Re: [RFC]: Removing old Falkor ifuncs

[Wilco Dijkstra <Wilco.Dijkstra@arm.com>]

Hi Siddhesh,

>>On 2022-12-09 10:14, Wilco Dijkstra wrote:
>>> Do we need the ifuncs for Falkor? The SIMD memcpy is now the default
>>> generic memcpy and that is quite similar to the Falkor one, so it seems
>>> time to remove the Falkor variants. Since you are the original author,
>>> what do you think?
>>
>> The key differentiator in memcpy/memmove at that time was the register 
>> number usage since that affected how the hardware prefetcher performed. 
>> Changing that might affect performance on falkor, although I don't 
>> exactly remember by how much.
>
> If there was a difference, it would likely be on large copies. But it would be hard
> to test without access to a machine...

I managed to get an old Falkor revived, so was able to finally run benchtests.
The new generic memcpy is about 10% faster on bench-memcpy-random test
when sizes fit in L1, and about 5% faster overall. Bench-memcpy-large and -walk
are very similar, so it doesn't seem to have any effect on prefetching in large copies.

So it looks like the new generic memcpy is better overall.

Cheers,
Wilco