From 74c953d396816c0ef3de80276c00d29f79cbf8bf Mon Sep 17 00:00:00 2001
From: Christian Heimes <christian@python.org>
Date: Thu, 7 Jul 2022 12:10:32 +0200
Subject: [PATCH] [3.11] gh-92228: disable the compiler's 'small exit block
inlining' optimization for blocks that have a line number (GH-94592)
(GH-94643)
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"..
(cherry picked from commit bde06e1b8381f140b296a397ddd1deb1c784ff8e)
Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>
---
Lib/test/test_dis.py | 18 ++++++++----------
Lib/test/test_peepholer.py | 2 ++
Lib/test/test_sys_settrace.py | 9 +++++++++
...22-07-06-14-02-26.gh-issue-92228.44Cbly.rst | 1 +
Python/compile.c | 14 ++++++++++++++
5 files changed, 34 insertions(+), 10 deletions(-)
create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-07-06-14-02-26.gh-issue-92228.44Cbly.rst
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index 4283c30e0a1..b00f329e006 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -366,14 +366,12 @@ def bug42562():
LOAD_CONST 2 (0)
--> BINARY_OP 11 (/)
POP_TOP
-
-%3d LOAD_FAST 1 (tb)
- RETURN_VALUE
+ JUMP_FORWARD 30 (to 76)
>> PUSH_EXC_INFO
%3d LOAD_GLOBAL 0 (Exception)
CHECK_EXC_MATCH
- POP_JUMP_FORWARD_IF_FALSE 18 (to 72)
+ POP_JUMP_FORWARD_IF_FALSE 17 (to 68)
STORE_FAST 0 (e)
%3d LOAD_FAST 0 (e)
@@ -383,9 +381,7 @@ def bug42562():
LOAD_CONST 0 (None)
STORE_FAST 0 (e)
DELETE_FAST 0 (e)
-
-%3d LOAD_FAST 1 (tb)
- RETURN_VALUE
+ JUMP_FORWARD 8 (to 76)
>> LOAD_CONST 0 (None)
STORE_FAST 0 (e)
DELETE_FAST 0 (e)
@@ -395,15 +391,17 @@ def bug42562():
>> COPY 3
POP_EXCEPT
RERAISE 1
+
+%3d >> LOAD_FAST 1 (tb)
+ RETURN_VALUE
ExceptionTable:
""" % (TRACEBACK_CODE.co_firstlineno,
TRACEBACK_CODE.co_firstlineno + 1,
TRACEBACK_CODE.co_firstlineno + 2,
- 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)
+ TRACEBACK_CODE.co_firstlineno + 3,
+ TRACEBACK_CODE.co_firstlineno + 5)
def _fstring(a, b, c, d):
return f'{a} {b:4} {c!r} {d!r:4}'
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 6a2f550d670..241644ad7d2 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -344,6 +344,8 @@ 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 7ec290dbf04..f03b03e19a2 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 00000000000..458ad897cef
--- /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 cfe4b6ec04f..a71e7d31eec 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -8976,6 +8976,16 @@ optimize_basic_block(struct compiler *c, 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_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.
*/
@@ -8992,6 +9002,10 @@ extend_block(basicblock *bb) {
}
if (last->i_target->b_exit && 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 = compiler_next_instr(bb);
--
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