[lldb] [llvm] Add support for using foreign type units in .debug_names. (PR #87740)

[David Blaikie via llvm-commits]

================
@@ -1726,44 +1725,59 @@ lldb::ModuleSP SymbolFileDWARF::GetExternalModule(ConstString name) {
   return pos->second;
 }
 
-DWARFDIE
-SymbolFileDWARF::GetDIE(const DIERef &die_ref) {
-  // This method can be called without going through the symbol vendor so we
-  // need to lock the module.
-  std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
-
-  SymbolFileDWARF *symbol_file = nullptr;
-
+SymbolFileDWARF *SymbolFileDWARF::GetDIERefSymbolFile(const DIERef &die_ref) {
   // Anytime we get a "lldb::user_id_t" from an lldb_private::SymbolFile API we
   // must make sure we use the correct DWARF file when resolving things. On
   // MacOSX, when using SymbolFileDWARFDebugMap, we will use multiple
   // SymbolFileDWARF classes, one for each .o file. We can often end up with
   // references to other DWARF objects and we must be ready to receive a
   // "lldb::user_id_t" that specifies a DIE from another SymbolFileDWARF
   // instance.
+
   std::optional<uint32_t> file_index = die_ref.file_index();
+
+  // If the file index matches, then we have the right SymbolFileDWARF already.
+  // This will work for both .dwo file and DWARF in .o files for mac. Also if
+  // both the file indexes are invalid, then we have a match.
+  if (GetFileIndex() == file_index)
+    return this;
+
+  // If we are currently in a .dwo file and our file index doesn't match we need
+  // to let the base symbol file handle this.
+  SymbolFileDWARFDwo *dwo = llvm::dyn_cast_or_null<SymbolFileDWARFDwo>(this);
+  if (dwo)
+    return dwo->GetBaseSymbolFile().GetDIERefSymbolFile(die_ref);
+
   if (file_index) {
-    if (SymbolFileDWARFDebugMap *debug_map = GetDebugMapSymfile()) {
-      symbol_file = debug_map->GetSymbolFileByOSOIndex(*file_index); // OSO case
-      if (symbol_file)
-        return symbol_file->DebugInfo().GetDIE(die_ref);
-      return DWARFDIE();
-    }
+    SymbolFileDWARFDebugMap *debug_map = GetDebugMapSymfile();
+    if (debug_map) {
+        // We have a SymbolFileDWARFDebugMap, so let it find the right file
+      return debug_map->GetSymbolFileByOSOIndex(*file_index);
+    } else {
+      // Handle the .dwp file case correctly
+      if (*file_index == DIERef::k_file_index_mask)
+        return GetDwpSymbolFile().get(); // DWP case
 
-    if (*file_index == DIERef::k_file_index_mask)
-      symbol_file = GetDwpSymbolFile().get(); // DWP case
-    else
-      symbol_file = this->DebugInfo()
-                        .GetUnitAtIndex(*die_ref.file_index())
+      // Handle the .dwo file case correctly
+      return DebugInfo().GetUnitAtIndex(*die_ref.file_index())
                         ->GetDwoSymbolFile(); // DWO case
-  } else if (die_ref.die_offset() == DW_INVALID_OFFSET) {
-    return DWARFDIE();
+    }
   }
+  return this;
+}
 
-  if (symbol_file)
-    return symbol_file->GetDIE(die_ref);
+DWARFDIE
+SymbolFileDWARF::GetDIE(const DIERef &die_ref) {
+  if (die_ref.die_offset() == DW_INVALID_OFFSET)
+    return DWARFDIE();
 
-  return DebugInfo().GetDIE(die_ref);
+  // This method can be called without going through the symbol vendor so we
+  // need to lock the module.
+  std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
+  SymbolFileDWARF *symbol_file = GetDIERefSymbolFile(die_ref);
+  if (symbol_file)
----------------
dwblaikie wrote:

Similar feedback others have given elsewhere, roll the variable declaration into the `if` condition

https://github.com/llvm/llvm-project/pull/87740