[lldb/DWARF] Add is_dwo member to DWARFUnit

Summary:
A skeleton unit can easily be detected by checking the m_dwo_symbol_file
member, but we cannot tell a split unit from a normal unit from the
"inside", which is sometimes useful.

This patch adds a m_is_dwo member to enable this, and align the code
with llvm::DWARFUnit. Right now it's only used to avoid creating a split
unit inside another split unit (which removes one override from
SymbolFileDWARFDwo and brings us a step closer to deleting it), but my
main motivation is fixing the handling of location lists in mixed v4&v5
files. This comes in a separate patch.

Reviewers: JDevlieghere, aprantl, clayborg

Subscribers: dblaikie, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D71750

lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h

@@ -24,8 +24,8 @@ private:
   DWARFCompileUnit(SymbolFileDWARF &dwarf, lldb::user_id_t uid,
                    const DWARFUnitHeader &header,
                    const DWARFAbbreviationDeclarationSet &abbrevs,
-                   DIERef::Section section)
-      : DWARFUnit(dwarf, uid, header, abbrevs, section) {}
+                   DIERef::Section section, bool is_dwo)
+      : DWARFUnit(dwarf, uid, header, abbrevs, section, is_dwo) {}
 
   DISALLOW_COPY_AND_ASSIGN(DWARFCompileUnit);
 

lldb/source/Plugins/SymbolFile/DWARF/DWARFContext.h

@@ -41,8 +41,6 @@ private:
   SectionData m_data_debug_str_offsets;
   SectionData m_data_debug_types;
 
-  bool isDwo() { return m_dwo_section_list != nullptr; }
-
   const DWARFDataExtractor &
   LoadOrGetSection(lldb::SectionType main_section_type,
                    llvm::Optional<lldb::SectionType> dwo_section_type,
@@ -67,6 +65,8 @@ public:
   const DWARFDataExtractor &getOrLoadStrOffsetsData();
   const DWARFDataExtractor &getOrLoadDebugTypesData();
 
+  bool isDwo() { return m_dwo_section_list != nullptr; }
+
   llvm::DWARFContext &GetAsLLVM();
 };
 } // namespace lldb_private

lldb/source/Plugins/SymbolFile/DWARF/DWARFTypeUnit.h

@@ -28,8 +28,8 @@ private:
   DWARFTypeUnit(SymbolFileDWARF &dwarf, lldb::user_id_t uid,
                 const DWARFUnitHeader &header,
                 const DWARFAbbreviationDeclarationSet &abbrevs,
-                DIERef::Section section)
-      : DWARFUnit(dwarf, uid, header, abbrevs, section) {}
+                DIERef::Section section, bool is_dwo)
+      : DWARFUnit(dwarf, uid, header, abbrevs, section, is_dwo) {}
 
   friend class DWARFUnit;
 };

lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp

@@ -32,9 +32,9 @@ extern int g_verbose;
 DWARFUnit::DWARFUnit(SymbolFileDWARF &dwarf, lldb::user_id_t uid,
                      const DWARFUnitHeader &header,
                      const DWARFAbbreviationDeclarationSet &abbrevs,
-                     DIERef::Section section)
+                     DIERef::Section section, bool is_dwo)
     : UserID(uid), m_dwarf(dwarf), m_header(header), m_abbrevs(&abbrevs),
-      m_cancel_scopes(false), m_section(section) {}
+      m_cancel_scopes(false), m_section(section), m_is_dwo(is_dwo) {}
 
 DWARFUnit::~DWARFUnit() = default;
 
@@ -336,6 +336,9 @@ void DWARFUnit::AddUnitDIE(const DWARFDebugInfoEntry &cu_die) {
     }
   }
 
+  if (m_is_dwo)
+    return;
+
   std::unique_ptr<SymbolFileDWARFDwo> dwo_symbol_file =
       m_dwarf.GetDwoSymbolFileForCompileUnit(*this, cu_die);
   if (!dwo_symbol_file)
@@ -872,11 +875,12 @@ DWARFUnit::extract(SymbolFileDWARF &dwarf, user_id_t uid,
     return llvm::make_error<llvm::object::GenericBinaryError>(
         "No abbrev exists at the specified offset.");
 
+  bool is_dwo = dwarf.GetDWARFContext().isDwo();
   if (expected_header->IsTypeUnit())
-    return DWARFUnitSP(
-        new DWARFTypeUnit(dwarf, uid, *expected_header, *abbrevs, section));
-  return DWARFUnitSP(
-      new DWARFCompileUnit(dwarf, uid, *expected_header, *abbrevs, section));
+    return DWARFUnitSP(new DWARFTypeUnit(dwarf, uid, *expected_header, *abbrevs,
+                                         section, is_dwo));
+  return DWARFUnitSP(new DWARFCompileUnit(dwarf, uid, *expected_header,
+                                          *abbrevs, section, is_dwo));
 }
 
 const lldb_private::DWARFDataExtractor &DWARFUnit::GetData() const {

lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.h

@@ -247,7 +247,7 @@ protected:
   DWARFUnit(SymbolFileDWARF &dwarf, lldb::user_id_t uid,
             const DWARFUnitHeader &header,
             const DWARFAbbreviationDeclarationSet &abbrevs,
-            DIERef::Section section);
+            DIERef::Section section, bool is_dwo);
 
   llvm::Error ExtractHeader(SymbolFileDWARF &dwarf,
                             const lldb_private::DWARFDataExtractor &data,
@@ -314,6 +314,7 @@ protected:
   llvm::Optional<llvm::DWARFListTableHeader> m_loclist_table_header;
 
   const DIERef::Section m_section;
+  bool m_is_dwo;
 
 private:
   void ParseProducerInfo();

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

@@ -287,7 +287,7 @@ public:
 
   lldb::user_id_t GetUID(DIERef ref);
 
-  virtual std::unique_ptr<SymbolFileDWARFDwo>
+  std::unique_ptr<SymbolFileDWARFDwo>
   GetDwoSymbolFileForCompileUnit(DWARFUnit &dwarf_cu,
                                  const DWARFDebugInfoEntry &cu_die);
 

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h

@@ -47,12 +47,6 @@ public:
   DWARFDIE
   GetDIE(const DIERef &die_ref) override;
 
-  std::unique_ptr<SymbolFileDWARFDwo>
-  GetDwoSymbolFileForCompileUnit(DWARFUnit &dwarf_cu,
-                                 const DWARFDebugInfoEntry &cu_die) override {
-    return nullptr;
-  }
-
   DWARFCompileUnit *GetBaseCompileUnit() override { return &m_base_dwarf_cu; }
 
   llvm::Optional<uint32_t> GetDwoNum() override { return GetID() >> 32; }