[Bug tree-optimization/88760] GCC unrolling is suboptimal

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88760

--- Comment #31 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Gimple passes know a lot about machine details, too.

Irrespective of if this is "low-level" or "high-level", it should be done
earlier than it is now.  It should either be done right after expand, or
somewhere before it.  Doing it in gimple seems easiest?