| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | "Devulapalli, Raghuveer" <raghuveer(dot)devulapalli(at)intel(dot)com>, "Shankaran, Akash" <akash(dot)shankaran(at)intel(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>, Ants Aasma <ants(dot)aasma(at)cybertec(dot)at>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, "Amonson, Paul D" <paul(dot)d(dot)amonson(at)intel(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Popcount optimization using AVX512 |
| Date: | 2024-07-31 03:12:18 |
| Message-ID: | Zqmrkt6Pyb543bIq@nathan |
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| Lists: | pgsql-hackers |
On Tue, Jul 30, 2024 at 10:01:50PM -0500, Nathan Bossart wrote:
> On Tue, Jul 30, 2024 at 07:43:08PM -0700, Andres Freund wrote:
>> My point is that _xgetbv() is made available by -mavx512vpopcntdq -mavx512bw
>> alone, without needing -mxsave:
>
> Oh, I see. I'll work on a patch to remove that compiler check, then...
As I started on this, I remembered why I needed it. The file
pg_popcount_avx512_choose.c is compiled without the AVX-512 flags in order
to avoid inadvertently issuing any AVX-512 instructions before determining
we have support. If that's not a concern, we could still probably remove
the XSAVE check.
--
nathan
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