[Dsymutil][Debuginfo][NFC] Refactor dsymutil to separate DWARF optimizing part 2.

That patch is extracted from the D70709. It moves CompileUnit, DeclContext
into llvm/DebugInfo/DWARF. It also adds new file DWARFOptimizer with
AddressesMap class. AddressesMap generalizes functionality
from RelocationManager.

Differential Revision: https://reviews.llvm.org/D71271

9 files changed, 82 insertions, 933 deletions

diff --git a/llvm/tools/dsymutil/CMakeLists.txt b/llvm/tools/dsymutil/CMakeLists.txt
index b8466baa634..e21215b2417 100644
--- a/llvm/tools/dsymutil/CMakeLists.txt
+++ b/llvm/tools/dsymutil/CMakeLists.txt
@@ -22,9 +22,7 @@ add_llvm_tool(dsymutil
   dsymutil.cpp
   BinaryHolder.cpp
   CFBundle.cpp
-  CompileUnit.cpp
   DebugMap.cpp
-  DeclContext.cpp
   DwarfLinker.cpp
   DwarfStreamer.cpp
   MachODebugMapParser.cpp
diff --git a/llvm/tools/dsymutil/CompileUnit.cpp b/llvm/tools/dsymutil/CompileUnit.cpp
deleted file mode 100644
index 036c61a6b92..00000000000
--- a/llvm/tools/dsymutil/CompileUnit.cpp
+++ /dev/null
@@ -1,146 +0,0 @@
-//===- tools/dsymutil/CompileUnit.h - Dwarf compile unit ------------------===//
-//
-// 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 "CompileUnit.h"
-#include "DeclContext.h"
-
-namespace llvm {
-namespace dsymutil {
-
-/// 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;
-}
-
-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() {
-  NextUnitOffset = StartOffset;
-  if (NewUnit) {
-    NextUnitOffset += 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 dsymutil
-} // namespace llvm
diff --git a/llvm/tools/dsymutil/CompileUnit.h b/llvm/tools/dsymutil/CompileUnit.h
deleted file mode 100644
index e0f5d3bc65b..00000000000
--- a/llvm/tools/dsymutil/CompileUnit.h
+++ /dev/null
@@ -1,331 +0,0 @@
-//===- tools/dsymutil/CompileUnit.h - Dwarf debug info linker ---*- C++ -*-===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_TOOLS_DSYMUTIL_COMPILEUNIT_H
-#define LLVM_TOOLS_DSYMUTIL_COMPILEUNIT_H
-
-#include "llvm/ADT/IntervalMap.h"
-#include "llvm/CodeGen/DIE.h"
-#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
-
-namespace llvm {
-namespace dsymutil {
-
-class DeclContext;
-
-template <typename KeyT, typename ValT>
-using HalfOpenIntervalMap =
-    IntervalMap<KeyT, ValT, IntervalMapImpl::NodeSizer<KeyT, ValT>::LeafSize,
-                IntervalMapHalfOpenInfo<KeyT>>;
-
-using FunctionIntervals = HalfOpenIntervalMap<uint64_t, int64_t>;
-
-// FIXME: Delete this structure.
-struct PatchLocation {
-  DIE::value_iterator I;
-
-  PatchLocation() = default;
-  PatchLocation(DIE::value_iterator I) : I(I) {}
-
-  void set(uint64_t New) const {
-    assert(I);
-    const auto &Old = *I;
-    assert(Old.getType() == DIEValue::isInteger);
-    *I = DIEValue(Old.getAttribute(), Old.getForm(), DIEInteger(New));
-  }
-
-  uint64_t get() const {
-    assert(I);
-    return I->getDIEInteger().getValue();
-  }
-};
-
-/// Stores all information relating to a compile unit, be it in its original
-/// instance in the object file to its brand new cloned and linked DIE tree.
-class CompileUnit {
-public:
-  /// Information gathered about a DIE in the object file.
-  struct DIEInfo {
-    /// Address offset to apply to the described entity.
-    int64_t AddrAdjust;
-
-    /// ODR Declaration context.
-    DeclContext *Ctxt;
-
-    /// Cloned version of that DIE.
-    DIE *Clone;
-
-    /// The index of this DIE's parent.
-    uint32_t ParentIdx;
-
-    /// Is the DIE part of the linked output?
-    bool Keep : 1;
-
-    /// Was this DIE's entity found in the map?
-    bool InDebugMap : 1;
-
-    /// Is this a pure forward declaration we can strip?
-    bool Prune : 1;
-
-    /// Does DIE transitively refer an incomplete decl?
-    bool Incomplete : 1;
-  };
-
-  CompileUnit(DWARFUnit &OrigUnit, unsigned ID, bool CanUseODR,
-              StringRef ClangModuleName)
-      : OrigUnit(OrigUnit), ID(ID), Ranges(RangeAlloc),
-        ClangModuleName(ClangModuleName) {
-    Info.resize(OrigUnit.getNumDIEs());
-
-    auto CUDie = OrigUnit.getUnitDIE(false);
-    if (!CUDie) {
-      HasODR = false;
-      return;
-    }
-    if (auto Lang = dwarf::toUnsigned(CUDie.find(dwarf::DW_AT_language)))
-      HasODR = CanUseODR && (*Lang == dwarf::DW_LANG_C_plus_plus ||
-                             *Lang == dwarf::DW_LANG_C_plus_plus_03 ||
-                             *Lang == dwarf::DW_LANG_C_plus_plus_11 ||
-                             *Lang == dwarf::DW_LANG_C_plus_plus_14 ||
-                             *Lang == dwarf::DW_LANG_ObjC_plus_plus);
-    else
-      HasODR = false;
-  }
-
-  DWARFUnit &getOrigUnit() const { return OrigUnit; }
-
-  unsigned getUniqueID() const { return ID; }
-
-  void createOutputDIE() {
-    NewUnit.emplace(OrigUnit.getVersion(), OrigUnit.getAddressByteSize(),
-                    OrigUnit.getUnitDIE().getTag());
-  }
-
-  DIE *getOutputUnitDIE() const {
-    if (NewUnit)
-      return &const_cast<BasicDIEUnit &>(*NewUnit).getUnitDie();
-    return nullptr;
-  }
-
-  bool hasODR() const { return HasODR; }
-  bool isClangModule() const { return !ClangModuleName.empty(); }
-  uint16_t getLanguage();
-
-  const std::string &getClangModuleName() const { return ClangModuleName; }
-
-  DIEInfo &getInfo(unsigned Idx) { return Info[Idx]; }
-  const DIEInfo &getInfo(unsigned Idx) const { return Info[Idx]; }
-
-  uint64_t getStartOffset() const { return StartOffset; }
-  uint64_t getNextUnitOffset() const { return NextUnitOffset; }
-  void setStartOffset(uint64_t DebugInfoSize) { StartOffset = DebugInfoSize; }
-
-  uint64_t getLowPc() const { return LowPc; }
-  uint64_t getHighPc() const { return HighPc; }
-  bool hasLabelAt(uint64_t Addr) const { return Labels.count(Addr); }
-
-  Optional<PatchLocation> getUnitRangesAttribute() const {
-    return UnitRangeAttribute;
-  }
-
