[Bug target/61837] missed loop invariant expression optimization

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61837

--- Comment #6 from Segher Boessenkool <segher at gcc dot gnu.org> ---
But -funswitch-loops is much stronger than we want here, and the wrong
thing to use at -O2 (it often generates *slower* code!)