[Bug rtl-optimization/64081] [5/6/7 Regression] r217827 prevents RTL loop unroll

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64081

--- Comment #60 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
Proposed all-inclusive patch for this PR.

https://gcc.gnu.org/ml/gcc-patches/2017-02/msg00691.html