-  const FunctionIntervals &getFunctionRanges() const { return Ranges; }
-
-  const std::vector<PatchLocation> &getRangesAttributes() const {
-    return RangeAttributes;
-  }
-
-  const std::vector<std::pair<PatchLocation, int64_t>> &
-  getLocationAttributes() const {
-    return LocationAttributes;
-  }
-
-  void setHasInterestingContent() { HasInterestingContent = true; }
-  bool hasInterestingContent() { return HasInterestingContent; }
-
-  /// Mark every DIE in this unit as kept. This function also
-  /// marks variables as InDebugMap so that they appear in the
-  /// reconstructed accelerator tables.
-  void markEverythingAsKept();
-
-  /// Compute the end offset for this unit. Must be called after the CU's DIEs
-  /// have been cloned.  \returns the next unit offset (which is also the
-  /// current debug_info section size).
-  uint64_t computeNextUnitOffset();
-
-  /// Keep track of a forward reference to DIE \p Die in \p RefUnit by \p
-  /// Attr. The attribute should be fixed up later to point to the absolute
-  /// offset of \p Die in the debug_info section or to the canonical offset of
-  /// \p Ctxt if it is non-null.
-  void noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
-                            DeclContext *Ctxt, PatchLocation Attr);
-
-  /// Apply all fixups recorded by noteForwardReference().
-  void fixupForwardReferences();
-
-  /// Add the low_pc of a label that is relocated by applying
-  /// offset \p PCOffset.
-  void addLabelLowPc(uint64_t LabelLowPc, int64_t PcOffset);
-
-  /// Add a function range [\p LowPC, \p HighPC) that is relocated by applying
-  /// offset \p PCOffset.
-  void addFunctionRange(uint64_t LowPC, uint64_t HighPC, int64_t PCOffset);
-
-  /// Keep track of a DW_AT_range attribute that we will need to patch up later.
-  void noteRangeAttribute(const DIE &Die, PatchLocation Attr);
-
-  /// Keep track of a location attribute pointing to a location list in the
-  /// debug_loc section.
-  void noteLocationAttribute(PatchLocation Attr, int64_t PcOffset);
-
-  /// Add a name accelerator entry for \a Die with \a Name.
-  void addNamespaceAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name);
-
-  /// Add a name accelerator entry for \a Die with \a Name.
-  void addNameAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
-                          bool SkipPubnamesSection = false);
-
-  /// Add various accelerator entries for \p Die with \p Name which is stored
-  /// in the string table at \p Offset. \p Name must be an Objective-C
-  /// selector.
-  void addObjCAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
-                          bool SkipPubnamesSection = false);
-
-  /// Add a type accelerator entry for \p Die with \p Name which is stored in
-  /// the string table at \p Offset.
-  void addTypeAccelerator(const DIE *Die, DwarfStringPoolEntryRef Name,
-                          bool ObjcClassImplementation,
-                          uint32_t QualifiedNameHash);
-
-  struct AccelInfo {
-    /// Name of the entry.
-    DwarfStringPoolEntryRef Name;
-
-    /// DIE this entry describes.
-    const DIE *Die;
-
-    /// Hash of the fully qualified name.
-    uint32_t QualifiedNameHash;
-
-    /// Emit this entry only in the apple_* sections.
-    bool SkipPubSection;
-
-    /// Is this an ObjC class implementation?
-    bool ObjcClassImplementation;
-
-    AccelInfo(DwarfStringPoolEntryRef Name, const DIE *Die,
-              bool SkipPubSection = false)
-        : Name(Name), Die(Die), SkipPubSection(SkipPubSection) {}
-
-    AccelInfo(DwarfStringPoolEntryRef Name, const DIE *Die,
-              uint32_t QualifiedNameHash, bool ObjCClassIsImplementation)
-        : Name(Name), Die(Die), QualifiedNameHash(QualifiedNameHash),
-          SkipPubSection(false),
-          ObjcClassImplementation(ObjCClassIsImplementation) {}
-  };
-
-  const std::vector<AccelInfo> &getPubnames() const { return Pubnames; }
-  const std::vector<AccelInfo> &getPubtypes() const { return Pubtypes; }
-  const std::vector<AccelInfo> &getNamespaces() const { return Namespaces; }
-  const std::vector<AccelInfo> &getObjC() const { return ObjC; }
-
-  /// Get the full path for file \a FileNum in the line table
-  StringRef getResolvedPath(unsigned FileNum) {
-    if (FileNum >= ResolvedPaths.size())
-      return StringRef();
-    return ResolvedPaths[FileNum];
-  }
-
-  /// Set the fully resolved path for the line-table's file \a FileNum
-  /// to \a Path.
-  void setResolvedPath(unsigned FileNum, StringRef Path) {
-    if (ResolvedPaths.size() <= FileNum)
-      ResolvedPaths.resize(FileNum + 1);
-    ResolvedPaths[FileNum] = Path;
-  }
-
-  MCSymbol *getLabelBegin() { return LabelBegin; }
-  void setLabelBegin(MCSymbol *S) { LabelBegin = S; }
-
-private:
-  DWARFUnit &OrigUnit;
-  unsigned ID;
-  std::vector<DIEInfo> Info; ///< DIE info indexed by DIE index.
-  Optional<BasicDIEUnit> NewUnit;
-  MCSymbol *LabelBegin = nullptr;
-
-  uint64_t StartOffset;
-  uint64_t NextUnitOffset;
-
-  uint64_t LowPc = std::numeric_limits<uint64_t>::max();
-  uint64_t HighPc = 0;
-
-  /// A list of attributes to fixup with the absolute offset of
-  /// a DIE in the debug_info section.
-  ///
-  /// The offsets for the attributes in this array couldn't be set while
-  /// cloning because for cross-cu forward references the target DIE's offset
-  /// isn't known you emit the reference attribute.
-  std::vector<
-      std::tuple<DIE *, const CompileUnit *, DeclContext *, PatchLocation>>
-      ForwardDIEReferences;
-
-  FunctionIntervals::Allocator RangeAlloc;
-
-  /// The ranges in that interval map are the PC ranges for
-  /// functions in this unit, associated with the PC offset to apply
-  /// to the addresses to get the linked address.
-  FunctionIntervals Ranges;
-
-  /// The DW_AT_low_pc of each DW_TAG_label.
