cosmetic change - simplify cse.c:preferable()

[Richard Guenther]

On Wed, 18 Jul 2012, Dodji Seketeli wrote:

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

I don't think it's any good or clearer to understand.

Richard.

> Thanks.
> 
> Dimitrios Apostolou <jimis@gmx.net> a ?crit:
> 
> > 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
> >
> 
> 

-- 
Richard Guenther <rguenther@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend