Re: [PATCH 3/3] tree-optimization/114052 - niter analysis from undefined behavior

[Richard Biener <rguenther@suse.de>]

On Fri, 5 Apr 2024, Jan Hubicka wrote:

> > +	  /* When there's a call that might not return the last iteration
> > +	     is possibly partial.  This matches what we check in invariant
> > +	     motion.
> > +	     ???  For the call argument evaluation it would be still OK.  */
> > +	  if (!may_have_exited
> > +	      && is_gimple_call (stmt)
> > +	      && gimple_has_side_effects (stmt))
> > +	    may_have_exited = true;
> 
> I think you are missing here non-call EH, volatile asms and traps.
>  We have stmt_may_terminate_function_p which tests there.

That returns true for all variable array accesses, I think we want
to catch traps explicitly here.  I'm going to do

          if (!may_have_exited
              && (gimple_has_side_effects (stmt)
                  || stmt_can_throw_external (cfun, stmt)))
            may_have_exited = true;

that should cover all but the generic trapping and not use IPA info
to prove no side-effects.

Richard.

> Honza
> > +
> > +	  infer_loop_bounds_from_array (loop, stmt,
> > +					reliable && !may_have_exited);
> >  
> > -	  if (reliable)
> > +	  if (reliable && !may_have_exited)
> >              {
> >                infer_loop_bounds_from_signedness (loop, stmt);
> >                infer_loop_bounds_from_pointer_arith (loop, stmt);
> >              }
> >    	}
> > -
> >      }
> >  }
> >  
> > @@ -4832,7 +4855,7 @@ estimate_numbers_of_iterations (class loop *loop)
> >       diagnose those loops with -Waggressive-loop-optimizations.  */
> >    number_of_latch_executions (loop);
> >  
> > -  basic_block *body = get_loop_body (loop);
> > +  basic_block *body = get_loop_body_in_rpo (cfun, loop);
> >    auto_vec<edge> exits = get_loop_exit_edges (loop, body);
> >    likely_exit = single_likely_exit (loop, exits);
> >    FOR_EACH_VEC_ELT (exits, i, ex)
> > -- 
> > 2.35.3
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)