Re: vectorized CRC on ARM64

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