https://github.com/python/cpython/commit/6b77af257c25d31f1f137e477cb23e63692ddf29
commit: 6b77af257c25d31f1f137e477cb23e63692ddf29
branch: main
author: mpage <mp...@meta.com>
committer: mpage <mp...@cs.stanford.edu>
date: 2025-06-04T16:07:58-07:00
summary:
gh-134889: Fix handling of a few opcodes when optimizing `LOAD_FAST` (#134958)
We were incorrectly handling a few opcodes that leave their operands on the
stack. Treat all of these conservatively; assume that they always leave
operands on the stack.
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2025-05-30-18-09-54.gh-issue-134889.Ic9UM-.rst
M Include/internal/pycore_magic_number.h
M Lib/test/test_dis.py
M Lib/test/test_peepholer.py
M Python/flowgraph.c
diff --git a/Include/internal/pycore_magic_number.h
b/Include/internal/pycore_magic_number.h
index cd1fc873623ed1..347d9762f26bff 100644
--- a/Include/internal/pycore_magic_number.h
+++ b/Include/internal/pycore_magic_number.h
@@ -280,6 +280,7 @@ Known values:
Python 3.15a0 3650 (Initial version)
Python 3.15a1 3651 (Simplify LOAD_CONST)
Python 3.15a1 3652 (Virtual iterators)
+ Python 3.15a1 3653 (Fix handling of opcodes that may leave operands on the
stack when optimizing LOAD_FAST)
Python 3.16 will start with 3700
@@ -293,7 +294,7 @@ PC/launcher.c must also be updated.
*/
-#define PYC_MAGIC_NUMBER 3652
+#define PYC_MAGIC_NUMBER 3653
/* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
(little-endian) and then appending b'\r\n'. */
#define PYC_MAGIC_NUMBER_TOKEN \
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index ec930a728aa5b3..355990ed58ee09 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -606,7 +606,7 @@ async def _asyncwith(c):
POP_TOP
L1: RESUME 0
-%4d LOAD_FAST_BORROW 0 (c)
+%4d LOAD_FAST 0 (c)
COPY 1
LOAD_SPECIAL 3 (__aexit__)
SWAP 2
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index f33de3d420ca34..ef596630b930f7 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -2614,6 +2614,90 @@ def test_send(self):
]
self.cfg_optimization_test(insts, expected, consts=[None])
+ def test_format_simple(self):
+ # FORMAT_SIMPLE will leave its operand on the stack if it's a unicode
+ # object. We treat it conservatively and assume that it always leaves
+ # its operand on the stack.
+ insts = [
+ ("LOAD_FAST", 0, 1),
+ ("FORMAT_SIMPLE", None, 2),
+ ("STORE_FAST", 1, 3),
+ ]
+ self.check(insts, insts)
+
+ insts = [
+ ("LOAD_FAST", 0, 1),
+ ("FORMAT_SIMPLE", None, 2),
+ ("POP_TOP", None, 3),
+ ]
+ expected = [
+ ("LOAD_FAST_BORROW", 0, 1),
+ ("FORMAT_SIMPLE", None, 2),
+ ("POP_TOP", None, 3),
+ ]
+ self.check(insts, expected)
+
+ def test_set_function_attribute(self):
+ # SET_FUNCTION_ATTRIBUTE leaves the function on the stack
+ insts = [
+ ("LOAD_CONST", 0, 1),
+ ("LOAD_FAST", 0, 2),
+ ("SET_FUNCTION_ATTRIBUTE", 2, 3),
+ ("STORE_FAST", 1, 4),
+ ("LOAD_CONST", 0, 5),
+ ("RETURN_VALUE", None, 6)
+ ]
+ self.cfg_optimization_test(insts, insts, consts=[None])
+
+ insts = [
+ ("LOAD_CONST", 0, 1),
+ ("LOAD_FAST", 0, 2),
+ ("SET_FUNCTION_ATTRIBUTE", 2, 3),
+ ("RETURN_VALUE", None, 4)
+ ]
+ expected = [
