Re: [PATCH] Fix PR62081

[Richard Biener <rguenther at suse dot de>]

On Thu, 14 Aug 2014, Sebastian Pop wrote:

> Richard Biener wrote:
> > 
> > The following fixes missing dominator computation before fixing loops.
> > Rather than doing even more such weird stuff in a pass gate function
> > this puts this into a new pass scheduled before the loop passes gate.
> > 
> 
> Ok.
> 
> > +unsigned int
> > +pass_fix_loops::execute (function *)
> > +{
> 
> I would add an early exit if there are no loops in the function
> (like in the original code below...)
> 
>     if (!loops_for_fn (fn))
>       return 0;

Note that's not how things work today - loops_for_fn () returns
non-NULL even for zero-loop functions as soon as we have CFG.
The "hack" below was for -fdump-passes which calls each gate
of every pass before the CFG is set up and thus would crash
gate_loop if we didn't do that check.  Of course -fdump-passes
reports sth that is not true for all functions here.

Richard.

> > +  if (loops_state_satisfies_p (LOOPS_NEED_FIXUP))
> > +    {
> > +      calculate_dominance_info (CDI_DOMINATORS);
> > +      fix_loop_structure (NULL);
> > +    }
> > +  return 0;
> > +}
> 
> [...]
> 
> >  /* Gate for loop pass group.  The group is controlled by -ftree-loop-optimize
> >     but we also avoid running it when the IL doesn't contain any loop.  */
> >  
> > @@ -57,9 +107,6 @@ gate_loop (function *fn)
> >    if (!loops_for_fn (fn))
> >      return true;
> 
> ... here.
> 
> >  
> > -  /* Make sure to drop / re-discover loops when necessary.  */
> > -  if (loops_state_satisfies_p (LOOPS_NEED_FIXUP))
> > -    fix_loop_structure (NULL);
> >    return number_of_loops (fn) > 1;
> >  }
>