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GH-100762: Don't call `gen.throw()` in `gen.close()`, unless necessary. (GH-101013) 

* Store exception stack depth in YIELD_VALUE's oparg and use it avoid expensive gen.throw() in gen.close() where possible.
This commit is contained in:
Mark Shannon 2023-01-24 17:25:37 +00:00 committed by GitHub
parent daec3a463c
commit f02fa64bf2
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9 changed files with 39 additions and 12 deletions
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5
Doc/library/dis.rst
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@ -700,7 +700,10 @@ iterations of the loop.
Yields ``STACK.pop()`` from a :term:`generator`.
.. versionchanged:: 3.11
oparg set to be the stack depth, for efficient handling on frames.
oparg set to be the stack depth.
.. versionchanged:: 3.12
oparg set to be the exception block depth, for efficient closing of generators.
.. opcode:: SETUP_ANNOTATIONS

5
Lib/importlib/_bootstrap_external.py
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@ -429,7 +429,8 @@ _code_type = type(_write_atomic.__code__)
# Python 3.12a1 3513 (Add CALL_INTRINSIC_1 instruction, removed STOPITERATION_ERROR, PRINT_EXPR, IMPORT_STAR)
# Python 3.12a1 3514 (Remove ASYNC_GEN_WRAP, LIST_TO_TUPLE, and UNARY_POSITIVE)
# Python 3.12a1 3515 (Embed jump mask in COMPARE_OP oparg)
# Python 3.12a1 3516 (Add COMAPRE_AND_BRANCH instruction)
# Python 3.12a1 3516 (Add COMPARE_AND_BRANCH instruction)
# Python 3.12a1 3517 (Change YIELD_VALUE oparg to exception block depth)
# Python 3.13 will start with 3550
@ -442,7 +443,7 @@ _code_type = type(_write_atomic.__code__)
# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
# in PC/launcher.c must also be updated.
MAGIC_NUMBER = (3516).to_bytes(2, 'little') + b'\r\n'
MAGIC_NUMBER = (3517).to_bytes(2, 'little') + b'\r\n'
_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c

4
Lib/test/test_dis.py
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@ -492,7 +492,7 @@ dis_asyncwith = """\
GET_AWAITABLE 1
LOAD_CONST 0 (None)
>> SEND 3 (to 22)
YIELD_VALUE 3
YIELD_VALUE 2
RESUME 3
JUMP_BACKWARD_NO_INTERRUPT 4 (to 14)
>> POP_TOP
@ -526,7 +526,7 @@ dis_asyncwith = """\
GET_AWAITABLE 2
LOAD_CONST 0 (None)
>> SEND 4 (to 92)
YIELD_VALUE 6
YIELD_VALUE 3
RESUME 3
JUMP_BACKWARD_NO_INTERRUPT 4 (to 82)
>> CLEANUP_THROW

3
Misc/NEWS.d/next/Core and Builtins/2023-01-13-12-56-20.gh-issue-100762.YvHaQJ.rst Normal file
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@ -0,0 +1,3 @@
Record the (virtual) exception block depth in the oparg of
:opcode:`YIELD_VALUE`. Use this to avoid the expensive ``throw()`` when
closing generators (and coroutines) that can be closed trivially.

24
Objects/genobject.c
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@ -354,6 +354,13 @@ gen_close(PyGenObject *gen, PyObject *args)
PyObject *yf = _PyGen_yf(gen);
int err = 0;
if (gen->gi_frame_state == FRAME_CREATED) {
gen->gi_frame_state = FRAME_COMPLETED;
Py_RETURN_NONE;
}
if (gen->gi_frame_state >= FRAME_COMPLETED) {
Py_RETURN_NONE;
}
if (yf) {
PyFrameState state = gen->gi_frame_state;
gen->gi_frame_state = FRAME_EXECUTING;
@ -361,8 +368,23 @@ gen_close(PyGenObject *gen, PyObject *args)
gen->gi_frame_state = state;
Py_DECREF(yf);
}
if (err == 0)
_PyInterpreterFrame *frame = (_PyInterpreterFrame *)gen->gi_iframe;
/* It is possible for the previous instruction to not be a
* YIELD_VALUE if the debugger has changed the lineno. */
if (err == 0 && frame->prev_instr->opcode == YIELD_VALUE) {
assert(frame->prev_instr[1].opcode == RESUME);
int exception_handler_depth = frame->prev_instr->oparg;
assert(exception_handler_depth > 0);
/* We can safely ignore the outermost try block
* as it automatically generated to handle
* StopIteration. */
if (exception_handler_depth == 1) {
Py_RETURN_NONE;
}
}
if (err == 0) {
PyErr_SetNone(PyExc_GeneratorExit);
}
retval = gen_send_ex(gen, Py_None, 1, 1);
if (retval) {
const char *msg = "generator ignored GeneratorExit";

1
Python/bytecodes.c
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@ -720,7 +720,6 @@ dummy_func(
// NOTE: It's important that YIELD_VALUE never raises an exception!
// The compiler treats any exception raised here as a failed close()
// or throw() call.
assert(oparg == STACK_LEVEL());
assert(frame != &entry_frame);
PyGenObject *gen = _PyFrame_GetGenerator(frame);
gen->gi_frame_state = FRAME_SUSPENDED;

6
Python/compile.c
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@ -7162,9 +7162,6 @@ stackdepth(basicblock *entryblock, int code_flags)
next = NULL;
break;
}
if (instr->i_opcode == YIELD_VALUE) {
instr->i_oparg = depth;
}
}
if (next != NULL) {
assert(BB_HAS_FALLTHROUGH(b));
@ -7332,6 +7329,9 @@ label_exception_targets(basicblock *entryblock) {
}
}
else {
if (instr->i_opcode == YIELD_VALUE) {
instr->i_oparg = except_stack->depth;
}
instr->i_except = handler;
}
}

1
Python/generated_cases.c.h generated
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@ -919,7 +919,6 @@
// NOTE: It's important that YIELD_VALUE never raises an exception!
// The compiler treats any exception raised here as a failed close()
// or throw() call.
assert(oparg == STACK_LEVEL());
assert(frame != &entry_frame);
PyGenObject *gen = _PyFrame_GetGenerator(frame);
gen->gi_frame_state = FRAME_SUSPENDED;

2
Python/opcode_metadata.h
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@ -59,7 +59,7 @@ static const struct {
[GET_ANEXT] = { 1, 2, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[GET_AWAITABLE] = { 1, 1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[SEND] = { -1, -1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[YIELD_VALUE] = { 1, 1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[YIELD_VALUE] = { 1, 1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[POP_EXCEPT] = { 1, 0, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },
[RERAISE] = { -1, -1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IB },
[PREP_RERAISE_STAR] = { 2, 1, DIR_NONE, DIR_NONE, DIR_NONE, true, INSTR_FMT_IX },