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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: 2026-04-06T02:38:45Z
Lists: pgsql-hackers 
On Sat, Apr 4, 2026 at 8:52 PM John Naylor <johncnaylorls@gmail.com> wrote:
> Let's see what the buildfarm thinks.

hoatzin is failing with:

[1481/2135] "link" @src/backend/postgres.exe.rsp
FAILED: src/backend/postgres.exe src/backend/postgres.pdb
"link" @src/backend/postgres.exe.rsp
   Creating library src\\backend\\postgres.lib
utils_hash_pg_crc.c.obj : error LNK2001: unresolved external symbol
__builtin_constant_p

That should have been pg_integer_constant_p to work on MSVC since
length in bytes is an integer. That symbol is new in the PG19 cycle
and I didn't know about it until now. I've pushed a fix using that,
and appropriate guards. The earlier use of __builtin_constant_p in the
x86 case didn't happen to cause any failures on MSVC for some reason.
That path needs a guard as well, but since that's backpatchable I
handle it later. It's unlikely anyone passing special CFLAGS is using
a non-mainstream compiler, but that's still a potential trap waiting
for someone.

--
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