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

[law at redhat dot com]

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

--- Comment #49 from Jeffrey A. Law <law at redhat dot com> ---
Note there's also been a series of fixes to the generic doloop code over the
last 18 months.  So that's another avenue that might be worth pursuing.