https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81958
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|spurious |[9/10/11 Regression]
|-Wmaybe-uninitialized |spurious
|warning in gcc-8, or with |-Wmaybe-uninitialized
|-O1 |warning in gcc-8, or with
| |-O1
Known to fail| |10.2.0, 11.0, 8.3.0, 9.3.0
CC| |msebor at gcc dot gnu.org
Known to work| |7.3.0
Last reconfirmed|2017-09-30 00:00:00 |2021-4-2
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Reconfirming with GCC 11 as a GCC 8 regression introduced in r249013. It fails
the same with -O1 and -O2. I think the warning seems to be doing what it's
designed to do. The IL below annotated with my comments in bb 7 shows that
there is a patch along which the use is uninitialized.
void lpfc_debug_dump_all_queues (unsigned int maxidx)
{
unsigned long ivtmp.7;
unsigned int eqidx;
struct lpfc_queue * eq;
struct lpfc_queue * cq_phba.0_1;
struct lpfc_queue * _2;
int _5;
unsigned int _23;
long unsigned int _24;
<bb 2> [count: 0]:
# .MEM_12 = VDEF <.MEM_11(D)>
printk ();
# VUSE <.MEM_12>
cq_phba.0_1 = cq_phba;
goto <bb 4>; [0.00%]
<bb 3> [count: 0]:
# VUSE <.MEM_12>
_2 = cq_phba.0_1->hba_eq;
_24 = ivtmp.7_25 * 16;
eq_16 = _2 + _24;
# VUSE <.MEM_12>
_5 = eq_16->queue_id;
ivtmp.7_26 = ivtmp.7_25 + 1;
if (_5 != 0)
goto <bb 9>; [0.00%]
else
goto <bb 8>; [0.00%]
<bb 9> [count: 0]:
goto <bb 7>; [100.00%]
<bb 8> [count: 0]:
<bb 4> [count: 0]:
# eq_7 = PHI <eq_14(D)(2), eq_16(8)>
# ivtmp.7_25 = PHI <0(2), ivtmp.7_26(8)>
_23 = (unsigned int) ivtmp.7_25;
if (maxidx_15(D) > _23)
goto <bb 3>; [0.00%]
else
goto <bb 5>; [0.00%]
<bb 5> [count: 0]:
if (maxidx_15(D) == _23)
goto <bb 6>; [0.00%]
else
goto <bb 10>; [0.00%]
<bb 10> [count: 0]:
goto <bb 7>; [100.00%]
<bb 6> [count: 0]:
# VUSE <.MEM_12>
eq_18 = cq_phba.0_1->hba_eq;
<bb 7> [count: 0]:
## eq_7(10) = PHI <eq_14(D)(2), eq_16(8)>
## eq_7(10) = eq_14(D)(2) (unconditional: 2 -> 4)
## eq_9 = eq_7 = eq_14(D)(2)
## if (maxidx_15(D) <= _23 && maxidx_15(D) != _23: 4 -> 5, 5 -> 10, 10 ->
7)
# eq_9 = PHI <eq_7(10), eq_18(6), eq_16(9)>
# .MEM_19 = VDEF <.MEM_12>
printk (eq_9); [tail call]
# VUSE <.MEM_19>
return;
}
Before r249013 there is no uninitialized read from eq in the IL:
; Function lpfc_debug_dump_all_queues (lpfc_debug_dump_all_queues,
funcdef_no=0, decl_uid=1800, cgraph_uid=0, symbol_order=1)
lpfc_debug_dump_all_queues (unsigned int maxidx)
{
unsigned int eqidx;
struct lpfc_queue * eq;
struct lpfc_queue * prephitmp_1;
unsigned long _2;
int _5;
struct lpfc_queue * _20;
int _22;
struct lpfc_queue * pretmp_23;
struct lpfc_queue * pretmp_24;
struct lpfc_queue * cq_phba.0_25;
struct lpfc_queue * _26;
unsigned long _28;
<bb 2> [14.44%]:
printk ();
if (maxidx_15(D) != 0)
goto <bb 4>; [92.50%]
else
goto <bb 3>; [7.50%]
<bb 3> [1.08%]:
pretmp_23 = cq_phba;
pretmp_24 = pretmp_23->hba_eq;
goto <bb 7>; [100.00%]
<bb 4> [13.32%]:
cq_phba.0_25 = cq_phba;
_26 = cq_phba.0_25->hba_eq;
_22 = _26->queue_id;
if (_22 != 0)
goto <bb 9>; [7.50%]
else
goto <bb 10>; [92.50%]
<bb 10> [12.32%]:
goto <bb 6>; [100.00%]
<bb 9> [1.00%]:
goto <bb 8>; [100.00%]
<bb 5> [79.18%]:
_2 = (unsigned long) eq_29;
_28 = _2 + 16;
_20 = (struct lpfc_queue *) _28;
_5 = MEM[base: _20, offset: 0B];
if (_5 != 0)
goto <bb 11>; [7.50%]
else
goto <bb 12>; [92.50%]
<bb 11> [5.94%]:
goto <bb 8>; [100.00%]
<bb 12> [73.24%]:
<bb 6> [85.60%]:
# eqidx_27 = PHI <eqidx_17(12), 0(10)>
# eq_29 = PHI <_20(12), _26(10)>
eqidx_17 = eqidx_27 + 1;
if (maxidx_15(D) != eqidx_17)
goto <bb 5>; [92.50%]
else
goto <bb 13>; [7.50%]
<bb 13> [6.42%]:
<bb 7> [5.44%]:
# prephitmp_1 = PHI <_26(13), pretmp_24(3)>
<bb 8> [14.44%]:
# eq_9 = PHI <_26(9), prephitmp_1(7), _20(11)>
printk (eq_9); [tail call]
return;
}
