Re: [PATCH 1v2/3][vect] Add main vectorized loop unrolling

["Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com>]

[-- Attachment #1: Type: text/plain, Size: 3009 bytes --]

Hi,

I don't think I ever ended up posting the rebased version on top of the 
epilogue mode patch. So here it is, I think I had a conditional OK if I 
split the epilogue mode patch, but just want to double check this is OK 
for trunk?


gcc/ChangeLog:

         * tree-vect-loop.c (vect_estimate_min_profitable_iters): Pass 
new argument
         suggested_unroll_factor.
         (vect_analyze_loop_costing): Likewise.
         (_loop_vec_info::_loop_vec_info): Initialize new member 
suggested_unroll_factor.
         (vect_determine_partial_vectors_and_peeling): Make epilogue of 
unrolled
         main loop use partial vectors.
         (vect_analyze_loop_2): Pass and use new argument 
suggested_unroll_factor.
         (vect_analyze_loop_1): Likewise.
         (vect_analyze_loop): Change to intialize local 
suggested_unroll_factor and use it.
         (vectorizable_reduction): Don't use single_defuse_cycle when 
unrolling.
         * tree-vectorizer.h (_loop_vec_info::_loop_vec_info): Add new 
member suggested_unroll_factor.
         (vector_costs::vector_costs): Add new member 
m_suggested_unroll_factor.
         (vector_costs::suggested_unroll_factor): New getter function.
         (finish_cost): Set return argument suggested_unroll_factor.



Regards,
Andre

On 30/11/2021 13:56, Richard Biener wrote:
> On Tue, 30 Nov 2021, Andre Vieira (lists) wrote:
>
>> On 25/11/2021 12:46, Richard Biener wrote:
>>> Oops, my fault, yes, it does.  I would suggest to refactor things so
>>> that the mode_i = first_loop_i case is there only once.  I also wonder
>>> if all the argument about starting at 0 doesn't apply to the
>>> not unrolled LOOP_VINFO_EPIL_USING_PARTIAL_VECTORS_P as well?  So
>>> what's the reason to differ here?  So in the end I'd just change
>>> the existing
>>>
>>>     if (LOOP_VINFO_EPIL_USING_PARTIAL_VECTORS_P (first_loop_vinfo))
>>>       {
>>>
>>> to
>>>
>>>     if (LOOP_VINFO_EPIL_USING_PARTIAL_VECTORS_P (first_loop_vinfo)
>>>         || first_loop_vinfo->suggested_unroll_factor > 1)
>>>       {
>>>
>>> and maybe revisit this when we have an actual testcase showing that
>>> doing sth else has a positive effect?
>>>
>>> Thanks,
>>> Richard.
>> So I had a quick chat with Richard Sandiford and he is suggesting resetting
>> mode_i to 0 for all cases.
>>
>> He pointed out that for some tunings the SVE mode might come after the NEON
>> mode, which means that even for not-unrolled loop_vinfos we could end up with
>> a suboptimal choice of mode for the epilogue. I.e. it could be that we pick
>> V16QI for main vectorization, but that's VNx16QI + 1 in the array, so we'd not
>> try VNx16QI for the epilogue.
>>
>> This would simplify the mode selecting cases, by just simply restarting at
>> mode_i in all epilogue cases. Is that something you'd be OK?
> Works for me with an updated comment.  Even better with showing a
> testcase exercising such tuning.
>
> Richard.

[-- Attachment #2: vect_unroll8.patch --]
[-- Type: text/plain, Size: 1148 bytes --]

Hi,

I don't think I ever ended up posting the rebased version on top of the epilogue mode patch. So here it is.

OK for trunk?


gcc/ChangeLog:

        * tree-vect-loop.c (vect_estimate_min_profitable_iters): Pass new argument
        suggested_unroll_factor.
        (vect_analyze_loop_costing): Likewise.
        (_loop_vec_info::_loop_vec_info): Initialize new member suggested_unroll_factor.
        (vect_determine_partial_vectors_and_peeling): Make epilogue of unrolled
        main loop use partial vectors.
        (vect_analyze_loop_2): Pass and use new argument suggested_unroll_factor.
        (vect_analyze_loop_1): Likewise.
        (vect_analyze_loop): Change to intialize local suggested_unroll_factor and use it.
        (vectorizable_reduction): Don't use single_defuse_cycle when unrolling.
        * tree-vectorizer.h (_loop_vec_info::_loop_vec_info): Add new member suggested_unroll_factor.
        (vector_costs::vector_costs): Add new member m_suggested_unroll_factor.
        (vector_costs::suggested_unroll_factor): New getter function.
        (finish_cost): Set return argument suggested_unroll_factor.



Regards,
Andre