bpo-24076: Inline single digit unpacking in the integer fastpath of s… · python/cpython@debd804 (original) (raw)

File tree

2 files changed

lines changed

Misc/NEWS.d/next/Core and Builtins

2 files changed

lines changed

Original file line number	Diff line number	Diff line change
@@ -0,0 +1 @@
	1	+sum() was further optimised for summing up single digit integers.

Original file line number	Diff line number	Diff line change
@@ -2479,7 +2479,15 @@ builtin_sum_impl(PyObject module, PyObject iterable, PyObject *start)
2479	2479	return PyLong_FromLong(i_result);
2480	2480	}
2481	2481	if (PyLong_CheckExact(item) \|
2482		-long b = PyLong_AsLongAndOverflow(item, &overflow);
	2482	+long b;
	2483	+overflow = 0;
	2484	+/* Single digits are common, fast, and cannot overflow on unpacking. */
	2485	+switch (Py_SIZE(item)) {
	2486	+case -1: b = -(sdigit) ((PyLongObject*)item)->ob_digit[0]; break;
	2487	+case 0: continue;
	2488	+case 1: b = ((PyLongObject*)item)->ob_digit[0]; break;
	2489	+default: b = PyLong_AsLongAndOverflow(item, &overflow); break;
	2490	+ }
2483	2491	if (overflow == 0 &&
2484	2492	(i_result >= 0 ? (b <= LONG_MAX - i_result)
2485	2493	: (b >= LONG_MIN - i_result)))