@@ -383,26 +383,26 @@ _PyCode_Quicken(PyCodeObject *code)
 #define SPEC_FAIL_CALL_COMPLEX_PARAMETERS 9
 #define SPEC_FAIL_CALL_CO_NOT_OPTIMIZED 10
 /* SPEC_FAIL_METHOD  defined as 11 above */
-
-#define SPEC_FAIL_CALL_INSTANCE_METHOD 11
-#define SPEC_FAIL_CALL_CMETHOD 12
-#define SPEC_FAIL_CALL_PYCFUNCTION 13
-#define SPEC_FAIL_CALL_PYCFUNCTION_WITH_KEYWORDS 14
-#define SPEC_FAIL_CALL_PYCFUNCTION_FAST_WITH_KEYWORDS 15
-#define SPEC_FAIL_CALL_PYCFUNCTION_NOARGS 16
-#define SPEC_FAIL_CALL_BAD_CALL_FLAGS 17
-#define SPEC_FAIL_CALL_CLASS 18
-#define SPEC_FAIL_CALL_PYTHON_CLASS 19
-#define SPEC_FAIL_CALL_METHOD_DESCRIPTOR 20
-#define SPEC_FAIL_CALL_BOUND_METHOD 21
-#define SPEC_FAIL_CALL_STR 22
-#define SPEC_FAIL_CALL_CLASS_NO_VECTORCALL 23
-#define SPEC_FAIL_CALL_CLASS_MUTABLE 24
-#define SPEC_FAIL_CALL_KWNAMES 25
-#define SPEC_FAIL_CALL_METHOD_WRAPPER 26
-#define SPEC_FAIL_CALL_OPERATOR_WRAPPER 27
-#define SPEC_FAIL_CALL_PYFUNCTION 28
-#define SPEC_FAIL_CALL_PEP_523 29
+/* code flag kind */
+#define SPEC_FAIL_CALL_CFUNCTION_FLAG_NOARGS 11
+#define SPEC_FAIL_CALL_CFUNCTION_FLAG_VARARGS 12
+#define SPEC_FAIL_CALL_CFUNCTION_FLAG_VARARGS_KW 13
+#define SPEC_FAIL_CALL_FLAG_VARARGS 14
+#define SPEC_FAIL_CALL_FLAG_VARARGS_KW 15
+#define SPEC_FAIL_CALL_BAD_CALL_FLAGS 16
+/* callable type kind */
+#define SPEC_FAIL_CALL_INSTANCE_METHOD 17
+#define SPEC_FAIL_CALL_CMETHOD 18
+#define SPEC_FAIL_CALL_OPERATOR_WRAPPER 19
+#define SPEC_FAIL_CALL_METHOD_WRAPPER 20
+/* unsupported cases */
+#define SPEC_FAIL_CALL_PYTHON_CLASS 21
+#define SPEC_FAIL_CALL_BOUND_METHOD 22
+#define SPEC_FAIL_CALL_STR 23
+#define SPEC_FAIL_CALL_CLASS_NO_VECTORCALL 24
+#define SPEC_FAIL_CALL_CLASS_MUTABLE 25
+#define SPEC_FAIL_CALL_KWNAMES 26
+#define SPEC_FAIL_CALL_PEP_523 27
 
 /* COMPARE_OP */
 #define SPEC_FAIL_COMPARE_OP_DIFFERENT_TYPES 12
@@ -1470,18 +1470,17 @@ specialize_class_call(PyObject *callable, _Py_CODEUNIT *instr, int nargs,
 
