[nfc] [lldb] Move `LookupAddress` to `DWARFCompileUnit`

[jankratochvil]

Summary

LookupAddress makes no sense for DWARFTypeUnit. Also make GetNonSkeletonUnit to preserve the called type.
It is just a part of my bigger DWZ patchset needing these but I find it useful on its own.

[labath]

This looks fine. The dwo construction code (SymbolFileDWARFDwo::GetDWOCompileUnitForHash) already ensures that the returned object is really a compile unit.

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

 class DWARFCompileUnit : public DWARFUnit {
 public:
   void BuildAddressRangeTable(DWARFDebugAranges *debug_aranges) override;
 
   void Dump(lldb_private::Stream *s) const override;
 
   static bool classof(const DWARFUnit *unit) { return !unit->IsTypeUnit(); }
 
+  DWARFCompileUnit &GetNonSkeletonUnit();
+
+  DWARFDIE LookupAddress(const dw_addr_t address);
+
 private:
   DWARFCompileUnit(SymbolFileDWARF &dwarf, lldb::user_id_t uid,
                    const DWARFUnitHeader &header,
                    const DWARFAbbreviationDeclarationSet &abbrevs,
                    DIERef::Section section, bool is_dwo)
       : DWARFUnit(dwarf, uid, header, abbrevs, section, is_dwo) {}
 
   DWARFCompileUnit(const DWARFCompileUnit &) = delete;
   const DWARFCompileUnit &operator=(const DWARFCompileUnit &) = delete;
 
   friend class DWARFUnit;
 };
 
 #endif // LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DWARFCOMPILEUNIT_H

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

if (sc.comp_unit) {
               file_ranges.GetEntryRef(idx);
           debug_aranges->AppendRange(GetOffset(), range.GetRangeBase(),
                                      range.GetRangeEnd());
         }
       }
     }
   }
 }
+
+DWARFCompileUnit &DWARFCompileUnit::GetNonSkeletonUnit() {
+  return llvm::cast<DWARFCompileUnit>(DWARFUnit::GetNonSkeletonUnit());
+}
+
+DWARFDIE DWARFCompileUnit::LookupAddress(const dw_addr_t address) {
+  if (DIE()) {
+    const DWARFDebugAranges &func_aranges = GetFunctionAranges();
+
+    // Re-check the aranges auto pointer contents in case it was created above
+    if (!func_aranges.IsEmpty())
+      return GetDIE(func_aranges.FindAddress(address));
+  }
+  return DWARFDIE();
+}

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

public:
     ~ScopedExtractDIEs();
     ScopedExtractDIEs(const ScopedExtractDIEs &) = delete;
     const ScopedExtractDIEs &operator=(const ScopedExtractDIEs &) = delete;
     ScopedExtractDIEs(ScopedExtractDIEs &&rhs);
     ScopedExtractDIEs &operator=(ScopedExtractDIEs &&rhs);
   };
   ScopedExtractDIEs ExtractDIEsScoped();
 
-  DWARFDIE LookupAddress(const dw_addr_t address);
   bool Verify(lldb_private::Stream *s) const;
   virtual void Dump(lldb_private::Stream *s) const = 0;
   /// Get the data that contains the DIE information for this unit.
   ///
   /// This will return the correct bytes that contain the data for
   /// this DWARFUnit. It could be .debug_info or .debug_types
   /// depending on where the data for this unit originates.
   ///

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

if (GetVersion() >= 5 &&
       dwo_symbol_file->GetDWARFContext().getOrLoadLocListsData().GetByteSize() >
           0)
     dwo_cu->SetLoclistsBase(llvm::DWARFListTableHeader::getHeaderSize(DWARF32));
   dwo_cu->SetBaseAddress(GetBaseAddress());
 
   m_dwo = std::shared_ptr<DWARFUnit>(std::move(dwo_symbol_file), dwo_cu);
 }
 
-DWARFDIE DWARFUnit::LookupAddress(const dw_addr_t address) {
-  if (DIE()) {
-    const DWARFDebugAranges &func_aranges = GetFunctionAranges();
-
-    // Re-check the aranges auto pointer contents in case it was created above
-    if (!func_aranges.IsEmpty())
-      return GetDIE(func_aranges.FindAddress(address));
-  }
-  return DWARFDIE();
-}
-
 size_t DWARFUnit::GetDebugInfoSize() const {
   return GetLengthByteSize() + GetLength() - GetHeaderByteSize();
 }
 
 const DWARFAbbreviationDeclarationSet *DWARFUnit::GetAbbreviations() const {
   return m_abbrevs;
 }
 

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

SymbolFileDWARF::GlobalVariableMap &SymbolFileDWARF::GetGlobalAranges() {
   }
   return *m_global_aranges_up;
 }
 
 void SymbolFileDWARF::ResolveFunctionAndBlock(lldb::addr_t file_vm_addr,
                                               bool lookup_block,
                                               SymbolContext &sc) {
   assert(sc.comp_unit);
-  DWARFUnit &cu = GetDWARFCompileUnit(sc.comp_unit)->GetNonSkeletonUnit();
+  DWARFCompileUnit &cu =
+      GetDWARFCompileUnit(sc.comp_unit)->GetNonSkeletonUnit();
   DWARFDIE function_die = 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 && lookup_block)