https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61837
--- Comment #9 from luoxhu at gcc dot gnu.org ---
(In reply to Segher Boessenkool from comment #8)
> -funswitch-loops changes things like
>
> for (...) {
> if (...)
> ...1;
> else
> ...2;
> }
>
> into
>
> if (...) {
> for (...)
> ...1;
> } else {
> for (...)
> ...2;
> }
>
> which often is not a good idea. This is why this is not done at -O2:
> -O2 is only for optimisations that almost never hurt performance.
Yes, for this case it performs better with unswitch-loops, and I see many usage
of -O2 with unswith-loops in testsuite. I thought you were meaning do this at
O2 without -funswitch-loops...
