RE: [PATCH] Fix for PR64081 in RTL loop unroller

["Zamyatin, Igor" <igor dot zamyatin at intel dot com>]

> 
> Is it really sufficient here to verify that all the defs are on latch predecessors,
> what about the case where there is a predecessor without a def.  How do
> you guarantee domination in that case?
> 
> ISTM that given the structure for the code you're writing that you'd want to
> verify that in the event of multiple definitions that all of them appear on
> immediate predecessors of the latch *and* that each immediate
> predecessor has a definition.

Yes, do you think it's better to check exactly immediate predecessors?

> > -
> > -      if (!just_once_each_iteration_p (current_loop, DF_REF_BB (adef)))
> > -       return false;
> > +       {
> > +         def_num++;
> > +         if (!(def_pred_latch = def_pred_latch_p (adef))
> > +             || !rtx_equal_p( PATTERN (DF_REF_INSN (single_rd)),
> 
> Whitespace nit here.  Whitespace goes before the open paren for the
> function call, not after.

Thanks for catching this!

> 
> 
> > @@ -351,10 +384,10 @@ latch_dominating_def (rtx reg, df_ref *def)
> >   static enum iv_grd_result
> >   iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
> 
> And in this routine, you appear to do both checks.  ie, each def is on an
> immediate predecessor and each immediate predecessor has a def.  Is there
> some reason why iv_get_reaching_def has the stronger check while
> latch_dominating_def does not?

Looks like I was sure that latch_dominating_def always goes after iv_get_reaching_def but now I see it is not true. Will add another check in latch_dominating_def.

Thanks,
Igor

> 
> jeff