How to get custom attributes in LLVM Pass

Question

I implemented a custom attribute in clang as described in the official manual:

How to add an attribute in Clang

I added a definition to include/clang/Basic/Attr.td

def attr : InheritableAttr {
  let Spellings = [GCC<"attr">, Declspec<"attr">];
  // FIXME: Does GCC allow this on the function instead?
  let Documentation = [Undocumented];
}

and implement the semantic processing of the attribute in SemaDeclAttr.cpp by adding a new case.

case AttributeList::AT_MyAttr:
   handleSimpleAttribute<MyAttrAttr>(S, D, Attr);
break;

After rebuilding clang, it obviously knows the attribute because i don't get an unknown attribute warning when using it.

But I can't get this attribute in LLVM Pass by function hasFnAttribute()

bool runOnFunction(Function &F) override {

            // it didn't work
            if (F.hasFnAttribute("attr")){ 
                  return false;
            }
            return false;
        }

Attribute::AttrKind doesn't have Attribute::attr. I try to change /llvm/include/llvm/IR/Attributes.td and some code to make clang run. But it didn't work.

Is there something else i need to consider or what could be the problem?