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GH-93621: reorder code in with/async-with exception exit path to reduce the size of the exception table #93622

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merged 6 commits into from
Jun 10, 2022
Merged

GH-93621: reorder code in with/async-with exception exit path to reduce the size of the exception table #93622

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acf066c
reorder code in with/async-with exception exit path to reduce the siz…
iritkatriel Jun 8, 2022
4966724
📜🤖 Added by blurb_it.
blurb-it[bot] Jun 9, 2022
dc96fbe
add direct dis tests for with and async-with
iritkatriel Jun 9, 2022
946a191
add some checks for the exception table in dis output
iritkatriel Jun 9, 2022
61729a3
Merge remote-tracking branch 'upstream/main' into with-exception
iritkatriel Jun 9, 2022
38b21f1
update tests after merge
iritkatriel Jun 9, 2022
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167 changes: 159 additions & 8 deletions Lib/test/test_dis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -389,6 +389,7 @@ def bug42562():
POP_EXCEPT
RERAISE 1
ExceptionTable:
4 rows
""" % (TRACEBACK_CODE.co_firstlineno,
TRACEBACK_CODE.co_firstlineno + 1,
TRACEBACK_CODE.co_firstlineno + 2,
Expand Down Expand Up @@ -421,6 +422,133 @@ def _fstring(a, b, c, d):
RETURN_VALUE
""" % (_fstring.__code__.co_firstlineno, _fstring.__code__.co_firstlineno + 1)

def _with(c):
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with c:
x = 1
y = 2

dis_with = """\
%3d RESUME 0

%3d LOAD_FAST 0 (c)
BEFORE_WITH
POP_TOP

%3d LOAD_CONST 1 (1)
STORE_FAST 1 (x)

%3d LOAD_CONST 0 (None)
LOAD_CONST 0 (None)
LOAD_CONST 0 (None)
CALL 2
POP_TOP

%3d LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE

%3d >> PUSH_EXC_INFO
WITH_EXCEPT_START
POP_JUMP_FORWARD_IF_TRUE 1 (to 46)
RERAISE 2
>> POP_TOP
POP_EXCEPT
POP_TOP
POP_TOP

%3d LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE
>> COPY 3
POP_EXCEPT
RERAISE 1
ExceptionTable:
2 rows
""" % (_with.__code__.co_firstlineno,
_with.__code__.co_firstlineno + 1,
_with.__code__.co_firstlineno + 2,
_with.__code__.co_firstlineno + 1,
_with.__code__.co_firstlineno + 3,
_with.__code__.co_firstlineno + 1,
_with.__code__.co_firstlineno + 3,
)

async def _asyncwith(c):
async with c:
x = 1
y = 2

dis_asyncwith = """\
%3d RETURN_GENERATOR
POP_TOP
RESUME 0

%3d LOAD_FAST 0 (c)
BEFORE_ASYNC_WITH
GET_AWAITABLE 1
LOAD_CONST 0 (None)
>> SEND 3 (to 22)
YIELD_VALUE 3
RESUME 3
JUMP_BACKWARD_NO_INTERRUPT 4 (to 14)
>> POP_TOP

%3d LOAD_CONST 1 (1)
STORE_FAST 1 (x)

%3d LOAD_CONST 0 (None)
LOAD_CONST 0 (None)
LOAD_CONST 0 (None)
CALL 2
GET_AWAITABLE 2
LOAD_CONST 0 (None)
>> SEND 3 (to 56)
YIELD_VALUE 2
RESUME 3
JUMP_BACKWARD_NO_INTERRUPT 4 (to 48)
>> POP_TOP

%3d LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE

%3d >> PUSH_EXC_INFO
WITH_EXCEPT_START
GET_AWAITABLE 2
LOAD_CONST 0 (None)
>> SEND 3 (to 82)
YIELD_VALUE 6
RESUME 3
JUMP_BACKWARD_NO_INTERRUPT 4 (to 74)
>> POP_JUMP_FORWARD_IF_TRUE 1 (to 86)
RERAISE 2
>> POP_TOP
POP_EXCEPT
POP_TOP
POP_TOP

%3d LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE
>> COPY 3
POP_EXCEPT
RERAISE 1
ExceptionTable:
2 rows
""" % (_asyncwith.__code__.co_firstlineno,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 2,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 3,
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 3,
)


def _tryfinally(a, b):
try:
return a
Expand Down Expand Up @@ -455,6 +583,7 @@ def _tryfinallyconst(b):
POP_EXCEPT
RERAISE 1
ExceptionTable:
2 rows
""" % (_tryfinally.__code__.co_firstlineno,
_tryfinally.__code__.co_firstlineno + 1,
_tryfinally.__code__.co_firstlineno + 2,
Expand Down Expand Up @@ -484,6 +613,7 @@ def _tryfinallyconst(b):
POP_EXCEPT
RERAISE 1
ExceptionTable:
1 row
""" % (_tryfinallyconst.__code__.co_firstlineno,
_tryfinallyconst.__code__.co_firstlineno + 1,
_tryfinallyconst.__code__.co_firstlineno + 2,
Expand Down Expand Up @@ -678,6 +808,18 @@ def assert_offsets_increasing(self, text, delta):
self.assertGreaterEqual(offset, expected_offset, line)
expected_offset = offset + delta

