Re: Improve CRC32C performance on SSE4.2

Andy Fan <zhihuifan1213@163.com>

From: Andy Fan <zhihuifan1213@163.com>

To: "Devulapalli, Raghuveer" <raghuveer.devulapalli@intel.com>

Cc: Nathan Bossart <nathandbossart@gmail.com>, John Naylor <johncnaylorls@gmail.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: 2025-06-16T23:40:19Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Include _mm512_zextsi128_si512() in AVX-512 configure probes.
- ccd5bc93fdfe 18.0 landed
Properly fix AVX-512 CRC calculation bug
- 43da394304fb 18.0 landed
Workaround code generation bug in clang
- f83f14881c7a 18.0 landed
Compute CRC32C using AVX-512 instructions where available
- 3c6e8c123896 18.0 landed
Inline CRC computation for small fixed-length input on x86
- e2809e3a1015 18.0 landed
Be more paranoid in configure's checks for CRC and POPCNT intrinsics.
- fdb5dd6331e3 18.0 cited

"Devulapalli, Raghuveer" <raghuveer.devulapalli@intel.com> writes:

> Great catch! From the intrinsic manual: 
>
> Cast vector of type __m128i to type __m512i; the upper 384 bits of the
> result are undefined.

Just be curious, what kind of optimization (like what -O2 does) could
mask this issue?

> Replacing that with _mm512_zextsi128_si512 fixes the problem.

congratulations!

-- 
Best Regards
Andy Fan