Re: Do not give realistic estimates for loop with array accesses

[Richard Biener <rguenther at suse dot de>]

On Wed, 30 Mar 2016, Jan Hubicka wrote:

> > 
> > You are only changing one place in this file.
> 
> You are right. I am attaching the updated patch which I am re-testing now.
> > 
> > The vectorizer already checks this (albeit indirectly):
> > 
> >   HOST_WIDE_INT max_niter
> >     = max_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
> >   if ((LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
> >        && (LOOP_VINFO_INT_NITERS (loop_vinfo) < vectorization_factor))
> >       || (max_niter != -1
> >           && (unsigned HOST_WIDE_INT) max_niter < vectorization_factor))
> >     {
> >       if (dump_enabled_p ())
> >         dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> >                          "not vectorized: iteration count smaller than "
> >                          "vectorization factor.\n");
> >       return false;
> >     }
> 
> Yes, but one tests only vectorization_factor and other min_profitable_estimate
> which probably should be greater than vectorization_factor.
> 
> The check above should therefore become redundant.  My reading of the code is
> that min_profiltable_estimate is computed after the check above, so it is
> probably an useful shortcut and the message is also bit more informative.
> I updated the later test to use max_niter variable once it is computed.
> 
> OK with those changes assuming testing passes?

Ok.

Richard.

> Honza
> 
> 	* tree-ssa-loop-niter.c (idx_infer_loop_bounds): We can't get realistic
> 	estimates here.
> 	* tree-ssa-loop-unswitch.c (tree_unswitch_single_loop): Use also
> 	max_loop_iterations_int.
> 	(tree_unswitch_outer_loop): Likewise.
> 	* tree-ssa-loop-ivopts.c (avg_loop_niter): Likewise.
> 	* tree-vect-loop.c (vect_analyze_loop_2): Likewise.
> Index: tree-ssa-loop-ivopts.c
> ===================================================================
> --- tree-ssa-loop-ivopts.c	(revision 234516)
> +++ tree-ssa-loop-ivopts.c	(working copy)
> @@ -121,7 +121,11 @@ avg_loop_niter (struct loop *loop)
>  {
>    HOST_WIDE_INT niter = estimated_stmt_executions_int (loop);
>    if (niter == -1)
> -    return AVG_LOOP_NITER (loop);
> +    {
> +      niter = max_stmt_executions_int (loop);
> +      if (niter == -1 || niter > AVG_LOOP_NITER (loop))
> +        return AVG_LOOP_NITER (loop);
> +    }
>  
>    return niter;
>  }
> Index: tree-ssa-loop-niter.c
> ===================================================================
> --- tree-ssa-loop-niter.c	(revision 234516)
> +++ tree-ssa-loop-niter.c	(working copy)
> @@ -3115,7 +3115,6 @@ idx_infer_loop_bounds (tree base, tree *
>    tree low, high, type, next;
>    bool sign, upper = true, at_end = false;
>    struct loop *loop = data->loop;
> -  bool reliable = true;
>  
>    if (TREE_CODE (base) != ARRAY_REF)
>      return true;
> @@ -3187,14 +3186,14 @@ idx_infer_loop_bounds (tree base, tree *
>        && tree_int_cst_compare (next, high) <= 0)
>      return true;
>  
> -  /* If access is not executed on every iteration, we must ensure that overlow may
> -     not make the access valid later.  */
> +  /* If access is not executed on every iteration, we must ensure that overlow
> +     may not make the access valid later.  */
>    if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
>        && scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
>  				step, data->stmt, loop, true))
> -    reliable = false;
> +    upper = false;
>  
> -  record_nonwrapping_iv (loop, init, step, data->stmt, low, high, reliable, upper);
> +  record_nonwrapping_iv (loop, init, step, data->stmt, low, high, false, upper);
>    return true;
>  }
>  
> Index: tree-ssa-loop-unswitch.c
> ===================================================================
> --- tree-ssa-loop-unswitch.c	(revision 234516)
> +++ tree-ssa-loop-unswitch.c	(working copy)
> @@ -223,6 +223,8 @@ tree_unswitch_single_loop (struct loop *
>        /* If the loop is not expected to iterate, there is no need
>  	 for unswitching.  */
>        iterations = estimated_loop_iterations_int (loop);
> +      if (iterations < 0)
> +        iterations = max_loop_iterations_int (loop);
>        if (iterations >= 0 && iterations <= 1)
>  	{
>  	  if (dump_file && (dump_flags & TDF_DETAILS))
> @@ -439,6 +441,8 @@ tree_unswitch_outer_loop (struct loop *l
>    /* If the loop is not expected to iterate, there is no need
>        for unswitching.  */
>    iterations = estimated_loop_iterations_int (loop);
> +  if (iterations < 0)
> +    iterations = max_loop_iterations_int (loop);
>    if (iterations >= 0 && iterations <= 1)
>      {
>        if (dump_file && (dump_flags & TDF_DETAILS))
> Index: tree-vect-loop.c
> ===================================================================
> --- tree-vect-loop.c	(revision 234516)
> +++ tree-vect-loop.c	(working copy)
> @@ -2063,6 +2063,8 @@ start_over:
>  
>    estimated_niter
>      = estimated_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
> +  if (estimated_niter != -1)
> +    estimated_niter = max_niter;
>    if (estimated_niter != -1
>        && ((unsigned HOST_WIDE_INT) estimated_niter
>            <= MAX (th, (unsigned)min_profitable_estimate)))
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)