def assert_exception_table_increasing(self, lines):
prev_start, prev_end = -1, -1
count = 0
for line in lines:
m = re.match(r' (\d+) to (\d+) -> \d+ \[\d+\]', line)
start, end = [int(g) for g in m.groups()]
self.assertGreaterEqual(end, start)
self.assertGreater(start, prev_end)
prev_start, prev_end = start, end
count += 1
return count

def strip_offsets(self, text):
lines = text.splitlines(True)
start, end = self.find_offset_column(lines)
Expand All @@ -691,6 +833,9 @@ def strip_offsets(self, text):
res.append(line)
else:
res.append(line[:start] + line[end:])
num_rows = self.assert_exception_table_increasing(lines)
if num_rows:
res.append(f"{num_rows} row{'s' if num_rows > 1 else ''}\n")
return "".join(res)

def do_disassembly_compare(self, got, expected, with_offsets=False):
Expand Down Expand Up @@ -883,6 +1028,12 @@ def test_disassemble_coroutine(self):
def test_disassemble_fstring(self):
self.do_disassembly_test(_fstring, dis_fstring)

def test_disassemble_with(self):
self.do_disassembly_test(_with, dis_with)

def test_disassemble_asyncwith(self):
self.do_disassembly_test(_asyncwith, dis_asyncwith)

def test_disassemble_try_finally(self):
self.do_disassembly_test(_tryfinally, dis_tryfinally)
self.do_disassembly_test(_tryfinallyconst, dis_tryfinallyconst)
Expand Down Expand Up @@ -1471,16 +1622,16 @@ def _prepare_test_cases():
Instruction(opname='RETURN_VALUE', opcode=83, arg=None, argval=None, argrepr='', offset=302, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='PUSH_EXC_INFO', opcode=35, arg=None, argval=None, argrepr='', offset=304, starts_line=25, is_jump_target=False, positions=None),
Instruction(opname='WITH_EXCEPT_START', opcode=49, arg=None, argval=None, argrepr='', offset=306, starts_line=None, is_jump_target=False, positions=None),
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),
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),
Instruction(opname='RERAISE', opcode=119, arg=2, argval=2, argrepr='', offset=310, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='COPY', opcode=120, arg=3, argval=3, argrepr='', offset=312, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=312, starts_line=None, is_jump_target=True, positions=None),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=314, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='RERAISE', opcode=119, arg=1, argval=1, argrepr='', offset=316, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=318, starts_line=None, is_jump_target=True, positions=None),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=320, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=322, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=324, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='JUMP_BACKWARD', opcode=140, arg=27, argval=274, argrepr='to 274', offset=326, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=316, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=318, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='JUMP_BACKWARD', opcode=140, arg=24, argval=274, argrepr='to 274', offset=320, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='COPY', opcode=120, arg=3, argval=3, argrepr='', offset=322, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='POP_EXCEPT', opcode=89, arg=None, argval=None, argrepr='', offset=324, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='RERAISE', opcode=119, arg=1, argval=1, argrepr='', offset=326, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='PUSH_EXC_INFO', opcode=35, arg=None, argval=None, argrepr='', offset=328, starts_line=None, is_jump_target=False, positions=None),
Instruction(opname='LOAD_GLOBAL', opcode=116, arg=4, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=330, starts_line=22, is_jump_target=False, positions=None),
Instruction(opname='CHECK_EXC_MATCH', opcode=36, arg=None, argval=None, argrepr='', offset=342, starts_line=None, is_jump_target=False, positions=None),
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-06-09-09-08-29.gh-issue-93621.-_Pn1d.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Change order of bytecode instructions emitted for :keyword:`with` and :keyword:`async with` to reduce the number of entries in the exception table.
20 changes: 13 additions & 7 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5551,20 +5551,26 @@ compiler_visit_keyword(struct compiler *c, keyword_ty k)
static int
compiler_with_except_finish(struct compiler *c, basicblock * cleanup) {
UNSET_LOC(c);
basicblock *exit;
exit = compiler_new_block(c);
if (exit == NULL)
basicblock *suppress = compiler_new_block(c);
if (suppress == NULL) {
return 0;
ADDOP_JUMP(c, POP_JUMP_IF_TRUE, exit);
}
ADDOP_JUMP(c, POP_JUMP_IF_TRUE, suppress);
ADDOP_I(c, RERAISE, 2);
compiler_use_next_block(c, cleanup);
POP_EXCEPT_AND_RERAISE(c);
compiler_use_next_block(c, exit);
compiler_use_next_block(c, suppress);
ADDOP(c, POP_TOP); /* exc_value */
ADDOP(c, POP_BLOCK);
ADDOP(c, POP_EXCEPT);
ADDOP(c, POP_TOP);
ADDOP(c, POP_TOP);
basicblock *exit = compiler_new_block(c);
if (exit == NULL) {
return 0;
}
ADDOP_JUMP(c, JUMP, exit);
compiler_use_next_block(c, cleanup);
POP_EXCEPT_AND_RERAISE(c);
compiler_use_next_block(c, exit);
return 1;
}

Expand Down