DWARF: Don't create lldb CompileUnits for DWARF type units

Summary:
Type units don't represent actual compilations and a lot of the
operations that we do with lldb compile units (getting their line
tables, variables, etc.) don't make sense for them. There is also a lot
more of them (sometimes over 100x), so making them more lightweight pays
off.

The main change in this patch is that we stop creating lldb CompileUnits
for DWARF type units. The trickiest part here is that the SymbolFile
interface requires that we assign consecutive sequence IDs to the
compile units we create. As DWARF type and compile units can come in any
order (in v5), this means we can no longer use 1-1 mapping between DWARF
and lldb compile units. Instead I build a translation table between the
two indices. To avoid pessimizing the case where there are no type
units, I build the translation table only in case we have at least one
type unit.

Additionaly, I also tried to strenghted type safete by replacing
DWARFUnit with DWARFCompileUnit where applicable. Though that was not
stricly necessary, I found it a good way to ensure that the
transformations I am doing here make sense. In the places where I was
changing the function signatures, and where it was obvious that the
objects being handled were not null, I also replaced pointers with
references.

There shouldn't be any major functional change with this patch. The only
change I observed is that now the types in the type units will not be
parsed when one calls Module::ParseAllDebugSymbols, unless they are
referenced from other compile units. This makes sense, given how
ParseAllDebugSymbols is implemented (it iterates over all compile
units), and it only matters for one hand-writted test where I did not
bother to reference the types from the compile units (which I now do).

Reviewers: clayborg, JDevlieghere, aprantl

Subscribers: jdoerfert, lldb-commits

Differential Revision: https://reviews.llvm.org/D63005

llvm-svn: 363250

13 files changed, 355 insertions, 199 deletions

diff --git a/lldb/lit/SymbolFile/DWARF/debug-types-dwarf5.s b/lldb/lit/SymbolFile/DWARF/debug-types-dwarf5.s
new file mode 100644
index 00000000000..9de61e48ef7
--- /dev/null
+++ b/lldb/lit/SymbolFile/DWARF/debug-types-dwarf5.s
@@ -0,0 +1,94 @@
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s > %t
+# RUN: %lldb %t -o "image lookup -v -s f1" -o exit | FileCheck %s
+
+# CHECK:  Function: id = {0x7fffffff0000003c}, name = "f1", range = [0x0000000000000000-0x0000000000000001)
+# CHECK:    Blocks: id = {0x7fffffff0000003c}, range = [0x00000000-0x00000001)
+
+
+        .text
+        .globl  f1
+        .type   f1,@function
+f1:
+        nop
+.Lfunc_end0:
+        .size   f1, .Lfunc_end0-f1
+                                        # -- End function
+        .section        .debug_str,"MS",@progbits,1
+.Lproducer:
+        .asciz  "Hand-written DWARF"
+.Lf1:
+        .asciz  "f1"
+.Le1:
+        .asciz  "e1"
+
+        .section        .debug_abbrev,"",@progbits
+        .byte   1                       # Abbreviation Code
+        .byte   17                      # DW_TAG_compile_unit
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   37                      # DW_AT_producer
+        .byte   14                      # DW_FORM_strp
+        .byte   17                      # DW_AT_low_pc
+        .byte   1                       # DW_FORM_addr
+        .byte   18                      # DW_AT_high_pc
+        .byte   6                       # DW_FORM_data4
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   2                       # Abbreviation Code
+        .byte   46                      # DW_TAG_subprogram
+        .byte   0                       # DW_CHILDREN_no
+        .byte   17                      # DW_AT_low_pc
+        .byte   1                       # DW_FORM_addr
+        .byte   18                      # DW_AT_high_pc
+        .byte   6                       # DW_FORM_data4
+        .byte   3                       # DW_AT_name
+        .byte   14                      # DW_FORM_strp
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   3                       # Abbreviation Code
+        .byte   65                      # DW_TAG_type_unit
+        .byte   1                       # DW_CHILDREN_yes
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   5                       # Abbreviation Code
+        .byte   4                       # DW_TAG_enumeration_type
+        .byte   0                       # DW_CHILDREN_no
+        .byte   3                       # DW_AT_name
+        .byte   14                      # DW_FORM_strp
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
+        .byte   0                       # EOM(3)
+
+        .section        .debug_info,"",@progbits
+.Ltu_begin0:
+        .long   .Ltu_end0-.Ltu_start0   # Length of Unit
+.Ltu_start0:
+        .short  5                       # DWARF version number
+        .byte   2                       # DWARF Unit Type
+        .byte   8                       # Address Size (in bytes)
+        .long   .debug_abbrev           # Offset Into Abbrev. Section
+        .quad   47                      # Type Signature
+        .long   .Ltype-.Ltu_begin0      # Type DIE Offset
+        .byte   3                       # Abbrev [1] 0x18:0x1d DW_TAG_type_unit
+.Ltype:
+        .byte   5                       # Abbrev [5] 0x2e:0x9 DW_TAG_enumeration_type
+        .long   .Le1                    # DW_AT_name
+        .byte   0                       # End Of Children Mark
+.Ltu_end0:
+
+.Lcu_begin0:
+        .long   .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+        .short  5                       # DWARF version number
+        .byte   1                       # DWARF Unit Type
+        .byte   8                       # Address Size (in bytes)
+        .long   .debug_abbrev           # Offset Into Abbrev. Section
+        .byte   1                       # Abbrev [1] 0xc:0x5f DW_TAG_compile_unit
+        .long   .Lproducer              # DW_AT_producer
+        .quad   f1                      # DW_AT_low_pc
+        .long   .Lfunc_end0-f1          # DW_AT_high_pc
+        .byte   2                       # Abbrev [2] 0x2b:0x37 DW_TAG_subprogram
+        .quad   f1                      # DW_AT_low_pc
+        .long   .Lfunc_end0-f1          # DW_AT_high_pc
+        .long   .Lf1                    # DW_AT_name
+        .byte   0                       # End Of Children Mark
+.Ldebug_info_end0:
diff --git a/lldb/lit/SymbolFile/DWARF/debug-types-line-tables.s b/lldb/lit/SymbolFile/DWARF/debug-types-line-tables.s
index 888c36afbf4..803f93ff679 100644
--- a/lldb/lit/SymbolFile/DWARF/debug-types-line-tables.s
+++ b/lldb/lit/SymbolFile/DWARF/debug-types-line-tables.s
@@ -169,6 +169,13 @@
         .byte   1                       # DW_CHILDREN_yes
         .byte   0                       # EOM(1)
         .byte   0                       # EOM(2)
+        .byte   5                       # Abbreviation Code
+        .byte   19                      # DW_TAG_structure_type
+        .byte   0                       # DW_CHILDREN_no
+        .byte   105                     # DW_AT_signature
+        .byte   32                      # DW_FORM_ref_sig8
+        .byte   0                       # EOM(1)
+        .byte   0                       # EOM(2)
         .byte   0                       # EOM(3)
         .section        .debug_info,"",@progbits
 .Lcu_begin0:
@@ -178,6 +185,16 @@
         .long   .debug_abbrev           # Offset Into Abbrev. Section
         .byte   8                       # Address Size (in bytes)
         .byte   4                       # Abbrev [4] 0xb:0x32 DW_TAG_compile_unit
+        .byte   5                       # Abbrev [5] DW_TAG_structure_type
+        .quad   5390450678491038984     # DW_AT_signature
+        .byte   5                       # Abbrev [5] DW_TAG_structure_type
+        .quad   5390450678491038985     # DW_AT_signature
+        .byte   5                       # Abbrev [5] DW_TAG_structure_type
+        .quad   5390450678491038986     # DW_AT_signature
+        .byte   5                       # Abbrev [5] DW_TAG_structure_type
+        .quad   5390450678491038987     # DW_AT_signature
+        .byte   5                       # Abbrev [5] DW_TAG_structure_type
+        .quad   5390450678491038988     # DW_AT_signature
         .byte   0                       # End Of Children Mark
 .Ldebug_info_end1:
 
