[lldb] Correctly reconstruct simplified names for type units (llvm#107240)

We need to resolve the type signature to get a hold of the template
argument dies.

The associated test case passes even without this patch, but it only
does it by accident (because the subsequent code considers the types to
be in an anonymous namespace and this not subject to uniqueing). This
will change once my other patch starts resolving names correctly.

Author: labath

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

@@ -58,7 +58,7 @@ class DWARFASTParser {
   virtual void EnsureAllDIEsInDeclContextHaveBeenParsed(
       CompilerDeclContext decl_context) = 0;
 
-  virtual std::string GetDIEClassTemplateParams(const DWARFDIE &die) = 0;
+  virtual std::string GetDIEClassTemplateParams(DWARFDIE die) = 0;
 
   static std::optional<SymbolFile::ArrayInfo>
   ParseChildArrayInfo(const DWARFDIE &parent_die,

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

@@ -818,8 +818,10 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
                          &attrs.decl, clang_type, resolve_state, payload);
 }
 
-std::string
-DWARFASTParserClang::GetDIEClassTemplateParams(const DWARFDIE &die) {
+std::string DWARFASTParserClang::GetDIEClassTemplateParams(DWARFDIE die) {
+  if (DWARFDIE signature_die = die.GetReferencedDIE(DW_AT_signature))
+    die = signature_die;
+
   if (llvm::StringRef(die.GetName()).contains("<"))
     return {};
 

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

@@ -106,8 +106,8 @@ class DWARFASTParserClang : public lldb_private::plugin::dwarf::DWARFASTParser {
   /// \return A string, including surrounding '<>', of the template parameters.
   /// If the DIE's name already has '<>', returns an empty string because
   /// it's assumed that the caller is using the DIE name anyway.
-  std::string GetDIEClassTemplateParams(
-      const lldb_private::plugin::dwarf::DWARFDIE &die) override;
+  std::string
+  GetDIEClassTemplateParams(lldb_private::plugin::dwarf::DWARFDIE die) override;
 
   void MapDeclDIEToDefDIE(const lldb_private::plugin::dwarf::DWARFDIE &decl_die,
                           const lldb_private::plugin::dwarf::DWARFDIE &def_die);

lldb/test/Shell/SymbolFile/DWARF/x86/type-definition-search.cpp

@@ -4,15 +4,20 @@
 
 // REQUIRES: lld
 
-// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-a.o -g -gsimple-template-names -DFILE_A
-// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-b.o -g -gsimple-template-names -DFILE_B
-// RUN: ld.lld %t-a.o %t-b.o -o %t
-// RUN: %lldb %t -o "target variable --ptr-depth 1 --show-types both_a both_b" -o exit | FileCheck %s
-
-// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-a.o -g -fdebug-types-section -DFILE_A
-// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-b.o -g -fdebug-types-section -DFILE_B
-// RUN: ld.lld %t-a.o %t-b.o -o %t
-// RUN: %lldb %t -o "target variable --ptr-depth 1 --show-types both_a both_b" -o exit | FileCheck %s
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-n-a.o -g -gsimple-template-names -DFILE_A
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-n-b.o -g -gsimple-template-names -DFILE_B
+// RUN: ld.lld %t-n-a.o %t-n-b.o -o %t-n
+// RUN: %lldb %t-n -o "target variable --ptr-depth 1 --show-types both_a both_b" -o exit | FileCheck %s
+
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-t-a.o -g -fdebug-types-section -DFILE_A
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-t-b.o -g -fdebug-types-section -DFILE_B
+// RUN: ld.lld %t-t-a.o %t-t-b.o -o %t-t
+// RUN: %lldb %t-t -o "target variable --ptr-depth 1 --show-types both_a both_b" -o exit | FileCheck %s
+
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-tn-a.o -g -fdebug-types-section -gsimple-template-names -DFILE_A
+// RUN: %clang --target=x86_64-pc-linux -c %s -o %t-tn-b.o -g -fdebug-types-section -gsimple-template-names -DFILE_B
+// RUN: ld.lld %t-tn-a.o %t-tn-b.o -o %t-tn
+// RUN: %lldb %t-tn -o "target variable --ptr-depth 1 --show-types both_a both_b" -o exit | FileCheck %s
 
 // CHECK: (lldb) target variable
 // CHECK-NEXT: (ReferencesBoth<'A'>) both_a = {