-  SmallDenseMap<uint64_t, uint64_t, 1> Labels;
-
-  /// DW_AT_ranges attributes to patch after we have gathered
-  /// all the unit's function addresses.
-  /// @{
-  std::vector<PatchLocation> RangeAttributes;
-  Optional<PatchLocation> UnitRangeAttribute;
-  /// @}
-
-  /// Location attributes that need to be transferred from the
-  /// original debug_loc section to the liked one. They are stored
-  /// along with the PC offset that is to be applied to their
-  /// function's address.
-  std::vector<std::pair<PatchLocation, int64_t>> LocationAttributes;
-
-  /// Accelerator entries for the unit, both for the pub*
-  /// sections and the apple* ones.
-  /// @{
-  std::vector<AccelInfo> Pubnames;
-  std::vector<AccelInfo> Pubtypes;
-  std::vector<AccelInfo> Namespaces;
-  std::vector<AccelInfo> ObjC;
-  /// @}
-
-  /// Cached resolved paths from the line table.
-  /// Note, the StringRefs here point in to the intern (uniquing) string pool.
-  /// This means that a StringRef returned here doesn't need to then be uniqued
-  /// for the purposes of getting a unique address for each string.
-  std::vector<StringRef> ResolvedPaths;
-
-  /// Is this unit subject to the ODR rule?
-  bool HasODR;
-
-  /// Did a DIE actually contain a valid reloc?
-  bool HasInterestingContent;
-
-  /// The DW_AT_language of this unit.
-  uint16_t Language = 0;
-
-  /// If this is a Clang module, this holds the module's name.
-  std::string ClangModuleName;
-};
-
-} // end namespace dsymutil
-} // end namespace llvm
-
-#endif // LLVM_TOOLS_DSYMUTIL_COMPILEUNIT_H
diff --git a/llvm/tools/dsymutil/DeclContext.cpp b/llvm/tools/dsymutil/DeclContext.cpp
deleted file mode 100644
index 1c33b672c26..00000000000
--- a/llvm/tools/dsymutil/DeclContext.cpp
+++ /dev/null
@@ -1,210 +0,0 @@
-//===- tools/dsymutil/DeclContext.cpp - Declaration context ---------------===//
-//
-// 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 "DeclContext.h"
-#include "llvm/DebugInfo/DWARF/DWARFContext.h"
-#include "llvm/DebugInfo/DWARF/DWARFDie.h"
-#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
-
-namespace llvm {
-namespace dsymutil {
-
-/// 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,
-    UniquingStringPool &StringPool, 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;
-  }
-
-  const char *Name = DIE.getName(DINameKind::LinkageName);
-  const char *ShortName = DIE.getName(DINameKind::ShortName);
-  StringRef NameRef;
-  StringRef ShortNameRef;
-  StringRef FileRef;
-
-  if (Name)
-    NameRef = StringPool.internString(Name);
-  else if (Tag == dwarf::DW_TAG_namespace)
-    // FIXME: For dsymutil-classic compatibility. I think uniquing within
-    // anonymous namespaces is wrong. There is no ODR guarantee there.
-    NameRef = StringPool.internString("(anonymous namespace)");
-
-  if (ShortName && ShortName != Name)
-    ShortNameRef = StringPool.internString(ShortName);
-  else
-    ShortNameRef = NameRef;
-
-  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 || !Name) {
-      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 (!Name && Tag == dwarf::DW_TAG_namespace)
-            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 expansive.
-            StringRef ResolvedPath = U.getResolvedPath(FileNum);
-            if (!ResolvedPath.empty()) {
-              FileRef = ResolvedPath;
-            } else {
-              std::string File;
-              bool FoundFileName = LT->getFileNameByIndex(
-                  FileNum, U.getOrigUnit().getCompilationDir(),
-                  DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath,
-                  File);
-              (void)FoundFileName;
-              assert(FoundFileName && "Must get file name from line table");
-              // Second level of caching, this time based on the file's parent
-              // path.
-              FileRef = PathResolver.resolve(File, StringPool);
-              U.setResolvedPath(FileNum, FileRef);
-            }
-          }
-        }
-      }
-    }
-  }
-
-  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 (Tag == dwarf::DW_TAG_namespace && NameRef == "(anonymous namespace)")
-    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);
-}
-} // namespace dsymutil
-} // namespace llvm
diff --git a/llvm/tools/dsymutil/DeclContext.h b/llvm/tools/dsymutil/DeclContext.h
deleted file mode 100644
index 36ef5094408..00000000000
--- a/llvm/tools/dsymutil/DeclContext.h
+++ /dev/null
@@ -1,171 +0,0 @@
-//===- tools/dsymutil/DeclContext.h - Dwarf debug info linker ---*- C++ -*-===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_TOOLS_DSYMUTIL_DECLCONTEXT_H
-#define LLVM_TOOLS_DSYMUTIL_DECLCONTEXT_H
-
-#include "CompileUnit.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/DenseMapInfo.h"
-#include "llvm/ADT/DenseSet.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/CodeGen/NonRelocatableStringpool.h"
-#include "llvm/DebugInfo/DWARF/DWARFDie.h"
-#include "llvm/Support/Path.h"
-
-namespace llvm {
-namespace dsymutil {
-
-struct DeclMapInfo;
-
-/// Small helper that resolves and caches file paths. This helps reduce the
-/// number of calls to realpath which is expensive. We assume the input are
-/// files, and cache the realpath of their parent. This way we can quickly
-/// resolve different files under the same path.
-class CachedPathResolver {
-public:
-  /// Resolve a path by calling realpath and cache its result. The returned
-  /// StringRef is interned in the given \p StringPool.
-  StringRef resolve(std::string Path, NonRelocatableStringpool &StringPool) {
-    StringRef FileName = sys::path::filename(Path);
-    SmallString<256> ParentPath = sys::path::parent_path(Path);
-
-    // If the ParentPath has not yet been resolved, resolve and cache it for
-    // future look-ups.
-    if (!ResolvedPaths.count(ParentPath)) {
-      SmallString<256> RealPath;