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
index c48ca235ec2..b3602c2cb89 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
@@ -70,7 +70,7 @@ void DWARFCompileUnit::BuildAddressRangeTable(
     // We got nothing from the functions, maybe we have a line tables only
     // situation. Check the line tables and build the arange table from this.
     SymbolContext sc;
-    sc.comp_unit = m_dwarf->GetCompUnitForDWARFCompUnit(this);
+    sc.comp_unit = m_dwarf->GetCompUnitForDWARFCompUnit(*this);
     if (sc.comp_unit) {
       SymbolFileDWARFDebugMap *debug_map_sym_file =
           m_dwarf->GetDebugMapSymfile();
@@ -96,7 +96,7 @@ void DWARFCompileUnit::BuildAddressRangeTable(
     // We got nothing from the functions, maybe we have a line tables only
     // situation. Check the line tables and build the arange table from this.
     SymbolContext sc;
-    sc.comp_unit = m_dwarf->GetCompUnitForDWARFCompUnit(this);
+    sc.comp_unit = m_dwarf->GetCompUnitForDWARFCompUnit(*this);
     if (sc.comp_unit) {
       if (LineTable *line_table = sc.comp_unit->GetLineTable()) {
         LineTable::FileAddressRanges file_ranges;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
index 0810afc8b1a..63970ccf40f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -182,6 +182,11 @@ DWARFTypeUnit *DWARFDebugInfo::GetTypeUnitForHash(uint64_t hash) {
   return llvm::cast<DWARFTypeUnit>(GetUnitAtIndex(pos->second));
 }
 
+bool DWARFDebugInfo::ContainsTypeUnits() {
+  ParseUnitHeadersIfNeeded();
+  return !m_type_hash_to_unit_index.empty();
+}
+
 DWARFDIE
 DWARFDebugInfo::GetDIEForDIEOffset(DIERef::Section section,
                                    dw_offset_t die_offset) {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
index 0fcf72c0bf0..266585790c3 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.h
@@ -48,6 +48,7 @@ public:
                                         dw_offset_t die_offset);
   DWARFUnit *GetUnit(const DIERef &die_ref);
   DWARFTypeUnit *GetTypeUnitForHash(uint64_t hash);
+  bool ContainsTypeUnits();
   DWARFDIE GetDIEForDIEOffset(DIERef::Section section,
                               dw_offset_t die_offset);
   DWARFDIE GetDIE(const DIERef &die_ref);
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 7bc46954309..7b68484efba 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -165,10 +165,6 @@ FileSpecList SymbolFileDWARF::GetSymlinkPaths() {
   return GetGlobalPluginProperties()->GetSymLinkPaths();
 }
 
-DWARFUnit *SymbolFileDWARF::GetBaseCompileUnit() {
-  return nullptr;
-}
-
 void SymbolFileDWARF::Initialize() {
   LogChannelDWARF::Initialize();
   PluginManager::RegisterPlugin(GetPluginNameStatic(),
@@ -651,51 +647,51 @@ DWARFDebugRangesBase *SymbolFileDWARF::GetDebugRngLists() {
   return m_rnglists.get();
 }
 
