Re: [PATCH] aarch64: Add support for -mcpu=grace

[Kyrylo Tkachov <ktkachov@nvidia.com>]

Hi Andrew,

> On 26 Jun 2024, at 23:02, Andrew Pinski <pinskia@gmail.com> wrote:
> 
> External email: Use caution opening links or attachments
> 
> 
> On Wed, Jun 26, 2024 at 12:40 AM Kyrylo Tkachov <ktkachov@nvidia.com> wrote:
>> 
>> Hi all,
>> 
>> This adds support for the NVIDIA Grace CPU to aarch64.
>> We reuse the tuning decisions for the Neoverse V2 core, but include a
>> number of architecture features that are not enabled by default in
>> -mcpu=neoverse-v2.
>> 
>> This allows Grace users to more simply target the CPU with -mcpu=grace
>> rather than remembering what extensions to tag on top of
>> -mcpu=neoverse-v2.
>> 
>> Bootstrapped and tested on aarch64-none-linux-gnu.
>> I’m pushing this to trunk.
> 
>> RNG
> 
> I noticed this is missing from grace but is included in neoverse-v2.
> Is that expected?

Yes, RNG is an optional configuration feature of Neoverse V2 (according to the TRM) and Grace doesn’t implement it. In fact, I don’t think the base -mcpu=neoverse-v2 should include it either (I’m testing a patch to remove it)

Thanks,
Kyrill


> 
> Thanks,
> Andrew Pinski
> 
> 
>> I have patches tested for the 14, 13, 12, 11 branches as well that I’d like to push there to make it simpler for our users to target Grace.
>> They are the same as this one logically, but they just account for slight syntactic differences and flag definitions that have happened since those branches.
>> Thanks,
>> Kyrill
>> 
>>        * config/aarch64/aarch64-cores.def (grace): New entry.
>>        * config/aarch64/aarch64-tune.md: Regenerate
>>        * doc/invoke.texi (AArch64 Options): Document the above.
>> 
>> Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>