Skip to content

gh-98831: Modernize the FOR_ITER family of instructions#101626

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
gvanrossum merged 7 commits into from
Feb 7, 2023
Merged

gh-98831: Modernize the FOR_ITER family of instructions #101626

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
5869fba
Modernize FOR_ITER
gvanrossum Feb 6, 2023
bd65e1c
Modernize FOR_ITER_LIST
gvanrossum Feb 6, 2023
872e156
Modernize FOR_ITER_TUPLE
gvanrossum Feb 6, 2023
a52a79d
Modernize FOR_ITER_RANGE (even weirder)
gvanrossum Feb 7, 2023
53cfd22
Modernize FOR_ITER_GEN
gvanrossum Feb 7, 2023
76a4a7b
Accept comment suggestion
gvanrossum Feb 7, 2023
b39cf90
Update generated file
gvanrossum Feb 7, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
83 changes: 47 additions & 36 deletions Python/bytecodes.c
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -2066,27 +2066,35 @@ dummy_func(
PREDICT(LOAD_CONST);
}

// stack effect: ( -- __0)
inst(FOR_ITER) {
// Most members of this family are "secretly" super-instructions.
// When the loop is exhausted, they jump, and the jump target is
// always END_FOR, which pops two values off the stack.
// This is optimized by skipping that instruction and combining
// its effect (popping 'iter' instead of pushing 'next'.)

family(for_iter, INLINE_CACHE_ENTRIES_FOR_ITER) = {
FOR_ITER,
FOR_ITER_LIST,
FOR_ITER_TUPLE,
FOR_ITER_RANGE,
FOR_ITER_GEN,
};

inst(FOR_ITER, (unused/1, iter -- iter, next)) {

@iritkatrieliritkatrielFeb 7, 2023

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should this be counter/1 instead of unused/1, and then the counter used in the body?

@gvanrossumgvanrossumFeb 7, 2023

Copy link
Copy Markdown
MemberAuthor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

In all cases where the counter is manipulated using ADAPTIVE_COUNTER_IS_ZERO / DECREMENT_ADAPTIVE_COUNTER I'm leaving this idiom unchanged -- the generator won't let you write back to cache entries, so it would become asymmetrical, and the common case is DECREMENT_ADAPTIVE_COUNTER anyway.

#if ENABLE_SPECIALIZATION
_PyForIterCache *cache = (_PyForIterCache *)next_instr;
if (ADAPTIVE_COUNTER_IS_ZERO(cache->counter)) {
assert(cframe.use_tracing == 0);
next_instr--;
_Py_Specialize_ForIter(TOP(), next_instr, oparg);
_Py_Specialize_ForIter(iter, next_instr, oparg);
DISPATCH_SAME_OPARG();
}
STAT_INC(FOR_ITER, deferred);
DECREMENT_ADAPTIVE_COUNTER(cache->counter);
#endif /* ENABLE_SPECIALIZATION */
/* before: [iter]; after: [iter, iter()] *or* [] */
PyObject *iter = TOP();
PyObject *next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next != NULL) {
PUSH(next);
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER);
}
else {
/* before: [iter]; after: [iter, iter()] *or* [] (and jump over END_FOR.) */
next = (*Py_TYPE(iter)->tp_iternext)(iter);
if (next == NULL) {
if (_PyErr_Occurred(tstate)) {
if (!_PyErr_ExceptionMatches(tstate, PyExc_StopIteration)) {
goto error;
Expand All@@ -2098,70 +2106,74 @@ dummy_func(
}
/* iterator ended normally */
assert(_Py_OPCODE(next_instr[INLINE_CACHE_ENTRIES_FOR_ITER + oparg]) == END_FOR);
STACK_SHRINK(1);
Py_DECREF(iter);
/* Skip END_FOR */
STACK_SHRINK(1);
/* Jump forward oparg, then skip following END_FOR instruction */
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1);
DISPATCH();
}
// Common case: no jump, leave it to the code generator
}

// stack effect: ( -- __0)
inst(FOR_ITER_LIST) {
inst(FOR_ITER_LIST, (unused/1, iter -- iter, next)) {
assert(cframe.use_tracing == 0);
_PyListIterObject *it = (_PyListIterObject *)TOP();
DEOPT_IF(Py_TYPE(it) != &PyListIter_Type, FOR_ITER);
DEOPT_IF(Py_TYPE(iter) != &PyListIter_Type, FOR_ITER);
_PyListIterObject *it = (_PyListIterObject *)iter;
STAT_INC(FOR_ITER, hit);
PyListObject *seq = it->it_seq;
if (seq) {
if (it->it_index < PyList_GET_SIZE(seq)) {
PyObject *next = PyList_GET_ITEM(seq, it->it_index++);
PUSH(Py_NewRef(next));
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER);
next = Py_NewRef(PyList_GET_ITEM(seq, it->it_index++));
goto end_for_iter_list; // End of this instruction
}
it->it_seq = NULL;
Py_DECREF(seq);
}
Py_DECREF(iter);
STACK_SHRINK(1);
Py_DECREF(it);
/* Jump forward oparg, then skip following END_FOR instruction */
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1);
DISPATCH();
end_for_iter_list:
// Common case: no jump, leave it to the code generator
}

