[Bug tree-optimization/100934] [9/10/11/12 Regression] wrong code at -O3 during unrolling since r9-6299

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100934

--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 14 Jun 2021, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100934
> 
> --- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #8)
> > --- a/gcc/tree-ssa-threadupdate.c
> > +++ b/gcc/tree-ssa-threadupdate.c
> > @@ -2379,12 +2379,15 @@ jump_thread_path_registry::duplicate_thread_path
> > (edge entry,
> >       missuses of the functions.  I.e. if you ask to copy something weird,
> >       it will work, but the state of structures probably will not be
> >       correct.  */
> > +  bool loop_header_duplicated = false;
> >    for (i = 0; i < n_region; i++)
> >      {
> >        /* We do not handle subloops, i.e. all the blocks must belong to the
> >          same loop.  */
> >        if (region[i]->loop_father != loop)
> >         return false;
> > +      if (region[i]->loop_father == loop)
> > +       loop_header_duplicated = true;
> 
> The if right above this returns false if loop_father is not loop, so
> wouldn't be loop_header_duplicated == true whenever n_region != 0 (or always)?

whoops yes, this should be region[i] == loop->header but as said the
issue is elsewhere (patch in testing) and the issue in 
duplicate_thread_path does not have a testcase yet.