentUnit : OptContext.CompileUnits)
+        lookForDIEsToKeep(*OptContext.File.Addresses,
+                          OptContext.File.Addresses->getValidAddressRanges(),
+                          OptContext.CompileUnits,
+                          CurrentUnit->getOrigUnit().getUnitDIE(),
+                          OptContext.File, *CurrentUnit, 0);
+    }
+
+    // The calls to applyValidRelocs inside cloneDIE will walk the reloc
+    // array again (in the same way findValidRelocsInDebugInfo() did). We
+    // need to reset the NextValidReloc index to the beginning.
+    if (OptContext.File.Addresses->hasValidRelocs() ||
+        LLVM_UNLIKELY(Options.Update)) {
+      SizeByObject[OptContext.File.FileName].Input =
+          getDebugInfoSize(*OptContext.File.Dwarf);
+      SizeByObject[OptContext.File.FileName].Output =
+          DIECloner(*this, TheDwarfEmitter, OptContext.File, DIEAlloc,
+                    OptContext.CompileUnits, Options.Update)
+              .cloneAllCompileUnits(*OptContext.File.Dwarf, OptContext.File,
+                                    OffsetsStringPool,
+                                    OptContext.File.Dwarf->isLittleEndian());
+    }
+    if (!Options.NoOutput && !OptContext.CompileUnits.empty() &&
+        LLVM_LIKELY(!Options.Update))
+      patchFrameInfoForObject(
+          OptContext.File, OptContext.File.Addresses->getValidAddressRanges(),
+          *OptContext.File.Dwarf,
+          OptContext.CompileUnits[0]->getOrigUnit().getAddressByteSize());
+
+    // Clean-up before starting working on the next object.
+    cleanupAuxiliarryData(OptContext);
+  };
+
+  auto EmitLambda = [&]() {
+    // Emit everything that's global.
+    if (!Options.NoOutput) {
+      TheDwarfEmitter->emitAbbrevs(Abbreviations, MaxDwarfVersion);
+      TheDwarfEmitter->emitStrings(OffsetsStringPool);
+      switch (Options.TheAccelTableKind) {
+      case AccelTableKind::Apple:
+        TheDwarfEmitter->emitAppleNames(AppleNames);
+        TheDwarfEmitter->emitAppleNamespaces(AppleNamespaces);
+        TheDwarfEmitter->emitAppleTypes(AppleTypes);
+        TheDwarfEmitter->emitAppleObjc(AppleObjc);
+        break;
+      case AccelTableKind::Dwarf:
+        TheDwarfEmitter->emitDebugNames(DebugNames);
+        break;
+      case AccelTableKind::Default:
+        llvm_unreachable("Default should have already been resolved.");
+        break;
+      }
+    }
+  };
+
+  auto AnalyzeAll = [&]() {
+    for (unsigned I = 0, E = NumObjects; I != E; ++I) {
+      AnalyzeLambda(I);
+
+      std::unique_lock<std::mutex> LockGuard(ProcessedFilesMutex);
+      ProcessedFiles.set(I);
+      ProcessedFilesConditionVariable.notify_one();
+    }
+  };
+
+  auto CloneAll = [&]() {
+    for (unsigned I = 0, E = NumObjects; I != E; ++I) {
+      {
+        std::unique_lock<std::mutex> LockGuard(ProcessedFilesMutex);
+        if (!ProcessedFiles[I]) {
+          ProcessedFilesConditionVariable.wait(
+              LockGuard, [&]() { return ProcessedFiles[I]; });
+        }
+      }
+
+      CloneLambda(I);
+    }
+    EmitLambda();
+  };
+
+  // To limit memory usage in the single threaded case, analyze and clone are
+  // run sequentially so the OptContext is freed after processing each object
+  // in endDebugObject.
+  if (Options.Threads == 1) {
+    for (unsigned I = 0, E = NumObjects; I != E; ++I) {
+      AnalyzeLambda(I);
+      CloneLambda(I);
+    }
+    EmitLambda();
+  } else {
+    ThreadPool Pool(hardware_concurrency(2));
+    Pool.async(AnalyzeAll);
+    Pool.async(CloneAll);
+    Pool.wait();
+  }
+
+  if (Options.Statistics) {
+    // Create a vector sorted in descending order by output size.
+    std::vector<std::pair<StringRef, DebugInfoSize>> Sorted;
+    for (auto &E : SizeByObject)
+      Sorted.emplace_back(E.first(), E.second);
+    llvm::sort(Sorted, [](auto &LHS, auto &RHS) {
+      return LHS.second.Output > RHS.second.Output;
+    });
+
+    auto ComputePercentange = [](int64_t Input, int64_t Output) -> float {
+      const float Difference = Output - Input;
+      const float Sum = Input + Output;
+      if (Sum == 0)
+        return 0;
+      return (Difference / (Sum / 2));
+    };
+
+    int64_t InputTotal = 0;
+    int64_t OutputTotal = 0;
+    const char *FormatStr = "{0,-45} {1,10}b  {2,10}b {3,8:P}\n";
+
+    // Print header.
+    outs() << ".debug_info section size (in bytes)\n";
+    outs() << "----------------------------------------------------------------"
+              "---------------\n";
+    outs() << "Filename                                           Object       "
+              "  dSYM   Change\n";
+    outs() << "----------------------------------------------------------------"
+              "---------------\n";
+
+    // Print body.
+    for (auto &E : Sorted) {
+      InputTotal += E.second.Input;
+      OutputTotal += E.second.Output;
+      llvm::outs() << formatv(
+          FormatStr, sys::path::filename(E.first).take_back(45), E.second.Input,
+          E.second.Output, ComputePercentange(E.second.Input, E.second.Output));
+    }
+    // Print total and footer.
+    outs() << "----------------------------------------------------------------"
+              "---------------\n";
+    llvm::outs() << formatv(FormatStr, "Total", InputTotal, OutputTotal,
+                            ComputePercentange(InputTotal, OutputTotal));
+    outs() << "----------------------------------------------------------------"
+              "---------------\n\n";
+  }
+
+  return true;
+}
+
+} // namespace llvm
diff --git a/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp
new file mode 100644
index 0000000000..925ab3d295
--- /dev/null
+++ b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp
@@ -0,0 +1,152 @@
+//===- DWARFLinkerCompileUnit.cpp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DWARFLinker/DWARFLinkerCompileUnit.h"
+#include "llvm/DWARFLinker/DWARFLinkerDeclContext.h"
+
+namespace llvm {
+
+/// Check if the DIE at \p Idx is in the scope of a function.
+static bool inFunctionScope(CompileUnit &U, unsigned Idx) {
+  while (Idx) {
+    if (U.getOrigUnit().getDIEAtIndex(Idx).getTag() == dwarf::DW_TAG_subprogram)
+      return true;
+    Idx = U.getInfo(Idx).ParentIdx;
+  }
+  return false;
+}
+
+uint16_t CompileUnit::getLanguage() {
+  if (!Language) {
+    DWARFDie CU = getOrigUnit().getUnitDIE();
+    Language = dwarf::toUnsigned(CU.find(dwarf::DW_AT_language), 0);
+  }
+  return Language;
+}
+
+StringRef CompileUnit::getSysRoot() {
+  if (SysRoot.empty()) {
+    DWARFDie CU = getOrigUnit().getUnitDIE();
+    SysRoot = dwarf::toStringRef(CU.find(dwarf::DW_AT_LLVM_sysroot)).str();
+  }
+  return SysRoot;
+}
+
+void CompileUnit::markEverythingAsKept() {
+  unsigned Idx = 0;
+
+  setHasInterestingContent();
+
+  for (auto &I : Info) {
+    // Mark everything that wasn't explicit marked for pruning.