-      sys::fs::real_path(ParentPath, RealPath);
-      ResolvedPaths.insert({ParentPath, StringRef(RealPath).str()});
-    }
-
-    // Join the file name again with the resolved path.
-    SmallString<256> ResolvedPath(ResolvedPaths[ParentPath]);
-    sys::path::append(ResolvedPath, FileName);
-    return StringPool.internString(ResolvedPath);
-  }
-
-private:
-  StringMap<std::string> ResolvedPaths;
-};
-
-/// A DeclContext is a named program scope that is used for ODR uniquing of
-/// types.
-///
-/// The set of DeclContext for the ODR-subject parts of a Dwarf link is
-/// expanded (and uniqued) with each new object file processed. We need to
-/// determine the context of each DIE in an linked object file to see if the
-/// corresponding type has already been emitted.
-///
-/// The contexts are conceptually organized as a tree (eg. a function scope is
-/// contained in a namespace scope that contains other scopes), but
-/// storing/accessing them in an actual tree is too inefficient: we need to be
-/// able to very quickly query a context for a given child context by name.
-/// Storing a StringMap in each DeclContext would be too space inefficient.
-///
-/// The solution here is to give each DeclContext a link to its parent (this
-/// allows to walk up the tree), but to query the existence of a specific
-/// DeclContext using a separate DenseMap keyed on the hash of the fully
-/// qualified name of the context.
-class DeclContext {
-public:
-  using Map = DenseSet<DeclContext *, DeclMapInfo>;
-
-  DeclContext() : DefinedInClangModule(0), Parent(*this) {}
-
-  DeclContext(unsigned Hash, uint32_t Line, uint32_t ByteSize, uint16_t Tag,
-              StringRef Name, StringRef File, const DeclContext &Parent,
-              DWARFDie LastSeenDIE = DWARFDie(), unsigned CUId = 0)
-      : QualifiedNameHash(Hash), Line(Line), ByteSize(ByteSize), Tag(Tag),
-        DefinedInClangModule(0), Name(Name), File(File), Parent(Parent),
-        LastSeenDIE(LastSeenDIE), LastSeenCompileUnitID(CUId) {}
-
-  uint32_t getQualifiedNameHash() const { return QualifiedNameHash; }
-
-  bool setLastSeenDIE(CompileUnit &U, const DWARFDie &Die);
-
-  uint32_t getCanonicalDIEOffset() const { return CanonicalDIEOffset; }
-  void setCanonicalDIEOffset(uint32_t Offset) { CanonicalDIEOffset = Offset; }
-
-  bool isDefinedInClangModule() const { return DefinedInClangModule; }
-  void setDefinedInClangModule(bool Val) { DefinedInClangModule = Val; }
-
-  uint16_t getTag() const { return Tag; }
-  StringRef getName() const { return Name; }
-
-private:
-  friend DeclMapInfo;
-
-  unsigned QualifiedNameHash = 0;
-  uint32_t Line = 0;
-  uint32_t ByteSize = 0;
-  uint16_t Tag = dwarf::DW_TAG_compile_unit;
-  unsigned DefinedInClangModule : 1;
-  StringRef Name;
-  StringRef File;
-  const DeclContext &Parent;
-  DWARFDie LastSeenDIE;
-  uint32_t LastSeenCompileUnitID = 0;
-  uint32_t CanonicalDIEOffset = 0;
-};
-
-/// This class gives a tree-like API to the DenseMap that stores the
-/// DeclContext objects. It holds the BumpPtrAllocator where these objects will
-/// be allocated.
-class DeclContextTree {
-public:
-  /// Get the child of \a Context described by \a DIE in \a Unit. The
-  /// required strings will be interned in \a StringPool.
-  /// \returns The child DeclContext along with one bit that is set if
-  /// this context is invalid.
-  ///
-  /// An invalid context means it shouldn't be considered for uniquing, but its
-  /// not returning null, because some children of that context might be
-  /// uniquing candidates.
-  ///
-  /// FIXME: The invalid bit along the return value is to emulate some
-  /// dsymutil-classic functionality.
-  PointerIntPair<DeclContext *, 1>
-  getChildDeclContext(DeclContext &Context, const DWARFDie &DIE,
-                      CompileUnit &Unit, UniquingStringPool &StringPool,
-                      bool InClangModule);
-
-  DeclContext &getRoot() { return Root; }
-
-private:
-  BumpPtrAllocator Allocator;
-  DeclContext Root;
-  DeclContext::Map Contexts;
-
-  /// Cache resolved paths from the line table.
-  CachedPathResolver PathResolver;
-};
-
-/// Info type for the DenseMap storing the DeclContext pointers.
-struct DeclMapInfo : private DenseMapInfo<DeclContext *> {
-  using DenseMapInfo<DeclContext *>::getEmptyKey;
-  using DenseMapInfo<DeclContext *>::getTombstoneKey;
-
-  static unsigned getHashValue(const DeclContext *Ctxt) {
-    return Ctxt->QualifiedNameHash;
-  }
-
-  static bool isEqual(const DeclContext *LHS, const DeclContext *RHS) {
-    if (RHS == getEmptyKey() || RHS == getTombstoneKey())
-      return RHS == LHS;
-    return LHS->QualifiedNameHash == RHS->QualifiedNameHash &&
-           LHS->Line == RHS->Line && LHS->ByteSize == RHS->ByteSize &&
-           LHS->Name.data() == RHS->Name.data() &&
-           LHS->File.data() == RHS->File.data() &&
-           LHS->Parent.QualifiedNameHash == RHS->Parent.QualifiedNameHash;
-  }
-};
-
-} // end namespace dsymutil
-} // end namespace llvm
-
-#endif // LLVM_TOOLS_DSYMUTIL_DECLCONTEXT_H
diff --git a/llvm/tools/dsymutil/DwarfLinker.cpp b/llvm/tools/dsymutil/DwarfLinker.cpp
index 64acab69843..521d3635dab 100644
--- a/llvm/tools/dsymutil/DwarfLinker.cpp
+++ b/llvm/tools/dsymutil/DwarfLinker.cpp
@@ -9,7 +9,6 @@
 #include "DwarfLinker.h"
 #include "BinaryHolder.h"
 #include "DebugMap.h"
-#include "DeclContext.h"
 #include "DwarfStreamer.h"
 #include "MachOUtils.h"
 #include "dsymutil.h"
@@ -45,6 +44,7 @@
 #include "llvm/DebugInfo/DWARF/DWARFDebugRangeList.h"
 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptDeclContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFSection.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
 #include "llvm/MC/MCAsmBackend.h"
@@ -374,30 +374,6 @@ static bool dieNeedsChildrenToBeMeaningful(uint32_t Tag) {
 }
 