-lldb::CompUnitSP SymbolFileDWARF::ParseCompileUnit(DWARFUnit *dwarf_cu) {
+lldb::CompUnitSP SymbolFileDWARF::ParseCompileUnit(DWARFCompileUnit &dwarf_cu) {
   CompUnitSP cu_sp;
-  if (dwarf_cu) {
-    CompileUnit *comp_unit = (CompileUnit *)dwarf_cu->GetUserData();
-    if (comp_unit) {
-      // We already parsed this compile unit, had out a shared pointer to it
-      cu_sp = comp_unit->shared_from_this();
+  CompileUnit *comp_unit = (CompileUnit *)dwarf_cu.GetUserData();
+  if (comp_unit) {
+    // We already parsed this compile unit, had out a shared pointer to it
+    cu_sp = comp_unit->shared_from_this();
+  } else {
+    if (dwarf_cu.GetSymbolFileDWARF() != this) {
+      return dwarf_cu.GetSymbolFileDWARF()->ParseCompileUnit(dwarf_cu);
+    } else if (dwarf_cu.GetOffset() == 0 && GetDebugMapSymfile()) {
+      // Let the debug map create the compile unit
+      cu_sp = m_debug_map_symfile->GetCompileUnit(this);
+      dwarf_cu.SetUserData(cu_sp.get());
     } else {
-      if (dwarf_cu->GetSymbolFileDWARF() != this) {
-        return dwarf_cu->GetSymbolFileDWARF()->ParseCompileUnit(dwarf_cu);
-      } else if (dwarf_cu->GetOffset() == 0 && GetDebugMapSymfile()) {
-        // Let the debug map create the compile unit
-        cu_sp = m_debug_map_symfile->GetCompileUnit(this);
-        dwarf_cu->SetUserData(cu_sp.get());
-      } else {
-        ModuleSP module_sp(m_obj_file->GetModule());
-        if (module_sp) {
-          const DWARFDIE cu_die = dwarf_cu->DIE();
-          if (cu_die) {
-            FileSpec cu_file_spec(cu_die.GetName(), dwarf_cu->GetPathStyle());
-            if (cu_file_spec) {
-              // If we have a full path to the compile unit, we don't need to
-              // resolve the file.  This can be expensive e.g. when the source
-              // files are NFS mounted.
-              cu_file_spec.MakeAbsolute(dwarf_cu->GetCompilationDirectory());
-
-              std::string remapped_file;
-              if (module_sp->RemapSourceFile(cu_file_spec.GetPath(),
-                                             remapped_file))
-                cu_file_spec.SetFile(remapped_file, FileSpec::Style::native);
-            }
+      ModuleSP module_sp(m_obj_file->GetModule());
+      if (module_sp) {
+        const DWARFDIE cu_die = dwarf_cu.DIE();
+        if (cu_die) {
+          FileSpec cu_file_spec(cu_die.GetName(), dwarf_cu.GetPathStyle());
+          if (cu_file_spec) {
+            // If we have a full path to the compile unit, we don't need to
+            // resolve the file.  This can be expensive e.g. when the source
+            // files are NFS mounted.
+            cu_file_spec.MakeAbsolute(dwarf_cu.GetCompilationDirectory());
+
+            std::string remapped_file;
+            if (module_sp->RemapSourceFile(cu_file_spec.GetPath(),
+                                           remapped_file))
+              cu_file_spec.SetFile(remapped_file, FileSpec::Style::native);
+          }
 
-            LanguageType cu_language = DWARFUnit::LanguageTypeFromDWARF(
-                cu_die.GetAttributeValueAsUnsigned(DW_AT_language, 0));
+          LanguageType cu_language = DWARFUnit::LanguageTypeFromDWARF(
+              cu_die.GetAttributeValueAsUnsigned(DW_AT_language, 0));
 
-            bool is_optimized = dwarf_cu->GetIsOptimized();
-            cu_sp = std::make_shared<CompileUnit>(
-                module_sp, dwarf_cu, cu_file_spec, dwarf_cu->GetID(),
-                cu_language, is_optimized ? eLazyBoolYes : eLazyBoolNo);
+          bool is_optimized = dwarf_cu.GetIsOptimized();
+          BuildCuTranslationTable();
+          cu_sp = std::make_shared<CompileUnit>(
+              module_sp, &dwarf_cu, cu_file_spec,
+              *GetDWARFUnitIndex(dwarf_cu.GetID()), cu_language,
+              is_optimized ? eLazyBoolYes : eLazyBoolNo);
 
-            dwarf_cu->SetUserData(cu_sp.get());
+          dwarf_cu.SetUserData(cu_sp.get());
 
-            m_obj_file->GetModule()->GetSymbolVendor()->SetCompileUnitAtIndex(
-                dwarf_cu->GetID(), cu_sp);
-          }
+          m_obj_file->GetModule()->GetSymbolVendor()->SetCompileUnitAtIndex(
+              dwarf_cu.GetID(), cu_sp);
         }
       }
     }
@@ -703,23 +699,56 @@ lldb::CompUnitSP SymbolFileDWARF::ParseCompileUnit(DWARFUnit *dwarf_cu) {
   return cu_sp;
 }
 
+void SymbolFileDWARF::BuildCuTranslationTable() {
+  if (!m_lldb_cu_to_dwarf_unit.empty())
+    return;
+
+  DWARFDebugInfo *info = DebugInfo();
+  if (!info)
+    return;
+
+  if (!info->ContainsTypeUnits()) {
+    // We can use a 1-to-1 mapping. No need to build a translation table.
+    return;
+  }
+  for (uint32_t i = 0, num = info->GetNumUnits(); i < num; ++i) {
+    if (auto *cu = llvm::dyn_cast<DWARFCompileUnit>(info->GetUnitAtIndex(i))) {
+      cu->SetID(m_lldb_cu_to_dwarf_unit.size());
+      m_lldb_cu_to_dwarf_unit.push_back(i);
+    }
+  }
+}
+
+llvm::Optional<uint32_t> SymbolFileDWARF::GetDWARFUnitIndex(uint32_t cu_idx) {
+  BuildCuTranslationTable();
+  if (m_lldb_cu_to_dwarf_unit.empty())
+    return cu_idx;
+  if (cu_idx >= m_lldb_cu_to_dwarf_unit.size())
+    return llvm::None;
+  return m_lldb_cu_to_dwarf_unit[cu_idx];
+}
+
 uint32_t SymbolFileDWARF::GetNumCompileUnits() {
   DWARFDebugInfo *info = DebugInfo();
-  if (info)
-    return info->GetNumUnits();
-  return 0;
+  if (!info)
+    return 0;
+  BuildCuTranslationTable();
+  return m_lldb_cu_to_dwarf_unit.empty() ? info->GetNumUnits()
+                                         : m_lldb_cu_to_dwarf_unit.size();
 }
 
