[lldb][DWARFIndex] Implement GetFullyQualifiedType query

Combines:
1. the accelerator table capability of finding parents
2. the DWARFUnit capability of finding the name of a DIE without parsing the
whole CU.

Author: felipepiovezan

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

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Plugins/SymbolFile/DWARF/DWARFIndex.h"
+#include "DWARFDeclContext.h"
 #include "Plugins/Language/ObjC/ObjCLanguage.h"
 #include "Plugins/SymbolFile/DWARF/DWARFDIE.h"
 #include "Plugins/SymbolFile/DWARF/SymbolFileDWARF.h"
@@ -112,3 +113,21 @@ void DWARFIndex::ReportInvalidDIERef(DIERef ref, llvm::StringRef name) const {
       "bad die {0:x16} for '{1}')\n",
       ref.die_offset(), name.str().c_str());
 }
+
+void DWARFIndex::GetFullyQualifiedType(
+    const DWARFDeclContext &context,
+    llvm::function_ref<bool(DWARFDIE die)> callback) {
+  auto qualified_names = context.GetQualifiedNameAsVector();
+  if (qualified_names.empty())
+    return;
+  auto parent_names = llvm::makeArrayRef(qualified_names).drop_front();
+  GetTypes(context, [&](DWARFDIE die) {
+    auto original_die = die;
+    for (auto parent_name : parent_names) {
+      die = die.GetParent();
+      if (!die || die.GetName() != parent_name)
+        return false;
+    }
+    return callback(original_die);
+  });
+}

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

@@ -53,6 +53,14 @@ class DWARFIndex {
                         llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
   virtual void GetTypes(const DWARFDeclContext &context,
                         llvm::function_ref<bool(DWARFDIE die)> callback) = 0;
+
+  /// Finds all DIEs whose fully qualified name matches `context`. A base
+  /// implementation is provided, and it uses the entire CU to check the DIE
+  /// parent hierarchy. Specializations should override this if they are able
+  /// to provide a faster implementation.
+  virtual void
+  GetFullyQualifiedType(const DWARFDeclContext &context,
+                        llvm::function_ref<bool(DWARFDIE die)> callback);
   virtual void
   GetNamespaces(ConstString name,
                 llvm::function_ref<bool(DWARFDIE die)> callback) = 0;

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

@@ -218,6 +218,55 @@ void DebugNamesDWARFIndex::GetCompleteObjCClass(
   m_fallback.GetCompleteObjCClass(class_name, must_be_implementation, callback);
 }
 
+void DebugNamesDWARFIndex::GetFullyQualifiedType(
+    const DWARFDeclContext &context,
+    llvm::function_ref<bool(DWARFDIE die)> callback) {
+  if (!m_debug_names_up->supportsIdxParent())
+    return DWARFIndex::GetFullyQualifiedType(context, callback);
+
+  auto qualified_names = context.GetQualifiedNameAsVector();
+  if (qualified_names.empty())
+    return;
+
+  auto CompareEntryATName = [this](llvm::StringRef expected_name,
+                                   const DebugNames::Entry &entry) {
+    auto maybe_dieoffset = entry.getDIEUnitOffset();
+    if (!maybe_dieoffset)
+      return false;
+    auto die_ref = ToDIERef(entry);
+    if (!die_ref)
+      return false;
+    return expected_name == m_debug_info.PeekDIEName(*die_ref);
+  };
+
+  auto parent_names = llvm::makeArrayRef(qualified_names).drop_front();
+  auto CheckParentChain = [&](DebugNames::Entry entry) {
+    for (auto expected_name : parent_names) {
+      auto maybe_parent_entry = entry.getParentDIEEntry();
+      if (!maybe_parent_entry) {
+        consumeError(maybe_parent_entry.takeError());
+        return false;
+      }
+      entry = *maybe_parent_entry;
+      if (!CompareEntryATName(expected_name, entry))
+        return false;
+    }
+    /// All expected names matched. The remaining entry should have no parent
+    /// for a match to occur.
+    auto maybe_parent_entry = entry.getParentDIEEntry();
+    if (maybe_parent_entry)
+      return false;
+    consumeError(maybe_parent_entry.takeError());
+    return true;
+  };
+
+  auto leaf_matches = m_debug_names_up->equal_range(qualified_names.front());
+  for (const DebugNames::Entry &entry : leaf_matches)
+    if (isType(entry.tag()) && CheckParentChain(entry) &&
+        (!ProcessEntry(entry, callback)))
+      return;
+}
+
 void DebugNamesDWARFIndex::GetTypes(
     ConstString name, llvm::function_ref<bool(DWARFDIE die)> callback) {
   for (const DebugNames::Entry &entry :

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

@@ -42,6 +42,11 @@ class DebugNamesDWARFIndex : public DWARFIndex {
   void GetCompleteObjCClass(
       ConstString class_name, bool must_be_implementation,
       llvm::function_ref<bool(DWARFDIE die)> callback) override;
+
+  /// Uses DWARF5's IDX_parent fields, when available, to speed up this query.
+  void GetFullyQualifiedType(
+      const DWARFDeclContext &context,
+      llvm::function_ref<bool(DWARFDIE die)> callback) override;
   void GetTypes(ConstString name,
                 llvm::function_ref<bool(DWARFDIE die)> callback) override;
   void GetTypes(const DWARFDeclContext &context,