 void DwarfLinker::startDebugObject(LinkContext &Context) {
-  // Iterate over the debug map entries and put all the ones that are
-  // functions (because they have a size) into the Ranges map. This map is
-  // very similar to the FunctionRanges that are stored in each unit, with 2
-  // notable differences:
-  //
-  //  1. Obviously this one is global, while the other ones are per-unit.
-  //
-  //  2. This one contains not only the functions described in the DIE
-  //     tree, but also the ones that are only in the debug map.
-  //
-  // The latter information is required to reproduce dsymutil's logic while
-  // linking line tables. The cases where this information matters look like
-  // bugs that need to be investigated, but for now we need to reproduce
-  // dsymutil's behavior.
-  // FIXME: Once we understood exactly if that information is needed,
-  // maybe totally remove this (or try to use it to do a real
-  // -gline-tables-only on Darwin.
-  for (const auto &Entry : Context.DMO.symbols()) {
-    const auto &Mapping = Entry.getValue();
-    if (Mapping.Size && Mapping.ObjectAddress)
-      Context.Ranges[*Mapping.ObjectAddress] = DebugMapObjectRange(
-          *Mapping.ObjectAddress + Mapping.Size,
-          int64_t(Mapping.BinaryAddress) - *Mapping.ObjectAddress);
-  }
 }
 
