[lldb/DWARF] Remove parsing recursion when searching for definition DIEs (#96484)

If ParseStructureLikeDIE (or ParseEnum) encountered a declaration DIE,
it would call FindDefinitionTypeForDIE. This returned a fully formed
type, which it achieved by recursing back into ParseStructureLikeDIE
with the definition DIE.

This obscured the control flow and caused us to repeat some work (e.g.
the UniqueDWARFASTTypeMap lookup), but it mostly worked until we tried
to delay the definition search in #90663. After this patch, the two
ParseStructureLikeDIE calls were no longer recursive, but rather the
second call happened as a part of the CompleteType() call. This opened
the door to inconsistencies, as the second ParseStructureLikeDIE call
was not aware it was called to process a definition die for an existing
type.

To make that possible, this patch removes the recusive type resolution
from this function, and leaves just the "find definition die"
functionality. After finding the definition DIE, we just go back to the
original ParseStructureLikeDIE call, and have it finish the parsing
process with the new DIE.

While this patch is motivated by the work on delaying the definition
searching, I believe it is also useful on its own.

Author: labath

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

@@ -3045,118 +3045,113 @@ TypeSP SymbolFileDWARF::FindCompleteObjCDefinitionTypeForDIE(
   return type_sp;
 }
 
-TypeSP
-SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
-  TypeSP type_sp;
+DWARFDIE
+SymbolFileDWARF::FindDefinitionDIE(const DWARFDIE &die) {
+  if (!die.GetName())
+    return {};
 
-  if (die.GetName()) {
-    const dw_tag_t tag = die.Tag();
+  const dw_tag_t tag = die.Tag();
 
-    Log *log = GetLog(DWARFLog::TypeCompletion | DWARFLog::Lookups);
-    if (log) {
-      GetObjectFile()->GetModule()->LogMessage(
-          log,
-          "SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(tag={0} "
-          "({1}), name='{2}')",
-          DW_TAG_value_to_name(tag), tag, die.GetName());
-    }
+  Log *log = GetLog(DWARFLog::TypeCompletion | DWARFLog::Lookups);
+  if (log) {
+    GetObjectFile()->GetModule()->LogMessage(
+        log,
+        "SymbolFileDWARF::FindDefinitionDIE(tag={0} "
+        "({1}), name='{2}')",
+        DW_TAG_value_to_name(tag), tag, die.GetName());
+  }
 
-    // Get the type system that we are looking to find a type for. We will
-    // use this to ensure any matches we find are in a language that this
-    // type system supports
-    const LanguageType language = GetLanguage(*die.GetCU());
-    TypeSystemSP type_system = nullptr;
-    if (language != eLanguageTypeUnknown) {
-      auto type_system_or_err = GetTypeSystemForLanguage(language);
-      if (auto err = type_system_or_err.takeError()) {
-        LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
-                       "Cannot get TypeSystem for language {1}: {0}",
-                       Language::GetNameForLanguageType(language));
-      } else {
-        type_system = *type_system_or_err;
-      }
+  // Get the type system that we are looking to find a type for. We will
+  // use this to ensure any matches we find are in a language that this
+  // type system supports
+  const LanguageType language = GetLanguage(*die.GetCU());
+  TypeSystemSP type_system = nullptr;
+  if (language != eLanguageTypeUnknown) {
+    auto type_system_or_err = GetTypeSystemForLanguage(language);
+    if (auto err = type_system_or_err.takeError()) {
+      LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
+                     "Cannot get TypeSystem for language {1}: {0}",
+                     Language::GetNameForLanguageType(language));
+    } else {
+      type_system = *type_system_or_err;
     }
+  }
 
