Re: Improve CRC32C performance on SSE4.2

Nathan Bossart <nathandbossart@gmail.com>

From: Nathan Bossart <nathandbossart@gmail.com>

To: Tomas Vondra <tomas@vondra.me>

Cc: Andy Fan <zhihuifan1213@163.com>, John Naylor <johncnaylorls@gmail.com>, "Devulapalli, Raghuveer" <raghuveer.devulapalli@intel.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "Shankaran, Akash" <akash.shankaran@intel.com>

Date: 2025-06-14T13:56:34Z

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

On Sat, Jun 14, 2025 at 03:47:33PM +0200, Tomas Vondra wrote:
> I suggest you try with a newer gcc, perhaps 13.4. There's been a bunch
> of fixes related to AVX512 since 13.0, chances are this was already
> fixed. I don't see this failure on 14.3.1.

From the config.log, it looks like Andy is using clang:

	configure:3998: clang --version >&5
	clang version 18.1.6 (https://gitee.com/mirrors/llvm-project.git 1118c2e05e67a36ed8ca250524525cdb66a55256)

And I see -O0 used, too, which would match the existing report [0],
although that report is for clang 19.1.7.

I'm also genuinely curious why folks are using -O0...

[0] https://postgr.es/m/CAE-ML%2B-OV6p9uvCFBcSQjZUEh__y0h-KjN%2BBseyGJHt7u8EP%2Bw%40mail.gmail.com

-- 
nathan