[Python-checkins] gh-92228: disable the compiler's 'small exit block inlining' optimization for blocks that have a line number (GH-94592)
miss-islington
webhook-mailer at python.org
Thu Jul 7 02:38:40 EDT 2022
https://github.com/python/cpython/commit/bde06e1b8381f140b296a397ddd1deb1c784ff8e
commit: bde06e1b8381f140b296a397ddd1deb1c784ff8e
branch: main
author: Irit Katriel <1055913+iritkatriel at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-07-06T23:38:36-07:00
summary:
gh-92228: disable the compiler's 'small exit block inlining' optimization for blocks that have a line number (GH-94592)
Inlining of code that corresponds to source code lines, can make it hard to distinguish later between code which is only reachable from except handlers, and that which is reachable in normal control flow. This caused problems with the debugger's jump feature.
This PR turns off the inlining optimisation for code which has line numbers. We still inline things like the implicit "return None".
files:
A Misc/NEWS.d/next/Core and Builtins/2022-07-06-14-02-26.gh-issue-92228.44Cbly.rst
M Lib/test/test_dis.py
M Lib/test/test_peepholer.py
M Lib/test/test_sys_settrace.py
M Python/compile.c
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index 256004855d4a6..440e4ed5eacfb 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -360,13 +360,13 @@ def bug42562():
--> BINARY_OP 11 (/)
POP_TOP
-%3d LOAD_FAST_CHECK 1 (tb)
+%3d >> LOAD_FAST_CHECK 1 (tb)
RETURN_VALUE
>> PUSH_EXC_INFO
%3d LOAD_GLOBAL 0 (Exception)
CHECK_EXC_MATCH
- POP_JUMP_FORWARD_IF_FALSE 23 (to 82)
+ POP_JUMP_FORWARD_IF_FALSE 22 (to 80)
STORE_FAST 0 (e)
%3d LOAD_FAST 0 (e)
@@ -376,9 +376,7 @@ def bug42562():
LOAD_CONST 0 (None)
STORE_FAST 0 (e)
DELETE_FAST 0 (e)
-
-%3d LOAD_FAST 1 (tb)
- RETURN_VALUE
+ JUMP_BACKWARD 29 (to 14)
>> LOAD_CONST 0 (None)
STORE_FAST 0 (e)
DELETE_FAST 0 (e)
@@ -396,7 +394,6 @@ def bug42562():
TRACEBACK_CODE.co_firstlineno + 5,
TRACEBACK_CODE.co_firstlineno + 3,
TRACEBACK_CODE.co_firstlineno + 4,
- TRACEBACK_CODE.co_firstlineno + 5,
TRACEBACK_CODE.co_firstlineno + 3)
def _fstring(a, b, c, d):
@@ -443,7 +440,7 @@ def _with(c):
CALL 2
POP_TOP
-%3d LOAD_CONST 2 (2)
+%3d >> LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE
@@ -456,11 +453,7 @@ def _with(c):
POP_EXCEPT
POP_TOP
POP_TOP
-
-%3d LOAD_CONST 2 (2)
- STORE_FAST 2 (y)
- LOAD_CONST 0 (None)
- RETURN_VALUE
+ JUMP_BACKWARD 13 (to 30)
>> COPY 3
POP_EXCEPT
RERAISE 1
@@ -472,7 +465,6 @@ def _with(c):
_with.__code__.co_firstlineno + 1,
_with.__code__.co_firstlineno + 3,
_with.__code__.co_firstlineno + 1,
- _with.__code__.co_firstlineno + 3,
)
async def _asyncwith(c):
@@ -510,7 +502,7 @@ async def _asyncwith(c):
JUMP_BACKWARD_NO_INTERRUPT 4 (to 48)
>> POP_TOP
-%3d LOAD_CONST 2 (2)
+%3d >> LOAD_CONST 2 (2)
STORE_FAST 2 (y)
LOAD_CONST 0 (None)
RETURN_VALUE
@@ -529,11 +521,7 @@ async def _asyncwith(c):
POP_EXCEPT
POP_TOP
POP_TOP
-
-%3d LOAD_CONST 2 (2)
- STORE_FAST 2 (y)
- LOAD_CONST 0 (None)
- RETURN_VALUE
+ JUMP_BACKWARD 19 (to 58)
>> COPY 3
POP_EXCEPT
RERAISE 1
@@ -545,7 +533,6 @@ async def _asyncwith(c):
_asyncwith.__code__.co_firstlineno + 1,
_asyncwith.__code__.co_firstlineno + 3,
_asyncwith.__code__.co_firstlineno + 1,
- _asyncwith.__code__.co_firstlineno + 3,
)
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 2c3b1ab65a8f9..e03c42c2f823d 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -345,6 +345,8 @@ def f(x):
self.assertEqual(len(returns), 1)
self.check_lnotab(f)
+ @unittest.skip("Following gh-92228 the return has two predecessors "
+ "and that prevents jump elimination.")
def test_elim_jump_to_return(self):
# JUMP_FORWARD to RETURN --> RETURN
def f(cond, true_value, false_value):
diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
index 7ec290dbf04ad..f03b03e19a252 100644
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -2042,6 +2042,15 @@ def test_no_jump_within_except_block(output):
output.append(6)
output.append(7)
+ @jump_test(6, 1, [1, 5, 1, 5])
+ def test_jump_over_try_except(output):
+ output.append(1)
+ try:
+ 1 / 0
+ except ZeroDivisionError as e:
+ output.append(5)
+ x = 42 # has to be a two-instruction block
+
@jump_test(2, 4, [1, 4, 5, -4])
def test_jump_across_with(output):
output.append(1)
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-06-14-02-26.gh-issue-92228.44Cbly.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-06-14-02-26.gh-issue-92228.44Cbly.rst
new file mode 100644
index 0000000000000..458ad897cefcb
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-07-06-14-02-26.gh-issue-92228.44Cbly.rst
@@ -0,0 +1 @@
+Disable the compiler's inline-small-exit-blocks optimization for exit blocks that are associated with source code lines. This fixes a bug where the debugger cannot tell where an exception handler ends and the following code block begins.
diff --git a/Python/compile.c b/Python/compile.c
index 77176893f60c5..f36a6e85a54c2 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -9224,6 +9224,16 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
return -1;
}
+static bool
+basicblock_has_lineno(const basicblock *bb) {
+ for (int i = 0; i < bb->b_iused; i++) {
+ if (bb->b_instr[i].i_loc.lineno > 0) {
+ return true;
+ }
+ }
+ return false;
+}
+
/* If this block ends with an unconditional jump to an exit block,
* then remove the jump and extend this block with the target.
*/
@@ -9240,6 +9250,10 @@ extend_block(basicblock *bb) {
}
if (basicblock_exits_scope(last->i_target) && last->i_target->b_iused <= MAX_COPY_SIZE) {
basicblock *to_copy = last->i_target;
+ if (basicblock_has_lineno(to_copy)) {
+ /* copy only blocks without line number (like implicit 'return None's) */
+ return 0;
+ }
last->i_opcode = NOP;
for (int i = 0; i < to_copy->b_iused; i++) {
int index = basicblock_next_instr(bb);
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