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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: 2026-04-02T13:16:27Z
Lists: pgsql-hackers

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On Wed, Apr 1, 2026 at 10:24 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> ... or maybe we should just use __attribute__((target("..."))) for the
> PMULL stuff.  That wouldn't work well for clang versions before 16, but it
> at least wouldn't regress anything.  They just wouldn't get PMULL support.

Okay, that works as far back as gcc 6.3, so v4 does it that way. The
attribute doesn't seem to be necessary on the inline helpers for
production builds, but they're needed to work with -O0.

Also
- removed the term 'intrinsics' from config variables, since we're not
checking those
- removed the crc intrinsic from the pmull tests
- fixed a failure to restore CFLAGS
- fixed it to work with +crc CFLAGS

For some reason, my CI builds with MacOS are failing on v3 (v2 skipped
the runtime check to get some exposure on CI) with the following, and
running CI from my Github account fails as well, so it's not a
temporary glitch. Adding a __linux__ guard to the runtime check didn't
help, so not yet sure what to make of it.

3/382 setup - postgresql:initdb_cache  TIMEOUT 300.51s   killed by
signal 15 SIGTERM

-- 
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