[PR45098,4/10] Iv init cost.

On 05/17/2011 09:17 AM, Tom de Vries wrote:
> 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

Resubmitting with comment.

The init cost of an iv will in general not be zero. It will be
exceptional that the iv register happens to be initialized with the
proper value at no cost. In general, there will at the very least be a
regcopy or a const set.

2011-05-05  Tom de Vries  <tom@codesourcery.com>

	PR target/45098
	* tree-ssa-loop-ivopts.c (determine_iv_cost): Prevent
	cost_base.cost == 0.

Hi,

> Resubmitting with comment.
> 
> The init cost of an iv will in general not be zero. It will be
> exceptional that the iv register happens to be initialized with the
> proper value at no cost. In general, there will at the very least be a
> regcopy or a const set.

OK.  Please add a comment explaining this to the code,

Zdenek

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

> Index: gcc/tree-ssa-loop-ivopts.c
> ===================================================================
> --- gcc/tree-ssa-loop-ivopts.c	(revision 173380)
> +++ gcc/tree-ssa-loop-ivopts.c	(working copy)
> @@ -4688,6 +4688,8 @@ determine_iv_cost (struct ivopts_data *d
>  
>    base = cand->iv->base;
>    cost_base = force_var_cost (data, base, NULL);
> +  if (cost_base.cost == 0)
> +      cost_base.cost = COSTS_N_INSNS (1);
>    cost_step = add_cost (TYPE_MODE (TREE_TYPE (base)), data->speed);
>  
>    cost = cost_step + adjust_setup_cost (data, cost_base.cost);

Sorry for being so late.  I was just curious...

Tom de Vries <vries@codesourcery.com> writes:
> The init cost of an iv will in general not be zero. It will be
> exceptional that the iv register happens to be initialized with the
> proper value at no cost. In general, there will at the very least be a
> regcopy or a const set.
>
> 2011-05-05  Tom de Vries  <tom@codesourcery.com>
>
> 	PR target/45098
> 	* tree-ssa-loop-ivopts.c (determine_iv_cost): Prevent
> 	cost_base.cost == 0.
> Index: gcc/tree-ssa-loop-ivopts.c
> ===================================================================
> --- gcc/tree-ssa-loop-ivopts.c	(revision 173380)
> +++ gcc/tree-ssa-loop-ivopts.c	(working copy)
> @@ -4688,6 +4688,8 @@ determine_iv_cost (struct ivopts_data *d
>  
>    base = cand->iv->base;
>    cost_base = force_var_cost (data, base, NULL);
> +  if (cost_base.cost == 0)
> +      cost_base.cost = COSTS_N_INSNS (1);
>    cost_step = add_cost (TYPE_MODE (TREE_TYPE (base)), data->speed);
>  
>    cost = cost_step + adjust_setup_cost (data, cost_base.cost);

...why does this reasoning apply only to this call to force_var_cost?

Richard