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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: Haibo Yan <tristan.yim@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-03-18T06:52:37Z
Lists: pgsql-hackers 
On Wed, Mar 18, 2026 at 10:34 AM Haibo Yan <tristan.yim@gmail.com> wrote:
>
> Hi John
>
> Thank yo for working on this. I had one question about the mixed use of intrinsics and inline asm here.

> Since the implementation already uses NEON intrinsics such as vld1q_u64, I was wondering why the pmull / pmull2 + eor helpers still need to be inline asm rather than intrinsics.
>
> Is that due to compiler/toolchain support, or because the intrinsic-based version produced noticeably worse code?

I answered that in the email you replied to, re-quoted here:

> To follow-up for curiosity's sake, [1] says that Apple chips can issue
> PMULL + EOR as a single uop if they are next to each other in the
> instruction stream.
> [1] https://dougallj.github.io/applecpu/firestorm.html

I don't know if that's relevant for current server hardware, so it
could be pointless. I'm personally not a fan of inline assembly, but I
also didn't yet want to put in the effort to alter generated code. I
don't think it would be very hard to do, however.

--
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