Re: Popcount optimization using AVX512

Nathan Bossart <nathandbossart@gmail.com>

From: Nathan Bossart <nathandbossart@gmail.com>

To: Alvaro Herrera <alvherre@alvh.no-ip.org>

Cc: "Amonson, Paul D" <paul.d.amonson@intel.com>, Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>, Andres Freund <andres@anarazel.de>, "Shankaran, Akash" <akash.shankaran@intel.com>, Noah Misch <noah@leadboat.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>

Date: 2024-03-29T15:42:41Z

Lists: pgsql-hackers

Commits

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Fix __attribute__((target(...))) usage.
- 41b98ddb77bf 18.0 landed
Use __attribute__((target(...))) for AVX-512 support.
- f78667bd910e 18.0 landed
Fix code for probing availability of AVX-512.
- 598e0114a3b1 17.0 landed
Optimize visibilitymap_count() with AVX-512 instructions.
- 41c51f0c68b2 17.0 landed
Optimize pg_popcount() with AVX-512 instructions.
- 792752af4eb5 17.0 landed
Inline pg_popcount() for small buffers.
- deb1486c7d36 17.0 landed
Avoid function call overhead of pg_popcount() in syslogger.c.
- 4133c1f45c54 17.0 landed
Refactor code for setting pg_popcount* function pointers.
- 6687430c98f3 17.0 landed
Inline pg_popcount{32,64} into pg_popcount().
- cc4826dd5e52 17.0 landed
Remove MSVC scripts
- 1301c80b2167 17.0 cited
Use ARMv8 CRC instructions where available.
- f044d71e331d 11.0 cited
Use Intel SSE 4.2 CRC instructions where available.
- 3dc2d62d0486 9.5.0 cited

On Thu, Mar 28, 2024 at 11:10:33PM +0100, Alvaro Herrera wrote:
> We don't do MSVC via autoconf/Make.  We used to have a special build
> framework for MSVC which parsed Makefiles to produce "solution" files,
> but it was removed as soon as Meson was mature enough to build.  See
> commit 1301c80b2167.  If it builds with Meson, you're good.

The latest cfbot build for this seems to indicate that at least newer MSVC
knows AVX512 intrinsics without any special compiler flags [0], so maybe
what I had in v14 is good enough.  A previous version of the patch set [1]
had the following lines:

+  if host_system == 'windows'
+    test_flags = ['/arch:AVX512']
+  endif

I'm not sure if this is needed for older MSVC or something else.  IIRC I
couldn't find any other examples of this sort of thing in the meson
scripts, either.  Paul, do you recall why you added this?

[0] https://cirrus-ci.com/task/5787206636273664?logs=configure#L159
[1] https://postgr.es/m/attachment/158206/v12-0002-Feature-Added-AVX-512-acceleration-to-the-pg_popcoun.patch

-- 
Nathan Bossart
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