 void DwarfLinker::endDebugObject(LinkContext &Context) {
@@ -560,7 +536,7 @@ bool DwarfLinker::RelocationManager::findValidRelocsInDebugInfo(
 /// This function must be called with offsets in strictly ascending
 /// order because it never looks back at relocations it already 'went past'.
 /// \returns true and sets Info.InDebugMap if it is the case.
-bool DwarfLinker::RelocationManager::hasValidRelocation(
+bool DwarfLinker::RelocationManager::hasValidRelocationAt(
     uint64_t StartOffset, uint64_t EndOffset, CompileUnit::DIEInfo &Info) {
   assert(NextValidReloc == 0 ||
          StartOffset > ValidRelocs[NextValidReloc - 1].Offset);
@@ -651,7 +627,8 @@ unsigned DwarfLinker::shouldKeepVariableDIE(RelocationManager &RelocMgr,
   // 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.hasValidRelocation(LocationOffset, LocationEndOffset, MyInfo) ||
+  if (!RelocMgr.hasValidRelocationAt(LocationOffset, LocationEndOffset,
+                                     MyInfo) ||
       (Flags & TF_InFunctionScope))
     return Flags;
 
@@ -689,7 +666,7 @@ unsigned DwarfLinker::shouldKeepSubprogramDIE(
   auto LowPc = dwarf::toAddress(DIE.find(dwarf::DW_AT_low_pc));
   assert(LowPc.hasValue() && "low_pc attribute is not an address.");
   if (!LowPc ||
-      !RelocMgr.hasValidRelocation(LowPcOffset, LowPcEndOffset, MyInfo))
+      !RelocMgr.hasValidRelocationAt(LowPcOffset, LowPcEndOffset, MyInfo))
     return Flags;
 
   if (Options.Verbose) {
@@ -724,7 +701,7 @@ unsigned DwarfLinker::shouldKeepSubprogramDIE(
   }
 
   // Replace the debug map range with a more accurate one.
-  Ranges[*LowPc] = DebugMapObjectRange(*HighPc, MyInfo.AddrAdjust);
+  Ranges[*LowPc] = ObjFileAddressRange(*HighPc, MyInfo.AddrAdjust);
   Unit.addFunctionRange(*LowPc, *HighPc, MyInfo.AddrAdjust);
   return Flags;
 }
@@ -1651,7 +1628,8 @@ DIE *DwarfLinker::DIECloner::cloneDIE(
   Data =
       DWARFDataExtractor(DIECopy, Data.isLittleEndian(), Data.getAddressSize());
   // Modify the copy with relocated addresses.
-  if (RelocMgr.applyValidRelocs(DIECopy, Offset, Data.isLittleEndian())) {
+  if (RelocMgr.areRelocationsResolved() &&
+      RelocMgr.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
@@ -2393,7 +2371,7 @@ Error DwarfLinker::loadClangModule(
 
   // Setup access to the debug info.
   auto DwarfContext = DWARFContext::create(*ErrOrObj);
-  RelocationManager RelocMgr(*this);
+  RelocationManager RelocMgr(*this, *ErrOrObj, DMO);
 
   for (const auto &CU : DwarfContext->compile_units()) {
     updateDwarfVersion(CU->getVersion());
@@ -2774,8 +2752,7 @@ bool DwarfLinker::link(const DebugMap &Map) {
     // Look for relocations that correspond to debug map entries.
 