 CompUnitSP SymbolFileDWARF::ParseCompileUnitAtIndex(uint32_t cu_idx) {
   ASSERT_MODULE_LOCK(this);
-  CompUnitSP cu_sp;
   DWARFDebugInfo *info = DebugInfo();
-  if (info) {
-    DWARFUnit *dwarf_cu = info->GetUnitAtIndex(cu_idx);
-    if (dwarf_cu)
-      cu_sp = ParseCompileUnit(dwarf_cu);
+  if (!info)
+    return {};
+
+  if (llvm::Optional<uint32_t> dwarf_idx = GetDWARFUnitIndex(cu_idx)) {
+    if (auto *dwarf_cu = llvm::cast_or_null<DWARFCompileUnit>(
+            info->GetUnitAtIndex(*dwarf_idx)))
+      return ParseCompileUnit(*dwarf_cu);
   }
-  return cu_sp;
+  return {};
 }
 
 Function *SymbolFileDWARF::ParseFunction(CompileUnit &comp_unit,
@@ -777,13 +806,7 @@ size_t SymbolFileDWARF::ParseFunctions(CompileUnit &comp_unit) {
 bool SymbolFileDWARF::ParseSupportFiles(CompileUnit &comp_unit,
                                         FileSpecList &support_files) {
   ASSERT_MODULE_LOCK(this);
-  DWARFUnit *unit = GetDWARFCompileUnit(&comp_unit);
-  if (auto *tu = llvm::dyn_cast_or_null<DWARFTypeUnit>(unit)) {
-    support_files = GetTypeUnitSupportFiles(*tu);
-    return true;
-  }
-
-  if (unit) {
+  if (DWARFUnit *unit = GetDWARFCompileUnit(&comp_unit)) {
     const dw_offset_t stmt_list = unit->GetLineTableOffset();
     if (stmt_list != DW_INVALID_OFFSET) {
       // All file indexes in DWARF are one based and a file of index zero is
@@ -798,9 +821,14 @@ bool SymbolFileDWARF::ParseSupportFiles(CompileUnit &comp_unit,
 }
 
 FileSpec SymbolFileDWARF::GetFile(DWARFUnit &unit, size_t file_idx) {
-  if (CompileUnit *lldb_cu = GetCompUnitForDWARFCompUnit(&unit))
-    return lldb_cu->GetSupportFiles().GetFileSpecAtIndex(file_idx);
-  return FileSpec();
+  if (auto *dwarf_cu = llvm::dyn_cast<DWARFCompileUnit>(&unit)) {
+    if (CompileUnit *lldb_cu = GetCompUnitForDWARFCompUnit(*dwarf_cu))
+      return lldb_cu->GetSupportFiles().GetFileSpecAtIndex(file_idx);
+    return FileSpec();
+  }
+
+  auto &tu = llvm::cast<DWARFTypeUnit>(unit);
+  return GetTypeUnitSupportFiles(tu).GetFileSpecAtIndex(file_idx);
 }
 
 const FileSpecList &
@@ -1425,14 +1453,15 @@ Type *SymbolFileDWARF::ResolveType(const DWARFDIE &die,
   return nullptr;
 }
 
-CompileUnit *SymbolFileDWARF::GetCompUnitForDWARFCompUnit(DWARFUnit *dwarf_cu) {
+CompileUnit *
+SymbolFileDWARF::GetCompUnitForDWARFCompUnit(DWARFCompileUnit &dwarf_cu) {
   // Check if the symbol vendor already knows about this compile unit?
-  if (dwarf_cu->GetUserData() == nullptr) {
+  if (dwarf_cu.GetUserData() == nullptr) {
     // The symbol vendor doesn't know about this compile unit, we need to parse
     // and add it to the symbol vendor object.
     return ParseCompileUnit(dwarf_cu).get();
   }
-  return (CompileUnit *)dwarf_cu->GetUserData();
+  return (CompileUnit *)dwarf_cu.GetUserData();
 }
 
 size_t SymbolFileDWARF::GetObjCMethodDIEOffsets(ConstString class_name,
@@ -1445,9 +1474,10 @@ size_t SymbolFileDWARF::GetObjCMethodDIEOffsets(ConstString class_name,
 bool SymbolFileDWARF::GetFunction(const DWARFDIE &die, SymbolContext &sc) {
   sc.Clear(false);
 
-  if (die) {
+  if (die && llvm::isa<DWARFCompileUnit>(die.GetCU())) {
     // Check if the symbol vendor already knows about this compile unit?
-    sc.comp_unit = GetCompUnitForDWARFCompUnit(die.GetCU());
+    sc.comp_unit =
+        GetCompUnitForDWARFCompUnit(llvm::cast<DWARFCompileUnit>(*die.GetCU()));
 
     sc.function = sc.comp_unit->FindFunctionByUID(die.GetID()).get();
     if (sc.function == nullptr)
@@ -1482,24 +1512,29 @@ SymbolFileDWARF::GetDIE(const DIERef &die_ref) {
 
 std::unique_ptr<SymbolFileDWARFDwo>
 SymbolFileDWARF::GetDwoSymbolFileForCompileUnit(
-    DWARFUnit &dwarf_cu, const DWARFDebugInfoEntry &cu_die) {
+    DWARFUnit &unit, const DWARFDebugInfoEntry &cu_die) {
   // If we are using a dSYM file, we never want the standard DWO files since
   // the -gmodules support uses the same DWO machanism to specify full debug
   // info files for modules.
   if (GetDebugMapSymfile())
     return nullptr;
 
