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Re: [PATCH, rs6000 v2] Make load cost more in vectorization cost for P8/P9
Hi Segher,
on 2019/11/8 上午6:36, Segher Boessenkool wrote:
> On Thu, Nov 07, 2019 at 11:22:12AM +0800, Kewen.Lin wrote:
>> One updated patch to enable it everywhere attached.
>
>> 2019-11-07 Kewen Lin <linkw@gcc.gnu.org>
>>
>> * config/rs6000/rs6000.c (rs6000_builtin_vectorization_cost): Make
>> scalar_load, vector_load, unaligned_load and vector_gather_load cost
>> more to conform hardware latency and insn cost settings.
>
>> case unaligned_load:
>> case vector_gather_load:
>
> ...
>
>> - /* Word aligned. */
>> - return 22;
>
>> + /* Word aligned. */
>> + return 44;
>
> I don't think it should go up from 22 all the way to 44 (not all insns here
> are loads). But exact cost doesn't really matter. Make it 30 perhaps?
>
Good point, I'll try the cost 33 (the avg. of 22 and 44).
> 44 (as well as 22) are awfully precise numbers for a very imprecise cost
> like this ;-)
Yep! ;-)
>
> With either cost, whatever seems reasonable to you and works well in your
> tests: approved for trunk. Thanks!
Thanks! I'll kick off two regression testing on both BE and LE with new cost,
then commit it if everything goes well.
BR,
Kewen