[PATCH] Fix up noce_try_abs again (PR rtl-optimization/68670)

[Bernd Schmidt]

On 12/09/2015 11:37 PM, Jakub Jelinek wrote:
> Not sure what I've been thinking when writing the previous noce_try_abs fix.
> I thought that the optimization can be applied for all the conditions,
> and whether it can be applied depends on if it is cond ? ~x : x or
> cond ? x : ~x.  But that is not the case, the optimization can be only
> applied to a subset of conditions, and when it can be applied, it can be
> applied to both the cond ? ~x : x and cond ? x : ~x cases (depending on
> the condition one is one_cmpl_abs (x) and the other ~one_cmpl_abs (x)).

Odd, I thought you made a good argument last time :-( Sorry for not 
catching the problem.

>   	switch (GET_CODE (cond))
>   	  {
> -	  case GT:
> -	    if (!negate)
> -	      return FALSE;
> -	    break;
>   	  case GE:
> -	    /* >= 0 is the same case as above > -1.  */
> -	    if (negate)
> -	      return FALSE;
> -	    break;
>   	  case LT:
> -	    if (negate)
> -	      return FALSE;
> -	    break;
> -	  case LE:
> -	    /* <= 0 is the same case as above < 1.  */
> -	    if (!negate)
> -	      return FALSE;
>   	    break;
>   	  default:
>   	    return FALSE;

This turns into a much simpler if statement, doesn't it? Ok with that 
change.

> +/* PR rtl-optimization/68670 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -ftracer" } */

Curious what effect -ftracer has here?


Bernd