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Re: vectorized CRC on ARM64

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: John Naylor <johncnaylorls@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-02T15:53:24Z
Lists: pgsql-hackers 
On Thu, Apr 02, 2026 at 08:16:27PM +0700, John Naylor wrote:
> 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.

I think the new pg_comp_crc32_choose() is infinitely recursing on macOS
because USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK is not defined but
pg_crc32c_armv8_available() returns false.  If I trace through that
function, I see that it's going straight to the

	#else
		return false;
	#endif

at the end.  And sure enough, both HAVE_ELF_AUX_INFO and HAVE_GETAUXVAL
aren't defined in pg_config.h.  I think we might need to use sysctlbyname()
to determine PMULL support on macOS, but at this stage of the development
cycle, I would probably lean towards just compiling in the sb8
implementation.

-- 
nathan

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