[lldb][DWARFIndex][nfc] Factor out fully qualified name query

This moves the functionally of finding a DIE based on a fully qualified name
from SymbolFileDWARF into DWARFIndex itself, so that specializations of
DWARFIndex can implement faster versions of this query.

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

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "Plugins/SymbolFile/DWARF/DWARFIndex.h"
+#include "DWARFDebugInfoEntry.h"
+#include "DWARFDeclContext.h"
 #include "Plugins/Language/ObjC/ObjCLanguage.h"
 #include "Plugins/SymbolFile/DWARF/DWARFDIE.h"
 #include "Plugins/SymbolFile/DWARF/SymbolFileDWARF.h"
@@ -112,3 +114,15 @@ 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) {
+  GetTypes(context, [&](DWARFDIE die) {
+    DWARFDeclContext dwarf_decl_ctx =
+        die.GetDIE()->GetDWARFDeclContext(die.GetCU());
+    if (dwarf_decl_ctx == context)
+      return callback(die);
+    return true;
+  });
+}

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/SymbolFileDWARF.cpp

@@ -3095,7 +3095,7 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
     }
 
     const DWARFDeclContext die_dwarf_decl_ctx = GetDWARFDeclContext(die);
-    m_index->GetTypes(die_dwarf_decl_ctx, [&](DWARFDIE type_die) {
+    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++.
@@ -3122,9 +3122,8 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
         return true;
       }
 
-      DWARFDeclContext type_dwarf_decl_ctx = GetDWARFDeclContext(type_die);
-
       if (log) {
+        DWARFDeclContext type_dwarf_decl_ctx = GetDWARFDeclContext(type_die);
         GetObjectFile()->GetModule()->LogMessage(
             log,
             "SymbolFileDWARF::"
@@ -3134,10 +3133,6 @@ SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
             type_dwarf_decl_ctx.GetQualifiedName());
       }
 
-      // Make sure the decl contexts match all the way up
-      if (die_dwarf_decl_ctx != type_dwarf_decl_ctx)
-        return true;
-
       Type *resolved_type = ResolveType(type_die, false);
       if (!resolved_type || resolved_type == DIE_IS_BEING_PARSED)
         return true;