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GH-93621: reorder code in with/async-with exception exit path to reduce the size of the exception table (GH-93622)
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3 files changed

+173
-15
lines changed

3 files changed

+173
-15
lines changed

‎Lib/test/test_dis.py

+159-8
Original file line numberDiff line numberDiff line change
@@ -389,6 +389,7 @@ def bug42562():
389389
POP_EXCEPT
390390
RERAISE 1
391391
ExceptionTable:
392+
4 rows
392393
""" % (TRACEBACK_CODE.co_firstlineno,
393394
TRACEBACK_CODE.co_firstlineno + 1,
394395
TRACEBACK_CODE.co_firstlineno + 2,
@@ -421,6 +422,133 @@ def _fstring(a, b, c, d):
421422
RETURN_VALUE
422423
""" % (_fstring.__code__.co_firstlineno, _fstring.__code__.co_firstlineno + 1)
423424

425+
def _with(c):
426+
with c:
427+
x = 1
428+
y = 2
429+
430+
dis_with = """\
431+
%3d RESUME 0
432+
433+
%3d LOAD_FAST 0 (c)
434+
BEFORE_WITH
435+
POP_TOP
436+
437+
%3d LOAD_CONST 1 (1)
438+
STORE_FAST 1 (x)
439+
440+
%3d LOAD_CONST 0 (None)
441+
LOAD_CONST 0 (None)
442+
LOAD_CONST 0 (None)
443+
CALL 2
444+
POP_TOP
445+
446+
%3d LOAD_CONST 2 (2)
447+
STORE_FAST 2 (y)
448+
LOAD_CONST 0 (None)
449+
RETURN_VALUE
450+
451+
%3d >> PUSH_EXC_INFO
452+
WITH_EXCEPT_START
453+
POP_JUMP_FORWARD_IF_TRUE 1 (to 46)
454+
RERAISE 2
455+
>> POP_TOP
456+
POP_EXCEPT
457+
POP_TOP
458+
POP_TOP
459+
460+
%3d LOAD_CONST 2 (2)
461+
STORE_FAST 2 (y)
462+
LOAD_CONST 0 (None)
463+
RETURN_VALUE
464+
>> COPY 3
465+
POP_EXCEPT
466+
RERAISE 1
467+
ExceptionTable:
468+
2 rows
469+
""" % (_with.__code__.co_firstlineno,
470+
_with.__code__.co_firstlineno + 1,
471+
_with.__code__.co_firstlineno + 2,
472+
_with.__code__.co_firstlineno + 1,
473+
_with.__code__.co_firstlineno + 3,
474+
_with.__code__.co_firstlineno + 1,
475+
_with.__code__.co_firstlineno + 3,
476+
)
477+
478+
async def _asyncwith(c):
479+
async with c:
480+
x = 1
481+
y = 2
482+
483+
dis_asyncwith = """\
484+
%3d RETURN_GENERATOR
485+
POP_TOP
486+
RESUME 0
487+
488+
%3d LOAD_FAST 0 (c)
489+
BEFORE_ASYNC_WITH
490+
GET_AWAITABLE 1
491+
LOAD_CONST 0 (None)
492+
>> SEND 3 (to 22)
493+
YIELD_VALUE 3
494+
RESUME 3
495+
JUMP_BACKWARD_NO_INTERRUPT 4 (to 14)
496+
>> POP_TOP
497+
498+
%3d LOAD_CONST 1 (1)
499+
STORE_FAST 1 (x)
500+
501+
%3d LOAD_CONST 0 (None)
502+
LOAD_CONST 0 (None)
503+
LOAD_CONST 0 (None)
504+
CALL 2
505+
GET_AWAITABLE 2
506+
LOAD_CONST 0 (None)
507+
>> SEND 3 (to 56)
508+
YIELD_VALUE 2
509+
RESUME 3
510+
JUMP_BACKWARD_NO_INTERRUPT 4 (to 48)
511+
>> POP_TOP
512+
513+
%3d LOAD_CONST 2 (2)
514+
STORE_FAST 2 (y)
515+
LOAD_CONST 0 (None)
516+
RETURN_VALUE
517+
518+
%3d >> PUSH_EXC_INFO
519+
WITH_EXCEPT_START
520+
GET_AWAITABLE 2
521+
LOAD_CONST 0 (None)
522+
>> SEND 3 (to 82)
523+
YIELD_VALUE 6
524+
RESUME 3
525+
JUMP_BACKWARD_NO_INTERRUPT 4 (to 74)
526+
>> POP_JUMP_FORWARD_IF_TRUE 1 (to 86)
527+
RERAISE 2
528+
>> POP_TOP
529+
POP_EXCEPT
530+
POP_TOP
531+
POP_TOP
532+
533+
%3d LOAD_CONST 2 (2)
534+
STORE_FAST 2 (y)
535+
LOAD_CONST 0 (None)
536+
RETURN_VALUE
537+
>> COPY 3
538+
POP_EXCEPT
539+
RERAISE 1
540+
ExceptionTable:
541+
2 rows
542+
""" % (_asyncwith.__code__.co_firstlineno,
543+
_asyncwith.__code__.co_firstlineno + 1,
544+
_asyncwith.__code__.co_firstlineno + 2,
545+
_asyncwith.__code__.co_firstlineno + 1,
546+
_asyncwith.__code__.co_firstlineno + 3,
547+
_asyncwith.__code__.co_firstlineno + 1,
548+
_asyncwith.__code__.co_firstlineno + 3,
549+
)
550+
551+
424552
def _tryfinally(a, b):
425553
try:
426554
return a
@@ -455,6 +583,7 @@ def _tryfinallyconst(b):
455583
POP_EXCEPT
456584
RERAISE 1
457585
ExceptionTable:
586+
2 rows
458587
""" % (_tryfinally.__code__.co_firstlineno,
459588
_tryfinally.__code__.co_firstlineno + 1,
460589
_tryfinally.__code__.co_firstlineno + 2,
@@ -484,6 +613,7 @@ def _tryfinallyconst(b):
484613
POP_EXCEPT
485614
RERAISE 1
486615
ExceptionTable:
616+
1 row
487617
""" % (_tryfinallyconst.__code__.co_firstlineno,
488618
_tryfinallyconst.__code__.co_firstlineno + 1,
489619
_tryfinallyconst.__code__.co_firstlineno + 2,
@@ -678,6 +808,18 @@ def assert_offsets_increasing(self, text, delta):
678808
self.assertGreaterEqual(offset, expected_offset, line)
679809
expected_offset = offset + delta
680810

