https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95685
--- Comment #1 from Jim Wilson <wilson at gcc dot gnu.org> --- The problem with the constant isn't apparent until we reach RTL generation and see that it requires two instructions to load. Then once in RTL optimization passes we have mostly block local optimizations that aren't going to notice the same constant used in 3 different blocks and optimize it. The if statement inside the unrolled loop bodies prevent RTL optimization passes from fixing this. So yes, this would work better if we could do loop invariant code motion before loop unrolling as you suggested.
