[lldb][DWARFASTParserClang][NFC] Extract condition for unnamed bitfield creation into helper function

[Michael137]

Summary

This patch adds a new private helper
DWARFASTParserClang::ShouldCreateUnnamedBitfield which
ParseSingleMember whether we should fill the current gap
in a structure layout with unnamed bitfields.

Extracting this logic will allow us to add additional
conditions in upcoming patches without jeoperdizing readability
of ParseSingleMember.

We also store some of the boolean conditions in local variables
to make the intent more obvious.

[aprantl]

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

239

Doxygen comment?

[Michael137]

• Add doxygen comment

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

struct FieldInfo {
 
     bool NextBitfieldOffsetIsValid(const uint64_t next_bit_offset) const {
       // Any subsequent bitfields must not overlap and must be at a higher
       // bit offset than any previous bitfield + size.
       return (bit_size + bit_offset) <= next_bit_offset;
     }
   };
 
+  /// Returns 'true' if we should create an unnamed bitfield
+  /// and add it to the parser's current AST.
+  ///
+  /// \param[in] last_field_info FieldInfo of the previous DW_TAG_member
+  ///            we parsed.
+  /// \param[in] last_field_end Offset (in bits) where the last parsed field
+  ///            ended.
+  /// \param[in] this_field_info FieldInfo of the current DW_TAG_member
+  ///            being parsed.
+  /// \param[in] layout_info Layout information of all decls parsed by the
+  ///            current parser.
+  bool ShouldCreateUnnamedBitfield(
+      FieldInfo const &last_field_info, uint64_t last_field_end,
+      FieldInfo const &this_field_info,
+      lldb_private::ClangASTImporter::LayoutInfo const &layout_info) const;
+
   /// Parses a DW_TAG_APPLE_property DIE and appends the parsed data to the
   /// list of delayed Objective-C properties.
   ///
   /// Note: The delayed property needs to be finalized to actually create the
   /// property declarations in the module AST.
   ///
   /// \param die The DW_TAG_APPLE_property DIE that will be parsed.
   /// \param parent_die The parent DIE.

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

if (detect_unnamed_bitfields) {
         // The last field was not a bit-field...
         // but if it did take up the entire word then we need to extend
         // last_field_end so the bit-field does not step into the last
         // fields padding.
         if (last_field_end != 0 && ((last_field_end % word_width) != 0))
           last_field_end += word_width - (last_field_end % word_width);
       }
 
-      // If we have a gap between the last_field_end and the current
-      // field we have an unnamed bit-field.
-      // If we have a base class, we assume there is no unnamed
-      // bit-field if this is the first field since the gap can be
-      // attributed to the members from the base class. This assumption
-      // is not correct if the first field of the derived class is
-      // indeed an unnamed bit-field. We currently do not have the
-      // machinary to track the offset of the last field of classes we
-      // have seen before, so we are not handling this case.
-      if (this_field_info.bit_offset > last_field_end &&
-          !(last_field_info.bit_offset == 0 && last_field_info.bit_size == 0 &&
-            layout_info.base_offsets.size() != 0)) {
+      if (ShouldCreateUnnamedBitfield(last_field_info, last_field_end,
+                                      this_field_info, layout_info)) {
         unnamed_field_info = FieldInfo{};
         unnamed_field_info->bit_size =
             this_field_info.bit_offset - last_field_end;
         unnamed_field_info->bit_offset = last_field_end;
       }
 
       if (unnamed_field_info) {
         clang::FieldDecl *unnamed_bitfield_decl =
if (dst_size_artificial) {
     for (idx = 0; idx < dst_size_artificial; ++idx) {
       failures.push_back(
           dst_name_to_die_artificial.GetValueAtIndexUnchecked(idx));
     }
   }
 
   return !failures.empty();
 }
+
+bool DWARFASTParserClang::ShouldCreateUnnamedBitfield(
+    FieldInfo const &last_field_info, uint64_t last_field_end,
+    FieldInfo const &this_field_info,
+    lldb_private::ClangASTImporter::LayoutInfo const &layout_info) const {
+  // If we have a gap between the last_field_end and the current
+  // field we have an unnamed bit-field.
+  if (this_field_info.bit_offset <= last_field_end)
+    return false;
+
+  // If we have a base class, we assume there is no unnamed
+  // bit-field if this is the first field since the gap can be
+  // attributed to the members from the base class. This assumption
+  // is not correct if the first field of the derived class is
+  // indeed an unnamed bit-field. We currently do not have the
+  // machinary to track the offset of the last field of classes we
+  // have seen before, so we are not handling this case.
+  const bool have_base = layout_info.base_offsets.size() != 0;
+  const bool this_is_first_field =
+      last_field_info.bit_offset == 0 && last_field_info.bit_size == 0;
+
+  if (have_base && this_is_first_field)
+    return false;
+
+  return true;
+}