[Bug c/90552] New: attribute((optimize(3))) not overriding -Os

[pskocik at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90552

            Bug ID: 90552
           Summary: attribute((optimize(3))) not overriding -Os
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pskocik at gmail dot com
  Target Milestone: ---

I test-compiled ( https://gcc.godbolt.org/z/8bhbNa ):

__attribute((optimize(3))) int div(int X) { return X/3; }

with -O{0,1,2,3,s}, expecting to get the same assembly in all cases, but
__attribute((optimize(3))) is failing to override the last case, namely -Os.

(I'd like the function to not use the idiv instruction even if the rest of the
file is compiled with -Os).

Please correct me if I'm wrong to expect `__attribute((optimize(3)))` to be
able to override `-Os`.

This behavior appears to exist on all gcc versions.