Re: [PATCH 01/15] rs6000: Split out rs6000_is_valid_and_mask_wide

[Richard Henderson <rth@redhat.com>]

On 08/12/2015 06:23 AM, Segher Boessenkool wrote:
> On Tue, Aug 11, 2015 at 06:11:30PM -0700, Richard Henderson wrote:
>> This allows testing for a mask without having to call GEN_INT.
>>
>> Cc: David Edelsohn <dje.gcc@gmail.com>
>> ---
>> 	* config/rs6000/rs6000.c (rs6000_is_valid_mask_wide): Split out from...
>> 	(rs6000_is_valid_mask): ... here.
>> 	(rs6000_is_valid_and_mask_wide): Split out from...
>> 	(rs6000_is_valid_and_mask): ... here.
> 
> I don't like these "_wide" names much.

It follows the existing practice within the backend.

>  You could overload the shorter
> name, if you really think creating some garbage const_int's is too much
> overhead (it might well be if you use it a lot more in later patches).

At one stage in the development (before I became much leaner with the search
for rotate), it really really mattered.

>> -bool
>> -rs6000_is_valid_mask (rtx mask, int *b, int *e, machine_mode mode)
>> +static bool
>> +rs6000_is_valid_mask_wide (unsigned HOST_WIDE_INT val, int *b, int *e, int n)
> 
> But why change the mode parameter?  The code was clearer before.

So that we don't have to look up GET_MODE_BITSIZE (mode).

>> +static bool
>> +rs6000_is_valid_and_mask_wide (unsigned HOST_WIDE_INT val, machine_mode mode)
>>  {
>>    int nb, ne;
>>  
>> -  if (!rs6000_is_valid_mask (mask, &nb, &ne, mode))
>> -    return false;
>> +  switch (mode)
>> +    {
>> +    case DImode:
>> +      if (!rs6000_is_valid_mask_wide (val, &nb, &ne, 64))
>> +	return false;
>> +      /* For DImode, we need a rldicl, rldicr, or a rlwinm with
>> +	 mask that does not wrap.  */
>> +      return (ne == 0 || nb == 63 || (nb < 32 && ne <= nb));
>>  
>> -  /* For DImode, we need a rldicl, rldicr, or a rlwinm with mask that
>> -     does not wrap.  */
>> -  if (mode == DImode)
>> -    return (ne == 0 || nb == 63 || (nb < 32 && ne <= nb));
>> +    case SImode:
>> +      if (!rs6000_is_valid_mask_wide (val, &nb, &ne, 32))
>> +	return false;
>> +      /* For SImode, rlwinm can do everything.  */
>> +      return (nb < 32 && ne < 32);
>>  
>> -  /* For SImode, rlwinm can do everything.  */
>> -  if (mode == SImode)
>> -    return (nb < 32 && ne < 32);
>> +    default:
>> +      return false;
>> +    }
>> +}
>>  
>> -  return false;
> 
> You don't need any of these changes then, either.

True, not *needed* per-se, but if you look closer I'm combining conditionals.
I think the replacement here is clearer.

>>    /* Otherwise, fill in the lowest "hole"; if we can do the result with
>>       one insn, we can do the whole thing with two.  */
>> -  unsigned HOST_WIDE_INT val = INTVAL (c);
>> +  unsigned HOST_WIDE_INT val = UINTVAL (c);
> 
> Does it matter?

No.


r~