+ ("LOAD_CONST", 0, 1),
+ ("LOAD_FAST_BORROW", 0, 2),
+ ("SET_FUNCTION_ATTRIBUTE", 2, 3),
+ ("RETURN_VALUE", None, 4)
+ ]
+ self.cfg_optimization_test(insts, expected, consts=[None])
+
+ def test_get_yield_from_iter(self):
+ # GET_YIELD_FROM_ITER may leave its operand on the stack
+ insts = [
+ ("LOAD_FAST", 0, 1),
+ ("GET_YIELD_FROM_ITER", None, 2),
+ ("LOAD_CONST", 0, 3),
+ send := self.Label(),
+ ("SEND", end := self.Label(), 5),
+ ("YIELD_VALUE", 1, 6),
+ ("RESUME", 2, 7),
+ ("JUMP", send, 8),
+ end,
+ ("END_SEND", None, 9),
+ ("LOAD_CONST", 0, 10),
+ ("RETURN_VALUE", None, 11),
+ ]
+ self.cfg_optimization_test(insts, insts, consts=[None])
+
+ def test_push_exc_info(self):
+ insts = [
+ ("LOAD_FAST", 0, 1),
+ ("PUSH_EXC_INFO", None, 2),
+ ]
+ self.check(insts, insts)
+
+ def test_load_special(self):
+ # LOAD_SPECIAL may leave self on the stack
+ insts = [
+ ("LOAD_FAST", 0, 1),
+ ("LOAD_SPECIAL", 0, 2),
+ ("STORE_FAST", 1, 3),
+ ]
+ self.check(insts, insts)
+
+
def test_del_in_finally(self):
# This loads `obj` onto the stack, executes `del obj`, then returns the
# `obj` from the stack. See gh-133371 for more details.
@@ -2630,6 +2714,14 @@ def create_obj():
gc.collect()
self.assertEqual(obj, [42])
+ def test_format_simple_unicode(self):
+ # Repro from gh-134889
+ def f():
+ var = f"{1}"
+ var = f"{var}"
+ return var
+ self.assertEqual(f(), "1")
+
if __name__ == "__main__":
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2025-05-30-18-09-54.gh-issue-134889.Ic9UM-.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2025-05-30-18-09-54.gh-issue-134889.Ic9UM-.rst
new file mode 100644
index 00000000000000..3b86134bf16800
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2025-05-30-18-09-54.gh-issue-134889.Ic9UM-.rst
@@ -0,0 +1,2 @@
+Fix handling of a few opcodes that leave operands on the stack when
+optimizing ``LOAD_FAST``.
diff --git a/Python/flowgraph.c b/Python/flowgraph.c
index 67ccf350b72ed6..2adc8c84d83974 100644
--- a/Python/flowgraph.c
+++ b/Python/flowgraph.c
@@ -2870,9 +2870,11 @@ optimize_load_fast(cfg_builder *g)
// how many inputs should be left on the stack.
// Opcodes that consume no inputs
+ case FORMAT_SIMPLE:
case GET_ANEXT:
case GET_ITER:
case GET_LEN:
+ case GET_YIELD_FROM_ITER:
case IMPORT_FROM:
case MATCH_KEYS:
case MATCH_MAPPING:
@@ -2907,6 +2909,16 @@ optimize_load_fast(cfg_builder *g)
break;
}
+ case END_SEND:
+ case SET_FUNCTION_ATTRIBUTE: {
+ assert(_PyOpcode_num_popped(opcode, oparg) == 2);
+ assert(_PyOpcode_num_pushed(opcode, oparg) == 1);
+ ref tos = ref_stack_pop(&refs);
+ ref_stack_pop(&refs);
+ PUSH_REF(tos.instr, tos.local);
+ break;
+ }
+
// Opcodes that consume some inputs and push new values
case CHECK_EXC_MATCH: {
ref_stack_pop(&refs);
@@ -2936,6 +2948,14 @@ optimize_load_fast(cfg_builder *g)
break;
}
+ case LOAD_SPECIAL:
+ case PUSH_EXC_INFO: {
+ ref tos = ref_stack_pop(&refs);
+ PUSH_REF(i, NOT_LOCAL);
+ PUSH_REF(tos.instr, tos.local);
+ break;
+ }
+
case SEND: {
load_fast_push_block(&sp, instr->i_target, refs.size);
ref_stack_pop(&refs);
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