-    // See comments below about -gsimple-template-names for why we attempt to
-    // compute missing template parameter names.
-    std::vector<std::string> template_params;
-    DWARFDeclContext die_dwarf_decl_ctx;
-    DWARFASTParser *dwarf_ast = type_system ? type_system->GetDWARFParser() : nullptr;
-    for (DWARFDIE ctx_die = die; ctx_die && !isUnitType(ctx_die.Tag());
-         ctx_die = ctx_die.GetParentDeclContextDIE()) {
-      die_dwarf_decl_ctx.AppendDeclContext(ctx_die.Tag(), ctx_die.GetName());
-      template_params.push_back(
-          (ctx_die.IsStructUnionOrClass() && dwarf_ast)
-              ? dwarf_ast->GetDIEClassTemplateParams(ctx_die)
-              : "");
-    }
-    const bool any_template_params = llvm::any_of(
-        template_params, [](llvm::StringRef p) { return !p.empty(); });
-
-    auto die_matches = [&](DWARFDIE type_die) {
-      // Resolve the type if both have the same tag or {class, struct} tags.
-      const bool tag_matches =
-          type_die.Tag() == tag ||
-          (IsStructOrClassTag(type_die.Tag()) && IsStructOrClassTag(tag));
-      if (!tag_matches)
-        return false;
-      if (any_template_params) {
-        size_t pos = 0;
-        for (DWARFDIE ctx_die = type_die;
-             ctx_die && !isUnitType(ctx_die.Tag()) &&
-             pos < template_params.size();
-             ctx_die = ctx_die.GetParentDeclContextDIE(), ++pos) {
-          if (template_params[pos].empty())
-            continue;
-          if (template_params[pos] != dwarf_ast->GetDIEClassTemplateParams(ctx_die))
-            return false;
-        }
-        if (pos != template_params.size())
+  // See comments below about -gsimple-template-names for why we attempt to
+  // compute missing template parameter names.
+  std::vector<std::string> template_params;
+  DWARFDeclContext die_dwarf_decl_ctx;
+  DWARFASTParser *dwarf_ast =
+      type_system ? type_system->GetDWARFParser() : nullptr;
+  for (DWARFDIE ctx_die = die; ctx_die && !isUnitType(ctx_die.Tag());
+       ctx_die = ctx_die.GetParentDeclContextDIE()) {
+    die_dwarf_decl_ctx.AppendDeclContext(ctx_die.Tag(), ctx_die.GetName());
+    template_params.push_back(
+        (ctx_die.IsStructUnionOrClass() && dwarf_ast)
+            ? dwarf_ast->GetDIEClassTemplateParams(ctx_die)
+            : "");
+  }
+  const bool any_template_params = llvm::any_of(
+      template_params, [](llvm::StringRef p) { return !p.empty(); });
+
+  auto die_matches = [&](DWARFDIE type_die) {
+    // Resolve the type if both have the same tag or {class, struct} tags.
+    const bool tag_matches =
+        type_die.Tag() == tag ||
+        (IsStructOrClassTag(type_die.Tag()) && IsStructOrClassTag(tag));
+    if (!tag_matches)
+      return false;
+    if (any_template_params) {
+      size_t pos = 0;
+      for (DWARFDIE ctx_die = type_die; ctx_die && !isUnitType(ctx_die.Tag()) &&
+                                        pos < template_params.size();
+           ctx_die = ctx_die.GetParentDeclContextDIE(), ++pos) {
+        if (template_params[pos].empty())
+          continue;
+        if (template_params[pos] !=
+            dwarf_ast->GetDIEClassTemplateParams(ctx_die))
           return false;
       }
+      if (pos != template_params.size())
+        return false;
+    }
+    return true;
+  };
+  DWARFDIE result;
+  m_index->GetFullyQualifiedType(die_dwarf_decl_ctx, [&](DWARFDIE type_die) {
+    // Make sure type_die's language matches the type system we are
+    // looking for. We don't want to find a "Foo" type from Java if we
+    // are looking for a "Foo" type for C, C++, ObjC, or ObjC++.
+    if (type_system &&
+        !type_system->SupportsLanguage(GetLanguage(*type_die.GetCU())))
       return true;
-    };
-    m_index->GetFullyQualifiedType(die_dwarf_decl_ctx, [&](DWARFDIE type_die) {
-      // Make sure type_die's language matches the type system we are
-      // looking for. We don't want to find a "Foo" type from Java if we
-      // are looking for a "Foo" type for C, C++, ObjC, or ObjC++.
-      if (type_system &&
-          !type_system->SupportsLanguage(GetLanguage(*type_die.GetCU())))
-        return true;
-
-      if (!die_matches(type_die)) {
-        if (log) {
-          GetObjectFile()->GetModule()->LogMessage(
-              log,
-              "SymbolFileDWARF::"
-              "FindDefinitionTypeForDWARFDeclContext(tag={0} ({1}), "
-              "name='{2}') ignoring die={3:x16} ({4})",
-              DW_TAG_value_to_name(tag), tag, die.GetName(),
-              type_die.GetOffset(), type_die.GetName());
-        }
-        return true;
-      }
 
+    if (!die_matches(type_die)) {
       if (log) {
-        DWARFDeclContext type_dwarf_decl_ctx = type_die.GetDWARFDeclContext();
         GetObjectFile()->GetModule()->LogMessage(
             log,
-            "SymbolFileDWARF::"
-            "FindDefinitionTypeForDWARFDeclContext(tag={0} ({1}), name='{2}') "
-            "trying die={3:x16} ({4})",
+            "SymbolFileDWARF::FindDefinitionDIE(tag={0} ({1}), "
+            "name='{2}') ignoring die={3:x16} ({4})",
             DW_TAG_value_to_name(tag), tag, die.GetName(), type_die.GetOffset(),
-            type_dwarf_decl_ctx.GetQualifiedName());
+            type_die.GetName());
       }
+      return true;
+    }
 