 #ifdef Py_STATS
 static int
-builtin_call_fail_kind(int ml_flags)
+code_flag_fail_kind(int co_flags, bool is_cfunc)
 {
-    switch (ml_flags & (METH_VARARGS | METH_FASTCALL | METH_NOARGS | METH_O |
+    switch (co_flags &
+        (METH_VARARGS | METH_FASTCALL | METH_NOARGS | METH_O |
         METH_KEYWORDS | METH_METHOD)) {
+        case METH_NOARGS:
+            return is_cfunc ? SPEC_FAIL_CALL_CFUNCTION_FLAG_NOARGS : SPEC_FAIL_CALL_BAD_CALL_FLAGS;
         case METH_VARARGS:
-            return SPEC_FAIL_CALL_PYCFUNCTION;
+            return is_cfunc ? SPEC_FAIL_CALL_CFUNCTION_FLAG_VARARGS : SPEC_FAIL_CALL_FLAG_VARARGS;
         case METH_VARARGS | METH_KEYWORDS:
-            return SPEC_FAIL_CALL_PYCFUNCTION_WITH_KEYWORDS;
-        case METH_FASTCALL | METH_KEYWORDS:
-            return SPEC_FAIL_CALL_PYCFUNCTION_FAST_WITH_KEYWORDS;
-        case METH_NOARGS:
-            return SPEC_FAIL_CALL_PYCFUNCTION_NOARGS;
+            return is_cfunc ? SPEC_FAIL_CALL_CFUNCTION_FLAG_VARARGS_KW : SPEC_FAIL_CALL_FLAG_VARARGS_KW;
         /* This case should never happen with PyCFunctionObject -- only
             PyMethodObject. See zlib.compressobj()'s methods for an example.
         */
@@ -1538,7 +1537,7 @@ specialize_method_descriptor(PyMethodDescrObject *descr, _Py_CODEUNIT *instr,
             return 0;
         }
     }
-    SPECIALIZATION_FAIL(CALL, builtin_call_fail_kind(descr->d_method->ml_flags));
+    SPECIALIZATION_FAIL(CALL, code_flag_fail_kind(descr->d_method->ml_flags, false));
     return -1;
 }
 
@@ -1646,8 +1645,7 @@ specialize_c_call(PyObject *callable, _Py_CODEUNIT *instr, int nargs,
             return 0;
         }
         default:
-            SPECIALIZATION_FAIL(CALL,
-                builtin_call_fail_kind(PyCFunction_GET_FLAGS(callable)));
+            SPECIALIZATION_FAIL(CALL, code_flag_fail_kind(PyCFunction_GET_FLAGS(callable), true));
             return 1;
     }
 }
@@ -1656,37 +1654,17 @@ specialize_c_call(PyObject *callable, _Py_CODEUNIT *instr, int nargs,
 static int
 call_fail_kind(PyObject *callable)
 {
-    if (PyCFunction_CheckExact(callable)) {
-        return SPEC_FAIL_CALL_PYCFUNCTION;
-    }
-    else if (PyFunction_Check(callable)) {
-        return SPEC_FAIL_CALL_PYFUNCTION;
-    }
-    else if (PyInstanceMethod_Check(callable)) {
+    if (PyInstanceMethod_Check(callable)) {
         return SPEC_FAIL_CALL_INSTANCE_METHOD;
     }
-    else if (PyMethod_Check(callable)) {
-        return SPEC_FAIL_CALL_BOUND_METHOD;
-    }
     // builtin method
     else if (PyCMethod_Check(callable)) {
         return SPEC_FAIL_CALL_CMETHOD;
     }
-    else if (PyType_Check(callable)) {
-        if (((PyTypeObject *)callable)->tp_new == PyBaseObject_Type.tp_new) {
-            return SPEC_FAIL_CALL_PYTHON_CLASS;
-        }
-        else {
-            return SPEC_FAIL_CALL_CLASS;
-        }
-    }
-    else if (Py_IS_TYPE(callable, &PyMethodDescr_Type)) {
-        return SPEC_FAIL_CALL_METHOD_DESCRIPTOR;
-    }
-    else if (Py_TYPE(callable) == &PyWrapperDescr_Type) {
+    else if (Py_IS_TYPE(callable, &PyWrapperDescr_Type)) {
         return SPEC_FAIL_CALL_OPERATOR_WRAPPER;
     }
-    else if (Py_TYPE(callable) == &_PyMethodWrapper_Type) {
+    else if (Py_IS_TYPE(callable, &_PyMethodWrapper_Type)) {
         return SPEC_FAIL_CALL_METHOD_WRAPPER;
     }
     return SPEC_FAIL_OTHER;
@@ -1718,7 +1696,7 @@ _Py_Specialize_Call(PyObject *callable, _Py_CODEUNIT *instr, int nargs,
         fail = specialize_method_descriptor((PyMethodDescrObject *)callable,
                                             instr, nargs, kwnames);
     }
-    else if (Py_TYPE(callable) == &PyMethod_Type) {
+    else if (Py_IS_TYPE(callable, &PyMethod_Type)) {
         PyObject *func = ((PyMethodObject *)callable)->im_func;
         if (PyFunction_Check(func)) {
             fail = specialize_py_call((PyFunctionObject *)func,