From bde06e1b8381f140b296a397ddd1deb1c784ff8e Mon Sep 17 00:00:00 2001 From: Irit Katriel <1055913+iritkatriel@users.noreply.github.com> Date: Thu, 7 Jul 2022 07:38:36 +0100 Subject: [PATCH] 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". --- Lib/test/test_dis.py | 27 +++++-------------- Lib/test/test_peepholer.py | 2 ++ Lib/test/test_sys_settrace.py | 9 +++++++ ...2-07-06-14-02-26.gh-issue-92228.44Cbly.rst | 1 + Python/compile.c | 14 ++++++++++ 5 files changed, 33 insertions(+), 20 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 256004855d4..440e4ed5eac 100644 --- a/Lib/test/test_dis.py +++ b/Lib/test/test_dis.py @@ -360,13 +360,13 @@ dis_traceback = """\ --> 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 @@ dis_traceback = """\ 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 @@ ExceptionTable: 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 @@ dis_with = """\ 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 @@ dis_with = """\ 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 @@ ExceptionTable: _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 @@ dis_asyncwith = """\ 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 @@ dis_asyncwith = """\ 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 @@ ExceptionTable: _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 2c3b1ab65a8..e03c42c2f82 100644 --- a/Lib/test/test_peepholer.py +++ b/Lib/test/test_peepholer.py @@ -345,6 +345,8 @@ class TestTranforms(BytecodeTestCase): 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 @@ class JumpTestCase(unittest.TestCase): 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 77176893f60..f36a6e85a54 100644 --- a/Python/compile.c +++ b/Python/compile.c @@ -9224,6 +9224,16 @@ error: 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);