Re: Popcount optimization using AVX512

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: "Amonson, Paul D" <paul(dot)d(dot)amonson(at)intel(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, "Shankaran, Akash" <akash(dot)shankaran(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: 2024-03-28 21:38:54
Message-ID: 20240328213854.GA916732@nathanxps13
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Here is a v14 of the patch that I think is beginning to approach something
committable. Besides general review and testing, there are two things that
I'd like to bring up:

* The latest patch set from Paul Amonson appeared to support MSVC in the
meson build, but not the autoconf one. I don't have much expertise here,
so the v14 patch doesn't have any autoconf/meson support for MSVC, which
I thought might be okay for now. IIUC we assume that 64-bit/MSVC builds
can always compile the x86_64 popcount code, but I don't know whether
that's safe for AVX512.

* I think we need to verify there isn't a huge performance regression for
smaller arrays. IIUC those will still require an AVX512 instruction or
two as well as a function call, which might add some noticeable overhead.

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Attachment Content-Type Size
v14-0001-AVX512-popcount-support.patch text/x-diff 22.7 KB

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