     if (LLVM_LIKELY(!Options.Update) &&
-        !LinkContext.RelocMgr.findValidRelocsInDebugInfo(
-            *LinkContext.ObjectFile, LinkContext.DMO)) {
+        !LinkContext.RelocMgr->hasValidRelocs()) {
       if (Options.Verbose)
         outs() << "No valid relocations found. Skipping.\n";
 
@@ -2892,7 +2869,7 @@ bool DwarfLinker::link(const DebugMap &Map) {
       Streamer->copyInvariantDebugSection(*LinkContext.ObjectFile);
     } else {
       for (auto &CurrentUnit : LinkContext.CompileUnits)
-        lookForDIEsToKeep(LinkContext.RelocMgr, LinkContext.Ranges,
+        lookForDIEsToKeep(*LinkContext.RelocMgr, LinkContext.Ranges,
                           LinkContext.CompileUnits,
                           CurrentUnit->getOrigUnit().getUnitDIE(),
                           LinkContext.DMO, *CurrentUnit, 0);
@@ -2901,10 +2878,9 @@ bool DwarfLinker::link(const DebugMap &Map) {
     // 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.
-    LinkContext.RelocMgr.resetValidRelocs();
-    if (LinkContext.RelocMgr.hasValidRelocs() || LLVM_UNLIKELY(Options.Update))
-      DIECloner(*this, LinkContext.RelocMgr, DIEAlloc, LinkContext.CompileUnits,
-                Options)
+    if (LinkContext.RelocMgr->hasValidRelocs() || LLVM_UNLIKELY(Options.Update))
+      DIECloner(*this, *LinkContext.RelocMgr, DIEAlloc,
+                LinkContext.CompileUnits, Options)
           .cloneAllCompileUnits(*LinkContext.DwarfContext, LinkContext.DMO,
                                 LinkContext.Ranges, OffsetsStringPool,
                                 LinkContext.DwarfContext->isLittleEndian());
diff --git a/llvm/tools/dsymutil/DwarfLinker.h b/llvm/tools/dsymutil/DwarfLinker.h
index b8d8e9d02e3..748377f802b 100644
--- a/llvm/tools/dsymutil/DwarfLinker.h
+++ b/llvm/tools/dsymutil/DwarfLinker.h
@@ -10,33 +10,17 @@
 #define LLVM_TOOLS_DSYMUTIL_DWARFLINKER_H
 
 #include "BinaryHolder.h"
-#include "CompileUnit.h"
 #include "DebugMap.h"
-#include "DeclContext.h"
 #include "DwarfStreamer.h"
 #include "LinkUtils.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptCompileUnit.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptDeclContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptimizer.h"
 
 namespace llvm {
 namespace dsymutil {
 
-/// Partial address range for debug map objects. Besides an offset, only the
-/// HighPC is stored. The structure is stored in a map where the LowPC is the
-/// key.
-struct DebugMapObjectRange {
-  /// Function HighPC.
-  uint64_t HighPC;
-  /// Offset to apply to the linked address.
-  int64_t Offset;
-
-  DebugMapObjectRange(uint64_t EndPC, int64_t Offset)
-      : HighPC(EndPC), Offset(Offset) {}
-
-  DebugMapObjectRange() : HighPC(0), Offset(0) {}
-};
-
-/// Map LowPC to DebugMapObjectRange.
-using RangesTy = std::map<uint64_t, DebugMapObjectRange>;
 using UnitListTy = std::vector<std::unique_ptr<CompileUnit>>;
 
 /// The core of the Dwarf linking logic.
@@ -89,7 +73,7 @@ private:
                               OffsetsStringPool &StringPool);
 
   /// Keeps track of relocations.
-  class RelocationManager {
+  class RelocationManager : public AddressesMap {
     struct ValidReloc {
       uint64_t Offset;
       uint32_t Size;
@@ -117,13 +101,50 @@ private:
     /// cheap lookup during the root DIE selection and during DIE cloning.
     unsigned NextValidReloc = 0;
 
+    RangesTy AddressRanges;
+
   public:
-    RelocationManager(DwarfLinker &Linker) : Linker(Linker) {}
+    RelocationManager(DwarfLinker &Linker, const object::ObjectFile &Obj,
+                      const DebugMapObject &DMO)
+        : Linker(Linker) {
+      findValidRelocsInDebugInfo(Obj, DMO);
+
+      // Iterate over the debug map entries and put all the ones that are
+      // functions (because they have a size) into the Ranges map. This map is
+      // very similar to the FunctionRanges that are stored in each unit, with 2
+      // notable differences:
+      //
+      //  1. Obviously this one is global, while the other ones are per-unit.
+      //
+      //  2. This one contains not only the functions described in the DIE
+      //     tree, but also the ones that are only in the debug map.
+      //
+      // The latter information is required to reproduce dsymutil's logic while
+      // linking line tables. The cases where this information matters look like
+      // bugs that need to be investigated, but for now we need to reproduce
+      // dsymutil's behavior.
+      // FIXME: Once we understood exactly if that information is needed,
+      // maybe totally remove this (or try to use it to do a real
+      // -gline-tables-only on Darwin.
+      for (const auto &Entry : DMO.symbols()) {
+        const auto &Mapping = Entry.getValue();
+        if (Mapping.Size && Mapping.ObjectAddress)
+          AddressRanges[*Mapping.ObjectAddress] = ObjFileAddressRange(
+              *Mapping.ObjectAddress + Mapping.Size,
+              int64_t(Mapping.BinaryAddress) - *Mapping.ObjectAddress);
+      }
+    }
+    virtual ~RelocationManager () override {
+        clear();
+    }
 
