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Re: vectorized CRC on ARM64

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-07T10:02:04Z
Lists: pgsql-hackers

Attachments

I wrote:
> In the end, I want to add a length check so
> that inputs smaller than 80 bytes go straight to the scalar path.
> Above 80, after alignment adjustments in the preamble, that still
> guarantees at least one loop iteration in the vector path.

Attached is how that would look. The idea is that small inputs will
encounter fewer branches. It'd be tricky to prove a difference with a
benchmark, and I see this as just making the small-input path more
similar to PG 18, as a risk-avoidance maneuver.

-- 
John Naylor
Amazon Web Services

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Use C11 alignas instead of pg_attribute_aligned

  2. Add missing guard for __builtin_constant_p

  3. Exit early from pg_comp_crc32c_pmull for small inputs

  4. Fix unused function warning on Arm platforms

  5. Compute CRC32C on ARM using the Crypto Extension where available