Re: [PATCH] Fix PR37053: Move tweaks of commutative precedence to target hook

[Maxim Kuvyrkov <maxim at codesourcery dot com>]

Maxim Kuvyrkov wrote:
> Luis Machado wrote:

...

> > I gave it a try with Maxim's patch from ticket #37053 and it degraded
> > performance pretty badly (> 30%), and galgel degraded more than 75%.
> > Both 32-bit and 64-bit saw degradations.
>
> The patch in PR37053 is the one adding target hook.  This patch should 
> not affect the generated code at all.  If it does, can you please send 
> the the difference in dumps?  I understand that this patch does not seem 
> to be a favorite here, but I'm curious where I've made a mistake.

The mistake is in rs6000_commutative_operand_precedence(); the 
precedence value should be decrement for everything but the pointers, 
current code does exactly the opposite.

The hook implementation should be:

static int
rs6000_commutative_operand_precedence (const_rtx op, int value)
{
  /* Prefer pointer objects over non pointer objects.
     For rationale see PR28690.  */
  if (GET_RTX_CLASS (GET_CODE (op)) == RTX_OBJ
      && ((REG_P (op) && REG_POINTER (op))
	  || (MEM_P (op) && MEM_POINTER (op))))
    /* value = -1 */;
  else
    /* value = -2 */
    --value;

  return value;
}

--
Maxim