+    I.Keep = !I.Prune;
+    auto DIE = OrigUnit.getDIEAtIndex(Idx++);
+
+    // Try to guess which DIEs must go to the accelerator tables. We do that
+    // just for variables, because functions will be handled depending on
+    // whether they carry a DW_AT_low_pc attribute or not.
+    if (DIE.getTag() != dwarf::DW_TAG_variable &&
+        DIE.getTag() != dwarf::DW_TAG_constant)
+      continue;
+
+    Optional<DWARFFormValue> Value;
+    if (!(Value = DIE.find(dwarf::DW_AT_location))) {
+      if ((Value = DIE.find(dwarf::DW_AT_const_value)) &&
+          !inFunctionScope(*this, I.ParentIdx))
+        I.InDebugMap = true;
+      continue;
+    }
+    if (auto Block = Value->getAsBlock()) {
+      if (Block->size() > OrigUnit.getAddressByteSize() &&
+          (*Block)[0] == dwarf::DW_OP_addr)
+        I.InDebugMap = true;
+    }
+  }
+}
+
+uint64_t CompileUnit::computeNextUnitOffset(uint16_t DwarfVersion) {
+  NextUnitOffset = StartOffset;
+  if (NewUnit) {
+    NextUnitOffset += (DwarfVersion >= 5) ? 12 : 11; // Header size
+    NextUnitOffset += NewUnit->getUnitDie().getSize();
+  }
+  return NextUnitOffset;
+}
+
+/// Keep track of a forward cross-cu reference from this unit
+/// to \p Die that lives in \p RefUnit.
+void CompileUnit::noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
+                                       DeclContext *Ctxt, PatchLocation Attr) {
+  ForwardDIEReferences.emplace_back(Die, RefUnit, Ctxt, Attr);
+}
+
+void CompileUnit::fixupForwardReferences() {
+  for (const auto &Ref : ForwardDIEReferences) {
+    DIE *RefDie;
+    const CompileUnit *RefUnit;
+    PatchLocation Attr;
+    DeclContext *Ctxt;
+    std::tie(RefDie, RefUnit, Ctxt, Attr) = Ref;
+    if (Ctxt && Ctxt->getCanonicalDIEOffset())
+      Attr.set(Ctxt->getCanonicalDIEOffset());
+    else
+      Attr.set(RefDie->getOffset() + RefUnit->getStartOffset());
+  }
+}
+
+void CompileUnit::addLabelLowPc(uint64_t LabelLowPc, int64_t PcOffset) {
+  Labels.insert({LabelLowPc, PcOffset});
+}
+
+void CompileUnit::addFunctionRange(uint64_t FuncLowPc, uint64_t FuncHighPc,
+                                   int64_t PcOffset) {
+  //  Don't add empty ranges to the interval map.  They are a problem because
+  //  the interval map expects half open intervals. This is safe because they
+  //  are empty anyway.
+  if (FuncHighPc != FuncLowPc)
+    Ranges.insert(FuncLowPc, FuncHighPc, PcOffset);
+  this->LowPc = std::min(LowPc, FuncLowPc + PcOffset);
+  this->HighPc = std::max(HighPc, FuncHighPc + PcOffset);
+}
+
+void CompileUnit::noteRangeAttribute(const DIE &Die, PatchLocation Attr) {
+  if (Die.getTag() != dwarf::DW_TAG_compile_unit)
+    RangeAttributes.push_back(Attr);
+  else
+    UnitRangeAttribute = Attr;
+}
+
+void CompileUnit::noteLocationAttribute(PatchLocation Attr, int64_t PcOffset) {
+  LocationAttributes.emplace_back(Attr, PcOffset);
+}
+
+void CompileUnit::addNamespaceAccelerator(const DIE *Die,
+                                          DwarfStringPoolEntryRef Name) {
+  Namespaces.emplace_back(Name, Die);
+}
+
+void CompileUnit::addObjCAccelerator(const DIE *Die,
+                                     DwarfStringPoolEntryRef Name,
+                                     bool SkipPubSection) {
+  ObjC.emplace_back(Name, Die, SkipPubSection);
+}
+
+void CompileUnit::addNameAccelerator(const DIE *Die,
+                                     DwarfStringPoolEntryRef Name,
+                                     bool SkipPubSection) {
+  Pubnames.emplace_back(Name, Die, SkipPubSection);
+}
+
+void CompileUnit::addTypeAccelerator(const DIE *Die,
+                                     DwarfStringPoolEntryRef Name,
+                                     bool ObjcClassImplementation,
+                                     uint32_t QualifiedNameHash) {
+  Pubtypes.emplace_back(Name, Die, QualifiedNameHash, ObjcClassImplementation);
+}
+
+} // namespace llvm
diff --git a/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerDeclContext.cpp b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerDeclContext.cpp
new file mode 100644
index 0000000000..d9b3c4235b
--- /dev/null
+++ b/contrib/libs/llvm12/lib/DWARFLinker/DWARFLinkerDeclContext.cpp
@@ -0,0 +1,215 @@
+//===- DWARFLinkerDeclContext.cpp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DWARFLinker/DWARFLinkerDeclContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFDie.h"
+#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
+
+namespace llvm {
+
+/// Set the last DIE/CU a context was seen in and, possibly invalidate the
+/// context if it is ambiguous.
+///
+/// In the current implementation, we don't handle overloaded functions well,
+/// because the argument types are not taken into account when computing the
+/// DeclContext tree.
+///
+/// Some of this is mitigated byt using mangled names that do contain the
+/// arguments types, but sometimes (e.g. with function templates) we don't have
+/// that. In that case, just do not unique anything that refers to the contexts
+/// we are not able to distinguish.
+///
+/// If a context that is not a namespace appears twice in the same CU, we know
+/// it is ambiguous. Make it invalid.
+bool DeclContext::setLastSeenDIE(CompileUnit &U, const DWARFDie &Die) {
+  if (LastSeenCompileUnitID == U.getUniqueID()) {
+    DWARFUnit &OrigUnit = U.getOrigUnit();
+    uint32_t FirstIdx = OrigUnit.getDIEIndex(LastSeenDIE);
+    U.getInfo(FirstIdx).Ctxt = nullptr;
+    return false;
+  }
+
+  LastSeenCompileUnitID = U.getUniqueID();
+  LastSeenDIE = Die;
+  return true;
+}
+
+PointerIntPair<DeclContext *, 1>
+DeclContextTree::getChildDeclContext(DeclContext &Context, const DWARFDie &DIE,
+                                     CompileUnit &U, bool InClangModule) {
+  unsigned Tag = DIE.getTag();
+
+  // FIXME: dsymutil-classic compat: We should bail out here if we
+  // have a specification or an abstract_origin. We will get the
+  // parent context wrong here.
+
+  switch (Tag) {
+  default:
+    // By default stop gathering child contexts.
+    return PointerIntPair<DeclContext *, 1>(nullptr);
+  case dwarf::DW_TAG_module:
+    break;
+  case dwarf::DW_TAG_compile_unit:
+    return PointerIntPair<DeclContext *, 1>(&Context);
+  case dwarf::DW_TAG_subprogram:
+    // Do not unique anything inside CU local functions.
+    if ((Context.getTag() == dwarf::DW_TAG_namespace ||
+         Context.getTag() == dwarf::DW_TAG_compile_unit) &&
+        !dwarf::toUnsigned(DIE.find(dwarf::DW_AT_external), 0))
+      return PointerIntPair<DeclContext *, 1>(nullptr);
+    LLVM_FALLTHROUGH;
+  case dwarf::DW_TAG_member:
+  case dwarf::DW_TAG_namespace:
+  case dwarf::DW_TAG_structure_type:
+  case dwarf::DW_TAG_class_type:
+  case dwarf::DW_TAG_union_type:
+  case dwarf::DW_TAG_enumeration_type:
+  case dwarf::DW_TAG_typedef:
+    // Artificial things might be ambiguous, because they might be created on
+    // demand. For example implicitly defined constructors are ambiguous
+    // because of the way we identify contexts, and they won't be generated
+    // every time everywhere.
+    if (dwarf::toUnsigned(DIE.find(dwarf::DW_AT_artificial), 0))
+      return PointerIntPair<DeclContext *, 1>(nullptr);
+    break;
+  }
+
+  StringRef NameRef;
+  StringRef FileRef;
+
+  if (const char *LinkageName = DIE.getLinkageName())
+    NameRef = StringPool.internString(LinkageName);
+  else if (const char *ShortName = DIE.getShortName())
+    NameRef = StringPool.internString(ShortName);
+
+  bool IsAnonymousNamespace = NameRef.empty() && Tag == dwarf::DW_TAG_namespace;
+  if (IsAnonymousNamespace) {
+    // FIXME: For dsymutil-classic compatibility. I think uniquing within
+    // anonymous namespaces is wrong. There is no ODR guarantee there.
+    NameRef = "(anonymous namespace)";
+  }
+
+  if (Tag != dwarf::DW_TAG_class_type && Tag != dwarf::DW_TAG_structure_type &&
+      Tag != dwarf::DW_TAG_union_type &&
+      Tag != dwarf::DW_TAG_enumeration_type && NameRef.empty())
+    return PointerIntPair<DeclContext *, 1>(nullptr);
+
+  unsigned Line = 0;
+  unsigned ByteSize = std::numeric_limits<uint32_t>::max();
+
+  if (!InClangModule) {
+    // Gather some discriminating data about the DeclContext we will be
+    // creating: File, line number and byte size. This shouldn't be necessary,
+    // because the ODR is just about names, but given that we do some
+    // approximations with overloaded functions and anonymous namespaces, use
+    // these additional data points to make the process safer.
+    //
+    // This is disabled for clang modules, because forward declarations of
+    // module-defined types do not have a file and line.
+    ByteSize = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_byte_size),
+                                 std::numeric_limits<uint64_t>::max());
+    if (Tag != dwarf::DW_TAG_namespace || IsAnonymousNamespace) {
+      if (unsigned FileNum =
+              dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_file), 0)) {
+        if (const auto *LT = U.getOrigUnit().getContext().getLineTableForUnit(
+                &U.getOrigUnit())) {
+          // FIXME: dsymutil-classic compatibility. I'd rather not
+          // unique anything in anonymous namespaces, but if we do, then
+          // verify that the file and line correspond.
+          if (IsAnonymousNamespace)
+            FileNum = 1;
+
+          if (LT->hasFileAtIndex(FileNum)) {
+            Line = dwarf::toUnsigned(DIE.find(dwarf::DW_AT_decl_line), 0);
+            // Cache the resolved paths based on the index in the line table,
+            // because calling realpath is expensive.
+            FileRef = getResolvedPath(U, FileNum, *LT);
+          }
+        }
+      }
+    }
+  }
+
+  if (!Line && NameRef.empty())
+    return PointerIntPair<DeclContext *, 1>(nullptr);
+
+  // We hash NameRef, which is the mangled name, in order to get most
+  // overloaded functions resolve correctly.
+  //
+  // Strictly speaking, hashing the Tag is only necessary for a
+  // DW_TAG_module, to prevent uniquing of a module and a namespace
+  // with the same name.
+  //
+  // FIXME: dsymutil-classic won't unique the same type presented
+  // once as a struct and once as a class. Using the Tag in the fully
+  // qualified name hash to get the same effect.
+  unsigned Hash = hash_combine(Context.getQualifiedNameHash(), Tag, NameRef);
+
+  // FIXME: dsymutil-classic compatibility: when we don't have a name,
+  // use the filename.
+  if (IsAnonymousNamespace)
+    Hash = hash_combine(Hash, FileRef);
+
+  // Now look if this context already exists.
+  DeclContext Key(Hash, Line, ByteSize, Tag, NameRef, FileRef, Context);
+  auto ContextIter = Contexts.find(&Key);
+
+  if (ContextIter == Contexts.end()) {
+    // The context wasn't found.
+    bool Inserted;
+    DeclContext *NewContext =
+        new (Allocator) DeclContext(Hash, Line, ByteSize, Tag, NameRef, FileRef,
+                                    Context, DIE, U.getUniqueID());
+    std::tie(ContextIter, Inserted) = Contexts.insert(NewContext);
+    assert(Inserted && "Failed to insert DeclContext");
+    (void)Inserted;
+  } else if (Tag != dwarf::DW_TAG_namespace &&
+             !(*ContextIter)->setLastSeenDIE(U, DIE)) {
+    // The context was found, but it is ambiguous with another context
+    // in the same file. Mark it invalid.
+    return PointerIntPair<DeclContext *, 1>(*ContextIter, /* Invalid= */ 1);
+  }
+
+  assert(ContextIter != Contexts.end());
+  // FIXME: dsymutil-classic compatibility. Union types aren't
+  // uniques, but their children might be.
+  if ((Tag == dwarf::DW_TAG_subprogram &&
+       Context.getTag() != dwarf::DW_TAG_structure_type &&
+       Context.getTag() != dwarf::DW_TAG_class_type) ||
+      (Tag == dwarf::DW_TAG_union_type))
+    return PointerIntPair<DeclContext *, 1>(*ContextIter, /* Invalid= */ 1);
+
+  return PointerIntPair<DeclContext *, 1>(*ContextIter);
+}
+
+StringRef
+DeclContextTree::getResolvedPath(CompileUnit &CU, unsigned FileNum,
+                                 const DWARFDebugLine::LineTable &LineTable) {
+  std::pair<unsigned, unsigned> Key = {CU.getUniqueID(), FileNum};
+
+  ResolvedPathsMap::const_iterator It = ResolvedPaths.find(Key);
+  if (It == ResolvedPaths.end()) {
+    std::string FileName;
+    bool FoundFileName = LineTable.getFileNameByIndex(
+        FileNum, CU.getOrigUnit().getCompilationDir(),
+        DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, FileName);
+    (void)FoundFileName;
+    assert(FoundFileName && "Must get file name from line table");
+
+    // Second level of caching, this time based on the file's parent
+    // path.
+    StringRef ResolvedPath = PathResolver.resolve(FileName, StringPool);
+
+    It = ResolvedPaths.insert(std::make_pair(Key, ResolvedPath)).first;
+  }
+
+  return It->second;
+}
+
+} // namespace llvm
diff --git a/contrib/libs/llvm12/lib/DWARFLinker/DWARFStreamer.cpp b/contrib/libs/llvm12/lib/DWARFLinker/DWARFStreamer.cpp
new file mode 100644
index 0000000000..c0043ae39e
--- /dev/null
+++ b/contrib/libs/llvm12/lib/DWARFLinker/DWARFStreamer.cpp
@@ -0,0 +1,800 @@
+//===- DwarfStreamer.cpp --------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DWARFLinker/DWARFStreamer.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/CodeGen/NonRelocatableStringpool.h"
+#include "llvm/DWARFLinker/DWARFLinkerCompileUnit.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCTargetOptions.h"
+#include "llvm/MC/MCTargetOptionsCommandFlags.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Target/TargetOptions.h"
+
+namespace llvm {
+
+bool DwarfStreamer::init(Triple TheTriple) {
+  std::string ErrorStr;
+  std::string TripleName;
+  StringRef Context = "dwarf streamer init";
+
+  // Get the target.
+  const Target *TheTarget =
+      TargetRegistry::lookupTarget(TripleName, TheTriple, ErrorStr);
+  if (!TheTarget)
+    return error(ErrorStr, Context), false;
+  TripleName = TheTriple.getTriple();
+
+  // Create all the MC Objects.
+  MRI.reset(TheTarget->createMCRegInfo(TripleName));
+  if (!MRI)
+    return error(Twine("no register info for target ") + TripleName, Context),
+           false;
+
+  MCTargetOptions MCOptions = mc::InitMCTargetOptionsFromFlags();
+  MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
+  if (!MAI)
+    return error("no asm info for target " + TripleName, Context), false;
+
+  MOFI.reset(new MCObjectFileInfo);
+  MC.reset(new MCContext(MAI.get(), MRI.get(), MOFI.get()));
+  MOFI->InitMCObjectFileInfo(TheTriple, /*PIC*/ false, *MC);
+
+  MSTI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
+  if (!MSTI)
+    return error("no subtarget info for target " + TripleName, Context), false;
+
+  MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, MCOptions);
+  if (!MAB)
+    return error("no asm backend for target " + TripleName, Context), false;
+
+  MII.reset(TheTarget->createMCInstrInfo());
+  if (!MII)
+    return error("no instr info info for target " + TripleName, Context), false;
+
+  MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, *MC);
+  if (!MCE)
+    return error("no code emitter for target " + TripleName, Context), false;
+
+  switch (OutFileType) {
+  case OutputFileType::Assembly: {
+    MIP = TheTarget->createMCInstPrinter(TheTriple, MAI->getAssemblerDialect(),
+                                         *MAI, *MII, *MRI);
+    MS = TheTarget->createAsmStreamer(
+        *MC, std::make_unique<formatted_raw_ostream>(OutFile), true, true, MIP,
+        std::unique_ptr<MCCodeEmitter>(MCE), std::unique_ptr<MCAsmBackend>(MAB),
+        true);
+    break;
+  }
+  case OutputFileType::Object: {
+    MS = TheTarget->createMCObjectStreamer(
+        TheTriple, *MC, std::unique_ptr<MCAsmBackend>(MAB),
+        MAB->createObjectWriter(OutFile), std::unique_ptr<MCCodeEmitter>(MCE),
+        *MSTI, MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
+        /*DWARFMustBeAtTheEnd*/ false);
+    break;
+  }
+  }
+
+  if (!MS)
+    return error("no object streamer for target " + TripleName, Context), false;
+
+  // Finally create the AsmPrinter we'll use to emit the DIEs.
+  TM.reset(TheTarget->createTargetMachine(TripleName, "", "", TargetOptions(),
+                                          None));
+  if (!TM)
+    return error("no target machine for target " + TripleName, Context), false;
+
+  Asm.reset(TheTarget->createAsmPrinter(*TM, std::unique_ptr<MCStreamer>(MS)));
+  if (!Asm)
+    return error("no asm printer for target " + TripleName, Context), false;
+
+  RangesSectionSize = 0;
+  LocSectionSize = 0;
+  LineSectionSize = 0;
+  FrameSectionSize = 0;
+  DebugInfoSectionSize = 0;
+
+  return true;
+}
+
+void DwarfStreamer::finish() { MS->Finish(); }
+
+void DwarfStreamer::switchToDebugInfoSection(unsigned DwarfVersion) {
+  MS->SwitchSection(MOFI->getDwarfInfoSection());
+  MC->setDwarfVersion(DwarfVersion);
+}
+
+/// Emit the compilation unit header for \p Unit in the debug_info section.
+///
+/// A Dwarf 4 section header is encoded as:
+///  uint32_t   Unit length (omitting this field)
+///  uint16_t   Version
+///  uint32_t   Abbreviation table offset
+///  uint8_t    Address size
+/// Leading to a total of 11 bytes.
+///
+/// A Dwarf 5 section header is encoded as:
+///  uint32_t   Unit length (omitting this field)
+///  uint16_t   Version
+///  uint8_t    Unit type
+///  uint8_t    Address size
+///  uint32_t   Abbreviation table offset
+/// Leading to a total of 12 bytes.
+void DwarfStreamer::emitCompileUnitHeader(CompileUnit &Unit,
+                                          unsigned DwarfVersion) {
+  switchToDebugInfoSection(DwarfVersion);
+
+  /// The start of the unit within its section.
+  Unit.setLabelBegin(Asm->createTempSymbol("cu_begin"));
+  Asm->OutStreamer->emitLabel(Unit.getLabelBegin());
+
+  // Emit size of content not including length itself. The size has already
+  // been computed in CompileUnit::computeOffsets(). Subtract 4 to that size to
+  // account for the length field.
+  Asm->emitInt32(Unit.getNextUnitOffset() - Unit.getStartOffset() - 4);
+  Asm->emitInt16(DwarfVersion);
+
+  if (DwarfVersion >= 5) {
+    Asm->emitInt8(dwarf::DW_UT_compile);
+    Asm->emitInt8(Unit.getOrigUnit().getAddressByteSize());
+    // We share one abbreviations table across all units so it's always at the
+    // start of the section.
+    Asm->emitInt32(0);
+    DebugInfoSectionSize += 12;
+  } else {
+    // We share one abbreviations table across all units so it's always at the
+    // start of the section.
+    Asm->emitInt32(0);
+    Asm->emitInt8(Unit.getOrigUnit().getAddressByteSize());
+    DebugInfoSectionSize += 11;
+  }
+
+  // Remember this CU.
+  EmittedUnits.push_back({Unit.getUniqueID(), Unit.getLabelBegin()});
+}
+
+/// Emit the \p Abbrevs array as the shared abbreviation table
+/// for the linked Dwarf file.
+void DwarfStreamer::emitAbbrevs(
+    const std::vector<std::unique_ptr<DIEAbbrev>> &Abbrevs,
+    unsigned DwarfVersion) {
+  MS->SwitchSection(MOFI->getDwarfAbbrevSection());
+  MC->setDwarfVersion(DwarfVersion);
+  Asm->emitDwarfAbbrevs(Abbrevs);
+}
+
+/// Recursively emit the DIE tree rooted at \p Die.
+void DwarfStreamer::emitDIE(DIE &Die) {
+  MS->SwitchSection(MOFI->getDwarfInfoSection());
+  Asm->emitDwarfDIE(Die);
+  DebugInfoSectionSize += Die.getSize();
+}
+
+/// Emit contents of section SecName From Obj.
+void DwarfStreamer::emitSectionContents(StringRef SecData, StringRef SecName) {
+  MCSection *Section =
+      StringSwitch<MCSection *>(SecName)
+          .Case("debug_line", MC->getObjectFileInfo()->getDwarfLineSection())
+          .Case("debug_loc", MC->getObjectFileInfo()->getDwarfLocSection())
+          .Case("debug_ranges",
+                MC->getObjectFileInfo()->getDwarfRangesSection())
+          .Case("debug_frame", MC->getObjectFileInfo()->getDwarfFrameSection())
+          .Case("debug_aranges",
+                MC->getObjectFileInfo()->getDwarfARangesSection())
+          .Default(nullptr);
+
+  if (Section) {
+    MS->SwitchSection(Section);
+
+    MS->emitBytes(SecData);
+  }
+}
+
+/// Emit DIE containing warnings.
+void DwarfStreamer::emitPaperTrailWarningsDie(DIE &Die) {
+  switchToDebugInfoSection(/* Version */ 2);
+  auto &Asm = getAsmPrinter();
+  Asm.emitInt32(11 + Die.getSize() - 4);
+  Asm.emitInt16(2);
+  Asm.emitInt32(0);
+  Asm.emitInt8(MOFI->getTargetTriple().isArch64Bit() ? 8 : 4);
+  DebugInfoSectionSize += 11;
+  emitDIE(Die);
+}
+
+/// Emit the debug_str section stored in \p Pool.
+void DwarfStreamer::emitStrings(const NonRelocatableStringpool &Pool) {
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfStrSection());
+  std::vector<DwarfStringPoolEntryRef> Entries = Pool.getEntriesForEmission();
+  for (auto Entry : Entries) {
+    // Emit the string itself.
+    Asm->OutStreamer->emitBytes(Entry.getString());
+    // Emit a null terminator.
+    Asm->emitInt8(0);
+  }
+
+#if 0
+  if (DwarfVersion >= 5) {
+    // Emit an empty string offset section.
+    Asm->OutStreamer->SwitchSection(MOFI->getDwarfStrOffSection());
+    Asm->emitDwarfUnitLength(4, "Length of String Offsets Set");
+    Asm->emitInt16(DwarfVersion);
+    Asm->emitInt16(0);
+  }
+#endif
+}
+
+void DwarfStreamer::emitDebugNames(
+    AccelTable<DWARF5AccelTableStaticData> &Table) {
+  if (EmittedUnits.empty())
+    return;
+
+  // Build up data structures needed to emit this section.
+  std::vector<MCSymbol *> CompUnits;
+  DenseMap<unsigned, size_t> UniqueIdToCuMap;
+  unsigned Id = 0;
+  for (auto &CU : EmittedUnits) {
+    CompUnits.push_back(CU.LabelBegin);
+    // We might be omitting CUs, so we need to remap them.
+    UniqueIdToCuMap[CU.ID] = Id++;
+  }
+
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfDebugNamesSection());
+  emitDWARF5AccelTable(
+      Asm.get(), Table, CompUnits,
+      [&UniqueIdToCuMap](const DWARF5AccelTableStaticData &Entry) {
+        return UniqueIdToCuMap[Entry.getCUIndex()];
+      });
+}
+
+void DwarfStreamer::emitAppleNamespaces(
+    AccelTable<AppleAccelTableStaticOffsetData> &Table) {
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfAccelNamespaceSection());
+  auto *SectionBegin = Asm->createTempSymbol("namespac_begin");
+  Asm->OutStreamer->emitLabel(SectionBegin);
+  emitAppleAccelTable(Asm.get(), Table, "namespac", SectionBegin);
+}
+
+void DwarfStreamer::emitAppleNames(
+    AccelTable<AppleAccelTableStaticOffsetData> &Table) {
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfAccelNamesSection());
+  auto *SectionBegin = Asm->createTempSymbol("names_begin");
+  Asm->OutStreamer->emitLabel(SectionBegin);
+  emitAppleAccelTable(Asm.get(), Table, "names", SectionBegin);
+}
+
+void DwarfStreamer::emitAppleObjc(
+    AccelTable<AppleAccelTableStaticOffsetData> &Table) {
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfAccelObjCSection());
+  auto *SectionBegin = Asm->createTempSymbol("objc_begin");
+  Asm->OutStreamer->emitLabel(SectionBegin);
+  emitAppleAccelTable(Asm.get(), Table, "objc", SectionBegin);
+}
+
+void DwarfStreamer::emitAppleTypes(
+    AccelTable<AppleAccelTableStaticTypeData> &Table) {
+  Asm->OutStreamer->SwitchSection(MOFI->getDwarfAccelTypesSection());
+  auto *SectionBegin = Asm->createTempSymbol("types_begin");
+  Asm->OutStreamer->emitLabel(SectionBegin);
+  emitAppleAccelTable(Asm.get(), Table, "types", SectionBegin);
+}
+
+/// Emit the swift_ast section stored in \p Buffers.
+void DwarfStreamer::emitSwiftAST(StringRef Buffer) {
+  MCSection *SwiftASTSection = MOFI->getDwarfSwiftASTSection();
+  SwiftASTSection->setAlignment(Align(32));
+  MS->SwitchSection(SwiftASTSection);
+  MS->emitBytes(Buffer);
+}
+
+/// Emit the debug_range section contents for \p FuncRange by
+/// translating the original \p Entries. The debug_range section
+/// format is totally trivial, consisting just of pairs of address
+/// sized addresses describing the ranges.
+void DwarfStreamer::emitRangesEntries(
+    int64_t UnitPcOffset, uint64_t OrigLowPc,
+    const FunctionIntervals::const_iterator &FuncRange,
+    const std::vector<DWARFDebugRangeList::RangeListEntry> &Entries,
+    unsigned AddressSize) {
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
+
+  // Offset each range by the right amount.
+  int64_t PcOffset = Entries.empty() ? 0 : FuncRange.value() + UnitPcOffset;
+  for (const auto &Range : Entries) {
+    if (Range.isBaseAddressSelectionEntry(AddressSize)) {
+      warn("unsupported base address selection operation",
+           "emitting debug_ranges");
+      break;
+    }
+    // Do not emit empty ranges.
+    if (Range.StartAddress == Range.EndAddress)
+      continue;
+
+    // All range entries should lie in the function range.
+    if (!(Range.StartAddress + OrigLowPc >= FuncRange.start() &&
+          Range.EndAddress + OrigLowPc <= FuncRange.stop()))
+      warn("inconsistent range data.", "emitting debug_ranges");
+    MS->emitIntValue(Range.StartAddress + PcOffset, AddressSize);
+    MS->emitIntValue(Range.EndAddress + PcOffset, AddressSize);
+    RangesSectionSize += 2 * AddressSize;
+  }
+
+  // Add the terminator entry.
+  MS->emitIntValue(0, AddressSize);
+  MS->emitIntValue(0, AddressSize);
+  RangesSectionSize += 2 * AddressSize;
+}
+
+/// Emit the debug_aranges contribution of a unit and
+/// if \p DoDebugRanges is true the debug_range contents for a
+/// compile_unit level DW_AT_ranges attribute (Which are basically the
+/// same thing with a different base address).
+/// Just aggregate all the ranges gathered inside that unit.
+void DwarfStreamer::emitUnitRangesEntries(CompileUnit &Unit,
+                                          bool DoDebugRanges) {
+  unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
+  // Gather the ranges in a vector, so that we can simplify them. The
+  // IntervalMap will have coalesced the non-linked ranges, but here
+  // we want to coalesce the linked addresses.
+  std::vector<std::pair<uint64_t, uint64_t>> Ranges;
+  const auto &FunctionRanges = Unit.getFunctionRanges();
+  for (auto Range = FunctionRanges.begin(), End = FunctionRanges.end();
+       Range != End; ++Range)
+    Ranges.push_back(std::make_pair(Range.start() + Range.value(),
+                                    Range.stop() + Range.value()));
+
+  // The object addresses where sorted, but again, the linked
+  // addresses might end up in a different order.
+  llvm::sort(Ranges);
+
+  if (!Ranges.empty()) {
+    MS->SwitchSection(MC->getObjectFileInfo()->getDwarfARangesSection());
+
+    MCSymbol *BeginLabel = Asm->createTempSymbol("Barange");
+    MCSymbol *EndLabel = Asm->createTempSymbol("Earange");
+
+    unsigned HeaderSize =
+        sizeof(int32_t) + // Size of contents (w/o this field
+        sizeof(int16_t) + // DWARF ARange version number
+        sizeof(int32_t) + // Offset of CU in the .debug_info section
+        sizeof(int8_t) +  // Pointer Size (in bytes)
+        sizeof(int8_t);   // Segment Size (in bytes)
+
+    unsigned TupleSize = AddressSize * 2;
+    unsigned Padding = offsetToAlignment(HeaderSize, Align(TupleSize));
+
+    Asm->emitLabelDifference(EndLabel, BeginLabel, 4); // Arange length
+    Asm->OutStreamer->emitLabel(BeginLabel);
+    Asm->emitInt16(dwarf::DW_ARANGES_VERSION); // Version number
+    Asm->emitInt32(Unit.getStartOffset());     // Corresponding unit's offset
+    Asm->emitInt8(AddressSize);                // Address size
+    Asm->emitInt8(0);                          // Segment size
+
+    Asm->OutStreamer->emitFill(Padding, 0x0);
+
+    for (auto Range = Ranges.begin(), End = Ranges.end(); Range != End;
+         ++Range) {
+      uint64_t RangeStart = Range->first;
+      MS->emitIntValue(RangeStart, AddressSize);
+      while ((Range + 1) != End && Range->second == (Range + 1)->first)
+        ++Range;
+      MS->emitIntValue(Range->second - RangeStart, AddressSize);
+    }
+
+    // Emit terminator
+    Asm->OutStreamer->emitIntValue(0, AddressSize);
+    Asm->OutStreamer->emitIntValue(0, AddressSize);
+    Asm->OutStreamer->emitLabel(EndLabel);
+  }
+
+  if (!DoDebugRanges)
+    return;
+
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
+  // Offset each range by the right amount.
+  int64_t PcOffset = -Unit.getLowPc();
+  // Emit coalesced ranges.
+  for (auto Range = Ranges.begin(), End = Ranges.end(); Range != End; ++Range) {
+    MS->emitIntValue(Range->first + PcOffset, AddressSize);
+    while (Range + 1 != End && Range->second == (Range + 1)->first)
+      ++Range;
+    MS->emitIntValue(Range->second + PcOffset, AddressSize);
+    RangesSectionSize += 2 * AddressSize;
+  }
+
+  // Add the terminator entry.
+  MS->emitIntValue(0, AddressSize);
+  MS->emitIntValue(0, AddressSize);
+  RangesSectionSize += 2 * AddressSize;
+}
+
+/// Emit location lists for \p Unit and update attributes to point to the new
+/// entries.
+void DwarfStreamer::emitLocationsForUnit(
+    const CompileUnit &Unit, DWARFContext &Dwarf,
+    std::function<void(StringRef, SmallVectorImpl<uint8_t> &)> ProcessExpr) {
+  const auto &Attributes = Unit.getLocationAttributes();
+
+  if (Attributes.empty())
+    return;
+
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfLocSection());
+
+  unsigned AddressSize = Unit.getOrigUnit().getAddressByteSize();
+  uint64_t BaseAddressMarker = (AddressSize == 8)
+                                   ? std::numeric_limits<uint64_t>::max()
+                                   : std::numeric_limits<uint32_t>::max();
+  const DWARFSection &InputSec = Dwarf.getDWARFObj().getLocSection();
+  DataExtractor Data(InputSec.Data, Dwarf.isLittleEndian(), AddressSize);
+  DWARFUnit &OrigUnit = Unit.getOrigUnit();
+  auto OrigUnitDie = OrigUnit.getUnitDIE(false);
+  int64_t UnitPcOffset = 0;
+  if (auto OrigLowPc = dwarf::toAddress(OrigUnitDie.find(dwarf::DW_AT_low_pc)))
+    UnitPcOffset = int64_t(*OrigLowPc) - Unit.getLowPc();
+
+  SmallVector<uint8_t, 32> Buffer;
+  for (const auto &Attr : Attributes) {
+    uint64_t Offset = Attr.first.get();
+    Attr.first.set(LocSectionSize);
+    // This is the quantity to add to the old location address to get
+    // the correct address for the new one.
+    int64_t LocPcOffset = Attr.second + UnitPcOffset;
+    while (Data.isValidOffset(Offset)) {
+      uint64_t Low = Data.getUnsigned(&Offset, AddressSize);
+      uint64_t High = Data.getUnsigned(&Offset, AddressSize);
+      LocSectionSize += 2 * AddressSize;
+      // End of list entry.
+      if (Low == 0 && High == 0) {
+        Asm->OutStreamer->emitIntValue(0, AddressSize);
+        Asm->OutStreamer->emitIntValue(0, AddressSize);
+        break;
+      }
+      // Base address selection entry.