-    bool hasValidRelocs() const { return !ValidRelocs.empty(); }
+    virtual bool areRelocationsResolved() const override { return true; }
 
-    /// Reset the NextValidReloc counter.
-    void resetValidRelocs() { NextValidReloc = 0; }
+    bool hasValidRelocs(bool resetRelocsPtr = true) override {
+      if (resetRelocsPtr)
+        NextValidReloc = 0;
+      return !ValidRelocs.empty();
+    }
 
     /// \defgroup FindValidRelocations Translate debug map into a list
     /// of relevant relocations
@@ -141,32 +162,43 @@ private:
                               const DebugMapObject &DMO);
     /// @}
 
-    bool hasValidRelocation(uint64_t StartOffset, uint64_t EndOffset,
-                            CompileUnit::DIEInfo &Info);
+    bool hasValidRelocationAt(uint64_t StartOffset, uint64_t EndOffset,
+                              CompileUnit::DIEInfo &Info) override;
 
     bool applyValidRelocs(MutableArrayRef<char> Data, uint64_t BaseOffset,
-                          bool IsLittleEndian);
+                          bool IsLittleEndian) override;
+
+    RangesTy &getValidAddressRanges() override { return AddressRanges; }
+
+    void clear() override {
+      AddressRanges.clear();
+      ValidRelocs.clear();
+      NextValidReloc = 0;
+    }
   };
 
   /// Keeps track of data associated with one object during linking.
   struct LinkContext {
+    DwarfLinker &Linker;
     DebugMapObject &DMO;
-    const object::ObjectFile *ObjectFile;
-    RelocationManager RelocMgr;
+    const object::ObjectFile *ObjectFile = nullptr;
+    std::unique_ptr<RelocationManager> RelocMgr;
     std::unique_ptr<DWARFContext> DwarfContext;
     RangesTy Ranges;
     UnitListTy CompileUnits;
 
     LinkContext(const DebugMap &Map, DwarfLinker &Linker, DebugMapObject &DMO)
-        : DMO(DMO), RelocMgr(Linker) {
+        : Linker(Linker), DMO(DMO) {
       // Swift ASTs are not object files.
       if (DMO.getType() == MachO::N_AST) {
         ObjectFile = nullptr;
         return;
       }
-      auto ErrOrObj = Linker.loadObject(DMO, Map);
-      ObjectFile = ErrOrObj ? &*ErrOrObj : nullptr;
-      DwarfContext = ObjectFile ? DWARFContext::create(*ObjectFile) : nullptr;
+      if (auto ErrOrObj = Linker.loadObject(DMO, Map)) {
+        ObjectFile = &*ErrOrObj;
+        DwarfContext = DWARFContext::create(*ObjectFile);
+        RelocMgr.reset(new RelocationManager(Linker, *ObjectFile, DMO));
+      }
     }
 
     /// Clear part of the context that's no longer needed when we're done with
@@ -175,6 +207,7 @@ private:
       DwarfContext.reset(nullptr);
       CompileUnits.clear();
       Ranges.clear();
+      RelocMgr->clear();
     }
   };
 
diff --git a/llvm/tools/dsymutil/DwarfStreamer.cpp b/llvm/tools/dsymutil/DwarfStreamer.cpp
index 8747aee458f..33dc9fc850b 100644
--- a/llvm/tools/dsymutil/DwarfStreamer.cpp
+++ b/llvm/tools/dsymutil/DwarfStreamer.cpp
@@ -7,11 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "DwarfStreamer.h"
-#include "CompileUnit.h"
 #include "LinkUtils.h"
 #include "MachOUtils.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptCompileUnit.h"
 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/MC/MCTargetOptionsCommandFlags.inc"
 #include "llvm/Support/LEB128.h"
diff --git a/llvm/tools/dsymutil/DwarfStreamer.h b/llvm/tools/dsymutil/DwarfStreamer.h
index baf215ac131..85e3d48b758 100644
--- a/llvm/tools/dsymutil/DwarfStreamer.h
+++ b/llvm/tools/dsymutil/DwarfStreamer.h
@@ -9,7 +9,6 @@
 #ifndef LLVM_TOOLS_DSYMUTIL_DWARFSTREAMER_H
 #define LLVM_TOOLS_DSYMUTIL_DWARFSTREAMER_H
 
-#include "CompileUnit.h"
 #include "DebugMap.h"
 #include "LinkUtils.h"
 #include "llvm/CodeGen/AccelTable.h"
@@ -17,6 +16,7 @@
 #include "llvm/CodeGen/NonRelocatableStringpool.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugRangeList.h"
+#include "llvm/DebugInfo/DWARF/DWARFOptCompileUnit.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCCodeEmitter.h"