[codeview][clang] Added support for unnamed bitfield type.

[aaboud]

Summary

Allow creating DI metadata for non-zero width unnamed bitfield members when emitting CodeView.
This is needed for patch D21489.

[majnemer]

As I said in the other differential, I do not think this is the right approach.
We should use the extraData for the bitfield member to indicate the offset of the storage unit.

[aaboud]

Different implementation was committed at rL274201.

lib/CodeGen/CGDebugInfo.cpp

 }
 
 void CGDebugInfo::CollectRecordNormalField(
     const FieldDecl *field, uint64_t OffsetInBits, llvm::DIFile *tunit,
     SmallVectorImpl<llvm::Metadata *> &elements, llvm::DIType *RecordTy,
     const RecordDecl *RD) {
   StringRef name = field->getName();
   QualType type = field->getType();
+  bool EmitCodeView = CGM.getCodeGenOpts().EmitCodeView;
 
   // Ignore unnamed fields unless they're anonymous structs/unions.
   if (name.empty() && !type->isRecordType())
+    // Do not ignore anonymous bitfield when emitting CodeView.
+    if(!EmitCodeView || !field->isBitField())
       return;
 
   uint64_t SizeInBitsOverride = 0;
   if (field->isBitField()) {
     SizeInBitsOverride = field->getBitWidthValue(CGM.getContext());
+    if (!SizeInBitsOverride && name.empty())
+      // Ignore unnamed 0-width bitfield.
+      return;
     assert(SizeInBitsOverride && "found named 0-width bitfield");
   }
 
   llvm::DIType *fieldType =
       createFieldType(name, type, SizeInBitsOverride, field->getLocation(),
                       field->getAccess(), OffsetInBits, tunit, RecordTy, RD);
 
   elements.push_back(fieldType);