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GH-96793: Specialize FOR_ITER for generators.#98772

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Merged
markshannon merged 7 commits into from
Nov 7, 2022
Merged

GH-96793: Specialize FOR_ITER for generators. #98772

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3d229cc
Specialize FOR_ITER for generators.
markshannon Oct 27, 2022
d8e88b0
Add news
markshannon Oct 28, 2022
e16d82c
Merge branch 'main' into specialize-for-iter-gen
markshannon Nov 4, 2022
86aa1a8
Clean up after merge.
markshannon Nov 4, 2022
a677191
Add test for nested exc_info in loop.
markshannon Nov 7, 2022
8256be6
Handle exc stack.
markshannon Nov 7, 2022
8fb80ca
Use new API for current exception
markshannon Nov 7, 2022
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2 changes: 1 addition & 1 deletion Include/internal/pycore_code.h
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Expand Up@@ -230,7 +230,7 @@ extern void _Py_Specialize_CompareOp(PyObject *lhs, PyObject *rhs,
_Py_CODEUNIT *instr, int oparg);
extern void _Py_Specialize_UnpackSequence(PyObject *seq, _Py_CODEUNIT *instr,
int oparg);
extern void _Py_Specialize_ForIter(PyObject *iter, _Py_CODEUNIT *instr);
extern void _Py_Specialize_ForIter(PyObject *iter, _Py_CODEUNIT *instr, int oparg);

/* Finalizer function for static codeobjects used in deepfreeze.py */
extern void _PyStaticCode_Fini(PyCodeObject *co);
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2 changes: 2 additions & 0 deletions Include/internal/pycore_frame.h
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Expand Up@@ -61,6 +61,7 @@ typedef struct _PyInterpreterFrame{
// over, or (in the case of a newly-created frame) a totally invalid value:
_Py_CODEUNIT *prev_instr;
int stacktop; /* Offset of TOS from localsplus */
uint16_t yield_offset;
bool is_entry; // Whether this is the "root" frame for the current _PyCFrame.
char owner;
/* Locals and stack */
Expand DownExpand Up@@ -110,6 +111,7 @@ _PyFrame_InitializeSpecials(
frame->frame_obj = NULL;
frame->prev_instr = _PyCode_CODE(code) - 1;
frame->is_entry = false;
frame->yield_offset = 0;
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@iritkatrieliritkatrielNov 1, 2022

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Why is this called "yield_offset", is it not the relative offset to jump by when the generator is exhausted? (the same as the arg to FOR_ITER?)

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@markshannonmarkshannonNov 1, 2022

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Because it's the offset for YIELD_VALUE to return to relative to RETURN_VALUE
https://github.com/python/cpython/pull/98772/files#diff-c22186367cbe20233e843261998dc027ae5f1f8c0d2e778abfa454ae74cc59deR2087

frame->owner = FRAME_OWNED_BY_THREAD;
}

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24 changes: 12 additions & 12 deletions Include/internal/pycore_opcode.h
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63 changes: 32 additions & 31 deletions Include/opcode.h
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1 change: 1 addition & 0 deletions Lib/opcode.py
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Expand Up@@ -328,6 +328,7 @@ def pseudo_op(name, op, real_ops):
"FOR_ITER_ADAPTIVE",
"FOR_ITER_LIST",
"FOR_ITER_RANGE",
"FOR_ITER_GEN",
],
"LOAD_ATTR": [
"LOAD_ATTR_ADAPTIVE",
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20 changes: 20 additions & 0 deletions Lib/test/test_generators.py
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Expand Up@@ -306,6 +306,26 @@ def gen():
self.assertEqual(next(g), "done")
self.assertEqual(sys.exc_info(), (None, None, None))

def test_nested_gen_except_loop(self):
def gen():
for i in range(100):
self.assertIsInstance(sys.exception(), TypeError)
yield "doing"

def outer():
try:
raise TypeError
except:
for x in gen():
yield x

try:
raise ValueError
except Exception:
for x in outer():
self.assertEqual(x, "doing")
self.assertEqual(sys.exception(), None)

def test_except_throw_exception_context(self):
def gen():
try:
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-10-28-09-42-51.gh-issue-96793.ucBfWO.rst
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@@ -0,0 +1,3 @@
Add specialization of :opcode:`FOR_ITER` for generators. Saves multiple
layers of dispatch and checking to get from the :opcode:`FOR_ITER`
instruction in the caller to the :opcode:`RESUME` in the generator.
8 changes: 4 additions & 4 deletions Objects/genobject.c
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Expand Up@@ -209,7 +209,8 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,

frame->previous = tstate->cframe->current_frame;

gen->gi_exc_state.previous_item = tstate->exc_info;
_PyErr_StackItem *prev_exc_info = tstate->exc_info;
gen->gi_exc_state.previous_item = prev_exc_info;
tstate->exc_info = &gen->gi_exc_state;