// stack effect: ( -- __0)
inst(FOR_ITER_TUPLE) {
inst(FOR_ITER_TUPLE, (unused/1, iter -- iter, next)) {
assert(cframe.use_tracing == 0);
_PyTupleIterObject *it = (_PyTupleIterObject *)TOP();
_PyTupleIterObject *it = (_PyTupleIterObject *)iter;
DEOPT_IF(Py_TYPE(it) != &PyTupleIter_Type, FOR_ITER);
STAT_INC(FOR_ITER, hit);
PyTupleObject *seq = it->it_seq;
if (seq) {
if (it->it_index < PyTuple_GET_SIZE(seq)) {
PyObject *next = PyTuple_GET_ITEM(seq, it->it_index++);
PUSH(Py_NewRef(next));
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER);
next = Py_NewRef(PyTuple_GET_ITEM(seq, it->it_index++));
goto end_for_iter_tuple; // End of this instruction
}
it->it_seq = NULL;
Py_DECREF(seq);
}
Py_DECREF(iter);
STACK_SHRINK(1);
Py_DECREF(it);
/* Jump forward oparg, then skip following END_FOR instruction */
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1);
DISPATCH();
end_for_iter_tuple:
// Common case: no jump, leave it to the code generator
}

// stack effect: ( -- __0)
inst(FOR_ITER_RANGE) {
// This is slightly different, when the loop isn't terminated we
// jump over the immediately following STORE_FAST instruction.
inst(FOR_ITER_RANGE, (unused/1, iter -- iter, unused)) {
assert(cframe.use_tracing == 0);
_PyRangeIterObject *r = (_PyRangeIterObject *)TOP();
_PyRangeIterObject *r = (_PyRangeIterObject *)iter;
DEOPT_IF(Py_TYPE(r) != &PyRangeIter_Type, FOR_ITER);
STAT_INC(FOR_ITER, hit);
_Py_CODEUNIT next = next_instr[INLINE_CACHE_ENTRIES_FOR_ITER];
assert(_PyOpcode_Deopt[_Py_OPCODE(next)] == STORE_FAST);
if (r->len <= 0) {
STACK_SHRINK(1);
Py_DECREF(r);
// Jump over END_FOR instruction.
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + oparg + 1);
}
else {
Expand All@@ -2174,11 +2186,13 @@ dummy_func(
// The STORE_FAST is already done.
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + 1);
}
DISPATCH();
}

inst(FOR_ITER_GEN) {
// This is *not* a super-instruction, unique in the family.
inst(FOR_ITER_GEN, (unused/1, iter -- iter, unused)) {
assert(cframe.use_tracing == 0);
PyGenObject *gen = (PyGenObject *)TOP();
PyGenObject *gen = (PyGenObject *)iter;
DEOPT_IF(Py_TYPE(gen) != &PyGen_Type, FOR_ITER);
DEOPT_IF(gen->gi_frame_state >= FRAME_EXECUTING, FOR_ITER);
STAT_INC(FOR_ITER, hit);
Expand DownExpand Up@@ -3173,9 +3187,6 @@ family(call, INLINE_CACHE_ENTRIES_CALL) = {
CALL_NO_KW_LIST_APPEND, CALL_NO_KW_METHOD_DESCRIPTOR_FAST, CALL_NO_KW_METHOD_DESCRIPTOR_NOARGS,
CALL_NO_KW_METHOD_DESCRIPTOR_O, CALL_NO_KW_STR_1, CALL_NO_KW_TUPLE_1,
CALL_NO_KW_TYPE_1 };
family(for_iter, INLINE_CACHE_ENTRIES_FOR_ITER) = {
FOR_ITER, FOR_ITER_LIST,
FOR_ITER_RANGE };
family(store_fast) = { STORE_FAST, STORE_FAST__LOAD_FAST, STORE_FAST__STORE_FAST };
family(unpack_sequence, INLINE_CACHE_ENTRIES_UNPACK_SEQUENCE) = {
UNPACK_SEQUENCE, UNPACK_SEQUENCE_LIST,
Expand Down
66 changes: 42 additions & 24 deletions Python/generated_cases.c.h
View file
Open in desktop

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

30 changes: 15 additions & 15 deletions Python/opcode_metadata.h
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -261,15 +261,15 @@ _PyOpcode_num_popped(int opcode, int oparg, bool jump) {
case GET_YIELD_FROM_ITER:
return 1;
case FOR_ITER:
return -1;
return 1;
case FOR_ITER_LIST:
return -1;
return 1;
case FOR_ITER_TUPLE:
return -1;
return 1;
case FOR_ITER_RANGE:
return -1;
return 1;
case FOR_ITER_GEN:
return -1;
return 1;
case BEFORE_ASYNC_WITH:
return 1;
case BEFORE_WITH:
Expand DownExpand Up@@ -607,15 +607,15 @@ _PyOpcode_num_pushed(int opcode, int oparg, bool jump) {
case GET_YIELD_FROM_ITER:
return 1;
case FOR_ITER:
return -1;
return 2;
case FOR_ITER_LIST:
return -1;
return 2;
case FOR_ITER_TUPLE:
return -1;
return 2;
case FOR_ITER_RANGE:
return -1;
return 2;
case FOR_ITER_GEN:
return -1;
return 2;
case BEFORE_ASYNC_WITH:
return 2;
case BEFORE_WITH:
Expand DownExpand Up@@ -829,11 +829,11 @@ struct opcode_metadata {
[MATCH_KEYS] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[GET_ITER] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[GET_YIELD_FROM_ITER] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[FOR_ITER] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[FOR_ITER_LIST] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[FOR_ITER_TUPLE] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[FOR_ITER_RANGE] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[FOR_ITER_GEN] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[FOR_ITER] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IBC },
[FOR_ITER_LIST] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IBC },
[FOR_ITER_TUPLE] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IBC },
[FOR_ITER_RANGE] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IBC },
[FOR_ITER_GEN] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IBC },
[BEFORE_ASYNC_WITH] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[BEFORE_WITH] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[WITH_EXCEPT_START] = { DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
Expand Down