Fix caching for clang::Decl in DWARFASTParserClang

[paulherman]

Fix caching for clang::Decl in DWARFASTParserClang

[paulherman]

Fix caching for clang::Decl in DWARFASTParserClang

Fixed small mistakes from previous commit.

[tberghammer]

Looks good with minor comment inline

source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

3228–3230

I think using a switch would be both simpler and faster

[paulherman]

Fix caching for clang::Decl in DWARFASTParserClang

Changed from std::set to switch. Rebased the patch.

source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

 }
 
 clang::Decl *
 DWARFASTParserClang::GetClangDeclForDIE (const DWARFDIE &die)
 {
     if (!die)
         return nullptr;
 
-    if (die.GetReferencedDIE(DW_AT_specification))
-        return GetClangDeclForDIE(die.GetReferencedDIE(DW_AT_specification));
+    const std::set<dw_tag_t> tags_with_decls { DW_TAG_variable, DW_TAG_constant, DW_TAG_formal_parameter, DW_TAG_imported_module, DW_TAG_imported_declaration };
+    if (tags_with_decls.find(die.Tag()) == tags_with_decls.end())
+        return nullptr;
+
+    DIEToDeclMap::iterator cache_pos = m_die_to_decl.find(die.GetDIE());
+    if (cache_pos != m_die_to_decl.end())
+        return cache_pos->second;
 
-    clang::Decl *decl = m_die_to_decl[die.GetDIE()];
-    if (decl != nullptr)
+    if (DWARFDIE spec_die = die.GetReferencedDIE(DW_AT_specification))
+    {
+        clang::Decl *decl = GetClangDeclForDIE(spec_die);
+        m_die_to_decl[die.GetDIE()] = decl;
+        m_decl_to_die[decl].insert(die.GetDIE());
         return decl;
+    }
 
+    clang::Decl *decl = nullptr;
     switch (die.Tag())
     {
         case DW_TAG_variable:
         case DW_TAG_constant:
         case DW_TAG_formal_parameter:
         {
             SymbolFileDWARF *dwarf = die.GetDWARF();
             Type *type = GetTypeForDIE(die);