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gh-131798: Remove bounds check when indexing into tuples with a constant index (#137607)

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* Remove bounds check when indexing into tuples with a constant index

* Add news entry

* fixup after rebase
This commit is contained in:
Tomas R. 2025-12-28 22:06:06 +01:00 • committed by GitHub
parent c3febba73b
commit 713684de53
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10 changed files with 1232 additions and 940 deletions
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21
Python/bytecodes.c
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@ -968,9 +968,16 @@ dummy_func(
}
macro(BINARY_OP_SUBSCR_TUPLE_INT) =
_GUARD_TOS_INT + _GUARD_NOS_TUPLE + unused/5 + _BINARY_OP_SUBSCR_TUPLE_INT + _POP_TOP_INT + POP_TOP;
_GUARD_TOS_INT +
_GUARD_NOS_TUPLE +
_GUARD_BINARY_OP_SUBSCR_TUPLE_INT_BOUNDS +
unused/5 +
_BINARY_OP_SUBSCR_TUPLE_INT +
_POP_TOP_INT +
POP_TOP;
op(_BINARY_OP_SUBSCR_TUPLE_INT, (tuple_st, sub_st -- res, ts, ss)) {
// A guard that checks that the tuple subscript is within bounds
op(_GUARD_BINARY_OP_SUBSCR_TUPLE_INT_BOUNDS, (tuple_st, sub_st -- tuple_st, sub_st)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
PyObject *tuple = PyStackRef_AsPyObjectBorrow(tuple_st);
@ -981,7 +988,17 @@ dummy_func(
DEOPT_IF(!_PyLong_IsNonNegativeCompact((PyLongObject *)sub));
Py_ssize_t index = ((PyLongObject*)sub)->long_value.ob_digit[0];
DEOPT_IF(index >= PyTuple_GET_SIZE(tuple));
}
op(_BINARY_OP_SUBSCR_TUPLE_INT, (tuple_st, sub_st -- res, ts, ss)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
PyObject *tuple = PyStackRef_AsPyObjectBorrow(tuple_st);
assert(PyLong_CheckExact(sub));
assert(PyTuple_CheckExact(tuple));
STAT_INC(BINARY_OP, hit);
Py_ssize_t index = ((PyLongObject*)sub)->long_value.ob_digit[0];
PyObject *res_o = PyTuple_GET_ITEM(tuple, index);
assert(res_o != NULL);
res = PyStackRef_FromPyObjectNew(res_o);