[lldb] [DWARF-5] Be lazier about loading .dwo files

This change makes sure that DwarfUnit does not load a .dwo file until
necessary. I also take advantage of DWARF 5's guarantee that the first
support file is also the primary file to make it possible to create
a compile unit without loading the .dwo file.

Review By: jankratochvil, dblaikie

Differential Revision: https://reviews.llvm.org/D100299

1 files changed, 8 insertions, 2 deletions

diff --git a/lldb/source/Symbol/CompileUnit.cpp b/lldb/source/Symbol/CompileUnit.cpp
index 588ed4976d65..1b258516fac8 100644
--- a/lldb/source/Symbol/CompileUnit.cpp
+++ b/lldb/source/Symbol/CompileUnit.cpp
@@ -52,7 +52,7 @@ void CompileUnit::DumpSymbolContext(Stream *s) {
 
 void CompileUnit::GetDescription(Stream *s,
                                  lldb::DescriptionLevel level) const {
-  const char *language = Language::GetNameForLanguageType(m_language);
+  const char *language = GetCachedLanguage();
   *s << "id = " << (const UserID &)*this << ", file = \""
      << this->GetPrimaryFile() << "\", language = \"" << language << '"';
 }
@@ -97,12 +97,18 @@ lldb::FunctionSP CompileUnit::FindFunction(
   return {};
 }
 
+const char *CompileUnit::GetCachedLanguage() const {
+  if (m_flags.IsClear(flagsParsedLanguage))
+    return "<not loaded>";
+  return Language::GetNameForLanguageType(m_language);
+}
+
 // Dump the current contents of this object. No functions that cause on demand
 // parsing of functions, globals, statics are called, so this is a good
 // function to call to get an idea of the current contents of the CompileUnit
 // object.
 void CompileUnit::Dump(Stream *s, bool show_context) const {
-  const char *language = Language::GetNameForLanguageType(m_language);
+  const char *language = GetCachedLanguage();
 
   s->Printf("%p: ", static_cast<const void *>(this));
   s->Indent();