bpo-42435: Speed up comparison of bytes and bytearray object (GH--23461)

* Speed up comparison of bytes objects with non-bytes objects when
  option -b is specified.
* Speed up comparison of bytarray objects with non-buffer object.
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 8b57fb6..805707a 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -1005,23 +1005,19 @@ bytearray_richcompare(PyObject *self, PyObject *other, int op)
 {
     Py_ssize_t self_size, other_size;
     Py_buffer self_bytes, other_bytes;
-    int cmp, rc;
+    int cmp;
 
     /* Bytes can be compared to anything that supports the (binary)
        buffer API.  Except that a comparison with Unicode is always an
        error, even if the comparison is for equality. */
-    rc = PyObject_IsInstance(self, (PyObject*)&PyUnicode_Type);
-    if (!rc)
-        rc = PyObject_IsInstance(other, (PyObject*)&PyUnicode_Type);
-    if (rc < 0)
-        return NULL;
-    if (rc) {
-        if (_Py_GetConfig()->bytes_warning && (op == Py_EQ || op == Py_NE)) {
-            if (PyErr_WarnEx(PyExc_BytesWarning,
-                            "Comparison between bytearray and string", 1))
-                return NULL;
+    if (!PyObject_CheckBuffer(self) || !PyObject_CheckBuffer(other)) {
+        if (PyUnicode_Check(self) || PyUnicode_Check(other)) {
+            if (_Py_GetConfig()->bytes_warning && (op == Py_EQ || op == Py_NE)) {
+                if (PyErr_WarnEx(PyExc_BytesWarning,
+                                "Comparison between bytearray and string", 1))
+                    return NULL;
+            }
         }
-
         Py_RETURN_NOTIMPLEMENTED;
     }