if (exc){
Expand All@@ -220,12 +221,11 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
gen->gi_frame_state = FRAME_EXECUTING;
EVAL_CALL_STAT_INC(EVAL_CALL_GENERATOR);
result = _PyEval_EvalFrame(tstate, frame, exc);
assert(tstate->exc_info == prev_exc_info);
assert(gen->gi_exc_state.previous_item == NULL);
if (gen->gi_frame_state == FRAME_EXECUTING){
gen->gi_frame_state = FRAME_COMPLETED;
}
tstate->exc_info = gen->gi_exc_state.previous_item;
gen->gi_exc_state.previous_item = NULL;

assert(tstate->cframe->current_frame == frame->previous);
/* Don't keep the reference to previous any longer than necessary. It
* may keep a chain of frames alive or it could create a reference
Expand Down
44 changes: 40 additions & 4 deletions Python/bytecodes.c
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Expand Up@@ -779,6 +779,11 @@ dummy_func(
goto resume_frame;
}
_Py_LeaveRecursiveCallTstate(tstate);
if (frame->owner == FRAME_OWNED_BY_GENERATOR){
PyGenObject *gen = _PyFrame_GetGenerator(frame);
tstate->exc_info = gen->gi_exc_state.previous_item;
gen->gi_exc_state.previous_item = NULL;
}
/* Restore previous cframe and return. */
tstate->cframe = cframe.previous;
tstate->cframe->use_tracing = cframe.use_tracing;
Expand DownExpand Up@@ -919,7 +924,6 @@ dummy_func(

// error: SEND stack effect depends on jump flag
inst(SEND){
assert(frame->is_entry);
assert(STACK_LEVEL() >= 2);
PyObject *v = POP();
PyObject *receiver = TOP();
Expand DownExpand Up@@ -984,13 +988,21 @@ dummy_func(
// The compiler treats any exception raised here as a failed close()
// or throw() call.
assert(oparg == STACK_LEVEL());
assert(frame->is_entry);
PyObject *retval = POP();
_PyFrame_GetGenerator(frame)->gi_frame_state = FRAME_SUSPENDED;
PyGenObject *gen = _PyFrame_GetGenerator(frame);
gen->gi_frame_state = FRAME_SUSPENDED;
_PyFrame_SetStackPointer(frame, stack_pointer);
TRACE_FUNCTION_EXIT();
DTRACE_FUNCTION_EXIT();
tstate->exc_info = gen->gi_exc_state.previous_item;
gen->gi_exc_state.previous_item = NULL;
_Py_LeaveRecursiveCallPy(tstate);
if (!frame->is_entry){
frame = cframe.current_frame = frame->previous;
frame->prev_instr -= frame->yield_offset;
_PyFrame_StackPush(frame, retval);
goto resume_frame;
}
_Py_LeaveRecursiveCallTstate(tstate);
/* Restore previous cframe and return. */
tstate->cframe = cframe.previous;
Expand DownExpand Up@@ -2820,7 +2832,7 @@ dummy_func(
_PyForIterCache *cache = (_PyForIterCache *)next_instr;
if (ADAPTIVE_COUNTER_IS_ZERO(cache)){
next_instr--;
_Py_Specialize_ForIter(TOP(), next_instr);
_Py_Specialize_ForIter(TOP(), next_instr, oparg);
DISPATCH_SAME_OPARG();
}
else{
Expand DownExpand Up@@ -2876,6 +2888,30 @@ dummy_func(
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + 1);
}

inst(FOR_ITER_GEN){
assert(cframe.use_tracing == 0);
PyGenObject *gen = (PyGenObject *)TOP();
DEOPT_IF(Py_TYPE(gen) != &PyGen_Type, FOR_ITER);
DEOPT_IF(gen->gi_frame_state >= FRAME_EXECUTING, FOR_ITER);
STAT_INC(FOR_ITER, hit);
_PyInterpreterFrame *gen_frame = (_PyInterpreterFrame *)gen->gi_iframe;
_PyFrame_SetStackPointer(frame, stack_pointer);
frame->yield_offset = oparg;
JUMPBY(INLINE_CACHE_ENTRIES_FOR_ITER + oparg);
assert(_Py_OPCODE(*next_instr) == END_FOR);
frame->prev_instr = next_instr - 1;
Py_INCREF(Py_None);
_PyFrame_StackPush(gen_frame, Py_None);
gen->gi_frame_state = FRAME_EXECUTING;
gen->gi_exc_state.previous_item = tstate->exc_info;
tstate->exc_info = &gen->gi_exc_state;
gen_frame->previous = frame;
gen_frame->is_entry = false;
frame = cframe.current_frame = gen_frame;
goto start_frame;
}


// stack effect: ( -- __0)
inst(BEFORE_ASYNC_WITH){
PyObject *mgr = TOP();
Expand Down
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