[Bug tree-optimization/84777] New: -Os inhibits all vectorization

[linux at carewolf dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84777

            Bug ID: 84777
           Summary: -Os inhibits all vectorization
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: linux at carewolf dot com
  Target Milestone: ---

Neither the command-line flag -ftree-loop-vectorize nor -fopenmp combined with
"#pragma omp simd" works when -Os is active.

It seems that it when specified manually vectorization should be work even in
-Os mode. I can almost see why -ftree-loop-vectorize wouldn't work, which is
why I tried the manual marking of loops to vectorize, but the latter didn't
work either.

I would suggest documenting this behavior and fix at least vectorizing manually
marked loops.