[DWARFASTParser] Remove special cases for `llvm-gcc`

[davide]

Summary

To the best of my understanding modern compilers handle all these cases correctly. So, I think this is basically dead code.

[aprantl]

I don't have a problem with dropping compatibility with llvm-gcc in LLDB, but I should point out that LLDB generally wants to be able to debug code produced by a wide range of compilers, including old ones.

[davide]

I think it's fair and correct supporting everything we can, but I guess llvm-gcc is largely dead at this point.

[aprantl]

People might have a legitimate reason to debug very old code, e.g., for backporting security fixes or similar. On the other hand one might argue that they could just do this with a debugger from the same era.

[labath]

I suppose this is fine. My main worry is whether llvm-gcc is the *only* situation where we rely on these tweaks, but I guess the best way to find out is to try removing them.

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

if (type_ptr == NULL) {
                 break;
               case DW_AT_decl_line:
                 decl.SetLine(form_value.Unsigned());
                 break;
               case DW_AT_decl_column:
                 decl.SetColumn(form_value.Unsigned());
                 break;
               case DW_AT_name:
-
                 type_name_cstr = form_value.AsCString();
-                // Work around a bug in llvm-gcc where they give a name to a
-                // reference type which doesn't include the "&"...
-                if (tag == DW_TAG_reference_type) {
-                  if (strchr(type_name_cstr, '&') == NULL)
-                    type_name_cstr = NULL;
-                }
                 if (type_name_cstr)
                   type_name_const_str.SetCString(type_name_cstr);
                 break;
               case DW_AT_byte_size:
                 byte_size = form_value.Unsigned();
                 break;
               case DW_AT_encoding:
                 encoding = form_value.Unsigned();
if (type_ptr == NULL) {
         const size_t num_attributes = die.GetAttributes(attributes);
         if (num_attributes > 0) {
           uint32_t i;
           for (i = 0; i < num_attributes; ++i) {
             attr = attributes.AttributeAtIndex(i);
             if (attributes.ExtractFormValueAtIndex(i, form_value)) {
               switch (attr) {
               case DW_AT_decl_file:
-                if (die.GetCU()->DW_AT_decl_file_attributes_are_invalid()) {
-                  // llvm-gcc outputs invalid DW_AT_decl_file attributes that
-                  // always point to the compile unit file, so we clear this
-                  // invalid value so that we can still unique types
-                  // efficiently.
-                  decl.SetFile(FileSpec("<invalid>", false));
-                } else
-                  decl.SetFile(
-                      sc.comp_unit->GetSupportFiles().GetFileSpecAtIndex(
-                          form_value.Unsigned()));
                 break;
 
               case DW_AT_decl_line:
                 decl.SetLine(form_value.Unsigned());
                 break;
 
               case DW_AT_decl_column:
                 decl.SetColumn(form_value.Unsigned());
case DW_TAG_APPLE_property: {
           bit_offset = 0;
         }
 
         // FIXME: Make Clang ignore Objective-C accessibility for expressions
         if (class_language == eLanguageTypeObjC ||
             class_language == eLanguageTypeObjC_plus_plus)
           accessibility = eAccessNone;
 
-        if (member_idx == 0 && !is_artificial && name &&
-            (strstr(name, "_vptr$") == name)) {
-          // Not all compilers will mark the vtable pointer member as
-          // artificial (llvm-gcc). We can't have the virtual members in our
-          // classes otherwise it throws off all child offsets since we end up
-          // having and extra pointer sized member in our class layouts.
-          is_artificial = true;
-        }
-
         // Handle static members
         if (is_external && member_byte_offset == UINT32_MAX) {
           Type *var_type = die.ResolveTypeUID(DIERef(encoding_form));
 
           if (var_type) {
             if (accessibility == eAccessNone)
               accessibility = eAccessPublic;
             ClangASTContext::AddVariableToRecordType(