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gh-153486: Factor non-negative compact int subscript guards #153487

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9a4d55e
gh-153486: Factor non-negative compact int subscript guards
KRRT7 Jul 10, 2026
12c8513
gh-153486: Add NEWS entry
KRRT7 Jul 10, 2026
7b711cc
gh-153486: Specialize negative list int subscripts
KRRT7 Jul 10, 2026
ea05f8d
Merge branch 'main' into list-int-compact-guard-main
KRRT7 Jul 10, 2026
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8 changes: 4 additions & 4 deletions Include/internal/pycore_opcode_metadata.h
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9 changes: 7 additions & 2 deletions Include/internal/pycore_uop_ids.h
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21 changes: 21 additions & 0 deletions Include/internal/pycore_uop_metadata.h
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2 changes: 2 additions & 0 deletions ...t/Core_and_Builtins/2026-07-10-10-05-00.gh-issue-153486.compact-index-guard.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve optimized handling of non-negative integer indices for lists,
tuples, and strings.
56 changes: 29 additions & 27 deletions Modules/_testinternalcapi/test_cases.c.h
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31 changes: 17 additions & 14 deletions Python/bytecodes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1134,7 +1134,8 @@ dummy_func(
macro(STORE_SLICE) = _SPECIALIZE_STORE_SLICE + _STORE_SLICE;

macro(BINARY_OP_SUBSCR_LIST_INT) =
_GUARD_TOS_INT + _GUARD_NOS_LIST + unused/5 + _BINARY_OP_SUBSCR_LIST_INT + _POP_TOP_INT + POP_TOP;
_GUARD_TOS_INT + _GUARD_NOS_LIST + unused/5 +
_BINARY_OP_SUBSCR_LIST_INT + _POP_TOP_INT + POP_TOP;

op(_BINARY_OP_SUBSCR_LIST_INT, (list_st, sub_st -- res, ls, ss)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
Expand Down Expand Up @@ -1185,15 +1186,15 @@ dummy_func(
}

macro(BINARY_OP_SUBSCR_STR_INT) =
_GUARD_TOS_INT + _GUARD_NOS_COMPACT_ASCII + unused/5 + _BINARY_OP_SUBSCR_STR_INT + _POP_TOP_INT + _POP_TOP_UNICODE;
_GUARD_TOS_NON_NEGATIVE_COMPACT_INT + _GUARD_NOS_COMPACT_ASCII +
unused/5 + _BINARY_OP_SUBSCR_STR_INT + _POP_TOP_INT + _POP_TOP_UNICODE;

op(_BINARY_OP_SUBSCR_STR_INT, (str_st, sub_st -- res, s, i)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
PyObject *str = PyStackRef_AsPyObjectBorrow(str_st);

assert(PyLong_CheckExact(sub));
assert(PyUnicode_CheckExact(str));
EXIT_IF(!_PyLong_IsNonNegativeCompact((PyLongObject*)sub));
Py_ssize_t index = ((PyLongObject*)sub)->long_value.ob_digit[0];
EXIT_IF(PyUnicode_GET_LENGTH(str) <= index);
uint8_t c = PyUnicode_1BYTE_DATA(str)[index];
Expand All @@ -1207,15 +1208,15 @@ dummy_func(
}

macro(BINARY_OP_SUBSCR_USTR_INT) =
_GUARD_TOS_INT + _GUARD_NOS_UNICODE + unused/5 + _BINARY_OP_SUBSCR_USTR_INT + _POP_TOP_INT + _POP_TOP_UNICODE;
_GUARD_TOS_NON_NEGATIVE_COMPACT_INT + _GUARD_NOS_UNICODE +
unused/5 + _BINARY_OP_SUBSCR_USTR_INT + _POP_TOP_INT + _POP_TOP_UNICODE;

op(_BINARY_OP_SUBSCR_USTR_INT, (str_st, sub_st -- res, s, i)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
PyObject *str = PyStackRef_AsPyObjectBorrow(str_st);

assert(PyLong_CheckExact(sub));
assert(PyUnicode_CheckExact(str));
EXIT_IF(!_PyLong_IsNonNegativeCompact((PyLongObject*)sub));
Py_ssize_t index = ((PyLongObject*)sub)->long_value.ob_digit[0];
EXIT_IF(PyUnicode_GET_LENGTH(str) <= index);
// Specialize for reading an ASCII character from any string:
Expand All @@ -1240,7 +1241,7 @@ dummy_func(
}

macro(BINARY_OP_SUBSCR_TUPLE_INT) =
_GUARD_TOS_INT +
_GUARD_TOS_NON_NEGATIVE_COMPACT_INT +
_GUARD_NOS_TUPLE +
_GUARD_BINARY_OP_SUBSCR_TUPLE_INT_BOUNDS +
unused/5 +
Expand All @@ -1256,8 +1257,7 @@ dummy_func(
assert(PyLong_CheckExact(sub));
assert(PyTuple_CheckExact(tuple));

// Deopt unless 0 <= sub < PyTuple_Size(list)
EXIT_IF(!_PyLong_IsNonNegativeCompact((PyLongObject *)sub));
// Deopt unless sub < PyTuple_Size(list)
Py_ssize_t index = ((PyLongObject*)sub)->long_value.ob_digit[0];
EXIT_IF(index >= PyTuple_GET_SIZE(tuple));
}
Expand Down Expand Up @@ -1411,8 +1411,15 @@ dummy_func(

macro(STORE_SUBSCR) = _SPECIALIZE_STORE_SUBSCR + _STORE_SUBSCR;

op(_GUARD_TOS_NON_NEGATIVE_COMPACT_INT, (value -- value)) {
PyObject *value_o = PyStackRef_AsPyObjectBorrow(value);
EXIT_IF(!PyLong_CheckExact(value_o));
EXIT_IF(!_PyLong_IsNonNegativeCompact((PyLongObject *)value_o));
}

macro(STORE_SUBSCR_LIST_INT) =
_GUARD_TOS_INT + _GUARD_NOS_LIST + unused/1 + _STORE_SUBSCR_LIST_INT + _POP_TOP_INT + POP_TOP;
_GUARD_TOS_NON_NEGATIVE_COMPACT_INT + _GUARD_NOS_LIST +
unused/1 + _STORE_SUBSCR_LIST_INT + _POP_TOP_INT + POP_TOP;

op(_STORE_SUBSCR_LIST_INT, (value, list_st, sub_st -- ls, ss)) {
PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
Expand All @@ -1424,11 +1431,7 @@ dummy_func(
Py_ssize_t index = _PyLong_CompactValue((PyLongObject *)sub);
DEOPT_IF(!LOCK_OBJECT(list));
Py_ssize_t len = PyList_GET_SIZE(list);
// Ensure index < len(list)
if (index < 0) {
index += len;
}
if (index < 0 || index >= len) {
if (index >= len) {
UNLOCK_OBJECT(list);
DEOPT_IF(true);
}
Expand Down
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