https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101335
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-07-05
Keywords| |wrong-code
Version|unknown |12.0
Summary|wrong code at -Os and above |wrong code at -O2 and above
|on x86_64-linux-gnu |
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also -fwrapv works around the issue, -fsanitize=undefined does not output any
undefined behavior either.
EVRP has the first difference.
Before EVRP we had:
a.0_1 = aD.1942; // -1u
_2 = ~a.0_1; //0u
c_9 = (intD.6) _2; //0
_3 = c_9 + -10; // -10
d_10 = (unsigned intD.9) _3; //-10u
if (_2 < d_10) // 0u < -10u which is true
But EVRP:
Predicate evaluates to: DON'T KNOW
folding with relation >
Predicate evaluates to: 0
EVRP:hybrid: Second query simplifed stmt
Folded into: if (0 != 0)
---- CUT ----
Looks like this value relation is being used but rather it should have just
converted to != rather < with the casts happening:
Registering value_relation (_3 < c_9) (bb2) at _3 = c_9 + -10;
