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GH-132554: "Virtual" iterators (GH-132555)

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* FOR_ITER now pushes either the iterator and NULL or leaves the iterable and pushes tagged zero

* NEXT_ITER uses the tagged int as the index into the sequence or, if TOS is NULL, iterates as before.
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Mark Shannon 2025-05-27 15:59:45 +01:00 • committed by GitHub
parent 9300a596d3
commit f6f4e8a662
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25 changed files with 713 additions and 618 deletions
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78
Python/specialize.c
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@ -2904,53 +2904,57 @@ int
#endif // Py_STATS
Py_NO_INLINE void
_Py_Specialize_ForIter(_PyStackRef iter, _Py_CODEUNIT *instr, int oparg)
_Py_Specialize_ForIter(_PyStackRef iter, _PyStackRef null_or_index, _Py_CODEUNIT *instr, int oparg)
{
assert(ENABLE_SPECIALIZATION_FT);
assert(_PyOpcode_Caches[FOR_ITER] == INLINE_CACHE_ENTRIES_FOR_ITER);
PyObject *iter_o = PyStackRef_AsPyObjectBorrow(iter);
PyTypeObject *tp = Py_TYPE(iter_o);
if (PyStackRef_IsNull(null_or_index)) {
#ifdef Py_GIL_DISABLED
// Only specialize for uniquely referenced iterators, so that we know
// they're only referenced by this one thread. This is more limiting
// than we need (even `it = iter(mylist); for item in it:` won't get
// specialized) but we don't have a way to check whether we're the only
// _thread_ who has access to the object.
if (!_PyObject_IsUniquelyReferenced(iter_o))
goto failure;
#endif
if (tp == &PyListIter_Type) {
#ifdef Py_GIL_DISABLED
_PyListIterObject *it = (_PyListIterObject *)iter_o;
if (!_Py_IsOwnedByCurrentThread((PyObject *)it->it_seq) &&
!_PyObject_GC_IS_SHARED(it->it_seq)) {
// Maybe this should just set GC_IS_SHARED in a critical
// section, instead of leaving it to the first iteration?
// Only specialize for uniquely referenced iterators, so that we know
// they're only referenced by this one thread. This is more limiting
// than we need (even `it = iter(mylist); for item in it:` won't get
// specialized) but we don't have a way to check whether we're the only
// _thread_ who has access to the object.
if (!_PyObject_IsUniquelyReferenced(iter_o)) {
goto failure;
}
#endif
specialize(instr, FOR_ITER_LIST);
return;
if (tp == &PyRangeIter_Type) {
specialize(instr, FOR_ITER_RANGE);
return;
}
else if (tp == &PyGen_Type && oparg <= SHRT_MAX) {
// Generators are very much not thread-safe, so don't worry about
// the specialization not being thread-safe.
assert(instr[oparg + INLINE_CACHE_ENTRIES_FOR_ITER + 1].op.code == END_FOR ||
instr[oparg + INLINE_CACHE_ENTRIES_FOR_ITER + 1].op.code == INSTRUMENTED_END_FOR
);
/* Don't specialize if PEP 523 is active */
if (_PyInterpreterState_GET()->eval_frame) {
goto failure;
}
specialize(instr, FOR_ITER_GEN);
return;
}
}
else if (tp == &PyTupleIter_Type) {
specialize(instr, FOR_ITER_TUPLE);
return;
}
else if (tp == &PyRangeIter_Type) {
specialize(instr, FOR_ITER_RANGE);
return;
}
else if (tp == &PyGen_Type && oparg <= SHRT_MAX) {
// Generators are very much not thread-safe, so don't worry about
// the specialization not being thread-safe.
assert(instr[oparg + INLINE_CACHE_ENTRIES_FOR_ITER + 1].op.code == END_FOR ||
instr[oparg + INLINE_CACHE_ENTRIES_FOR_ITER + 1].op.code == INSTRUMENTED_END_FOR
);
/* Don't specialize if PEP 523 is active */
if (_PyInterpreterState_GET()->eval_frame)
goto failure;
specialize(instr, FOR_ITER_GEN);
return;
else {
if (tp == &PyList_Type) {
#ifdef Py_GIL_DISABLED
// Only specialize for lists owned by this thread or shared
if (!_Py_IsOwnedByCurrentThread(iter_o) && !_PyObject_GC_IS_SHARED(iter_o)) {
goto failure;
}
#endif
specialize(instr, FOR_ITER_LIST);
return;
}
else if (tp == &PyTuple_Type) {
specialize(instr, FOR_ITER_TUPLE);
return;
}
}
failure:
SPECIALIZATION_FAIL(FOR_ITER,