TOS Caching does not handle `Py_DECREF`

[Fidget-Spinner]

Bug report

Bug description:

For example for the following code from #142703

def foo(l):
 for _ in range(4099):
 l[0] = 1
foo([0]

The following trace is generated:

 0 OPTIMIZED: _START_EXECUTOR_r00 (0, jump_target=21, operand0=0x61d7aa5bc790, operand1=0, error_target=0)
 1 OPTIMIZED: _MAKE_WARM_r00 (0, target=0, operand0=0, operand1=0)
 2 OPTIMIZED: _SET_IP_r00 (0, target=20, operand0=0x795204f5c498, operand1=0)
 3 OPTIMIZED: _CHECK_PERIODIC_r00 (0, jump_target=0, operand0=0, operand1=0)
 4 OPTIMIZED: _CHECK_VALIDITY_r00 (0, jump_target=23, operand0=0, operand1=0)
 5 OPTIMIZED: _ITER_CHECK_RANGE_r02 (8, jump_target=24, operand0=0, operand1=0, error_target=0)
 6 OPTIMIZED: _GUARD_NOT_EXHAUSTED_RANGE_r22 (8, jump_target=25, operand0=0, operand1=0, error_target=0)
 7 OPTIMIZED: _ITER_NEXT_RANGE_r23 (8, jump_target=0, operand0=0, operand1=0, error_target=26)
 8 OPTIMIZED: _SET_IP_r33 (0, target=14, operand0=0x795204f5c48c, operand1=0)
 9 OPTIMIZED: _SPILL_OR_RELOAD_r31 (0, target=0, operand0=0, operand1=0)
 10 OPTIMIZED: _STORE_FAST_1_r10 (1, target=14, operand0=0, operand1=0, error_target=0)
 11 OPTIMIZED: _CHECK_VALIDITY_r00 (0, jump_target=27, operand0=0, operand1=0)
 12 OPTIMIZED: _LOAD_CONST_INLINE_BORROW_r01 (0, target=15, operand0=0x61d7973c0508, operand1=0)
 13 OPTIMIZED: _LOAD_FAST_BORROW_0_r12 (0, target=16, operand0=0, operand1=0)
 14 OPTIMIZED: _LOAD_CONST_INLINE_BORROW_r23 (0, target=17, operand0=0x61d7973c04e8, operand1=0)
 15 OPTIMIZED: _SET_IP_r33 (0, target=18, operand0=0x795204f5c494, operand1=0)
 16 OPTIMIZED: _GUARD_NOS_LIST_r33 (0, jump_target=28, operand0=0, operand1=0)
 17 OPTIMIZED: _STORE_SUBSCR_LIST_INT_r32 (0, jump_target=29, operand0=0, operand1=0)
 18 OPTIMIZED: _POP_TOP_NOP_r21 (0, target=18, operand0=0, operand1=0)
 19 OPTIMIZED: _POP_TOP_NOP_r10 (0, target=18, operand0=0, operand1=0)
 20 OPTIMIZED: _JUMP_TO_TOP_r00 (0, jump_target=1, operand0=0, operand1=0)

_STORE_SUBSCR_LIST_INT has a Py_DECREF of the old value inside, but it doesn't seem to be spilling. The same thing is happening for POP_TOP.

@markshannon

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

[markshannon]

Is the bug in the trace or in _STORE_SUBSCR_LIST_INT_r32?

[Fidget-Spinner]

Sorry it seems I was wrong, it is being handled, but inside the uop body not in SPILL_OR_RELOAD. Sorry for the noise!