811+
def assert_exception_table_increasing(self, lines):
812+
prev_start, prev_end = -1, -1
813+
count = 0
814+
for line in lines:
815+
m = re.match(r' (\d+) to (\d+) -> \d+ \[\d+\]', line)
816+
start, end = [int(g) for g in m.groups()]
817+
self.assertGreaterEqual(end, start)
818+
self.assertGreater(start, prev_end)
819+
prev_start, prev_end = start, end
820+
count += 1
821+
return count
822+
681823
def strip_offsets(self, text):
682824
lines = text.splitlines(True)
683825
start, end = self.find_offset_column(lines)
@@ -691,6 +833,9 @@ def strip_offsets(self, text):
691833
res.append(line)
692834
else:
693835
res.append(line[:start] + line[end:])
836+
num_rows = self.assert_exception_table_increasing(lines)
837+
if num_rows:
838+
res.append(f"{num_rows} row{'s' if num_rows > 1 else ''}\n")
694839
return "".join(res)
695840

696841
def do_disassembly_compare(self, got, expected, with_offsets=False):
@@ -883,6 +1028,12 @@ def test_disassemble_coroutine(self):
8831028
def test_disassemble_fstring(self):
8841029
self.do_disassembly_test(_fstring, dis_fstring)
8851030

1031+
def test_disassemble_with(self):
1032+
self.do_disassembly_test(_with, dis_with)
1033+
1034+
def test_disassemble_asyncwith(self):
1035+
self.do_disassembly_test(_asyncwith, dis_asyncwith)
1036+
8861037
def test_disassemble_try_finally(self):
8871038
self.do_disassembly_test(_tryfinally, dis_tryfinally)
8881039
self.do_disassembly_test(_tryfinallyconst, dis_tryfinallyconst)
@@ -1471,16 +1622,16 @@ def _prepare_test_cases():
14711622
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=302, starts_line=None, is_jump_target=False, positions=None),
14721623
Instruction(opname='PUSH_EXC_INFO', opcode=35, arg=None, argval=None, argrepr='', offset=304, starts_line=25, is_jump_target=False, positions=None),
14731624
Instruction(opname='WITH_EXCEPT_START', opcode=49, arg=None, argval=None, argrepr='', offset=306, starts_line=None, is_jump_target=False, positions=None),
1474-
Instruction(opname='POP_JUMP_FORWARD_IF_TRUE', opcode=115, arg=4, argval=318, argrepr='to 318', offset=308, starts_line=None, is_jump_target=False, positions=None),
1625+
Instruction(opname='POP_JUMP_FORWARD_IF_TRUE', opcode=115, arg=1, argval=312, argrepr='to 312', offset=308, starts_line=None, is_jump_target=False, positions=None),
14751626
Instruction(opname='RERAISE', opcode=119, arg=2, argval=2, argrepr='', offset=310, starts_line=None, is_jump_target=False, positions=None),
1476-
Instruction(opname='COPY', opcode=120, arg=3, argval=3, argrepr='', offset=312, starts_line=None, is_jump_target=False, positions=None),
1627+
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=312, starts_line=None, is_jump_target=True, positions=None),
14771628
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=314, starts_line=None, is_jump_target=False, positions=None),
1478-
Instruction(opname='RERAISE', opcode=119, arg=1, argval=1, argrepr='', offset=316, starts_line=None, is_jump_target=False, positions=None),
1479-
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=318, starts_line=None, is_jump_target=True, positions=None),
1480-
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=320, starts_line=None, is_jump_target=False, positions=None),
1481-