+  DWARFCompileUnit *dwarf_cu = llvm::dyn_cast<DWARFCompileUnit>(&unit);
+  // Only compile units can be split into two parts.
+  if (!dwarf_cu)
+    return nullptr;
+
   const char *dwo_name =
-      cu_die.GetAttributeValueAsString(&dwarf_cu, DW_AT_GNU_dwo_name, nullptr);
+      cu_die.GetAttributeValueAsString(dwarf_cu, DW_AT_GNU_dwo_name, nullptr);
   if (!dwo_name)
     return nullptr;
 
   SymbolFileDWARFDwp *dwp_symfile = GetDwpSymbolFile();
   if (dwp_symfile) {
     uint64_t dwo_id =
-        cu_die.GetAttributeValueAsUnsigned(&dwarf_cu, DW_AT_GNU_dwo_id, 0);
+        cu_die.GetAttributeValueAsUnsigned(dwarf_cu, DW_AT_GNU_dwo_id, 0);
     std::unique_ptr<SymbolFileDWARFDwo> dwo_symfile =
-        dwp_symfile->GetSymbolFileForDwoId(&dwarf_cu, dwo_id);
+        dwp_symfile->GetSymbolFileForDwoId(*dwarf_cu, dwo_id);
     if (dwo_symfile)
       return dwo_symfile;
   }
@@ -1508,7 +1543,7 @@ SymbolFileDWARF::GetDwoSymbolFileForCompileUnit(
   FileSystem::Instance().Resolve(dwo_file);
   if (dwo_file.IsRelative()) {
     const char *comp_dir =
-        cu_die.GetAttributeValueAsString(&dwarf_cu, DW_AT_comp_dir, nullptr);
+        cu_die.GetAttributeValueAsString(dwarf_cu, DW_AT_comp_dir, nullptr);
     if (!comp_dir)
       return nullptr;
 
@@ -1530,7 +1565,7 @@ SymbolFileDWARF::GetDwoSymbolFileForCompileUnit(
   if (dwo_obj_file == nullptr)
     return nullptr;
 
-  return llvm::make_unique<SymbolFileDWARFDwo>(dwo_obj_file, &dwarf_cu);
+  return llvm::make_unique<SymbolFileDWARFDwo>(dwo_obj_file, *dwarf_cu);
 }
 
 void SymbolFileDWARF::UpdateExternalModuleListIfNeeded() {
@@ -1706,10 +1741,10 @@ uint32_t SymbolFileDWARF::ResolveSymbolContext(const Address &so_addr,
         }
       } else {
         uint32_t cu_idx = DW_INVALID_INDEX;
-        DWARFUnit *dwarf_cu = debug_info->GetUnitAtOffset(DIERef::Section::DebugInfo,
-                                                          cu_offset, &cu_idx);
-        if (dwarf_cu) {
-          sc.comp_unit = GetCompUnitForDWARFCompUnit(dwarf_cu);
+        if (auto *dwarf_cu = llvm::dyn_cast_or_null<DWARFCompileUnit>(
+                debug_info->GetUnitAtOffset(DIERef::Section::DebugInfo,
+                                            cu_offset, &cu_idx))) {
+          sc.comp_unit = GetCompUnitForDWARFCompUnit(*dwarf_cu);
           if (sc.comp_unit) {
             resolved |= eSymbolContextCompUnit;
 
@@ -1802,110 +1837,100 @@ uint32_t SymbolFileDWARF::ResolveSymbolContext(const FileSpec &file_spec,
                                                SymbolContextList &sc_list) {
   const uint32_t prev_size = sc_list.GetSize();
   if (resolve_scope & eSymbolContextCompUnit) {
-    DWARFDebugInfo *debug_info = DebugInfo();
-    if (debug_info) {
-      uint32_t cu_idx;
-      DWARFUnit *dwarf_cu = nullptr;
-
-      for (cu_idx = 0;
-           (dwarf_cu = debug_info->GetUnitAtIndex(cu_idx)) != nullptr;
-           ++cu_idx) {
-        CompileUnit *dc_cu = GetCompUnitForDWARFCompUnit(dwarf_cu);
-        const bool full_match = (bool)file_spec.GetDirectory();
-        bool file_spec_matches_cu_file_spec =
-            dc_cu != nullptr && FileSpec::Equal(file_spec, *dc_cu, full_match);
-        if (check_inlines || file_spec_matches_cu_file_spec) {
-          SymbolContext sc(m_obj_file->GetModule());
-          sc.comp_unit = GetCompUnitForDWARFCompUnit(dwarf_cu);
-          if (sc.comp_unit) {
-            uint32_t file_idx = UINT32_MAX;
+    for (uint32_t cu_idx = 0, num_cus = GetNumCompileUnits(); cu_idx < num_cus;
+         ++cu_idx) {
+      CompileUnit *dc_cu = ParseCompileUnitAtIndex(cu_idx).get();
+      if (!dc_cu)
+        continue;
+
+      const bool full_match = (bool)file_spec.GetDirectory();
+      bool file_spec_matches_cu_file_spec =
+          FileSpec::Equal(file_spec, *dc_cu, full_match);
+      if (check_inlines || file_spec_matches_cu_file_spec) {
+        SymbolContext sc(m_obj_file->GetModule());
+        sc.comp_unit = dc_cu;
+        uint32_t file_idx = UINT32_MAX;
+
+        // If we are looking for inline functions only and we don't find it
+        // in the support files, we are done.
+        if (check_inlines) {
+          file_idx =
+              sc.comp_unit->GetSupportFiles().FindFileIndex(1, file_spec, true);
+          if (file_idx == UINT32_MAX)
+            continue;
+        }
+
+        if (line != 0) {
+          LineTable *line_table = sc.comp_unit->GetLineTable();
 
