[PR45098,3/10]

On 05/17/2011 09:10 AM, Tom de Vries wrote:
> Hi Zdenek,
> 
> I have a patch set for for PR45098.
> 
> 01_object-size-target.patch
> 02_pr45098-rtx-cost-set.patch
> 03_pr45098-computation-cost.patch
> 04_pr45098-iv-init-cost.patch
> 05_pr45098-bound-cost.patch
> 06_pr45098-bound-cost.test.patch
> 07_pr45098-nowrap-limits-iterations.patch
> 08_pr45098-nowrap-limits-iterations.test.patch
> 09_pr45098-shift-add-cost.patch
> 10_pr45098-shift-add-cost.test.patch
> 
> I will sent out the patches individually.
> 

OK for trunk?

Thanks,
- Tom

Hi,

> 2011-05-05  Tom de Vries  <tom@codesourcery.com>
> 
> 	PR target/45098
> 	* tree-ssa-loop-ivopts.c (computation_cost): Prevent cost of 0.

this looks strange.  Something like

  cost = seq_cost (seq, speed);
  if (MEM_P (rslt))
    the current code;
  else
    cost += rtx_cost (rslt, SET, speed));

would make more sense to me (if I understand correctly what you are
trying to achieve).

Zdenek

> Index: gcc/tree-ssa-loop-ivopts.c
> ===================================================================
> --- gcc/tree-ssa-loop-ivopts.c	(revision 173380)
> +++ gcc/tree-ssa-loop-ivopts.c	(working copy)
> @@ -2862,7 +2862,9 @@ computation_cost (tree expr, bool speed)
>    default_rtl_profile ();
>    node->frequency = real_frequency;
>  
> -  cost = seq_cost (seq, speed);
> +  cost = (seq != NULL_RTX
> +          ? seq_cost (seq, speed)
> +          : (unsigned)rtx_cost (rslt, SET, speed));
>    if (MEM_P (rslt))
>      cost += address_cost (XEXP (rslt, 0), TYPE_MODE (type),
>  			  TYPE_ADDR_SPACE (type), speed);

Hi Zdenek,

thanks for the review.

On 05/18/2011 09:26 AM, Zdenek Dvorak wrote:
>> 2011-05-05  Tom de Vries  <tom@codesourcery.com>
>>
>> 	PR target/45098
>> 	* tree-ssa-loop-ivopts.c (computation_cost): Prevent cost of 0.
> 
> this looks strange.  Something like
> 
>   cost = seq_cost (seq, speed);
>   if (MEM_P (rslt))
>     the current code;
>   else
>     cost += rtx_cost (rslt, SET, speed));
> 
> would make more sense to me (if I understand correctly what you are
> trying to achieve).
> 

Sorry for not putting an explanation in the first place.

I'm trying to achieve that the cost of forcing an int into a reg is not
0. Currently, if the expansion results in an rtx expression rather than
an insn, seq is NULL and seq_cost returns 0, after which
computation_cost returns 0:
...
(gdb) call debug_generic_expr (expr)
2000
(gdb) call debug_rtx (rslt)
(const_int 2000 [0x7d0])
(gdb) p seq
$5 = (rtx) 0x0
...

Using an assert on an x86_64 build, I found this case where seq != NULL_RTX:
...
gdb) call debug_generic_expr (expr)
(int) ((unsigned int) ivtmp.11 * 8)
(gdb) call debug_rtx (rslt)
(reg:SI 62)
(gdb) call debug_rtx (seq)
(insn 4 0 0 (parallel [
            (set (reg:SI 62)
                (ashift:SI (subreg:SI (reg:DI 59 [ ivtmp.11 ]) 0)
                    (const_int 3 [0x3])))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))
...
we don't need to additionally count a regcopy of r62 on top of seq_cost
in this case.

How about:
...
@@ -2866,6 +2878,8 @@ computation_cost (tree expr, bool speed)
   if (MEM_P (rslt))
     cost += address_cost (XEXP (rslt, 0), TYPE_MODE (type),
 			  TYPE_ADDR_SPACE (type), speed);
+  else if (!REG_P (rslt))
+    cost += (unsigned)rtx_cost (rslt, SET, speed);

   return cost;
 }
...
?

Thanks
- Tom

Hi Zdenek,

On 05/18/2011 05:24 PM, Zdenek Dvorak wrote:
> Hi,
> 
>> How about:
>> ...
>> @@ -2866,6 +2878,8 @@ computation_cost (tree expr, bool speed)
>>    if (MEM_P (rslt))
>>      cost += address_cost (XEXP (rslt, 0), TYPE_MODE (type),
>>  			  TYPE_ADDR_SPACE (type), speed);
>> +  else if (!REG_P (rslt))
>> +    cost += (unsigned)rtx_cost (rslt, SET, speed);
>>
>>    return cost;
>>  }
>> ...
>> ?
> 
> this looks ok to me 
> 

thanks for the review.

> (the cast to unsigned is not necessary, though?)

You're right, it's not, that was only necessary to prevent a warning in the
conditional expression originally proposed.

Checked in without cast.

Thanks,
- Tom