+      if (Low == BaseAddressMarker) {
+        Asm->OutStreamer->emitIntValue(BaseAddressMarker, AddressSize);
+        Asm->OutStreamer->emitIntValue(High + Attr.second, AddressSize);
+        LocPcOffset = 0;
+        continue;
+      }
+      // Location list entry.
+      Asm->OutStreamer->emitIntValue(Low + LocPcOffset, AddressSize);
+      Asm->OutStreamer->emitIntValue(High + LocPcOffset, AddressSize);
+      uint64_t Length = Data.getU16(&Offset);
+      Asm->OutStreamer->emitIntValue(Length, 2);
+      // Copy the bytes into to the buffer, process them, emit them.
+      Buffer.reserve(Length);
+      Buffer.resize(0);
+      StringRef Input = InputSec.Data.substr(Offset, Length);
+      ProcessExpr(Input, Buffer);
+      Asm->OutStreamer->emitBytes(
+          StringRef((const char *)Buffer.data(), Length));
+      Offset += Length;
+      LocSectionSize += Length + 2;
+    }
+  }
+}
+
+void DwarfStreamer::emitLineTableForUnit(MCDwarfLineTableParams Params,
+                                         StringRef PrologueBytes,
+                                         unsigned MinInstLength,
+                                         std::vector<DWARFDebugLine::Row> &Rows,
+                                         unsigned PointerSize) {
+  // Switch to the section where the table will be emitted into.
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfLineSection());
+  MCSymbol *LineStartSym = MC->createTempSymbol();
+  MCSymbol *LineEndSym = MC->createTempSymbol();
+
+  // The first 4 bytes is the total length of the information for this
+  // compilation unit (not including these 4 bytes for the length).
+  Asm->emitLabelDifference(LineEndSym, LineStartSym, 4);
+  Asm->OutStreamer->emitLabel(LineStartSym);
+  // Copy Prologue.
+  MS->emitBytes(PrologueBytes);
+  LineSectionSize += PrologueBytes.size() + 4;
+
+  SmallString<128> EncodingBuffer;
+  raw_svector_ostream EncodingOS(EncodingBuffer);
+
+  if (Rows.empty()) {
+    // We only have the dummy entry, dsymutil emits an entry with a 0
+    // address in that case.
+    MCDwarfLineAddr::Encode(*MC, Params, std::numeric_limits<int64_t>::max(), 0,
+                            EncodingOS);
+    MS->emitBytes(EncodingOS.str());
+    LineSectionSize += EncodingBuffer.size();
+    MS->emitLabel(LineEndSym);
+    return;
+  }
+
+  // Line table state machine fields
+  unsigned FileNum = 1;
+  unsigned LastLine = 1;
+  unsigned Column = 0;
+  unsigned IsStatement = 1;
+  unsigned Isa = 0;
+  uint64_t Address = -1ULL;
+
+  unsigned RowsSinceLastSequence = 0;
+
+  for (unsigned Idx = 0; Idx < Rows.size(); ++Idx) {
+    auto &Row = Rows[Idx];
+
+    int64_t AddressDelta;
+    if (Address == -1ULL) {
+      MS->emitIntValue(dwarf::DW_LNS_extended_op, 1);
+      MS->emitULEB128IntValue(PointerSize + 1);
+      MS->emitIntValue(dwarf::DW_LNE_set_address, 1);
+      MS->emitIntValue(Row.Address.Address, PointerSize);
+      LineSectionSize += 2 + PointerSize + getULEB128Size(PointerSize + 1);
+      AddressDelta = 0;
+    } else {
+      AddressDelta = (Row.Address.Address - Address) / MinInstLength;
+    }
+
+    // FIXME: code copied and transformed from MCDwarf.cpp::EmitDwarfLineTable.
+    // We should find a way to share this code, but the current compatibility
+    // requirement with classic dsymutil makes it hard. Revisit that once this
+    // requirement is dropped.
+
+    if (FileNum != Row.File) {
+      FileNum = Row.File;
+      MS->emitIntValue(dwarf::DW_LNS_set_file, 1);
+      MS->emitULEB128IntValue(FileNum);
+      LineSectionSize += 1 + getULEB128Size(FileNum);
+    }
+    if (Column != Row.Column) {
+      Column = Row.Column;
+      MS->emitIntValue(dwarf::DW_LNS_set_column, 1);
+      MS->emitULEB128IntValue(Column);
+      LineSectionSize += 1 + getULEB128Size(Column);
+    }
+
+    // FIXME: We should handle the discriminator here, but dsymutil doesn't
+    // consider it, thus ignore it for now.
+
+    if (Isa != Row.Isa) {
+      Isa = Row.Isa;
+      MS->emitIntValue(dwarf::DW_LNS_set_isa, 1);
+      MS->emitULEB128IntValue(Isa);
+      LineSectionSize += 1 + getULEB128Size(Isa);
+    }
+    if (IsStatement != Row.IsStmt) {
+      IsStatement = Row.IsStmt;
+      MS->emitIntValue(dwarf::DW_LNS_negate_stmt, 1);
+      LineSectionSize += 1;
+    }
+    if (Row.BasicBlock) {
+      MS->emitIntValue(dwarf::DW_LNS_set_basic_block, 1);
+      LineSectionSize += 1;
+    }
+
+    if (Row.PrologueEnd) {
+      MS->emitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
+      LineSectionSize += 1;
+    }
+
+    if (Row.EpilogueBegin) {
+      MS->emitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
+      LineSectionSize += 1;
+    }
+
+    int64_t LineDelta = int64_t(Row.Line) - LastLine;
+    if (!Row.EndSequence) {
+      MCDwarfLineAddr::Encode(*MC, Params, LineDelta, AddressDelta, EncodingOS);
+      MS->emitBytes(EncodingOS.str());
+      LineSectionSize += EncodingBuffer.size();
+      EncodingBuffer.resize(0);
+      Address = Row.Address.Address;
+      LastLine = Row.Line;
+      RowsSinceLastSequence++;
+    } else {
+      if (LineDelta) {
+        MS->emitIntValue(dwarf::DW_LNS_advance_line, 1);
+        MS->emitSLEB128IntValue(LineDelta);
+        LineSectionSize += 1 + getSLEB128Size(LineDelta);
+      }
+      if (AddressDelta) {
+        MS->emitIntValue(dwarf::DW_LNS_advance_pc, 1);
+        MS->emitULEB128IntValue(AddressDelta);
+        LineSectionSize += 1 + getULEB128Size(AddressDelta);
+      }
+      MCDwarfLineAddr::Encode(*MC, Params, std::numeric_limits<int64_t>::max(),
+                              0, EncodingOS);
+      MS->emitBytes(EncodingOS.str());
+      LineSectionSize += EncodingBuffer.size();
+      EncodingBuffer.resize(0);
+      Address = -1ULL;
+      LastLine = FileNum = IsStatement = 1;
+      RowsSinceLastSequence = Column = Isa = 0;
+    }
+  }
+
+  if (RowsSinceLastSequence) {
+    MCDwarfLineAddr::Encode(*MC, Params, std::numeric_limits<int64_t>::max(), 0,
+                            EncodingOS);
+    MS->emitBytes(EncodingOS.str());
+    LineSectionSize += EncodingBuffer.size();
+    EncodingBuffer.resize(0);
+  }
+
+  MS->emitLabel(LineEndSym);
+}
+
+/// Copy the debug_line over to the updated binary while unobfuscating the file
+/// names and directories.
