https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101912
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Known to fail| |10.3.0, 11.2.0, 12.0,
| |6.5.0, 7.5.0, 8.5.0, 9.3.0
Keywords| |diagnostic
Status|UNCONFIRMED |NEW
CC| |msebor at gcc dot gnu.org
Last reconfirmed| |2021-08-16
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed, not a regression. The warning pass considers only one condition: n
> 0. It doesn't consider the conjunction of that condition with those implied
by not using the other unintialized PHI operand and that the use is unreachable
otherwise (i.e., that !(corr == 1 && leapcnt != 0 && prevcorr - 1 > 1 && n !=
leapcnt) cannot be true at the point of the use). The logic seem too
complicated to me to figure it out but I could be missing something.
int tzloadbody ()
{
int corr;
int leapcnt;
int prevcorr;
int n;
_Bool _1;
_Bool _2;
_Bool _5;
unsigned int _6;
int _8;
unsigned int _9;
_Bool _21;
_Bool _27;
<bb 2> [local count: 95397018]:
# .MEM_12 = VDEF <.MEM_11(D)>
n_13 = getint ();
if (n_13 > 0)
goto <bb 7>; [96.34%] >>> if n > 0...
else
goto <bb 9>; [3.66%]
<bb 7> [local count: 91905487]: <<<
...prevcorr_14(D)(7) uninitialized here
<bb 3> [local count: 1034442874]: <<< if n > 0 && !(corr
== 1 && leapcnt != 0 && prevcorr - 1 > 1 && n != leapcnt)
# prevcorr_18 = PHI <corr_16(8), prevcorr_14(D)(7)> <<<
# leapcnt_23 = PHI <leapcnt_17(8), 0(7)>
# .MEM_20 = PHI <.MEM_15(8), .MEM_12(7)>
# .MEM_15 = VDEF <.MEM_20>
corr_16 = getint ();
if (corr_16 <= 0)
goto <bb 10>; [3.66%]
else
goto <bb 4>; [96.34%]
<bb 4> [local count: 996582264]:
_1 = corr_16 == 1;
_2 = leapcnt_23 != 0;
_9 = (unsigned int) prevcorr_18; <<<
-Wmaybe-uninitialized
_6 = _9 + 4294967295;
_5 = _6 > 1;
_21 = _1 & _2;
_27 = _5 & _21;
if (_27 != 0)
goto <bb 11>; [21.78%]
else
goto <bb 5>; [78.22%] >>> corr == 1 &&
leapcnt != 0 && prevcorr - 1 > 1
<bb 11> [local count: 217055616]:
goto <bb 6>; [100.00%]
<bb 5> [local count: 978344809]:
leapcnt_17 = leapcnt_23 + 1;
if (n_13 != leapcnt_17)
goto <bb 8>; [96.34%] >>> corr == 1 &&
leapcnt != 0 && prevcorr - 1 > 1 && n != leapcnt
else
goto <bb 12>; [3.66%]
<bb 12> [local count: 35807421]:
goto <bb 6>; [100.00%]
<bb 8> [local count: 942537388]:
goto <bb 3>; [100.00%] >>> corr == 1 &&
leapcnt != 0 && prevcorr - 1 > 1 && n != leapcnt
<bb 9> [local count: 3491531]:
<bb 6> [local count: 95397019]:
# _8 = PHI <0(9), n_13(12), -1(11), -1(10)>
# .MEM_10 = PHI <.MEM_12(9), .MEM_15(12), .MEM_15(11), .MEM_15(10)>
# VUSE <.MEM_10>
return _8;
}