-      Type *resolved_type = ResolveType(type_die, false);
-      if (!resolved_type || resolved_type == DIE_IS_BEING_PARSED)
-        return true;
+    if (log) {
+      DWARFDeclContext type_dwarf_decl_ctx = type_die.GetDWARFDeclContext();
+      GetObjectFile()->GetModule()->LogMessage(
+          log,
+          "SymbolFileDWARF::FindDefinitionTypeDIE(tag={0} ({1}), name='{2}') "
+          "trying die={3:x16} ({4})",
+          DW_TAG_value_to_name(tag), tag, die.GetName(), type_die.GetOffset(),
+          type_dwarf_decl_ctx.GetQualifiedName());
+    }
 
-      type_sp = resolved_type->shared_from_this();
-      return false;
-    });
-  }
-  return type_sp;
+    result = type_die;
+    return false;
+  });
+  return result;
 }
 
 TypeSP SymbolFileDWARF::ParseType(const SymbolContext &sc, const DWARFDIE &die,

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

@@ -360,8 +360,7 @@ class SymbolFileDWARF : public SymbolFileCommon {
 
   SymbolFileDWARFDebugMap *GetDebugMapSymfile();
 
-  virtual lldb::TypeSP
-  FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die);
+  virtual DWARFDIE FindDefinitionDIE(const DWARFDIE &die);
 
   virtual lldb::TypeSP FindCompleteObjCDefinitionTypeForDIE(
       const DWARFDIE &die, ConstString type_name, bool must_be_implementation);

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

@@ -1147,14 +1147,13 @@ SymbolFileDWARFDebugMap::ParseCallEdgesInFunction(
   return {};
 }
 
-TypeSP SymbolFileDWARFDebugMap::FindDefinitionTypeForDWARFDeclContext(
-    const DWARFDIE &die) {
-  TypeSP type_sp;
+DWARFDIE SymbolFileDWARFDebugMap::FindDefinitionDIE(const DWARFDIE &die) {
+  DWARFDIE result;
   ForEachSymbolFile([&](SymbolFileDWARF *oso_dwarf) {
-    type_sp = oso_dwarf->FindDefinitionTypeForDWARFDeclContext(die);
-    return type_sp ? IterationAction::Stop : IterationAction::Continue;
+    result = oso_dwarf->FindDefinitionDIE(die);
+    return result ? IterationAction::Stop : IterationAction::Continue;
   });
-  return type_sp;
+  return result;
 }
 
 bool SymbolFileDWARFDebugMap::Supports_DW_AT_APPLE_objc_complete_type(

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

@@ -277,7 +277,7 @@ class SymbolFileDWARFDebugMap : public SymbolFileCommon {
 
   CompileUnitInfo *GetCompileUnitInfo(SymbolFileDWARF *oso_dwarf);
 
-  lldb::TypeSP FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die);
+  DWARFDIE FindDefinitionDIE(const DWARFDIE &die);
 
   bool Supports_DW_AT_APPLE_objc_complete_type(SymbolFileDWARF *skip_dwarf_oso);
 

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

@@ -125,9 +125,8 @@ UniqueDWARFASTTypeMap &SymbolFileDWARFDwo::GetUniqueDWARFASTTypeMap() {
   return GetBaseSymbolFile().GetUniqueDWARFASTTypeMap();
 }
 
-lldb::TypeSP
-SymbolFileDWARFDwo::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
-  return GetBaseSymbolFile().FindDefinitionTypeForDWARFDeclContext(die);
+DWARFDIE SymbolFileDWARFDwo::FindDefinitionDIE(const DWARFDIE &die) {
+  return GetBaseSymbolFile().FindDefinitionDIE(die);
 }
 
 lldb::TypeSP SymbolFileDWARFDwo::FindCompleteObjCDefinitionTypeForDIE(

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

@@ -78,8 +78,7 @@ class SymbolFileDWARFDwo : public SymbolFileDWARF {
 
   UniqueDWARFASTTypeMap &GetUniqueDWARFASTTypeMap() override;
 
-  lldb::TypeSP
-  FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) override;
+  DWARFDIE FindDefinitionDIE(const DWARFDIE &die) override;
 
   lldb::TypeSP
   FindCompleteObjCDefinitionTypeForDIE(const DWARFDIE &die,