+void DwarfStreamer::translateLineTable(DataExtractor Data, uint64_t Offset) {
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfLineSection());
+  StringRef Contents = Data.getData();
+
+  // We have to deconstruct the line table header, because it contains to
+  // length fields that will need to be updated when we change the length of
+  // the files and directories in there.
+  unsigned UnitLength = Data.getU32(&Offset);
+  uint64_t UnitEnd = Offset + UnitLength;
+  MCSymbol *BeginLabel = MC->createTempSymbol();
+  MCSymbol *EndLabel = MC->createTempSymbol();
+  unsigned Version = Data.getU16(&Offset);
+
+  if (Version > 5) {
+    warn("Unsupported line table version: dropping contents and not "
+         "unobfsucating line table.");
+    return;
+  }
+
+  Asm->emitLabelDifference(EndLabel, BeginLabel, 4);
+  Asm->OutStreamer->emitLabel(BeginLabel);
+  Asm->emitInt16(Version);
+  LineSectionSize += 6;
+
+  MCSymbol *HeaderBeginLabel = MC->createTempSymbol();
+  MCSymbol *HeaderEndLabel = MC->createTempSymbol();
+  Asm->emitLabelDifference(HeaderEndLabel, HeaderBeginLabel, 4);
+  Asm->OutStreamer->emitLabel(HeaderBeginLabel);
+  Offset += 4;
+  LineSectionSize += 4;
+
+  uint64_t AfterHeaderLengthOffset = Offset;
+  // Skip to the directories.
+  Offset += (Version >= 4) ? 5 : 4;
+  unsigned OpcodeBase = Data.getU8(&Offset);
+  Offset += OpcodeBase - 1;
+  Asm->OutStreamer->emitBytes(Contents.slice(AfterHeaderLengthOffset, Offset));
+  LineSectionSize += Offset - AfterHeaderLengthOffset;
+
+  // Offset points to the first directory.
+  while (const char *Dir = Data.getCStr(&Offset)) {
+    if (Dir[0] == 0)
+      break;
+
+    StringRef Translated = Translator(Dir);
+    Asm->OutStreamer->emitBytes(Translated);
+    Asm->emitInt8(0);
+    LineSectionSize += Translated.size() + 1;
+  }
+  Asm->emitInt8(0);
+  LineSectionSize += 1;
+
+  while (const char *File = Data.getCStr(&Offset)) {
+    if (File[0] == 0)
+      break;
+
+    StringRef Translated = Translator(File);
+    Asm->OutStreamer->emitBytes(Translated);
+    Asm->emitInt8(0);
+    LineSectionSize += Translated.size() + 1;
+
+    uint64_t OffsetBeforeLEBs = Offset;
+    Asm->emitULEB128(Data.getULEB128(&Offset));
+    Asm->emitULEB128(Data.getULEB128(&Offset));
+    Asm->emitULEB128(Data.getULEB128(&Offset));
+    LineSectionSize += Offset - OffsetBeforeLEBs;
+  }
+  Asm->emitInt8(0);
+  LineSectionSize += 1;
+
+  Asm->OutStreamer->emitLabel(HeaderEndLabel);
+
+  // Copy the actual line table program over.
+  Asm->OutStreamer->emitBytes(Contents.slice(Offset, UnitEnd));
+  LineSectionSize += UnitEnd - Offset;
+
+  Asm->OutStreamer->emitLabel(EndLabel);
+  Offset = UnitEnd;
+}
+
+/// Emit the pubnames or pubtypes section contribution for \p
+/// Unit into \p Sec. The data is provided in \p Names.
+void DwarfStreamer::emitPubSectionForUnit(
+    MCSection *Sec, StringRef SecName, const CompileUnit &Unit,
+    const std::vector<CompileUnit::AccelInfo> &Names) {
+  if (Names.empty())
+    return;
+
+  // Start the dwarf pubnames section.
+  Asm->OutStreamer->SwitchSection(Sec);
+  MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + SecName + "_begin");
+  MCSymbol *EndLabel = Asm->createTempSymbol("pub" + SecName + "_end");
+
+  bool HeaderEmitted = false;
+  // Emit the pubnames for this compilation unit.
+  for (const auto &Name : Names) {
+    if (Name.SkipPubSection)
+      continue;
+
+    if (!HeaderEmitted) {
+      // Emit the header.
+      Asm->emitLabelDifference(EndLabel, BeginLabel, 4); // Length
+      Asm->OutStreamer->emitLabel(BeginLabel);
+      Asm->emitInt16(dwarf::DW_PUBNAMES_VERSION); // Version
+      Asm->emitInt32(Unit.getStartOffset());      // Unit offset
+      Asm->emitInt32(Unit.getNextUnitOffset() - Unit.getStartOffset()); // Size
+      HeaderEmitted = true;
+    }
+    Asm->emitInt32(Name.Die->getOffset());
+
+    // Emit the string itself.
+    Asm->OutStreamer->emitBytes(Name.Name.getString());
+    // Emit a null terminator.
+    Asm->emitInt8(0);
+  }
+
+  if (!HeaderEmitted)
+    return;
+  Asm->emitInt32(0); // End marker.
+  Asm->OutStreamer->emitLabel(EndLabel);
+}
+
+/// Emit .debug_pubnames for \p Unit.
+void DwarfStreamer::emitPubNamesForUnit(const CompileUnit &Unit) {
+  if (Minimize)
+    return;
+  emitPubSectionForUnit(MC->getObjectFileInfo()->getDwarfPubNamesSection(),
+                        "names", Unit, Unit.getPubnames());
+}
+
+/// Emit .debug_pubtypes for \p Unit.
+void DwarfStreamer::emitPubTypesForUnit(const CompileUnit &Unit) {
+  if (Minimize)
+    return;
+  emitPubSectionForUnit(MC->getObjectFileInfo()->getDwarfPubTypesSection(),
+                        "types", Unit, Unit.getPubtypes());
+}
+
+/// Emit a CIE into the debug_frame section.
+void DwarfStreamer::emitCIE(StringRef CIEBytes) {
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfFrameSection());
+
+  MS->emitBytes(CIEBytes);
+  FrameSectionSize += CIEBytes.size();
+}
+
+/// Emit a FDE into the debug_frame section. \p FDEBytes
+/// contains the FDE data without the length, CIE offset and address
+/// which will be replaced with the parameter values.
+void DwarfStreamer::emitFDE(uint32_t CIEOffset, uint32_t AddrSize,
+                            uint32_t Address, StringRef FDEBytes) {
+  MS->SwitchSection(MC->getObjectFileInfo()->getDwarfFrameSection());
+
+  MS->emitIntValue(FDEBytes.size() + 4 + AddrSize, 4);
+  MS->emitIntValue(CIEOffset, 4);
+  MS->emitIntValue(Address, AddrSize);
+  MS->emitBytes(FDEBytes);
+  FrameSectionSize += FDEBytes.size() + 8 + AddrSize;
+}
+
+} // namespace llvm