Re: add AVX2 support to simd.h

Nathan Bossart <nathandbossart@gmail.com>

From: Nathan Bossart <nathandbossart@gmail.com>

To: John Naylor <johncnaylorls@gmail.com>

Cc: Ants Aasma <ants@cybertec.at>, pgsql-hackers@postgresql.org

Date: 2024-01-02T16:11:23Z

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 →

Improve style of pg_lfind32().
- 7188a7806d20 17.0 landed
Fix compiler warning for pg_lfind32().
- 1f42337be535 17.0 landed
Micro-optimize pg_lfind32().
- 7644a7340c8a 17.0 landed
Introduce helper SIMD functions for small byte arrays
- 9f225e992bed 17.0 cited
Optimize xid/subxid searches in XidInMVCCSnapshot().
- 37a6e5df3713 16.0 cited

On Mon, Jan 01, 2024 at 07:12:26PM +0700, John Naylor wrote:
> On Thu, Nov 30, 2023 at 12:15 AM Nathan Bossart
> <nathandbossart@gmail.com> wrote:
>> I don't intend for this patch to be
>> seriously considered until we have better support for detecting/compiling
>> AVX2 instructions and a buildfarm machine that uses them.
> 
> That's completely understandable, yet I'm confused why there is a
> commitfest entry for it marked "needs review".

Perhaps I was too optimistic about adding support for newer instructions...

I'm tempted to propose that we move forward with this patch as-is after
adding a buildfarm machine that compiles with -mavx2 or -march=x86-64-v3.
There is likely still follow-up work to make these improvements more
accessible, but I'm not sure that is a strict prerequisite here.

(In case it isn't clear, I'm volunteering to set up such a buildfarm
machine.)

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com