Horton

Re: add AVX2 support to simd.h

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: John Naylor <johncnaylorls@gmail.com>
Cc: Ants Aasma <ants@cybertec.at>, pgsql-hackers@postgresql.org
Date: 2024-01-03T15:29:54Z
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 →

  1. Improve style of pg_lfind32().

  2. Fix compiler warning for pg_lfind32().

  3. Micro-optimize pg_lfind32().

  4. Introduce helper SIMD functions for small byte arrays

  5. Optimize xid/subxid searches in XidInMVCCSnapshot().

On Wed, Jan 03, 2024 at 09:13:52PM +0700, John Naylor wrote:
> On Tue, Jan 2, 2024 at 11:11 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>> 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.
> 
> That means that we would be on the hook to fix it if it breaks, even
> though nothing uses it yet in a normal build. I have pending patches
> that will break, or get broken by, this, so minus-many from me until
> there is an availability story.

How will this break your patches?  Is it just a matter of adding more AVX2
support, or something else?

If the requirement is that normal builds use AVX2, then I fear we will be
waiting a long time.  IIUC the current proposals (building multiple
binaries or adding a configuration option that maps to compiler flags)
would still be opt-in, and I'm not sure we can mandate AVX2 support for all
x86_64 builds anytime soon.

-- 
Nathan Bossart
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