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Re: [PATCH][ARM] Implement vectorizer cost hooks


Richard,

Thanks for your comments.

Here a new version with the changes you suggested.

Christophe


On 11 February 2013 11:57, Richard Earnshaw <rearnsha@arm.com> wrote:
> On 05/02/13 18:18, Christophe Lyon wrote:
>>
>> Hi,
>>
>> Following the discussion about "disable peeling" [1] a few weeks ago,
>> it turned out that the vectorizer cost model needed some
>> implementation for ARM.
>>
>> The attached patch implements arm_builtin_vectorization_cost and
>> arm_add_stmt_cost, providing default costs when aligned and unaligned
>> loads/stores have the same cost (=1). init_cost and finish_cost still
>> use the default implementation (I noticed that x86 has chosen to
>> duplicate the default implementation without changing it, why?)
>>
>> Benchmarking shows very little variation, expect a noticeable +1.6% on
>> coremark.
>>
>> If this is OK, we can then discuss how to disable peeling completely
>> when aligned and unaligned accesses have the same cost (and thus where
>> peeling is a loss of performance). I think adding a new hook is
>> necessary, since target descriptions may use different models for
>> these costs (eg x86 makes no difference between unaligned loads and
>> unaligned stores).
>>
>> Thanks,
>>
>> Christophe.
>>
>> [1] http://gcc.gnu.org/ml/gcc/2012-12/msg00036.html
>>
>> 2013-02-05  Christophe Lyon <christophe.lyon@linaro.org>
>>
>>          * config/arm/arm.c (arm_builtin_vectorization_cost)
>>          (arm_add_stmt_cost): New functions.
>>          (TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST)
>>          (TARGET_VECTORIZE_ADD_STMT_COST): Define.
>>          (struct processor_costs): New struct type.
>>          (default_arm_cost): New struct of type processor_costs.=
>>
>
> Christophe,
>
> Thanks for the patch.  This is mostly OK, but please can you make the
> following changes.
>
> +struct processor_costs {
>
> Please name this something like cpu_vec_costs.  It's not the only cost table
> in the back-end.
>
> +struct processor_costs default_arm_cost = {    /* arm generic costs.  */
>
> Similarly, use something like default_arm_vec_cost.
>
> +const struct processor_costs *arm_cost = &default_arm_cost;
>
> And here.  But better still, link this through the current_tune table rather
> than introducing a new global.
>
> Finally,
>
> @@ -27256,4 +27272,130 @@ arm_validize_comparison (rtx *comparison, rtx *
> op1, rtx * op2)
>
>  }
>
> +/* Vectorizer cost model implementation.  */
>
>
> Please put the patch in a more suitable location rather than just dumping it
> at the end of the file.  There are already numerous functions related to
> costs that are mostly grouped together.  I suggest this goes near the
> rtx_costs code.
>
> R.
>
>

Attachment: vect-cost-model2.txt
Description: Text document

Attachment: vect-cost-model2.patch
Description: Binary data


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