https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119470
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2025-03-26
Keywords| |missed-optimization
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
In VRP1 we have:
```
<bb 3> [local count: 955630224]:
_1 = inc (i_5);
_2 = i_5 + 1;
if (_1 != _2)
goto <bb 4>; [0.00%]
else
goto <bb 5>; [100.00%]
<bb 4> [count: 0]:
__builtin_unreachable ();
<bb 5> [local count: 1073741824]:
# i_5 = PHI <0(2), _1(3)>
```
Figuring out if we should reference _1 or _2 from i_5 is "hard", Sometimes GCC
do the replacement but not always and I am not sure we know which one is
correct always. In this case it is easy to use _2 is defined by i_5 but more
complex examples are out there.
