Horton

Re: Improve CRC32C performance on SSE4.2

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: John Naylor <johncnaylorls@gmail.com>, Andy Fan <zhihuifan1213@163.com>, "Devulapalli, Raghuveer" <raghuveer.devulapalli@intel.com>, Jesper Pedersen <jesperpedersen.db@gmail.com>, Tomas Vondra <tomas@vondra.me>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "Shankaran, Akash" <akash.shankaran@intel.com>
Date: 2025-06-23T15:05:49Z
Lists: pgsql-hackers

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  1. Include _mm512_zextsi128_si512() in AVX-512 configure probes.

  2. Properly fix AVX-512 CRC calculation bug

  3. Workaround code generation bug in clang

  4. Compute CRC32C using AVX-512 instructions where available

  5. Inline CRC computation for small fixed-length input on x86

  6. Be more paranoid in configure's checks for CRC and POPCNT intrinsics.

On Mon, Jun 23, 2025 at 10:51:21AM -0400, Tom Lane wrote:
> This has broken the build completely on my RHEL8 x86_64 box,
> with gcc 8.5.0:
> 
> $ ./configure ...
> $ make -s
> pg_crc32c_sse42.c: In function 'pg_comp_crc32c_avx512':
> pg_crc32c_sse42.c:126:25: warning: implicit declaration of function '_mm512_zextsi128_si512'; did you mean '_mm512_castsi128_si512'? [-Wimplicit-function-declaration]
>    x0 = _mm512_xor_si512(_mm512_zextsi128_si512(_mm_cvtsi32_si128(crc0)), x0);
>                          ^~~~~~~~~~~~~~~~~~~~~~
>                          _mm512_castsi128_si512

It looks like thse weren't added until GCC 10 [0].

> I see similar symptoms on buildfarm animal conchuela, which
> is DragonFly BSD of some vintage or other.  Not sure why
> more animals aren't complaining.  Anyway, it seems that the
> configure probe to see if this facility is available had
> better be adjusted to match the new code.

Unfortunately, this will probably require more than replacing
_mm512_castsi512_si128 with _mm512_zextsi512_si128 because the latter
doesn't exist.

[0] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83250

-- 
nathan