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: 2025-02-12T21:48:57Z

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

> I think the idea behind USE_SSE42_CRC32C is to avoid the function pointer
> overhead if possible.  I looked at switching to always using runtime checks for this
> stuff, and we concluded that we'd better not [0].
> 
> [0] https://postgr.es/m/flat/20231030161706.GA3011%40nathanxps13

Does that mean we want this feature for the new PCLMUL (and AVX-512) crc32c implementations too? The code for that will look a little ugly, I might need to think about a cleaner way to do this. 

Raghuveer