optimise built-in callable() function

Cython/Compiler/Builtin.py

@@ -333,6 +333,8 @@ builtin_function_table = [
                             ],
                         is_strict_signature = True)),
     BuiltinFunction('abs',        "O",    "O",     "PyNumber_Absolute"),
+    BuiltinFunction('callable',   "O",    "b",     "__Pyx_PyCallable_Check",
+                    utility_code = UtilityCode.load_cached("CallableCheck", "ObjectHandling.c")),
     #('chr',       "",     "",      ""),
     #('cmp', "",   "",     "",      ""), # int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
     #('compile',   "",     "",      ""), # PyObject* Py_CompileString(    char *str, char *filename, int start)

Cython/Utility/ObjectHandling.c

@@ -432,3 +432,11 @@ static CYTHON_INLINE int __Pyx_TypeTest(PyObject *obj, PyTypeObject *type) {
                  Py_TYPE(obj)->tp_name, type->tp_name);
     return 0;
 }
+
+/////////////// CallableCheck.proto ///////////////
+
+#if CYTHON_COMPILING_IN_CPYTHON
+#define __Pyx_PyCallable_Check(obj)   ((obj)->ob_type->tp_call != NULL)
+#else
+#define __Pyx_PyCallable_Check(obj)   PyCallable_Check(obj)
+#endif

tests/run/builtin_callable.pyx

+# mode: run
+# tag: builtin, callable
+
+cimport cython
+
+@cython.test_assert_path_exists("//SimpleCallNode[@type.is_pyobject = False]")
+def test_callable(x):
+    """
+    >>> test_callable(None)
+    False
+    >>> test_callable('ABC')
+    False
+    >>> test_callable(int)
+    True
+    >>> test_callable(test_callable)
+    True
+    """
+    b = callable(x)
+    return b