[Lldb-commits] [PATCH] D61783: [DWARF] Use sequential integers for the IDs of the SymbolFileDWOs

[Pavel Labath via Phabricator via lldb-commits]

labath created this revision.
labath added reviewers: JDevlieghere, clayborg, aprantl.
Herald added subscribers: dexonsmith, mehdi_amini.

Instead of using the offset of the contained compile unit, we use it's
ID. The goal of this change is two-fold:

- free up space in the user_id_t representation to enable storing the debug-info-carrying section (debug_types/debug_info) without decreasing the amount of debug info we can address (as would be the case with D61503 <https://reviews.llvm.org/D61503>).
- be a step towards supporting DWO files containing more than one unit (important for debug_types+dwo, but can also happen with regular dwo+lto). For this part to fully work we'd still need to add a way to lookup the SymbolFileDWO without going through GetCompileUnitAtIndex, but making sure things don't accidentally work because the SymbolFile ID is the same as compile unit offset is a step towards that.


https://reviews.llvm.org/D61783

Files:
  source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
  source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp


Index: source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
+++ source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp
@@ -23,7 +23,7 @@
                                        DWARFUnit *dwarf_cu)
     : SymbolFileDWARF(objfile.get()), m_obj_file_sp(objfile),
       m_base_dwarf_cu(dwarf_cu) {
-  SetID(((lldb::user_id_t)dwarf_cu->GetOffset()) << 32);
+  SetID(((lldb::user_id_t)dwarf_cu->GetID()) << 32);
 }
 
 void SymbolFileDWARFDwo::LoadSectionData(lldb::SectionType sect_type,
@@ -158,6 +158,7 @@
 
 DWARFDIE
 SymbolFileDWARFDwo::GetDIE(const DIERef &die_ref) {
-  lldbassert(m_base_dwarf_cu->GetOffset() == die_ref.cu_offset);
+  lldbassert(die_ref.cu_offset == m_base_dwarf_cu->GetOffset() ||
+             die_ref.cu_offset == DW_INVALID_OFFSET);
   return DebugInfo()->GetDIEForDIEOffset(die_ref.die_offset);
 }
Index: source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1259,7 +1259,20 @@
         debug_map->GetOSOIndexFromUserID(uid));
     return {dwarf, {DW_INVALID_OFFSET, dw_offset_t(uid)}};
   }
-  return {this, {dw_offset_t(uid >> 32), dw_offset_t(uid)}};
+  uint32_t dwarf_id = uid >> 32;
+  dw_offset_t die_offset = uid;
+
+  if (die_offset == DW_INVALID_OFFSET)
+    return {nullptr, DIERef()};
+
+  SymbolFileDWARF *dwarf = this;
+  if (DebugInfo()) {
+    if (DWARFUnit *unit = DebugInfo()->GetCompileUnitAtIndex(dwarf_id)) {
+      if (unit->GetDwoSymbolFile())
+        dwarf = unit->GetDwoSymbolFile();
+    }
+  }
+  return {dwarf, {DW_INVALID_OFFSET, die_offset}};
 }
 
 DWARFDIE


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