[llvm] [llvm][dsymutil] Use the DW_AT_name of the uniqued DIE for insertion into .debug_names (PR #168513)

[Michael Buch via llvm-commits]

================
@@ -151,22 +151,84 @@ static bool isTypeTag(uint16_t Tag) {
   return false;
 }
 
-bool DWARFLinker::DIECloner::getDIENames(const DWARFDie &Die,
-                                         AttributesInfo &Info,
-                                         OffsetsStringPool &StringPool,
-                                         bool StripTemplate) {
+/// Recurse through the input DIE's canonical references until we find a
+/// DW_AT_name.
+llvm::StringRef
+DWARFLinker::DIECloner::getCanonicalDIEName(DWARFDie Die, const DWARFFile &File,
+                                            CompileUnit *Unit) {
+  if (!Die)
+    return {};
+
+  std::optional<DWARFFormValue> Ref;
+
+  auto GetDieName = [](const DWARFDie &D) -> llvm::StringRef {
+    auto NameForm = D.find(llvm::dwarf::DW_AT_name);
+    if (!NameForm)
+      return {};
+
+    auto NameOrErr = NameForm->getAsCString();
+    if (!NameOrErr) {
+      llvm::consumeError(NameOrErr.takeError());
+      return {};
+    }
+
+    return *NameOrErr;
+  };
+
+  llvm::StringRef Name = GetDieName(Die);
+  if (!Name.empty())
+    return Name;
+
+  while (true) {
+    if (!(Ref = Die.find(llvm::dwarf::DW_AT_specification)) &&
+        !(Ref = Die.find(llvm::dwarf::DW_AT_abstract_origin)))
+      break;
+
+    Die = Linker.resolveDIEReference(File, CompileUnits, *Ref, Die, Unit);
+    if (!Die)
+      break;
+
+    assert(Unit);
----------------
Michael137 wrote:

It's always valid if the returned `Die` is valid (which we check right beforehand). Might be misunderstanding your suggestion, but we can't hoist any of this out of the loop because both `Die` and `Unit` get set by the `Linker.resolveDIEReference` (note, `Unit` is an output parameter).

https://github.com/llvm/llvm-project/pull/168513