dom requires PROP_loops

[Paulo Matos]

> -----Original Message-----
> From: Richard Biener [mailto:richard.guenther@gmail.com]
> Sent: 13 March 2014 18:46
> To: Paulo Matos
> Cc: gcc@gcc.gnu.org
> Subject: RE: dom requires PROP_loops
> 
> On March 13, 2014 5:00:53 PM CET, Paulo Matos <pmatos@broadcom.com> wrote:
> >> -----Original Message-----
> >> From: Richard Biener [mailto:richard.guenther@gmail.com]
> >> Sent: 13 March 2014 13:24
> >> To: Paulo Matos
> >> Cc: gcc@gcc.gnu.org
> >> Subject: Re: dom requires PROP_loops
> >>
> >>
> >> Probably RTL cfgcleaup needs the same treatment as GIMPLE cfgcleanup
> >> then - allow removal if loop properties allows it.
> >>
> >
> >In both cfgcleanup.c and tree-cfgcleanup.c I can see code that protects
> >loop latches, but I see no code that allows removal of latch if
> >property allows it.
> >From what you say I would expect this would already be implemented in
> >tree-cfgcleanup.c, however what actually happens is that since
> >current_loops is non-null (PROP_loops is not destroyed in tree
> >loopdone), tree-cfgcleanup call chain ends up calling
> >cleanup_tree_cfg_bb on the bb loop latch and tree_forwarder_block_p
> >returns false for bb because of the following code thereby not removing
> >the latch:
> >  if (current_loops)
> >    {
> >      basic_block dest;
> >      /* Protect loop latches, headers and preheaders.  */
> >      if (bb->loop_father->header == bb)
> >	return false;
> >      dest = EDGE_SUCC (bb, 0)->dest;
> >
> >      if (dest->loop_father->header == dest)
> >	return false;
> >    }
> >
> >Why do we need to protect the latch?
> 
> You are looking at old sources.
>

That's correct. I was looking at 4.8. Let me take a look at what trunk is doing... :)
 
> Richard.
> 
> >Paulo Matos
> >
> >> Richard.
> >>
>