-            // If we are looking for inline functions only and we don't find it
-            // in the support files, we are done.
-            if (check_inlines) {
+          if (line_table != nullptr && line != 0) {
+            // We will have already looked up the file index if we are
+            // searching for inline entries.
+            if (!check_inlines)
               file_idx = sc.comp_unit->GetSupportFiles().FindFileIndex(
                   1, file_spec, true);
-              if (file_idx == UINT32_MAX)
-                continue;
-            }
-
-            if (line != 0) {
-              LineTable *line_table = sc.comp_unit->GetLineTable();
 
-              if (line_table != nullptr && line != 0) {
-                // We will have already looked up the file index if we are
-                // searching for inline entries.
-                if (!check_inlines)
-                  file_idx = sc.comp_unit->GetSupportFiles().FindFileIndex(
-                      1, file_spec, true);
-
-                if (file_idx != UINT32_MAX) {
-                  uint32_t found_line;
-                  uint32_t line_idx = line_table->FindLineEntryIndexByFileIndex(
-                      0, file_idx, line, false, &sc.line_entry);
-                  found_line = sc.line_entry.line;
-
-                  while (line_idx != UINT32_MAX) {
-                    sc.function = nullptr;
-                    sc.block = nullptr;
-                    if (resolve_scope &
-                        (eSymbolContextFunction | eSymbolContextBlock)) {
-                      const lldb::addr_t file_vm_addr =
-                          sc.line_entry.range.GetBaseAddress().GetFileAddress();
-                      if (file_vm_addr != LLDB_INVALID_ADDRESS) {
-                        DWARFDIE function_die =
-                            dwarf_cu->LookupAddress(file_vm_addr);
-                        DWARFDIE block_die;
-                        if (function_die) {
-                          sc.function =
-                              sc.comp_unit
-                                  ->FindFunctionByUID(function_die.GetID())
-                                  .get();
-                          if (sc.function == nullptr)
-                            sc.function =
-                                ParseFunction(*sc.comp_unit, function_die);
-
-                          if (sc.function &&
-                              (resolve_scope & eSymbolContextBlock))
-                            block_die =
-                                function_die.LookupDeepestBlock(file_vm_addr);
-                        }
+            if (file_idx != UINT32_MAX) {
+              uint32_t found_line;
+              uint32_t line_idx = line_table->FindLineEntryIndexByFileIndex(
+                  0, file_idx, line, false, &sc.line_entry);
+              found_line = sc.line_entry.line;
+
+              while (line_idx != UINT32_MAX) {
+                sc.function = nullptr;
+                sc.block = nullptr;
+                if (resolve_scope &
+                    (eSymbolContextFunction | eSymbolContextBlock)) {
+                  const lldb::addr_t file_vm_addr =
+                      sc.line_entry.range.GetBaseAddress().GetFileAddress();
+                  if (file_vm_addr != LLDB_INVALID_ADDRESS) {
+                    DWARFDIE function_die =
+                        GetDWARFCompileUnit(dc_cu)->LookupAddress(file_vm_addr);
+                    DWARFDIE block_die;
+                    if (function_die) {
+                      sc.function =
+                          sc.comp_unit->FindFunctionByUID(function_die.GetID())
+                              .get();
+                      if (sc.function == nullptr)
+                        sc.function =
+                            ParseFunction(*sc.comp_unit, function_die);
+
+                      if (sc.function && (resolve_scope & eSymbolContextBlock))
+                        block_die =
+                            function_die.LookupDeepestBlock(file_vm_addr);
+                    }
 
-                        if (sc.function != nullptr) {
-                          Block &block = sc.function->GetBlock(true);
+                    if (sc.function != nullptr) {
+                      Block &block = sc.function->GetBlock(true);
 
-                          if (block_die)
-                            sc.block = block.FindBlockByID(block_die.GetID());
-                          else if (function_die)
-                            sc.block =
-                                block.FindBlockByID(function_die.GetID());
-                        }
-                      }
+                      if (block_die)
+                        sc.block = block.FindBlockByID(block_die.GetID());
+                      else if (function_die)
+                        sc.block = block.FindBlockByID(function_die.GetID());
                     }
-
-                    sc_list.Append(sc);
-                    line_idx = line_table->FindLineEntryIndexByFileIndex(
-                        line_idx + 1, file_idx, found_line, true,
-                        &sc.line_entry);
                   }
                 }
-              } else if (file_spec_matches_cu_file_spec && !check_inlines) {
-                // only append the context if we aren't looking for inline call
-                // sites by file and line and if the file spec matches that of
-                // the compile unit
+
                 sc_list.Append(sc);
+                line_idx = line_table->FindLineEntryIndexByFileIndex(
+                    line_idx + 1, file_idx, found_line, true, &sc.line_entry);
               }
-            } else if (file_spec_matches_cu_file_spec && !check_inlines) {
-              // only append the context if we aren't looking for inline call
-              // sites by file and line and if the file spec matches that of
-              // the compile unit
-              sc_list.Append(sc);
             }
-
-            if (!check_inlines)
-              break;
+          } else if (file_spec_matches_cu_file_spec && !check_inlines) {
+            // only append the context if we aren't looking for inline call
+            // sites by file and line and if the file spec matches that of
+            // the compile unit
+            sc_list.Append(sc);
           }
+        } else if (file_spec_matches_cu_file_spec && !check_inlines) {
+          // only append the context if we aren't looking for inline call
+          // sites by file and line and if the file spec matches that of
+          // the compile unit
+          sc_list.Append(sc);
         }
+
+        if (!check_inlines)
+          break;
       }
     }
   }
@@ -2007,7 +2032,10 @@ uint32_t SymbolFileDWARF::FindGlobalVariables(
           break;
 
         case DW_TAG_variable: {
-          sc.comp_unit = GetCompUnitForDWARFCompUnit(die.GetCU());
+          auto *dwarf_cu = llvm::dyn_cast<DWARFCompileUnit>(die.GetCU());
+          if (!dwarf_cu)
+            continue;
+          sc.comp_unit = GetCompUnitForDWARFCompUnit(*dwarf_cu);
 
           if (parent_decl_ctx) {
             DWARFASTParser *dwarf_ast = die.GetDWARFParser();
@@ -2089,7 +2117,11 @@ uint32_t SymbolFileDWARF::FindGlobalVariables(const RegularExpression &regex,
       DWARFDIE die = GetDIE(die_ref);
 
       if (die) {
-        sc.comp_unit = GetCompUnitForDWARFCompUnit(die.GetCU());
+        DWARFCompileUnit *dwarf_cu =
+            llvm::dyn_cast<DWARFCompileUnit>(die.GetCU());
+        if (!dwarf_cu)
+          continue;
+        sc.comp_unit = GetCompUnitForDWARFCompUnit(*dwarf_cu);
 
