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

[segher at gcc dot gnu.org]

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

--- Comment #52 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Aldy Hernandez from comment #50)
> Though at this
> point, I'd rather we figure out why the erroneous code is being generated in
> comment 45.

If you can send me the output (.s and .c.*) with -dap I can probably
figure it out.  But please with a cut-down testcase -- this 2.5MB source
file results in 2.5GB of output files.