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[3.12] gh-112356: LOAD_GLOBAL can only include one PUSH_NULL #112566

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Merged
sweeneyde merged 3 commits into from
Dec 1, 2023
Merged

[3.12] gh-112356: LOAD_GLOBAL can only include one PUSH_NULL #112566

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abe507d
LOAD_GLOBAL can only include one PUSH_NULL
sweeneyde Nov 30, 2023
ebe9e71
📜🤖 Added by blurb_it.
blurb-it[bot] Nov 30, 2023
c021aa9
Use b_instr[i+1] for consistency
sweeneyde Dec 1, 2023
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21 changes: 21 additions & 0 deletions Lib/test/test_peepholer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1075,5 +1075,26 @@ def test_no_unsafe_static_swap(self):
]
self.cfg_optimization_test(insts, insts, consts=list(range(3)), nlocals=1)

def test_only_one_push_null_per_load_global(self):
# When optimizing func()(), a second pass shouldn't
# let the LOAD_GLOBAL absorb another PUSH_NULL.
before = [
('PUSH_NULL', 0, 1),
('PUSH_NULL', 0, 1),
('LOAD_GLOBAL', 0, 1),
('CALL', 0, 1),
('CALL', 0, 1),
('RETURN_VALUE', 0, 1),
]
after = [
('PUSH_NULL', 0, 1),
('LOAD_GLOBAL', 1, 1),
('CALL', 0, 1),
('CALL', 0, 1),
('RETURN_VALUE', 0, 1),
]
self.cfg_optimization_test(before, expected_insts=after, consts=[])
self.cfg_optimization_test(after, expected_insts=after, consts=[])

if __name__ == "__main__":
unittest.main()
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-11-30-23-47-56.gh-issue-112356.g2BqyK.rst
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@@ -0,0 +1 @@
Stopped erroneously deleting a ``LOAD_NULL`` bytecode instruction when optimized twice.
4 changes: 2 additions & 2 deletions Python/flowgraph.c
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Expand Up @@ -1554,9 +1554,9 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
case KW_NAMES:
break;
case PUSH_NULL:
if (nextop == LOAD_GLOBAL && (inst[1].i_opcode & 1) == 0) {
if (nextop == LOAD_GLOBAL && (bb->b_instr[i+1].i_oparg & 1) == 0) {
INSTR_SET_OP0(inst, NOP);
inst[1].i_oparg |= 1;
bb->b_instr[i+1].i_oparg |= 1;
}
break;
default:
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