         ParseVariables(sc, die, LLDB_INVALID_ADDRESS, false, false, &variables);
 
@@ -2533,9 +2565,13 @@ TypeSP SymbolFileDWARF::GetTypeForDIE(const DWARFDIE &die,
   if (die) {
     Type *type_ptr = GetDIEToType().lookup(die.GetDIE());
     if (type_ptr == nullptr) {
-      CompileUnit *lldb_cu = GetCompUnitForDWARFCompUnit(die.GetCU());
-      assert(lldb_cu);
-      SymbolContext sc(lldb_cu);
+      SymbolContextScope *scope;
+      if (auto *dwarf_cu = llvm::dyn_cast<DWARFCompileUnit>(die.GetCU()))
+        scope = GetCompUnitForDWARFCompUnit(*dwarf_cu);
+      else
+        scope = GetObjectFile()->GetModule().get();
+      assert(scope);
+      SymbolContext sc(scope);
       const DWARFDebugInfoEntry *parent_die = die.GetParent().GetDIE();
       while (parent_die != nullptr) {
         if (parent_die->Tag() == DW_TAG_subprogram)
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
index b56089d052a..815ae42da19 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -40,7 +40,7 @@
 class DebugMapModule;
 class DWARFAbbreviationDeclaration;
 class DWARFAbbreviationDeclarationSet;
-class DWARFileUnit;
+class DWARFCompileUnit;
 class DWARFDebugAbbrev;
 class DWARFDebugAranges;
 class DWARFDebugInfo;
@@ -239,7 +239,8 @@ public:
   bool
   HasForwardDeclForClangType(const lldb_private::CompilerType &compiler_type);
 
-  lldb_private::CompileUnit *GetCompUnitForDWARFCompUnit(DWARFUnit *dwarf_cu);
+  lldb_private::CompileUnit *
+  GetCompUnitForDWARFCompUnit(DWARFCompileUnit &dwarf_cu);
 
   virtual size_t GetObjCMethodDIEOffsets(lldb_private::ConstString class_name,
                                          DIEArray &method_die_offsets);
@@ -250,7 +251,7 @@ public:
 
   static DWARFDIE GetParentSymbolContextDIE(const DWARFDIE &die);
 
-  virtual lldb::CompUnitSP ParseCompileUnit(DWARFUnit *dwarf_cu);
+  virtual lldb::CompUnitSP ParseCompileUnit(DWARFCompileUnit &dwarf_cu);
 
   virtual lldb_private::DWARFExpression::LocationListFormat
   GetLocationListFormat() const;
@@ -285,7 +286,7 @@ public:
   // For regular SymbolFileDWARF instances the method returns nullptr,
   // for the instances of the subclass SymbolFileDWARFDwo
   // the method returns a pointer to the base compile unit.
-  virtual DWARFUnit *GetBaseCompileUnit();
+  virtual DWARFCompileUnit *GetBaseCompileUnit() { return nullptr; }
 
   static bool
   DIEInDeclContext(const lldb_private::CompilerDeclContext *parent_decl_ctx,
@@ -433,6 +434,9 @@ protected:
     return m_forward_decl_clang_type_to_die;
   }
 
+  void BuildCuTranslationTable();
+  llvm::Optional<uint32_t> GetDWARFUnitIndex(uint32_t cu_idx);
+
   struct DecodedUID {
     SymbolFileDWARF *dwarf;
     DIERef ref;
@@ -483,6 +487,7 @@ protected:
   ClangTypeToDIE m_forward_decl_clang_type_to_die;
   llvm::DenseMap<dw_offset_t, lldb_private::FileSpecList>
       m_type_unit_support_files;
+  std::vector<uint32_t> m_lldb_cu_to_dwarf_unit;
 };
 
 #endif // SymbolFileDWARF_SymbolFileDWARF_h_
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
index 3e35ff1579e..0e0e5ebafbe 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
@@ -13,18 +13,19 @@
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Utility/LLDBAssert.h"
 
-#include "DWARFUnit.h"
+#include "DWARFCompileUnit.h"
 #include "DWARFDebugInfo.h"
+#include "DWARFUnit.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
 SymbolFileDWARFDwo::SymbolFileDWARFDwo(ObjectFileSP objfile,
-                                       DWARFUnit *dwarf_cu)
+                                       DWARFCompileUnit &dwarf_cu)
     : SymbolFileDWARF(objfile.get(), objfile->GetSectionList(
                                          /*update_module_section_list*/ false)),
       m_obj_file_sp(objfile), m_base_dwarf_cu(dwarf_cu) {
-  SetID(((lldb::user_id_t)dwarf_cu->GetID()) << 32);
+  SetID(((lldb::user_id_t)dwarf_cu.GetID()) << 32);
 }
 
 void SymbolFileDWARFDwo::LoadSectionData(lldb::SectionType sect_type,
@@ -45,10 +46,11 @@ void SymbolFileDWARFDwo::LoadSectionData(lldb::SectionType sect_type,
   SymbolFileDWARF::LoadSectionData(sect_type, data);
 }
 
