8000 GH-131798: Narrow the return type of _GET_LEN to int (GH-133345) · python/cpython@e1c0c45 · GitHub
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GH-131798: Narrow the return type of _GET_LEN to int (GH-133345)
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‎Lib/test/test_capi/test_opt.py

Lines changed: 44 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1925,6 +1925,50 @@ def testfunc(n):
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self.assertNotIn("_GUARD_NOS_INT", uops)
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self.assertNotIn("_GUARD_TOS_INT", uops)
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1928+
def test_get_len_with_const_tuple(self):
1929+
def testfunc(n):
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x = 0.0
1931+
for _ in range(n):
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match (1, 2, 3, 4):
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case [_, _, _, _]:
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x += 1.0
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return x
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res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
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self.assertEqual(int(res), TIER2_THRESHOLD)
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uops = get_opnames(ex)
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self.assertNotIn("_GUARD_NOS_INT", uops)
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self.assertNotIn("_GET_LEN", uops)
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self.assertIn("_LOAD_CONST_INLINE_BORROW", uops)
1942+
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def test_get_len_with_non_const_tuple(self):
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def testfunc(n):
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x = 0.0
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for _ in range(n):
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match object(), object():
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case [_, _]:
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x += 1.0
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return x
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res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
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self.assertEqual(int(res), TIER2_THRESHOLD)
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uops = get_opnames(ex)
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self.assertNotIn("_GUARD_NOS_INT", uops)
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self.assertNotIn("_GET_LEN", uops)
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self.assertIn("_LOAD_CONST_INLINE_BORROW", uops)
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1958+
def test_get_len_with_non_tuple(self):
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def testfunc(n):
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x = 0.0
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for _ in range(n):
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match [1, 2, 3, 4]:
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case [_, _, _, _]:
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x += 1.0
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return x
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res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
1967+
self.assertEqual(int(res), TIER2_THRESHOLD)
1968+
uops = get_opnames(ex)
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self.assertNotIn("_GUARD_NOS_INT", uops)
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self.assertIn("_GET_LEN", uops)
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19281972
def test_binary_op_subscr_tuple_int(self):
19291973
def testfunc(n):
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x = 0

‎Misc/NEWS.d/next/Core_and_Builtins/2025-05-03-22-31-53.gh-issue-131798.fQ0ato.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
1+
Allow the JIT to remove int guards after ``_GET_LEN`` by setting the return
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type to int.

‎Python/optimizer_bytecodes.c

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1116,6 +1116,25 @@ dummy_func(void) {
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res = sym_new_type(ctx, &PyLong_Type);
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}
11181118

1119+
op(_GET_LEN, (obj -- obj, len)) {
1120+
int tuple_length = sym_tuple_length(obj);
1121+
if (tuple_length == -1) {
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len = sym_new_type(ctx, &PyLong_Type);
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}
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else {
1125+
assert(tuple_length >= 0);
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PyObject *temp = PyLong_FromLong(tuple_length);
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if (temp == NULL) {
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goto error;
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}
1130+
if (_Py_IsImmortal(temp)) {
1131+
REPLACE_OP(this_instr, _LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)temp);
1132+
}
1133+
len = sym_new_const(ctx, temp);
1134+
Py_DECREF(temp);
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}
1136+
}
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11191138
op(_GUARD_CALLABLE_LEN, (callable, unused, unused -- callable, unused, unused)) {
11201139
PyObject *len = _PyInterpreterState_GET()->callable_cache.len;
11211140
if (sym_get_const(ctx, callable) == len) {

‎Python/optimizer_cases.c.h

Lines changed: 22 additions & 1 deletion
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