RE: Improve CRC32C performance on SSE4.2

Devulapalli, Raghuveer <raghuveer.devulapalli@intel.com>

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

To: Nathan Bossart <nathandbossart@gmail.com>

Cc: John Naylor <johncnaylorls@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "Shankaran, Akash" <akash.shankaran@intel.com>

Date: 2025-02-12T22:12:20Z

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

> Well, I suspect the AVX-512 version will pretty much always need the runtime
> check given that its not available on a lot of newer hardware and requires a
> bunch of extra runtime checks (see pg_popcount_avx512.c).  But it might be
> worth doing for PCLMUL.  Otherwise, I think we'd have to leave out the PCLMUL
> optimizations if built with -msse4.2 -mpclmul because we don't want to regress
> existing -msse4.2 users with a runtime check.

Sounds good to me. Although, users building with just -msse4.2 will now encounter an 
an additional pclmul runtime check. That would be a regression unless they update to 
building with both -msse4.2 and -mpclmul. 

Raghuveer