Re: Popcount optimization using AVX512

On Tue, Mar 19, 2024 at 10:02:18AM +1300, David Rowley wrote:
> I looked at your latest patch and tried out the performance on a Zen4
> running windows and a Zen2 running on Linux. As follows:

Thanks for taking a look.

> The only thing I'd question in the patch is in pg_popcount_fast(). It
> looks like you've opted to not do the 32-bit processing on 32-bit
> machines. I think that's likely still worth coding in a similar way to
> how pg_popcount_slow() works. i.e. use "#if SIZEOF_VOID_P >= 8".
> Probably one day we'll remove that code, but it seems strange to have
> pg_popcount_slow() do it and not pg_popcount_fast().

The only reason I left it out was because I couldn't convince myself that
it wasn't dead code, given we assume that popcntq is available in
pg_popcount64_fast() today.  But I don't see any harm in adding that just
in case.

-- 
Nathan Bossart
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