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=322, starts_line=None, is_jump_target=False, positions=None),
1482-
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=324, starts_line=None, is_jump_target=False, positions=None),
1483-
Instruction(opname='JUMP_BACKWARD', opcode=140, arg=27, argval=274, argrepr='to 274', offset=326, starts_line=None, is_jump_target=False, positions=None),
1629+
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=316, starts_line=None, is_jump_target=False, positions=None),
1630+
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=318, starts_line=None, is_jump_target=False, positions=None),
1631+
Instruction(opname='JUMP_BACKWARD', opcode=140, arg=24, argval=274, argrepr='to 274', offset=320, starts_line=None, is_jump_target=False, positions=None),
1632+
Instruction(opname='COPY', opcode=120, arg=3, argval=3, argrepr='', offset=322, starts_line=None, is_jump_target=False, positions=None),
1633+
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=324, starts_line=None, is_jump_target=False, positions=None),
1634+
Instruction(opname='RERAISE', opcode=119, arg=1, argval=1, argrepr='', offset=326, starts_line=None, is_jump_target=False, positions=None),
14841635
Instruction(opname='PUSH_EXC_INFO', opcode=35, arg=None, argval=None, argrepr='', offset=328, starts_line=None, is_jump_target=False, positions=None),
14851636
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=4, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=330, starts_line=22, is_jump_target=False, positions=None),
14861637
Instruction(opname='CHECK_EXC_MATCH', opcode=36, arg=None, argval=None, argrepr='', offset=342, starts_line=None, is_jump_target=False, positions=None),

‎Misc/NEWS.d/next/Core and Builtins/2022-06-09-09-08-29.gh-issue-93621.-_Pn1d.rst

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
Change order of bytecode instructions emitted for :keyword:`with` and :keyword:`async with` to reduce the number of entries in the exception table.

‎Python/compile.c

+13-7
Original file line numberDiff line numberDiff line change
@@ -5551,20 +5551,26 @@ compiler_visit_keyword(struct compiler *c, keyword_ty k)
55515551
static int
55525552
compiler_with_except_finish(struct compiler *c, basicblock * cleanup) {
55535553
UNSET_LOC(c);
5554-
basicblock *exit;
5555-
exit = compiler_new_block(c);
5556-
if (exit == NULL)
5554+
basicblock *suppress = compiler_new_block(c);
5555+
if (suppress == NULL) {
55575556
return 0;
5558-
ADDOP_JUMP(c, POP_JUMP_IF_TRUE, exit);
5557+
}
5558+
ADDOP_JUMP(c, POP_JUMP_IF_TRUE, suppress);
55595559
ADDOP_I(c, RERAISE, 2);
5560-
compiler_use_next_block(c, cleanup);
5561-
POP_EXCEPT_AND_RERAISE(c);
5562-
compiler_use_next_block(c, exit);
5560+
compiler_use_next_block(c, suppress);
55635561
ADDOP(c, POP_TOP); /* exc_value */
55645562
ADDOP(c, POP_BLOCK);
55655563
ADDOP(c, POP_EXCEPT);
55665564
ADDOP(c, POP_TOP);
55675565
ADDOP(c, POP_TOP);
5566+
basicblock *exit = compiler_new_block(c);
5567+
if (exit == NULL) {
5568+
return 0;
5569+
}
5570+
ADDOP_JUMP(c, JUMP, exit);
5571+
compiler_use_next_block(c, cleanup);
5572+
POP_EXCEPT_AND_RERAISE(c);
5573+
compiler_use_next_block(c, exit);
55685574
return 1;
55695575
}
55705576

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