-lldb::CompUnitSP SymbolFileDWARFDwo::ParseCompileUnit(DWARFUnit *dwarf_cu) {
-  assert(GetCompileUnit() == dwarf_cu && "SymbolFileDWARFDwo::ParseCompileUnit "
-                                         "called with incompatible compile "
-                                         "unit");
+lldb::CompUnitSP
+SymbolFileDWARFDwo::ParseCompileUnit(DWARFCompileUnit &dwarf_cu) {
+  assert(GetCompileUnit() == &dwarf_cu &&
+         "SymbolFileDWARFDwo::ParseCompileUnit called with incompatible "
+         "compile unit");
   return GetBaseSymbolFile()->ParseCompileUnit(m_base_dwarf_cu);
 }
 
@@ -106,12 +108,8 @@ lldb::TypeSP SymbolFileDWARFDwo::FindCompleteObjCDefinitionTypeForDIE(
       die, type_name, must_be_implementation);
 }
 
-DWARFUnit *SymbolFileDWARFDwo::GetBaseCompileUnit() {
-  return m_base_dwarf_cu;
-}
-
 SymbolFileDWARF *SymbolFileDWARFDwo::GetBaseSymbolFile() {
-  return m_base_dwarf_cu->GetSymbolFileDWARF();
+  return m_base_dwarf_cu.GetSymbolFileDWARF();
 }
 
 DWARFExpression::LocationListFormat
@@ -126,7 +124,7 @@ SymbolFileDWARFDwo::GetTypeSystemForLanguage(LanguageType language) {
 
 DWARFDIE
 SymbolFileDWARFDwo::GetDIE(const DIERef &die_ref) {
-  lldbassert(die_ref.cu_offset == m_base_dwarf_cu->GetOffset() ||
+  lldbassert(die_ref.cu_offset == m_base_dwarf_cu.GetOffset() ||
              die_ref.cu_offset == DW_INVALID_OFFSET);
   return DebugInfo()->GetDIEForDIEOffset(die_ref.section, die_ref.die_offset);
 }
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h
index 5b5d73da753..453f6723f4b 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h
@@ -13,11 +13,11 @@
 
 class SymbolFileDWARFDwo : public SymbolFileDWARF {
 public:
-  SymbolFileDWARFDwo(lldb::ObjectFileSP objfile, DWARFUnit *dwarf_cu);
+  SymbolFileDWARFDwo(lldb::ObjectFileSP objfile, DWARFCompileUnit &dwarf_cu);
 
   ~SymbolFileDWARFDwo() override = default;
 
-  lldb::CompUnitSP ParseCompileUnit(DWARFUnit *dwarf_cu) override;
+  lldb::CompUnitSP ParseCompileUnit(DWARFCompileUnit &dwarf_cu) override;
 
   DWARFUnit *GetCompileUnit();
 
@@ -42,7 +42,7 @@ public:
     return nullptr;
   }
 
-  DWARFUnit *GetBaseCompileUnit() override;
+  DWARFCompileUnit *GetBaseCompileUnit() override { return &m_base_dwarf_cu; }
 
 protected:
   void LoadSectionData(lldb::SectionType sect_type,
@@ -68,7 +68,7 @@ protected:
   SymbolFileDWARF *GetBaseSymbolFile();
 
   lldb::ObjectFileSP m_obj_file_sp;
-  DWARFUnit *m_base_dwarf_cu;
+  DWARFCompileUnit &m_base_dwarf_cu;
 };
 
 #endif // SymbolFileDWARFDwo_SymbolFileDWARFDwo_h_
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.cpp
index 17f91a7b91a..efea192b17c 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.cpp
@@ -21,7 +21,7 @@ using namespace lldb_private;
 
 SymbolFileDWARFDwoDwp::SymbolFileDWARFDwoDwp(SymbolFileDWARFDwp *dwp_symfile,
                                              ObjectFileSP objfile,
-                                             DWARFUnit *dwarf_cu,
+                                             DWARFCompileUnit &dwarf_cu,
                                              uint64_t dwo_id)
     : SymbolFileDWARFDwo(objfile, dwarf_cu), m_dwp_symfile(dwp_symfile),
       m_dwo_id(dwo_id) {}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.h
index 4e57b1c265e..2105e1a8f6c 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwoDwp.h
@@ -15,7 +15,7 @@
 class SymbolFileDWARFDwoDwp : public SymbolFileDWARFDwo {
 public:
   SymbolFileDWARFDwoDwp(SymbolFileDWARFDwp *dwp_symfile,
-                        lldb::ObjectFileSP objfile, DWARFUnit *dwarf_cu,
+                        lldb::ObjectFileSP objfile, DWARFCompileUnit &dwarf_cu,
                         uint64_t dwo_id);
 
 protected:
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.cpp
index 4d00a81afd7..08e6e1c8c2f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.cpp
@@ -81,7 +81,7 @@ SymbolFileDWARFDwp::SymbolFileDWARFDwp(lldb::ModuleSP module_sp,
 {}
 
 std::unique_ptr<SymbolFileDWARFDwo>
-SymbolFileDWARFDwp::GetSymbolFileForDwoId(DWARFUnit *dwarf_cu,
+SymbolFileDWARFDwp::GetSymbolFileForDwoId(DWARFCompileUnit &dwarf_cu,
                                           uint64_t dwo_id) {
   return std::unique_ptr<SymbolFileDWARFDwo>(
       new SymbolFileDWARFDwoDwp(this, m_obj_file, dwarf_cu, dwo_id));
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.h b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.h
index 452ef0ab07d..ef06b9dca8b 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.h
@@ -24,7 +24,7 @@ public:
   Create(lldb::ModuleSP module_sp, const lldb_private::FileSpec &file_spec);
 
   std::unique_ptr<SymbolFileDWARFDwo>
-  GetSymbolFileForDwoId(DWARFUnit *dwarf_cu, uint64_t dwo_id);
+  GetSymbolFileForDwoId(DWARFCompileUnit &dwarf_cu, uint64_t dwo_id);
 
   bool LoadSectionData(uint64_t dwo_id, lldb::SectionType sect_type,
                        lldb_private::DWARFDataExtractor &data);