From: Nathan Bossart <nathandbossart@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Devulapalli, Raghuveer <raghuveer.devulapalli@intel.com>
Cc: Shankaran, Akash <akash.shankaran@intel.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David Rowley <dgrowleyml@gmail.com>
Cc: Ants Aasma <ants.aasma@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Amonson, Paul D <paul.d.amonson@intel.com>
Cc: Noah Misch <noah@leadboat.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
Subject: Re: Popcount optimization using AVX512
Date: Tue, 30 Jul 2024 22:12:18 -0500
Message-ID: <Zqmrkt6Pyb543bIq@nathan> (raw)
In-Reply-To: <ZqmpHjuDlJSjoZVT@nathan>
References: <20240418221358.GA3927188@nathanxps13>
<20240423160207.GA841237@nathanxps13>
<20240730210701.oyn2wr4zduu2efrg@awork3.anarazel.de>
<Zqlb1_-BWlzVMbZv@nathan>
<20240731004959.6ys24432n6xlgemk@awork3.anarazel.de>
<ZqmRYh3iikm1Kh3D@nathan>
<20240731014651.byn3exbu6n5v2yqa@awork3.anarazel.de>
<Zqma-_guYhQmA9_A@nathan>
<20240731024308.xma56fxidkdydzlo@awork3.anarazel.de>
<ZqmpHjuDlJSjoZVT@nathan>
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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To: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, andres@anarazel.de, raghuveer.devulapalli@intel.com, akash.shankaran@intel.com, tgl@sss.pgh.pa.us, dgrowleyml@gmail.com, ants.aasma@cybertec.at, alvherre@alvh.no-ip.org, paul.d.amonson@intel.com, noah@leadboat.com, boekewurm+postgres@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Popcount optimization using AVX512
In-Reply-To: <Zqmrkt6Pyb543bIq@nathan>
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