cosmetic change - simplify cse.c:preferable()

[Dodji Seketeli]

Hey Dimitrios,

I can't say much about your patch, so I am CC-ing the maintainers.

Thanks.

Dimitrios Apostolou <jimis@gmx.net> a écrit:

> Hello,
>
> I've had this patch some time now, it's simple and cosmetic only, I
> had done it while trying to understand expression costs in CSE. I
> think it's more readable than the previous one. FWIW it passed all
> tests on x86.
>
>
> Thanks,
> Dimitris
>
> === modified file 'gcc/cse.c'
> --- gcc/cse.c	2012-06-15 09:22:00 +0000
> +++ gcc/cse.c	2012-07-08 07:28:52 +0000
> @@ -713,32 +713,25 @@ approx_reg_cost (rtx x)
>  static int
>  preferable (int cost_a, int regcost_a, int cost_b, int regcost_b)
>  {
> -  /* First, get rid of cases involving expressions that are entirely
> -     unwanted.  */
> -  if (cost_a != cost_b)
> -    {
> -      if (cost_a == MAX_COST)
> -	return 1;
> -      if (cost_b == MAX_COST)
> -	return -1;
> -    }
> +  int cost_diff = cost_a - cost_b;
> +  int regcost_diff = regcost_a - regcost_b;
>  
> -  /* Avoid extending lifetimes of hardregs.  */
> -  if (regcost_a != regcost_b)
> +  if (cost_diff != 0)
>      {
> -      if (regcost_a == MAX_COST)
> -	return 1;
> -      if (regcost_b == MAX_COST)
> -	return -1;
> +      /* If none of the expressions are entirely unwanted */
> +      if ((cost_a != MAX_COST) && (cost_b != MAX_COST)
> +	  /* AND only one of the regs is HARD_REG */
> +	  && (regcost_diff != 0)
> +	  && ((regcost_a == MAX_COST) || (regcost_b == MAX_COST))
> +	  )
> +	/* Then avoid extending lifetime of HARD_REG */
> +	return regcost_diff;
> +
> +      return cost_diff;
>      }
>  
> -  /* Normal operation costs take precedence.  */
> -  if (cost_a != cost_b)
> -    return cost_a - cost_b;
> -  /* Only if these are identical consider effects on register pressure.  */
> -  if (regcost_a != regcost_b)
> -    return regcost_a - regcost_b;
> -  return 0;
> +  /* cost_a == costb, consider effects on register pressure */
> +  return regcost_diff;
>  }
>  
>  /* Internal function, to compute cost when X is not a register; called
>

-- 
		Dodji