Re: [AArch64][PR65375] Fix RTX cost for vector SET

[Kugan <kugan.vivekanandarajah@linaro.org>]

ping?

Thanks,
Kugan

On 17/03/15 12:19, Kugan wrote:
> 
> 
> On 17/03/15 03:48, Kyrill Tkachov wrote:
>>
>> On 16/03/15 13:15, Kugan wrote:
>>> On 16/03/15 23:32, Kugan wrote:
>>>>>> lower-subreg.c:compute_costs() only cares about the cost of a (set
>>>>>> (reg)
>>>>>> (const_int )) move but I think the intention, at least for now, is to
>>>>>> return extra_cost->vect.alu for all the vector operations.
>>>>> Almost, what we want at the moment is COSTS_N_INSNS (1) +
>>>>> extra_cost->vect.alu
>>>> Thanks Kyrill for the review.
>>>>
>>>>>> Regression tested on aarch64-linux-gnu with no new regression. Is this
>>>>>> OK for trunk?
>>>>> Are you sure it's a (set (reg) (const_int)) that's being costed here? I
>>>>> thought for moves into vecto registers it would be a (set (reg)
>>>>> (const_vector)) which we don't handle in our rtx costs currently. I
>>>>> think the correct approach would be to extend the aarch64_rtx_costs
>>>>> switch statement to handle the CONST_VECT case. I believe you can use
>>>>> aarch64_simd_valid_immediate to check whether x is a valid immediate
>>>>> for
>>>>> a simd instruction and give it a cost of extra_cost->vect.alu. The
>>>>> logic
>>>>> should be similar to the CONST_INT case.
>>>> Sorry about the (set (reg) (const_int)) above. But the actual RTL that
>>>> is being split at 220r.subreg2 is
>>>>
>>>> (insn 11 10 12 2 (set (subreg:V4SF (reg/v:OI 77 [ __o ]) 0)
>>>>           (subreg:V4SF (reg/v:OI 73 [ __o ]) 0))
>>>> /home/kugan/work/builds/gcc-fsf-gcc/tools/lib/gcc/aarch64-none-linux-gnu/5.0.0/include/arm_neon.h:22625
>>>>
>>>> 800 {*aarch64_simd_movv4sf}
>>>>        (nil))
>>>>
>>>> And also, if we return RTX cost above COSTS_N_INSNS (1), it will be
>>>> split and it dosent recover from there. Therefore we need something like
>>>> the below to prevent that happening.
>>>>
>>> Hi Kyrill,
>>>
>>> How about the attached patch? It is similar to what is currently done
>>> for scalar register move.
>>
>> Hi Kugan,
>> yeah, I think this is a better approach, though I can't approve.
>>
> 
> Here is the patch with minor comment update. Regression tested on
> aarch64-linux-gnu with no new regression. Is this
> OK for trunk?
> 
> Thanks,
> Kugan
> 
> gcc/ChangeLog:
> 
> 2015-03-17  Kugan Vivekanandarajah  <kuganv@linaro.org>
>             Jim Wilson  <jim.wilson@linaro.org>
> 
> 	PR target/65375
> 	* config/aarch64/aarch64.c (aarch64_rtx_costs): Handle
> 	vector register copies.
> 
> 
>