bpo-37207: Use PEP 590 vectorcall to speed up tuple() (GH-18936)

Master: ./python.exe -m pyperf timeit "tuple((1, 2, 3, 4, 5))" Mean +- std dev: 361 ns +- 15 ns PEP-590: ./python.exe -m pyperf timeit "tuple((1, 2, 3, 4, 5))" Mean +- std dev: 203 ns +- 13 ns

Author: corona10

Misc/NEWS.d/next/Core and Builtins/2020-03-12-02-41-12.bpo-37207.ye7OM3.rst

@@ -0,0 +1,2 @@
+Speed up calls to ``tuple()`` by using the :pep:`590` ``vectorcall`` calling
+convention. Patch by Dong-hee Na.

Objects/tupleobject.c

@@ -705,6 +705,26 @@ tuple_new_impl(PyTypeObject *type, PyObject *iterable)
  return PySequence_Tuple(iterable);
 }
 
+static PyObject *
+tuple_vectorcall(PyObject *type, PyObject * const*args,
+ size_t nargsf, PyObject *kwnames)
+{
+ if (kwnames && PyTuple_GET_SIZE(kwnames) != 0) {
+ PyErr_Format(PyExc_TypeError, "tuple() takes no keyword arguments");
+ return NULL;
+ }
+ Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
+ if (nargs > 1) {
+ PyErr_Format(PyExc_TypeError, "tuple() expected at most 1 argument, got %zd", nargs);
+ return NULL;
+ }
+
+ if (nargs) {
+ return tuple_new_impl((PyTypeObject *)type, args[0]);
+ }
+ return PyTuple_New(0);
+}
+
 static PyObject *
 tuple_subtype_new(PyTypeObject *type, PyObject *iterable)
 {
@@ -863,6 +883,7 @@ PyTypeObject PyTuple_Type = {
  0, /* tp_alloc */
  tuple_new, /* tp_new */
  PyObject_GC_Del, /* tp_free */
+ .tp_vectorcall = tuple_vectorcall,
 };
 
 /* The following function breaks the notion that tuples are immutable: