RFR: 8256318: AArch64: Add support for floating-point absolute difference [v3]

[Andrew Haley]

On 16/11/2020 13:31, dongbo (E) wrote:
> On 2020/11/16 19:57, Andrew Haley wrote:
>> On 11/16/20 3:15 AM, Ningsheng Jian wrote:
>>> On Mon, 16 Nov 2020 02:51:05 GMT, Dong Bo <dongbo at openjdk.org> wrote:
>>>
>>>> But I feel a little bit inconsistent that only the new fabd is added into aarch64_neon.ad,
>>>> while other NEON intructions (i.e. fabs, fsub, fdiv, fsqrt, etc) are still in aarch64.ad.
>>>> And moving them all from aarch64.ad to aarch64_neon.ad deviates far away from this patch.
>>> Yes, I think when we introduced aarch64_neon.ad (m4), we just tried to keep that patch simple and would move other vector rules in future patches. Maybe Andrew can comment on this?
>> I wonder: I'm not sure if we should do the lot in one bang.
>>
>> I can't quite figure out the best thing to do. It'll be tricky to move
>> all of the SIMD instructions, but I guess it's the best thing to do. It'll
>> make backports hard, but we don't see many in this area.
>
> Yes. Moving all NEON instructions to aarch64_neon.ad would make the code 
> clearer and more consistent.

OK. This should definitely be done as a stand-alone change/

> I put ABS/FABS/FABD into aarch64_neon.ad, hope it would be a good start
> for this work. Thanks.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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