https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106155
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-07-01
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Target Milestone|--- |12.2
Ever confirmed|0 |1
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
init_from_control_deps {{0 -> 3}}:
i_44 != 2 (expanded)
NOT (i_44 == 2)
After normalization [DEF]:
i_44 != 2 (expanded)
NOT (i_44 == 2)
After normalization [USE]:
f2 (emax_8);
is conditional on:
ivtmp.7_37 == 2 (expanded)
ivtmp.7_37 == 2
Which is funny we get:
# ivtmp.7_37 = PHI <ivtmp.7_38(9), 0(2)>
i_44 = (int) ivtmp.7_37;
if (i_44 == 2)
goto <bb 4>; [12.49%]
else
goto <bb 10>; [87.51%]
....
if (ivtmp.7_37 == 2)
goto <bb 8>; [12.49%]
else
goto <bb 9>; [87.51%]
<bb 8> [local count: 268435456]:
f2 (emax_8);
I don't know why ivopts only changed the second if and not the first.
Oh because the second is the exit check:
Replacing exit test: if (ivtmp_39 != 0)
Replacing exit test: if (i_40 == 2)
If we change the size to 4 and keep the 2 as 2, there would be no warning.
And if then change 2 to 3, the warning is back.
So there is a missed optimization of changing the internal comparison for the
IV to the new type if the right side is a constant.
